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2018 Flood Season Summary

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Select desired 'Date' to see corresponding 24-hour rainfall map ending at 7AM the following day.

 

 

 

 

 

 

 

 

> 0.6" RADAR ESTIMATE OR 0.5" GAUGED IN FORECAST AREA

Event

Date

Max ALERT

Max CoCoRaHS

QPE STP

ALERT

Alarms

ALERT

Rain

Alarms

Note

ADAM

ARAP

AURA

BLDR

BROM

DENV

DOUG

JEFF

1
0.87"
1.05"
>0.96"
Message 1 issued for Adams, Boulder, Broomfield, and Jefferson Counties at 1850

Weak to moderate thunderstorms developed over Boulder Cnty around 6:00pm and moved from SW to NE across Boulder
County. A stronger cell developed over Boulder County around 6:50pm producing heavy rainfall. Total rainfall was around 0.5"-1.0" across Boulder Cnty. A rainfall alarm was triggered at the Louisville Lake rain gauge for 0.5” in 10 minutes.



X




2
0.87"
1.22"
>2.96"

Message 1 issued for entire District at 1409. Between 1500 and 1700, weak storms moved across Boulder County.  Storm strength increased until 2045 producing heavy rain.  Storm weakened as it left the District after 2130. Rain records in Boulder county were commonly between 0.5" and 0.9". The highest readings from ALERT and CoCoRaHS were from Denver County. No alarms were triggered.
X
X
X
X

X
X
X
3
2.09"
2.70"
>2.21"
Message 1 issued at 0016 for Arapahoe/Aurora, Adams, Denver/DIA, and Douglas County. Scattered weak to moderate thunderstorms produced brief heavy rain and small hail between 2400 and 0230 with some rainfall totals measuring 1.0" over 3 hours. Storms weakened but continued between 0300 and 0400.  CoCoRaHS readings varied between 0.10" and 1.25" with larger readings in the center of the District. Moderate runoff led to rising rate alarms on creeks and streams, but rainfall fell short of the criteria for LIF's.

Message 1 issued for entire District at 1101. A thunderstorm developed in Jefferson County between 1000 and 1100, moving over Denver from 1100 to 1200, and leaving the District at 1400. This storm produced heavy rain and hail. A seperate thunderstorm moved across Douglas County between 1200 and 1400 producing heavy rain and large hail. Scattered showers in the western part of the District developed around 1800, producing light rain until dissapating between 2200 and 2300. Additional showers and thunderstorms producing light rain were in the District between 2300 and 0200. Total rainfall readings between 0.5" and 0.9" were common in Jefferson, Denver, Arapahoe, and Douglas Counties. Maximum readings from CoCoRaHS included 1.15" in southeast Denver and 1.40" near Morrison. Northeren areas of the District experienced less than 0.25". No alarms were triggered.
X
X
X
X

X
X
X
4
2.36"
3.60"
>2.82"
Message 2 issued for all jurisdictions, in coordination with NWS at 1118. Message 1 issued for Boulder County at 1515, with LIF added at 1519. Message 3 issued for Boulder County at 1612. Message 4 issued at 0649. Thunderstorms west of the District developed between 1300 and 1500, moving into the District around 1500. The strongest storms moved over Boulder County between 1500 and 1700, producing heavy rain, and hail.  Up to 3" of rain was produced over these 2 hours (2.85", NCAR per NWS), prompting NWS to issue a Flash Flood Warning for central and eastern Boulder County. Strong thunderstorms producing heavy rain and hail developed over portions of Jefferson and Adams Counties around 1700, with lighter showers between. By 1900, storms had weakened to light to moderate showers. Message 3's cancelled early along I-25 corridor. 
X


