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2017 Season Summary

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Click on desired 'Date' below to see a regional map with gauge and radar-estimated 24-hour rainfall totals.

 

 

 

 

 

 

 

 

> 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
1.73"
1.90"
>2.03"
Message 1 issued for the entire District at 1238.

Showers and thunderstorms developed over the foothills between 11am-noon. A severe thunderstorm developed over the Jefferson County foothills shortly after 2pm, strengthening and impacting the northern part of the District through 5pm with severe rainfail and large hail reported up to 2.5" in diameter. A second round of storms developed over Douglas and Jefferson but was much weaker in strength. Light to moderate rain showers would
continue to move through the District well into the evening hours with isolated light showers continuing
overnight. Several rainfall alarms were triggered in Denver for 0.5" in 10 minutes, and 1" in 1 hour.
X
X
X
X
X
X
X
X
2
0.28"
0.81"
>0.70"
M1 issued for Adams, Denver/DIA, Arapahoe/Aurora, Douglas at 1741.

Late in the afternoon a lone moderate to strong thunderstorm devoloped over far SE portions of the District. This storm produced moderate to briefly heavy rainfall along with hail. Additional isolated showers developed overnight into the early am hours on Wednesday. No rainfall alarms were reported.
X
X
X



 
3
1.50"
3.10"
>3.05"
M1 issued for the entire District at 1947.

A cold front arrived from the north early Wednesday evening, allowing thunderstorms to develop across the District shortly after 7pm, before transitioning to a more widespread steady rainfall event later in the evening. The first thunderstorm developed over Boulder County around 7:00pm, and over the next two hours this storm became strong and slowly tracked eastward across Broomfield and Adams Counties. A second stronger storm cell developed over northern Douglas County and impacted southern portions of the District. Steady rainfall developed over the entire district overnight eventually transitioning to snowfall. No rainfall alarms were reported
X
X
X
X
X
X
X
X
4
1.46"
3.10"
>2.11"
The storm from the 17th continued through the day, while messages expired at 10am because no heavy rainfall events were likely to occur with precipitation falling mostly as snow. However, total precipitation amounts with this system through Friday morning were significant, ranging from 1.5‐3 across southern portions of the District and 2‐4 across northern portions of the District. No rainfall alarms were reported.
X
X
X
X
X
X
X
X
5
0.31"
0.45"
>1.41"
M1 issued for the entire district at 1305.

Thunderstorms formed prior to noon over parts of the foothills and by around 1pm storms began to develop along a surface convergence line over SE areas of the District. The strongest initial cell developed along the Douglas/Arapahoe County line and lifted to the NE producing moderate/brief heavy rain and small to moderate sized hail. Additional storms developed later in the afternoon, mainly S of I‐70 but only increased to moderate in strength through around 5pm. no rainfall alarms were reported.

Message 4 issued for the entire district at 1827.
X
X
X
X
X
6
0.83"
0.72"
>1.46"
M1 issued for Adams, Arapahoe, Denver, and Douglas Counties, including DIA and the City of Aurora, at 1503.

Storms were able to initiate over the foothills and Palmer Divide between 11am‐2pm and slow storm motions to the SE resulted in an increasing threat for heavy rainfall. Thunderstorm activity increased between 2‐3pm, with a stronger storm cell developing over downtown Denver. This storm strengthened as it moved eastward into Arapahoe County, prompting Messages to be issued for eastern portions of the District. Thunderstorm activity decreased after 4pm following this stronger storm, with lingering showers and weak thunderstorms mainly confined to the foothills. No rainfall alarms were reported.
X
X
X
7
0.55"
0.29"
>1.11"
M1 issued for the entire District at 914.

Thunderstorms initially developed over the higher foothills as early as 11am, before increasing in coverage over the lower foothills between 1‐2pm. Thunderstorms also developed across the lower elevations of Jefferson, Broomfield and Boulder Counties, as well as Denver and Arapahoe Counties, between 2‐4pm. Storms then tapered off from south to north shortly after 4pm. No rainfall alarms were
triggered.
X
X
X
X
X
8
0.71"
0.98"
>1.23"
M1 issued for the entire District at 1213.

