Flash Flood Warning 25, NWS Denver/Boulder, CO

334 
WGUS75 KBOU 130732
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
132 AM MDT Tue Aug 13 2024

COC123-130900-
/O.CON.KBOU.FF.W.0025.000000T0000Z-240813T0900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Weld CO-
132 AM MDT Tue Aug 13 2024

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 3 AM MDT EARLY THIS 
MORNING FOR NORTH CENTRAL WELD COUNTY...

At 132 AM MDT, Doppler radar indicated thunderstorms producing heavy 
rain across the warned area. Between 2 and 4 inches of rain have 
fallen, with the heaviest rain west of Grover to county road 77 and 
west of Hereford to county road 71. Additional rainfall amounts up 
to 0.5 inches are possible in the warned area. Flash flooding is 
likely ongoing in these areas and in creeks that drain into areas 
west and southwest of Grover.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar indicated.

IMPACT...Flash flooding of small creeks and streams, gulches,
         roads, and poor drainage and low-lying areas.

Some locations that will experience flash flooding include...
  Grover and Hereford.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 4082 10420 4064 10433 4073 10435 4100 10460
      4100 10423

FLASH FLOOD...RADAR INDICATED

$$

Gimmestad

034 
WGUS75 KBOU 130903
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
303 AM MDT Tue Aug 13 2024

COC123-130913-
/O.EXP.KBOU.FF.W.0025.000000T0000Z-240813T0900Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Weld CO-
303 AM MDT Tue Aug 13 2024

...FLASH FLOOD WARNING HAS EXPIRED FOR NORTH CENTRAL WELD COUNTY...

The most intense flash flooding has subsided. However, flooding of 
fields, small creeks, and low lying areas west of Grover and 
Hereford is likely continuing. A flood warning for this is now in 
effect until 600 AM.

&&

LAT...LON 4082 10420 4064 10433 4073 10435 4100 10460
      4100 10423

$$

Gimmestad

Area Forecast Discussion
National Weather Service Denver/Boulder CO
923 PM MDT Mon Aug 12 2024

.KEY MESSAGES...

- Flash flood threat slowly decreasing through midnight.

- Tuesday appears to be just as active, with another round of
  thunderstorms with heavy rain, some flooding threat, and a
  greater risk of severe weather.

- Gradual drying trend expected from Wednesday through the end of
  the work week with near to slightly above normal temperatures.

&&

.UPDATE...
Issued at 908 PM MDT Mon Aug 12 2024

Busy late aftn and evening as slow moving tstms produced
very heavy rainfall in a few areas with amounts exceeding 4".
In addition some of the storms were severe.

Still have widely scattered storms over portions of the plains
which are producing heavy rain. Meanwhile, there is still decent
instability along nrn portions of the I-25 Corridor where
favorable low level easterly flow exists. Some of the hi res data
is showing possible redevelopment of stronger storms along and
north of a Fort Collins to Greeley line between 10 pm and
midnight. If they do redevelop, with high precipitable water
values, there will be potential for heavy rain and a marginal
severe storm.

&&

.SHORT TERM /Through Tuesday/...
Issued at 248 PM MDT Mon Aug 12 2024

Main concern remains flash flooding through much of this evening.

Satellite and observations show we've reached convective
temperatures on the plains roughly from Denver into east central
Colorado. CIN (convective inhibition) analysis from SPC shows the
same, but still some CIN to the north where morning stratus
delayed surface heating. Where CIN has been eliminated, anywhere
from shallow cumulus to towering cumulus, to cumulonimbus is
developing. A Flash Flood Warning has already been issued for
portions of the Cameron Peak burn area, where initial storms were
just creeping along and backbuilding. We see the flash flood
threat growing through the late afternoon and evening, as storms
continue to fire and eventually organize. We think the greatest
organization and higher threat will likely occur from the
south/east sections of Denver metro and Palmer Divide (due to
urban flooding) and especially as we head farther east into Elbert
and Lincoln Counties where further storm organization is expected
due to increasing low level inflow, aiding further storm
development by offsetting cold pool interactions. That threat
could very well continue through the late evening hours there, but
some chance (30-40%) storms organize linearly and keep moving
along through 8-9 pm. More details about the ingredients in the
hydrology discussion below. The Flood Watch for flash flooding we
issued earlier for the foothills (main threat remains in the burn
areas), Denver and south/east suburbs (urban flooding), and Palmer
Divide/east central Colorado plains (heavier rain and
creek/stream flooding) will remain in effect. The greatest threat
is expected to wind down from west to east across the area during
the mid to late evening hours, but could continue til close to
midnight for the east central plains. Watch is timed accordingly.