X
X

X
X
5
0.79"
1.50"
>1.57"
Message 1 issued for entire district at 1431. Strong thunderstorms developed over the mountains and moved into Jefferson and Douglass Counties between 1400 and 1500 causing Message 1's to be issued. Storms increased in strength between 1500 and 1600. Storms then moved over lower elevations in the southern and central areas of the district between 1600 and 1730, resulting in heavy rain and hail.  The storms weakened as they left the district to the east around 1800. Weak, short-lived showers and thunderstorms moved over southern Jefferson and Douglas Counties between 1800 and 2100. Total rainfall records of between 0.25-0.75" were common in Jefferson, Denver and Douglas Counties, while records of less than 0.25" were common in Boulder and Broomfield Counties. Rainfall alarms for rainfall exceeding 0.50" in 10 minutes were triggered at the Indian Creek, Plum Creek at Sedalia, and Happy Canyon UDFCD gauges in Douglas County, and the Aurora Town Hall gauge.
X
X
X
X
X
X
X
X
6
0.94"
0.59"
>2.15"
Message 1 issued at 1248 for entire district. Message 1 with LIF issued for Douglas County at 1339 and at 1715 for Boulder County. Message 4 issued at 2204. Around 1330, a severe thunderstorm moved northward into southern Jefferson County producing heavy rain (0.55" in 15 minutes and 0.79" in 1 hour at the Russelville Gulch gauge) and quarter sized hail. Moderate thunderstorms moved northwest into the district between 1330 and 1630, producing light to moderate rainfall. Around 1645 strong, slow-moving thunderstorms moved across Boulder County including the City of Boulder and the Four Mile Burn Area. Weak to moderate thunderstorm activity moved northeast across the district producing light to moderate rainfall until 1730. The Sunshine gauge gave an alert for 0.55" in 30 minutes and the Filter Plant gauge gave an alert for 0.59" in 10 minutes, both in Boulder County.
X


X
X

X
X
7
0.63"
0.85"
>1.01"
Message 1 issued at 1324 for entire district. Storms formed over northern Douglas County between 1100-1200 and moved northward at 20-25 mph. Around 1300, weak storms moved north into the district and strengthened, producing breif, heavy rainfall. Additional storms formed over Jefferson County and strengthened as they moved north into Boulder County.  These storms produced lightning and heavy rainfall until around 1500. Radar indicated a stronger storm east of I-25 that produced 0.25-0.75" of rainfall in 10-20 minutes. A rainfall rate alarm in Boulder County was triggered. Message 4 issued at 2247 as expected evening storms failed to develop.
X

X
X

X


8
1.54"
1.68"
>2.74"
Message 1 issued for entire district at 1022. NWS Aerial Flood Advisory issued for Douglas County from 1436-1630. Thunderstorms developed between 1000-1200 and became strong at times over Douglas Couty and Arapahoe County through the evening. Rain fell on much of the rest of the district with weak thunderstorms through late afternoon, weakening into rain showers through the evening, ending approximately 0100 June 18. Storms moved from S-N initially, then moved WSW-ENE in the late afternoon. Most areas reported 0.4-1.0" in 12 hours with the highest ammounts over 1.0" in Douglas and Arapahoe Counties. A couple rain alarms were triggered in Douglas County.
X
X
X
X

X
X
X
9
1.18"
1.57"
>3.68"
Message 1 issued for Adams, Broomfield, Jefferson, and Boulder Counties at 1737. NWS Severe Thunderstorm Warnings issued for Boulder, Broomfield, Adams, Jefferson, and Denver Counties between 1744 and 2016, expiring between 1815 and 2130. Weak thunderstorms developed over Jefferson and Boulder Counties at 1700. A storm west of Boulder strengthened rapidly, prompting Message 1 to be issued for Adams, Broomfield, Jefferson, and Boulder at 1737. At 1744, the thunderstorm moved into the district and became severe, with very large hail and heavy rainfall. Additional severe thunderstorms producing large hail and heavy rain moved across Boulder County for the next 3-4 hours, triggering 5 NWS Severe Thunderstorm warnings. Thunderstorms gradually weakened and finally moved out of the district to the north at 2100. Weak rain showers moved back into the district from the northeast at 0118. Thunderstorms for the day triggered 8 Alert Gauge Alarms in Boulder County for rainfall in 10 and rainfall in 30 minute periods. CoCoRaHS reported 0.65" in Louisville, 0.66" in Lafayette, 0.90" in Broomfield, and 1.02" in Brighton.
X