Thunderstorms initially developed over the higher terrain between 11am‐noon and eventually strengthened and slowly tracked across the lower elevations of the District between 1‐3pm. The strongest cell tracked from south Denver metro through Aurora around 2pm, and this is where the heaviest rainfall occurred.  A second round of weaker but slow‐moving showers and thunderstorms moved across the norther portions of the District between about 3‐6pm, with lighter rainfall.  NWS Areal Flood Advisory was  issued for SW Arapahoe and South Denver Counties at 1441, valid until 1745.
X
X
X
X
X
X
X
9
0.43"
1.11"
>1.61"
M1 issued for Adams, Arapahoe/Aurora, Denver/DIA, Douglas Counties at 1351.
A gust front passed over the District, rapid thunderstorm development only occurred over the eastern portion of the District.  Heavy rainfall with hail was observed over far SE areas of District with some pockets of moderate rain over Adams County.
X
X
X


X
10
0.91"
1.84"
>1.77"
M1 issued ALL areas at 1645.

Storms developed early over the mountains before noon, slow moving thunderstorms developed at 1700. Heaviest rainfall from these storms was East of DIA and over more rural portions of Arapahoe County and far NE Douglas County. 0.91 of rain was measured from UDFCD gauges at Fire Station #47 in Douglas County.  Another round of storms occurred at 10pm.
X
X
X

X
X
X
X
11
0.98"
0.87"
>1.56"
M1 issued for ALL areas at 1321.

Between 1‐2pm storms developed in the foothills.  After 3pm thunderstorms began to intensify over eastern and southern areas of the District. Strongest storms were E of I‐25. Another weaker round of storms occurred in the late evening and overnight.  This was the 3rd day in a row where far SE areas of the District observed heavy rainfall.
X
X
X
X
X
X
X
12
0.35"
0.07"
>0.75"
M1 issued for ALL areas at 2028. Around 8‐8:30 pm a single thunderstorm cell developed SW of the District over Jefferson County.  This storm tracked ENE and dissipated due to an atmospheric cap. Had storms been able to develop they could have been strong to severe with the potential for heavy
rain.


X
X
13
0.63"
1.25"
>1.95"
M1 issued for Arapahoe/Aurora, Denver, Jefferson and Douglas Counties at 1534.