There should be partial clearing late, which means - you guessed
it, more stratus and fog across the plains mainly north and east
of Denver.

Tuesday will feature another active weather day. The upper level
ridge axis will shift off to the east, with a more southwesterly
flow aloft pushing across the forecast area. Ingredients for heavy
rain remain favorable, and there are signs storms may even become
widespread/more organized. There doesn't seem much forcing yet
(best jet streak a little too far to the northwest), but CAMs are
showing a cluster of convection developing in the mountains and
then spreading east across the I-25 Corridor/nearby adjacent plains
during the afternoon. We've increased PoPs accordingly. We will
also see a greater risk of severe storms including wet microbursts
and large hail given an increase in MLCAPE to 1500-2500 J/kg -
greatest likely just east of I-25. Would not be surprised to see
SPC risk get upgraded to Slight Risk for tomorrow given the
increased CAPE and shear.

&&

.LONG TERM /Tuesday night through Monday/...
Issued at 116 PM MDT Mon Aug 12 2024

Thunderstorms will progress across eastern Colorado Tuesday
evening. Severe threat is expected to taper off during the
evening, but the heavy rainfall will continue through the evening
hours. Could see a few showers linger past midnight, but the vast
majority of showers and storms will be finished by midnight.

Upper level high currently over the Southern Plains will slowly
migrate westward Wednesday through Friday, eventually ending up
over the Southern Rockies. A short wave trough embedded in the
westerly flow aloft is expected to bring another round of
afternoon thunderstorms Wednesday. Precipitable water values
decrease to around normal, so heavy rain won't be as big as a
threat. However, there still should be enough moisture for
scattered storms with brief heavy rain.

A subsident northwest flow aloft will prevail behind an upper
level trough moving across the Northern Plains on Thursday.
Perhaps there will be enough moisture for isolated high-based
showers and storms. Any rainfall is expected to be light with
gusty winds being the main threat from the showers and storms. The
drier airmass will stay in place for Friday. Temperatures will be
near to slightly above normal with highs in the mid 80s to lower
90s.

For the weekend and next Monday, upper level high will build over
the Central and Southern Rockies. Temperatures are expected to be
warm with highs over northeast Colorado reaching the lower to mid
90s. Moisture begins to wrap around the ridge and by Sunday
(possibly as early as Saturday) precipitable water values climb to
130-150 percent of normal. Moisture begins to increase Saturday
and with this, we should see an uptick in storms. By Sunday,
expect to see scattered to numerous thunderstorms to return to the
area due to the increase in moisture.

&&

.AVIATION /00Z TAFS through 00Z Wednesday/...
Issued at 503 PM MDT Mon Aug 12 2024

Tstm activity over DIA should end by 00Z based on current trends.
Overnight, stratus will move in between 10z and 11z with LIFR
ceilings, visibility may drop down to 1-3sm. Stratus should lift
by 15z. Expect a line of tstms will move across between 21z and
00z with gusty winds and brief heavy rain. Visibility may drop to
3-5sm as they move across. Winds will be southeast this evening
and then more south by 06z. By 10z winds may become light west.
Winds by midday will become ENE.

&&

.HYDROLOGY...
Issued at 116 PM MDT Mon Aug 12 2024

Additional storms overnight mainly along and north of a Fort
Collins to Greeley to Fort Morgan line will have the potential
to produce heavy rainfall of 1 to 2 inches in 30 to 45 minutes
if redevelopment occurs.

Tuesday could see a similar flash flood threat unfold, although
storm motions will be a little faster as mid level shear/flow
increases.

Drier air starts to move into the area Wednesday, lowering the flash
flood threat. By Thursday, if any storms are able to form, they are
only expected to produce light rainfall. The drier conditions are
expected to continue into Friday. Moisture begins to increase
Saturday and by Sunday the heavy rainfall/flash flooding threat is
expected to increase.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Flood Watch until midnight MDT tonight for COZ045>047-049.