X
X


X
10
1.26"
1.04"
>2.69"
Message 1 issued for entire district at 1058. NWS Severe Thunderstorm Warning issued for Boulder County from 1206-1230 and 1229-1315. NWS Tornado Watch issued for all of NE Colorado from 1222-1900.  NWS Severe Thunderstorm Warning issued from 1309-1345 for Arahaphe, Denver, and Jefferson Counties. NWS Severe Thunderstorm Warning issued from 1329-1415 for Adams and Arapahoe Counties. NWS Severe Thunderstorm Warning issued from 1532-1615 for Douglas and Arapahoe Counties. Thunderstorms moved E to NE into the district through the evening. All counties except Broomfield experienced large hail and heavy rainfall, with very large hail measuring 1-3". New thunderstorms developed between 1800-1830 with the arrival of a cold front from the north. These storms did not become severe, but did produce heavy rain and hail. The heaviest rainfall from this round of storms occured in Denver County and Aurora. Storms weakened and moved out of the district to the east/southeast between 1900-2000. Showers formedin Douglas and Jefferson Counties between 2000-2100, but were weak and short lived.  Showers across the district weakened to cessation between 2100-2200. One UDFCD rainfall alarm was triggered twice,at the Gunbarrel rain gauge in Boulder County. The initial alarm was at 1236 for 0.5" in 10 minute, and again at 1255 for 0.5" in 10 minutes. Rainfall of 0.5-1.0" were common in Aurora and Boulder and Denver Counties. The highest rainfall reading was at the Gunbarrel rain gauge with 1.26".
X
X
X
X
X
X
X
X
11
1.10"
1.00"
>1.83"
Message 1 issued for entire district at 1102. Thunderstorms north and west of the district developed between 1030 and 1100, moving across the district between 1100 and 1200. Multiple waves of thunderstorms moved west to east across the district between 1100 and 1400. These storms produced moderate to heavy rainfall and hail. Weaker rain showers and thundersotrms developed between 1400 and 1600. Rain ended in the district around 2000. Rainfall readings of 0.5-1.0" were common across most of the district with the highest reading at the Murphy Creek Golf Course UDFCD gauge with 1.10". rainfall alarms of 0.5" in 10 minutes were triggered between 1330 and 1400 at the Havana Pond, Side Creek Park, Murphy Creek Golf Course, No Name at Quincy, and Quincy Reservoir gauges. The Murphy Creek Golf Course gauge also had an alarm for 1" in one hour.
X
X
X
X

X
X
X
12
0.24"
0.20"
>0.85"

Message 1 issued for Adams, Arapahoe, Denver and Douglas Counties, and Aurora and DIA at 1731. NWS Severe Thunderstorm Watch issued at 1404 and cancelled at 1853. Heavy rains to the north, and a southward gust front around 1700 prompted issuance of Message 1. However, the expected scattered storms over the district failed to develop. No heavy rainfall was recorded in the district, though neighboring counties to the north received upwards of 1.00". No alarms were triggered in the district.

X
X



X

13
0.43"
0.35"
>1.36"

Message 1 issued for entire district at 1518. Storms developed south and east of the district between 1400-1500, prompting issuance of Message 1. Slow-moving thuderstorms mved from south to north across eastern portions of the district, east of DIA, producing local heavy rainfall. Isolated pulse-type thunderstorms developed over the western and southern portions of the district between 2000 and 2200. Total rainfall in most of the district was less than 0.25", but parts of Douglas and Arapahoe Counties experienced 0.25-0.50". No rainfall alarms were triggered.
 X
X
X


X
X
X
14
1.50"
0.76"
>2.73"
Message 2 issued for Boulder, Jefferson, and Douglas Counties at 1058. Message 1 isued for remainder of district at 1403. NWS issued Flash Flood Watch at 1016 for Jefferson, Douglas, and Boulder Counties above 6,000'. Slow-moving thunderstorms entered the district from the west between 1400-1500. LIF issued for Arapahoe, Douglas, and Jefferson Counties, and the City of Aurora at 1518. Storms moved very slowly ENE. Additional slow-moving thunderstorms developed over eastern Boulder and NW Adams Counties, prompting LIF issuance at 1558 for Boulder and Adams Counties. Storms slowly moved out of the district to the east around 1900. NWS Flash Flood Watch cancelled at 1944 with Message 4 issued shortly thereafter. Rainfall alarms were triggered at Indian Creek gauge in NW Douglas County for rainfall of 0.50" in 10 minutes and 1.00" in one hour. CoCoRaHS observers reported 0.68" near Ken Caryl, 0.76" near Northglenn, and 0.56" near Erie.
X
X
X
X
X