Thunderstorms developed over the higher mountains and foothills west of the District around noon. Thunderstorms developed over the District at 3:30 pm.  The first storm quickly became severe with large hail and brief heavy rain, existing the District around 5pm.  More thunderstorms would develop just east of the District after 5pm and remain to the east over very rural areas diminishing prior to 7pm.
X
X
X
X
X
X
14
0.39"
1.38"
>0.66"
M1 issued for all areas at 1150.  
Abundant moisture and thick cloud cover produced rain showers starting in the early afternoon with more widespread showers throughout the late afternoon and evening. Temperatures were too cool for thunderstorm development.
X
15
0.79"
0.62"
>1.08"
M1 issued for Arapahoe/Aurora, Denver, Douglas, Jefferson at 1556.  
Thunderstorms developed south of the District during the early afternoon.  A moderate thunderstorm formed just east of the Adams/Arapahoe/Denver
County junction causing brief moderate rainfall. Strongest storms with heavy rainfall remained south of the District boundary.
X
X
X
16
1.06"
1.55"
>1.89"
M1 issued for all areas of the District except Boulder and Broomfield Counties at 1512.
Storms would develop south of the District between noon and 2pm. Isolated weak thunderstorms reached northern areas of the District between 4‐5pm, before thunderstorm activity subsided after 5pm.
X
X
X
X
17
0.84"
0.41"
>1.23"
M1 issued for Douglas and Arapahoe Counties, including the City of Aurora, at 1258.
Very slow moving storms developed resulting in a heavy rainfall threat. Ultimately, thunderstorm
intensity remained weak enough to keep rainfall amounts light and thunderstorms tapered off after 5pm with dry conditions developing by early evening.
X
18
1.18"
1.02"
>2.52"
M1 issued at 1325 for the entire District. Scattered, slow-moving thunderstorms during the afternoon and evening. These storms were initially stationary, producing heavy rainfall.  Foothills storms moved NE prompting a NWS severe thuderstorm warning at 1503.  Weak thunderstorm activity continued over the central andsouthern portions of the District through 9:00 PM
X
X
X
X
X
X
19
0.75"
1.42"
>2.59"
M1 issued for the entire District at 1338. Thunderstorms initially developed over the higher foothills around noon and moved slowly toward the District between 1‐3pm. Weak thunderstorms increased in coverage over the lower elevations of the District between 3‐5pm. Isolated rain showers continued across the District late into the evening, but only produced light rainfall amounts.
X
X
X
X
X
X
20
0.79"
0.79"
>1.08"
M1 issued for Douglas County at 1626. A slow moving storm developed over Rampart Range of Douglas County moving E/NE into the South portion of the District. Storm activity ended before 7pm.
X
21
0.67"
1.42"
>1.51"
M1 issued for ALL areas at 1433. Thunderstorms developed over the higher terrain west of the District prior to 2pm. Rain showers and weak thunderstorms moved into the District from the west between 2-7pm then decreased towidely scattered showers into the later evening.
X
X
22
3.78"
3.18"
>2.70"
M1 issued for ALL areas at 1441. Thunderstorms producing heavy rainfall developed between 2:30 PM and 3:30 PM over the Jefferson and Douglas County foothills moving into the SE areas of the District by around 6pm. The NWS issued a Flash Flood Warning at 6:32 PM for NE Douglas County, indicating 2.5 rainfall in about 40 minutes near Franktown. Spotter reports and gauge data indicated rainfall of 1.5‐2.5 near Castle Rock and the surrounding areas. A total of (6) Low Impact Flood Messages were issued between 6:18 PM and 9:51 PM.
X
X
X
X
X
X
X
23
0.16"
1.01"
>1.10"
M1 issued at 1800 for all areas of the District except Boulder and Broomfield Counties. Isolated thunderstorms showered over southern and eastern portions of the District around 6:00pm. Additional short‐lived pulse showers and weak thunderstorms developed over central and eastern portions of the District through 9pm.
X
X
24
2.01"
1.73"
>2.52"
M1 issued for ALL except Boulder and Broomfield Counties at 1433. Thunderstorms developed over far southern Jefferson and Douglas Counties between 2-3pm remaining nearly stationary. Thunderstorms also developed over the Boulder County foothills in the mid afternoon but no totals were greater than 0.5.
X
X
X
X
X
25
0.55"
0.87"
>0.91"
M1 issued for the entire District at 2002. overcast skies and isolated rain showers occured throughout the morning. Rain showers would increase over the District by late in the morning and continue into early afternoon.
X
X
26
0.98"
1.31"
>1.45"
M1 issued for ALL areas at 1345. Thunderstorms developed over the mountains between 12-1pm moving into the mid foothills by around 2pm. After 2pm storms began to spread over the plains producing moderate to heavy rainfall. Scattered storms would impact most areas of the District with the stronger storms mainly along and east of I‐25 through 7pm with multiple Low Impact Flood updates issued.
X
X
X
X
X
X
X
27
0.31"
0.34"
>1.09"