&&

UPDATE...RPK
SHORT TERM...Barjenbruch
LONG TERM...Meier
AVIATION...RPK
HYDROLOGY...Barjenbruch/Meier/RPK

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
214 PM MDT Mon Aug 12 2024

COZ030>051-132015-
Jackson County Below 9000 Feet-
West Jackson and West Grand Counties Above 9000 Feet-
Grand and Summit Counties Below 9000 Feet-
South and East Jackson/Larimer/North and Northeast Grand/
Northwest Boulder Counties Above 9000 Feet-
South and Southeast Grand/West Central and Southwest Boulder/
Gilpin/Clear Creek/Summit/North and West Park Counties Above
9000 Feet-Larimer and Boulder Counties Between 6000 and 9000 Feet-
Jefferson and West Douglas Counties Above 6000 Feet/Gilpin/Clear
Creek/Northeast Park Counties Below 9000 Feet-
Central and Southeast Park County-
Larimer County Below 6000 Feet/Northwest Weld County-
Boulder And Jefferson Counties Below 6000 Feet/West Broomfield
County-
North Douglas County Below 6000 Feet/Denver/West Adams and
Arapahoe Counties/East Broomfield County-
Elbert/Central and East Douglas Counties Above 6000 Feet-
Northeast Weld County-Central and South Weld County-Morgan County-
Central and East Adams and Arapahoe Counties-
North and Northeast Elbert County Below 6000 Feet/North Lincoln
County-
Southeast Elbert County Below 6000 Feet/South Lincoln County-
Logan County-Washington County-Sedgwick County-Phillips County-
214 PM MDT Mon Aug 12 2024

This hazardous weather outlook is for northeast and north central
Colorado.

...FLOOD WATCH FOR FLASH FLOODING IN EFFECT FOR THE FRONT RANGE
FOOTHILLS...DENVER AND SOUTHERN AND EASTERN SUBURBS...PALMER
DIVIDE...AND EAST CENTRAL COLORADO PLAINS THIS AFTERNOON AND
EVENING...

.DAY ONE...Today and Tonight

Thunderstorms will continue to develop and spread east across the
plains through late this afternoon and evening. The risk of flash
flooding will be higher today, as stronger storms will be capable
of producing 1 to 2 inches of rain in 30 to 45 minutes. The
heaviest rainfall totals are likely to occur over east central
Colorado, including eastern Elbert and Lincoln Counties where
localized totals of 3-4 inches or more will be possible. Burn
scars, urban areas, and rural areas in east central Colorado will
be the most prone to flooding impacts. Avoid low lying areas,
ditches, and fast moving water, and never drive through flooded
roads.

A couple storms will likely become severe, mainly along and east
of a line from Kimball, Nebraska to Fort Morgan to Kiowa where
more instability exists. The main threat is damaging wind gusts to
around 60 mph, but large hail is also possible.

Storms will diminish from northwest to southeast across the area
this evening.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Thunderstorms are likely again Tuesday afternoon and evening.
Locally heavy rainfall is possible with the stronger storms that
will elevate the flash flood threat for sensitive areas like our
burn scars. A few severe storms are possible on the plains.

There will be a gradual warming and drying trend beginning
Wednesday continuing into Saturday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected today or tonight. However, any
reports of heavy rainfall, flooding, or severe weather will be
appreciated.

Preliminary Local Storm Report
National Weather Service Denver CO
826 PM MDT Mon Aug 12 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0824 PM     Rain             1 WNW Brush             40.26N 103.65W
08/12/2024  M4.07 Inch       Morgan             CO   Mesonet

            Rainfall from 6:49-8:09 PM.

&&

Preliminary Local Storm Report
National Weather Service Denver CO
828 PM MDT Mon Aug 12 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0824 PM     Rain             1 WNW Brush             40.26N 103.65W
08/12/2024  M4.07 Inch       Morgan             CO   Mesonet

            Corrects previous rain report from 1 WNW
            Brush. Rainfall from 6:49-8:09 PM.

&&

Preliminary Local Storm Report...Summary
National Weather Service Denver CO
830 PM MDT Mon Aug 12 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0643 PM     Tstm Wnd Gst     8 NNW Boyero            39.03N 103.35W
08/12/2024  M68 MPH          Lincoln            CO   Mesonet

0651 PM     Tstm Wnd Gst     9 SE Hugo               39.05N 103.35W
08/12/2024  M58 MPH          Lincoln            CO   Mesonet

0727 PM     Tstm Wnd Dmg     1 NNW Brush             40.28N 103.64W
08/12/2024                   Morgan             CO   Trained Spotter

            Reports of apparent tornado damage.
            Powerlines and trees down.

0806 PM     Tstm Wnd Dmg     Brush                   40.26N 103.63W
08/12/2024                   Morgan             CO   Trained Spotter

            Windows blown out in Brush, estimated due to
            high straight line winds.

0824 PM     Rain             1 WNW Brush             40.26N 103.65W
08/12/2024  M4.07 Inch       Morgan             CO   Mesonet

            Corrects previous rain report from 1 WNW
            Brush. Rainfall from 6:49-8:09 PM.