X
X
15
0.47"
0.75"
>1.29"

Message 1 issued for entire district at 1738. Pulse-type storms developed over Arapahoe and Douglas Counties between 1430-1530.  Storms moved relatively slow to the SW at 5-15 mph. Additional pulses of thunderstorms developed and dispersed throughout the afternoon, with the convergence line moving to the west, precipitating on the central and western portions of the district. Development of a stronger, almost stationary storm in Adams County along I-25 prompted issuance of Message 1 at 1730, with the storm persisting until around 1830. There was poor rain gauge coverage in the area, but radar indicated in excess of 1.00" of rainfall. Thunderstorms weakend quickly between 1830-1930. Total rainfall from stronger storms was between 0.25-0.50", with no gauges recording greater than 0.50". There may have been more rainfall than that in Adams County, but rain gauge coverage is poor. No rainfall alarms were triggered.
X
X
X
X
X

X
X
16
0.31"
0.86"
>1.17"

Message 1 issued for Jefferson, Douglas, Adams, Denver, and Arapahoe Counties, including DIA, the City of Aurora, Wheat Ridge, and Lakewood at 1752. Thunderstorms developed east of the district in the early afternoon, and the first thunderstorms entered the district from the north east around 1700. Storms strengthened and came together as they moved south west across Arapahoe County, prompting issuance of Message 1 for much of the district at 1752. The storm moved south west over parts of Aurora, Centennial, Littleton, and Ken Caryl, producing heavy rainfall. By 1920, the storm had weakened and moved out of the district over the foothills in Jefferson and Douglas Counties. There was no further precipitation. Alert Gauge data was not consistent during the message period. Rainfall recordings were either not consistent with radar-derived estimates and local observations, or non-existent. No Alert Gauge alarms were triggered, but CoCoRaHS observers reported 0.86" near Chatfield, 0.63" near SW Centennial, 0.58" near SW Aurora, and 0.51" near Ken Caryl.
X
X
X


X
X
X
17
0.79"
2.24"
>1.80"
Message 1 issued for entire District at 1212.  An intense but small rain shower that produced 0.75" in 20 minutes over the Deckers Alert Gauge outside the district around 1130, in addition to rainfall north, west, and south of the district prompted the issuance of Message 1's.  Isolated storms moved from west to east into the northeast corner of the district around 1700, but did not produce heavy rainfall.  No alarms within the District were triggered.
X


X


X
X
18
2.05"
1.58"
>1.35"
Message 2 issued for Boulder, Jefferson, and Douglas Counties above 6,000' at 649. Message 2 issued for Adams, Arapahoe, Denver, and Douglas Counties below 6,000' at 1005. Message 1 issued for Broomfield, Boulder, and Jefferson Counties below 6,000' at 1011. A cold front from the north moved through the district during the early morning hours resulting in record precipitable water for the date in the AM sounding. Lower temperatures prevented thunderstorms from developing. Two main rounds of showers developed and were efficient rainfall producers. Wave one moved west to east across the District from 1400-1700. Wave two moved across the District NW to SE between 1730-2030. After this, showers quickly weakened and ended across the District between 2030-2130. Rainfall of 1-2" was recorded in Adams, Arapahoe, Douglas, and Jefferson Counties with the highest value of 2.05" at the Cherry Creek at Cottonwood Park gauge. Rainfall of 0.5-1.0" was common across the District, but lesser in Broomfield, eastern Boulder, and northern Adams Counties. The first wave triggered alarms of 0.5"/10 minutes and 1"/hour at the Cherry Creek at Cottonwood Park gauge. The second wave triggered alarms of 1"/hour at the Shop Creek, Mission Vieho, and Quincy Reservoir gauges in Arapahoe County.
X
X
X


X
X
X
19
1.57"
1.38"
>2.87"
Message 1 issued for Aurora, DIA, and Arapahoe, Dnever, and Douglas Counties at 1814. Message 1 issued for Jefferson County at 1815. NWS Severe Thunderstorm Warning for south/central Arapahoe County issued from 1844-1915. NWS Severe Thunderstorm Warning issued for NE Douglas County from 1934-2000. NWS Aerial Flood Advisory issued for NE Douglas and south/central Arapahoe County from 1945-2115, cancelled at 2041. A gust front from storms south of the District caused development of storms over southern and eastern portions of the District around 1800. Storms rapidly grew in strength between 1830-1840, but were mostly stationary. The strongest storms developed SE Aurora and just south of DIA. These storms slowly moved SW over Douglas County by 1930, and by 2030, the storms had left the District. Strong storm duration was between 45-75 minutes and became severe with large hail, heavy rain and gusty winds. Multiple heavy rainfall alarms were triggered in Arapahoe and Douglas Counties.
X
X
X