M1 issued for the entire District at 1523. The first stronger storm developed just north of the District along with Boulder/Larimer County Line. Another cluster of stronger thunderstorms impacted areas on the plains just southeast of the District between 4-6pm and a cluster of lighter rain showers moved across Douglas County. Shower and thunderstorm activity quickly cleared out after 7pm.
X
28
0.94"
1.01"
>1.12"
M1 issued for Adams, Arapahoe/Aurora, Denver/DIA, Douglas, Jefferson Counties at 1616.Thunderstorms developed outside the District over portions of Jefferson County between 3-4pm entering the SW areas of the District around 415pm. This storm grew into a large thunderstorm complex that impacted areas south of I-70. This storm triggered multiple rainfall rate alarms and CoCoRaHS showed 4 locations over northern Douglas County that reported right around 1.
X
X
X
X
X
X
29
0.79"
0.58"
>0.65"
M1 issued for the entire District at 1617. The first thunderstorms developed over Douglas County in the afternoon which produced light to moderate rainfall amounts. Additional short storms formed over Denver and Aurora producing heavy rainfall. The Horse Creek gage reported 0.75" in 25 minutes.
X
X
30
1.46"
1.75"
>1.18"
M1 issued for entire District at 1755. Widespread steady showers persisted over the District for much of the day, with generally light to moderate rainfall rates observed. By early evening, heavier rain showers developed over the foothills of Jefferson and Douglas Counties. Rainfall slowly decreased in intensity, eventually coming to an end by mid evening.The Indian Creek gage reported 0.96" in one hour.
X
X
X
X
X
X
31
0.55"
0.59"
>0.84"
M1 issued ALL areas at 1508. Thunderstorms started over Boulder and Jefferson county and moved over the District creating a severe thunderstorm warning producing brief moderate to heavy rainfall as well as hail. Most areas reported under 0.5" of rain with the heaviest rains of the day remaining outside of the District in Fort Collins and Greeley.
X
X
X
X
X
32
0.98"
0.70"
>1.20"
M1 issued for ALL areas at 1531. Rapidly strengthening thunderstorms developed over the elevated terrain of N Jefferson County and S Boulder County by around 3pm becoming a strong thunderstorm. Pockets of heavy rainfall were produced  in a broken line of storms over the Eastern and Southern areas of the District. Heaviest thunderstorm activity exited the District between 5-6pm with minimal storm activity after that time. The Van Bibber gage set off an alarm, along with several alarms south of the District.
X
X
X
X
X
33
0.55"
0.59"
>1.10"
M1 issued for the entire District at 1440. A strong, slow moving thunderstorm cell developed over Boulder County and moved southeast through central portions of the District between 2:30-5:00pm. Under the core of the storm areas of moderate to briefly heavy rainfall occurred over northern Jefferson and Broomfield Counties. Lingering storms produced minimal rainfall between 5:00-6:00pm. No rainfall alarms were triggered.
X
X
X
X
X
X
X
34
1.10"
0.69"
>0.83"
M1 issued for Adams and Arapahoe Counties at 1829. Weak thunderstorms developed over west and northwest during the afternoon hours producing minor rainfall. These initial storms were weak with light to moderate rainfall. There was one strong cell over northern Douglas County that was able to produce total rainfall amounts of 0.50-0.75 in about an hour. Other storms over Aurora produced locally heavy rainfall. Two rainfall alarms were triggered at Pump Station #3 (0.5/10min and 1.0/hr).
X
X
X
X
35
1.34"
1.03"
>2.65"
M1 issued for entire District at 1405. Isolated slow-moving thunderstormed developed over the foothills at 1-2pm.  A strong slow-moving storm developed over Douglas County.  An approaching cold front from the north triggered new storm development 6-8pm with storms decreasing after 8:30pm.
X
X
X
X
X
X
X
36
0.31"
0.19"
>0.58"
M1 issued for Boulder, Jefferson and Douglas Counties at 1314.  Isolated storms developed over the foothills after noon with a few stong cells over Boulder and N. Jefferson Counties.  Thunderstorm activity decreased after 3pm, but weaker rain showers moved from W to E across the District 5-7pm.
37
0.28"
0.30"
>1.13"
M1 issued for Boulder, Jefferson, and Douglas Counties at 1928. Isolated storms developed over the foothills 12-3pm.  A strong storm developed over the northern Boulder County foothills at 7pm.
X
X
X
38
0.47"
0.84"
>1.49"
M1 issued at 1507 for Douglas, Adams, Denver, Arapahoe; including DIA, the City of Aurora.  Storms developed over the foothills at 1pm. with storm development over the District around 3pm.
X
X
X
X
X
39
0.79"
0.89"
>1.80"
M1 issued at 1745 for Adams, Arapahoe/Aurora, DIA.  A weak cold front moved through overnight. Thunderstorms developed S and SE of the District during the middle afternoon hours. Shower and thunderstorm activity occurred between 5-8pm over SE areas of the District.
X
X
40
0.59"
0.40"
>0.54"
M1 issued for the entire District at 1443. Thunderstorms developed over the foothills shortly after noon.  A strong thunderstorm cell developed over the Jefferson County foothills around 2:30pm prompting messages to be issued for the entire District. The storms weakened as they moved through the District.
X

 

 

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