0530 PM     Hail             3 NE Pawnee Buttes      40.85N 103.93W
08/12/2024  M2.00 Inch       Weld               CO   Storm Chaser

0752 PM     Flood            5 S Keota               40.63N 104.07W
08/12/2024                   Weld               CO   Public

            Report from mPING: River/Creek overflowing;
            Cropland/Yard/Basement Flooding.

0659 PM     Flash Flood      4 N Snyder              40.37N 103.60W
08/12/2024                   Morgan             CO   Public

            Report from mPING: Street/road flooding;
            Street/road closed; Vehicles stranded.

0700 PM     Flash Flood      3 NW Snyder             40.36N 103.60W
08/12/2024                   Morgan             CO   Public

            Report from mPING: Street/road flooding;
            Street/road closed; Vehicles stranded.

&&

Preliminary Local Storm Report
National Weather Service Denver CO
836 PM MDT Mon Aug 12 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0834 PM     Rain             5 N Punkin Center       38.93N 103.69W
08/12/2024  M3.97 Inch       Lincoln            CO   Mesonet

&&

Preliminary Local Storm Report...Summary
National Weather Service Denver CO
851 PM MDT Mon Aug 12 2024

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0850 PM     Flash Flood      2 W Punkin Center       38.85N 103.74W
08/12/2024                   Lincoln            CO   Storm Chaser

0834 PM     Rain             5 N Punkin Center       38.93N 103.69W
08/12/2024  M3.97 Inch       Lincoln            CO   Mesonet

0824 PM     Rain             1 WNW Brush             40.26N 103.65W
08/12/2024  M4.07 Inch       Morgan             CO   Mesonet

            Corrects previous rain report from 1 WNW
            Brush. Rainfall from 6:49-8:09 PM.

0814 PM     Flash Flood      Brush                   40.26N 103.63W
08/12/2024                   Morgan             CO   Amateur Radio

            Widespread Flash Flooding in Brush.

0806 PM     Tstm Wnd Dmg     Brush                   40.26N 103.63W
08/12/2024                   Morgan             CO   Trained Spotter

            Windows blown out in Brush, estimated due to
            high straight line winds.

0752 PM     Flood            5 S Keota               40.63N 104.07W
08/12/2024                   Weld               CO   Public

            Report from mPING: River/Creek overflowing;
            Cropland/Yard/Basement Flooding.

0727 PM     Tstm Wnd Dmg     1 NNW Brush             40.28N 103.64W
08/12/2024                   Morgan             CO   Trained Spotter

            Reports of apparent tornado damage.
            Powerlines and trees down.

0700 PM     Flash Flood      3 NW Snyder             40.36N 103.60W
08/12/2024                   Morgan             CO   Public

            Report from mPING: Street/road flooding;
            Street/road closed; Vehicles stranded.

0659 PM     Flash Flood      4 N Snyder              40.37N 103.60W
08/12/2024                   Morgan             CO   Public

            Report from mPING: Street/road flooding;
            Street/road closed; Vehicles stranded.

0651 PM     Tstm Wnd Gst     9 SE Hugo               39.05N 103.35W
08/12/2024  M58 MPH          Lincoln            CO   Mesonet

0643 PM     Tstm Wnd Gst     8 NNW Boyero            39.03N 103.35W
08/12/2024  M68 MPH          Lincoln            CO   Mesonet

0530 PM     Hail             3 NE Pawnee Buttes      40.85N 103.93W
08/12/2024  M2.00 Inch       Weld               CO   Storm Chaser

0452 PM     Hail             11 N Pawnee Buttes      40.98N 104.00W
08/12/2024  M2.00 Inch       Weld               CO   Storm Chaser

            Corrects previous hail report from 11 N
            Pawnee Buttes.

&&

Special Weather Statement
National Weather Service Denver CO
903 PM MDT Mon Aug 12 2024

COZ038-042-130345-
Northeast Weld County CO-
Larimer County Below 6000 Feet/Northwest Weld County CO-
903 PM MDT Mon Aug 12 2024

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN WELD COUNTY THROUGH
945 PM MDT...

At 903 PM MDT, Doppler radar was tracking a strong thunderstorm near
Hereford, or 28 miles southeast of Cheyenne, moving east at 40 mph.

HAZARD...Wind gusts up to 50 mph and half inch hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Grover, Pawnee Buttes, and Hereford.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 4076 10371 4084 10441 4100 10441 4100 10364
TIME...MOT...LOC 0303Z 268DEG 35KT 4094 10432

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

HEAVENER