X
X

20
1.50"
1.98"
>2.47"
Message 1 issued for entire District at 1259. Thunderstorms over the foothills west of the District that developed around 1200 failed to move into the District utnil around 1530. This storm impacted areas SW of Evergreen. Over the next hour, storms propogated SE across Douglas County producing moderate to heavy rainfall. The NWS issued an Aerial Flood Advisory for north-central Douglas County at 1709, prompted by the CW1793 weather station near Castle Rock recording 0.86" in 30 minutes and 1.89" in 60 minutes. Over the next half-hour, thunderstorm activity weakened and moved away from the District. Around 1900, a storm moved over Broomfield, but produced only light-moderate rainfall. Starting at 1530, Alert alarms were triggered at the Brook Forest gauge for 0.50" in 10 minutes, and the DC Public Works gauge for 0.63" in 10 minutes and 1.10" in 30 minutes. At 1700, the Bingham Lake Park gauge near The Pinery recorded 0.51" in 10 minutes.






X
X
21
0.59"
0.24"
>1.35"
Message 1 issued for entire District at 1511. Thunderstorms initially developed over the mountains and foothills of Douglas and Jefferson Counties in the early afternoon. Around 1500, a stronger storm developed over the Decker's and Cheesman Canyon area, producing heavy rainfall and prompting issuance of Message 1 for entire District. A west-to-east propagating outflow boundary moved through the district during the evening hours, but served to stabilize the storms instead of strengthen them. Much of the lower elevations of the District remained dry, with the only significant rainfall during the evening occuring west of Boulder and south-east of Evergreen. The storm around 1500 triggered an alarm at the Four Mile Creek gauge for 0.50" in 30 minutes.






X
X
22
0.67"
0.73"
>1.47"
Message 1 issued for entire District at 1422. Thunderstorms developed over the foothills between 1300-1400, and quickly strengthened as they moved onto the plains. A front moved in from the north around 1500. The strongest storm of the day developed over northern Jefferson County and moved north-east at 15mph, producing moderate to heavy rainfall over parts of Boulder, Broomfield, and Adams Counties. Weaker showers developed around 1700 over Boulder County and southern portions of the District, persisting until drying out around 2200. After 2200, weak showers developed and persisted until the early morning hours of the 23rd. Much of the District experienced rainfall with readings of 0.05" - 0.30" common. The strong, fast moving storm triggered an rainfall rate alarm at the Upper Leyden Gauge.

X
X
X


X
X
23
1.73"
1.96"
>1.75"
Message 1 issued for Boulder, Douglas, and Jefferson Counties at 1324. Message 1 issued for remainder of District at 1754. M3 issued for Adams, Denver, and Arapahoe Counties and the City of Aurora at 1849.NWS Severe Thunderstorm Warning issued for Araphaoe, Douglas, Denver, and Jefferson Counties from 1756-1845. NWS Aerial Flood Advisory for Arapahoe, Denver, Douglas, and Jefferson Counties from 1841-1945. NWS Flash Flood Warning issued for Adams, Arapahoe, and Denver Counties from 1841-2045. Around 1300, a thunderstorm formed over the Boulder County foothills and the Four Mile Burn Area producing moderate to heavy rainfall, prompting Message 1's to be issued. Scattered showers and thunderstorms stayed over the foothills until a stronger storm formed over central Jefferson County around 1730, prompting the issuance of more Message 1's. As the storm moved east into the district, it strengthened into a severe thunderstorm at 1756. This storm produced heavy rainfall, large hail, and high wind for parts of Jefferson, Douglas, Denver, Adams, and Arapahoe Counties over the next hour. This storm prompted NWS Aerial Flood Advisories, NWS Flash Flood Warnings, and Message 3's to be issued. 44 Alert Gauge alarms were triggered at 12 different sites between 1820-1900 for rainfall of 0.50"/10 minutes and 1.00"/hour. CoCoRaHS reported heavy rainfall of 1.96" in NW Littleton, 1.56" in S Denver, and 1.50" in S Aurora.
X
X
X


X
X
X
24
2.01"
1.25"
>1.49"
Message 2 issued for all areas of the District except the foothills of Boulder, Douglas, and Jefferson Counties at 1058, valid from 1400-2359. Message 1 issued for the foothills of Boulder, Douglas, and Jefferson Counties at 1101, valid from 1300-2359. Message 2's downgraded to Message 1's at 2140. NWS Severe Thunderstorm Watch issued for entire District from 1324-1900. NWS Severe Thunderstorm Warning issued for east-central Broomfield, NW Adams, and east-central Boulder Counties from 1833-1915, Broomfield, north-central Denver, NW Adams, and east-central Boulder Counties from 1838-1930, NW Arapahoe, central Denver, and SW Adams Counties from 1925-2015, and E Douglas County from 2009-2100. NWS Urban and Small Stream Flood Advisories issued for central Denver and W Adams Counties from 1908-2045, and NE Douglas, W Arapahoe, couth-central Denver, and south-central Adams Counties from 1946-2115. Isolated thunderstorms developed over the foothills around 1300. Strong thunderstorms moved from NW to SE across northern, central, and eastern portions of the District between 1754-2030. These storms produced locally heavy rainfall, and triggered several NWS Severe Thunderstorm Warnings. Weaker thunderstorms tracked across Douglas and Jefferson Counties between 2030-2300. Total rainfall readings across the District were commonly between 0.50"-1.00". Denver and Jefferson Counties generally recieved less than 0.50", while Douglas County had several readings between 1.00"-1.50". The severe thunderstorms triggered several alarms for both 0.50"/10 minutes and 1.00"/hour.
X
X
X
X
X
X
X
X
25
0.31"
1.10"
>1.38"
Message 1 issued for Entire District at 1322. Message 1 issued for entire District at 0159 on 7/27. NWS Severe Thunderstorm Watch issued for entire District from 1350-2100. NWS Severe Thunderstorm Warning issued for central Adams and NE Denver Counties from 2109-2145. Afternoon thunderstorms around the District did not enter the District, but did trigger an alarm in Elbert County. Storm activity over the District during the afternoon was limited. Strong thunderstorms entered the District from the N/NW around 2100, extending Message 1's until 2330. Approaching thunderstorms from the north further extended Message 1's until 0200. Overnight showers moved into the district from the north, producing light to moderate rainfall over Boulder County until 0245. These storms moved SSE across the District, producing moderate to heavy rainfall over Jefferson and Douglas Counties with Alert gauges registering between 0.30"-0.47" of rainfall. Storms eventually exited the district around 0530. No alarms within the district were triggered.
X
X
X
X
X
X
X
X
26
0.67"
0.85"
>1.60"
Message 1 issued for entire District at 1405. NWS Tornado Watch issued for Arapahoe and Adams Counties from 1304-2100, cancelled at 1918. Weak thunderstorms developed over the foothills between 1300-1400 and moved across the I-25 corridor through 1600. As the storms left the District to the south and east, they encountered a convergence line and developed into severe thunderstorms, but prevailing winds kept them out of the District, with the exception of small portions of southern Douglas and Jefferson Counties. Rainfall alarms for 0.50"/10 minutes were triggered at the Westcreek Fire Station, EPC at Hwy 105, and Dakan Road gauges.






X
X
27
0.28"
0.22"
>1.00"
Message 1 issued for entire District at 1449. between 1700-2000, weak showers moved from NW to SE across the district. Most portions of the district recorded rainfall of less than 0.10", with no heavy rainfall. Strong thunderstorms were observed in Larimer and El Paso Counties. No alarms were triggered for the District.






X

28
0.63"
0.60"
>2.16"
Message 1 issued for entire District at 1315. NWS Severe Thunderstorm Watch issued for Douglas County from 1307-2100, remainder of District from 1437-2100, central Adams County from 2025-2100, and NE Douglas and SW Arapahoe Counties from 2028-2115. Strong to severe thunderstorms developed over central and eastern portions of the District, moving south east at 20-30 mph between 1930-2130. These storms were pulse-type and produced brief moderate to heavy rainfall and large hail. After messages expired at 2200, weaker thunderstorms moved across the district until 2300. No rainfall alarms were triggered.
X
X
X


X
X
X
29
0.75"
1.50"
>2.42"
Message 1 issued for entire District at 1522. NWS Severe Thunderstorm Warnings issued for Douglas and Elbert Counties from 1346-2100, Boulder, Larimer, and Weld Counties from 1718-1800, and Adams and Denver Counties from 1814-1900. A severe thunderstorm south of the District propogated northward into Douglas County around 1522, prompting issuance of Message 1. Around 1600, a strong thunderstorm rapidly developed over NE Douglas County and became severe at 1609, exiting the district by 1700. At the same time, a strong thunderstorm developed north of the district and tracked SE across Boulder and Weld Counties, entering the district around 1800 in Adams County. This storm became severe at 1814, but tracked over portions of the district with poor Alert gauge coverage east of Brighton and north of DIA. Storm activity dissipated and moved east of the district by 1900. The severe thunderstorm in Douglas County triggered a rainfall rate alarm for 0.50"/10 minutes at the Fire Station #47 gauge east of Parker, and a CoCoRaHS observer reported 1.50"/20 minutes.
X
X
X


X
X
X
30
2.05"
1.91"
>0.06"
RADAR data incomplete for day
Message 1 issued for the entire District at 1214.  An upper level disturbance arrived during the late afternoon. Widespread strong storms developed over northern and western portion of the District after 1530 resulting in heavy rainfall and large hail across portions of the District.  The strongest thunderstorms exited the District to the southeast around 2000, with isolated weaker showers and thunderstorms eventually tapering off across the remainder of the District between 2100-2200. Numerous rainfall alarms were triggered in Jefferson, Arapahoe, Douglas, and Adams Counties, for both 0.5”/10 minutes and for 1”/hour. The highest recorded rainfall amounts over 1"  occurred over Adams, Arapahoe, and Douglas Counties.







31
0.59"
1.19"
>2.79"
M1’s issued for Adams, Arapahoe, Denver, Douglas and Jefferson Counties at 1302. Thunderstorms developed over the mountains by 1300. Thunderstorms then impacted S and E portions of the District through roughly 1700 producing areas of heavy rainfall and small hail. Hardest hit areas were over Douglas County and E of E‐470 in Arapahoe County and just E and S of DIA in Adams County. Typical rainfall amounts from stronger storms 0.4‐1.5”. Heaviest rainfall occurred S  of the District in Douglas County and E of the District in Adams and Arapahoe County.
X
X
X



X

32
1.06"
1.82"
>1.23"
M1 Street Flooding Potential issued for entire District at 1136. A strong upper-level distrubance brought cooler temperatures and thunderstorms into the District starting at 1115. Thunderstorms weakened quickly producing only light rainfall.  M1's expired at 2100. M1’s were re‐issued for ALL areas at 2145 after an upper-level distrubance brought storms from Larimer and Weld counties.  This line of storms moved through the District from 2200-2400 and produced brief but heavy rainfall. 
Rates of 3‐4”/hr  with totals of 0.25‐0.75” from quick storms.
Heaviest amounts in excess of 0.50” occurred over Boulder, Broomfield, N Jefferson, W Adams, Denver and portions of Arapahoe County including Aurora. Most of the rain fell in 10‐20 minutes which resulted in brief excessive runoff roadways prompting LIF issuance for multiple Counties. NWS also issued a Severe Thunderstorm Warning due to hail over NW portions of the District.  
X
X
X
X
X
X
X
X
33
0.75"
0.71"
>0.98"
M1’s issued for all areas at 1357. High pressure shifted E drawing a plume of subtropical monsoon moisture northward into the District. Between 1300-1400 showers and isolated thunderstorms began to develop over the higher terrain. Between 1400-1800 a couple rounds of showers and weak to moderate thunderstorms tracked along and S of I-70 producing generally 0.10-0.65” of rain over S areas of the District. A late evening round of showers produced only light rain showers with generally a trace to 0.10” reported. Cloud cover and a weak front inhibited good surface warming resulting in only weak thunderstorms.  After  midnight there were isolated light rain showers.

X



X
X
X
34
0.51"
1.02"
>1.39"
Message 1 issued for the entire District at 1719. Low level moisture remained in place across the District. An isolated strong thunderstorm developed
over the Jefferson County foothills shortly after 1700, and given the moisture in place, Message 1’s were issued for the entire District. This storm ended up falling apart as it moved off of the foothills. Over the next 3 hours, additional thunderstorms would develop over the Jefferson County foothills and across central and southern Douglas County, with only showers and weak thunderstorms inside the District.






X
X
35
2.09"
2.14"
>2.64"
Message 1’s issued for all counties at 1035. Heavy rainfall event began late in the evening on September 4th and continued
into the early morning hours on September 5th.  Three factors combined to produce this large precioitation event: 1) a cold front moving through during the evening,  2) and increase in moisture behind the front and 3) an upper level disturbance moving in from the SW CO. Another factor was the light steering winds aloft which allowed storms to move very slowly and produce heavy rainfall amounts of 0.5-2.0” in 10-40 minutes. Thunderstorm coverage was widespread with all but Douglas County reporting heavy rainfall. Douglas County did receive rain but it was more light to moderate in intensity. Storms were nearly stationary initially and then began to move from N/NNW to S/SSE at 5-15mph. All Metro area creeks and streams were running high or out of banks due to this event with numerous LIF’s issued as well as Aerial Flood Advisories from the NWS.
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36
1.89"
2.25"
>2.33"
Message 1 Street Flooding Potential issued 1325 for entire District. A broad trough of low pressure remained over the Four Corners on September 5th, pumping mid and upper‐level moisture NE into the Central and Southern Rockies. Showers and thunderstorms developed over the mountains and foothills shortly after 1200, and also along the Palmer Divide by about 1300. A line of slow‐moving storms then intensified and tracked N towards the District. Thunderstorm activity largely decreased by 1600, but light to moderate rain showers were slow to clear out of the District through early evening, but only produced light to
briefly‐moderate additional rainfall. A total of (66) Alert Gauge alarms were triggered at (14) unique gauge sites, for rainfall at/exceeding 0.50”/10 minutes and also 1.00”/hour. The heaviest rainfall measured by Alert Gauges occurred at West Metro Fire Station near Ken Caryl (1.14”), Maple Grove Reservoir (1.89”), and Lakewood CC (1.65”).
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X

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37
0.51"
0.63"
>1.61"
Message 1 Street Flooding Potential issued 1515 for the entire District. A trough of low pressure moved NE across Colorado producing afternoon
and evening showers and thunderstorms. Showers and
thunderstorms formed over the mountains and foothills shortly after 1200, increasing in coverage and intensity during the afternoon. Thunderstorms producing moderate rainfall impacted portions of Boulder, Weld, and Jefferson Counties (outside District boundaries). Additional slow‐moving storms then formed on a convergence line along and E of District boundaries in Weld, Adams, Arapahoe, and Elbert Counties. This enhanced line of thunderstorms slowly tracked E through the late‐afternoon and early‐evening hours, with only light additional rainfall observed over the District.
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38
1.26"
1.44"
>1.21"
M1 Street Flooding Potential issued 1658 for entire District. A plume of subtropical moisture streamed N over Colorado. A cold front arrived during the morning, ushering in elevated surface moisture and upslope easterly winds against the Front Range. Shower and thunderstorms were slow to develop for much of the day, before better moisture and lift arrived by late afternoon. Foothills shower activity steadily strengthened into a line of thunderstorms. Alert Gauge alarms were triggered in Aurora at Murphy Creek Golf Course (1.26” total), Confluence Pond (0.87” total), Mission Viejo
Park (0.91” total), and Shop Creek (0.63” total), and also the Iliff Pond gauge in SE Denver (1.10” total). The NWS issued a Small Stream Flood Advisory at 1749 for portions of Denver and Arapahoe Counties. This line of heavy storms exited the District to the E around 1800. Additional rain showers moved across the District through the late‐evening, overnight, and early‐morning hours, but only light rainfall amounts were observed.
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Maximum 24-hour value

Maximum 24-hour value

Maximum

Radar

estimated

24-hour

precip

Alarm Log

Rainfall

Rate Alarm

 

ADAM

ARAP

AURA

BLDR

BROM

DENV

DOUG

JEFF