Flash Flood Warning 73, NWS Denver/Boulder, CO

481 
WGUS75 KBOU 050929
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
329 AM MDT Sat Aug 5 2023

COC121-051130-
/O.CON.KBOU.FF.W.0073.000000T0000Z-230805T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Washington CO-
329 AM MDT Sat Aug 5 2023

...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 530 AM MDT EARLY THIS 
MORNING FOR SOUTHWESTERN WASHINGTON COUNTY...

At 329 AM MDT, Doppler radar indicated thunderstorms produced 
between 2.5 and 3.5 inches of rain in the warning area earlier. 
Flash flooding is ongoing or expected to begin shortly.

HAZARD...Flash flooding caused by thunderstorms.

SOURCE...Radar.

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...
  Woodlin School.

This includes the following streams and drainages...
  Jack Creek, Vega Creek, Sand Creek, East Fork Plumb Bush Creek and 
  Plum Bush Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move to higher ground now. Act quickly to protect your life.

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

&&

LAT...LON 3987 10352 3991 10317 3977 10312 3976 10351
      3979 10356 3987 10353

FLASH FLOOD...RADAR INDICATED

$$

RPK

962 
WGUS75 KBOU 051134
FFSBOU

Flash Flood Statement
National Weather Service Denver CO
534 AM MDT Sat Aug 5 2023

COC121-051144-
/O.EXP.KBOU.FF.W.0073.000000T0000Z-230805T1130Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Washington CO-
534 AM MDT Sat Aug 5 2023

...FLASH FLOOD WARNING HAS EXPIRED FOR SOUTHWESTERN WASHINGTON 
COUNTY...

Flood waters have receded. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

LAT...LON 3987 10352 3991 10317 3977 10312 3976 10351
      3979 10356 3987 10353

$$

RPK

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1115 PM MDT Fri Aug 4 2023

.UPDATE...
Issued at 710 PM MDT Fri Aug 4 2023

Main update involved dropping or lowering thunderstorm coverage
from the urban/corridor and Palmer Divide westward into the Front
Range Mountains/Foothills this evening. Still some showers/storms
over the far northeast plains, with isolated coverage along the
northern border so will hang onto some pops there through this
evening. Overall the trend will continue to be diminishing
coverage from west to east this evening.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 252 PM MDT Fri Aug 4 2023

Radars are showing isolated convection across the CWA at this
time. There is a bit over the high mountains of Larimer and
Boulder Counties and some over southern Elbert County. The winds
across the CWA are pretty weak.

Models have flat upper ridging for the CWA overnight with pretty
weak flow aloft.  On Saturday, stronger west-northwesterly flow aloft
will push into the CWA through the day. The QG Omega fields show
weak downward vertical velocity for the CWA tonight and Saturday.
The thickness fields show a cold front moving into the CWA late
Saturday afternoon.

The precipitable water values will be around 0.50 inch in the
mountains tonight and Saturday. Values will range from 0.5 over
the higher foothills to 1.2 inches over the southeastern CWA
tonight and Saturday. The highest CAPE values are over the
eastern border area early this evening, with the highest values on
Saturday afternoon to be over the foothills and immediate plains.
For pops will go with mainly 10-30%s this evening. Pops should be
a bit higher on Saturday afternoon with 20-40%s for the foothills
and western half of the plains, including the Palmer Ridge. Cells
should be moving fairly quick on Saturday afternoon.

.LONG TERM...(Saturday night through Friday)
Issued at 242 PM MDT Fri Aug 4 2023

Saturday night into Sunday, another cold front will bring in a
reinforcing push of cool air into the region. Behind the previous
shortwave, the upper level ridge weakens, helping cool temperatures
aloft as well. As a result, highs will feel a lot more like early
Fall rather than late Summer with highs in the mid 70s. Surface flow
becomes easterly in the afternoon bringing in sufficient moisture
across the plains. MLCAPE builds into the 500-1000 J/kg range with
less instability over the east plains and more over the Palmer
Divide/south foothills. This will translate to where the higher
shower/storm chances are in the afternoon/early evening with higher
chances confined to the higher terrain and Palmer Divide and less
eastward. A more ENE component may provide additional convergence to
get some storms developing over the Palmer Divide. Will have to
watch the presence of the upper jet which may bring additional
synoptic support for additional showers/storms through the evening
hours.

Monday, the weak ridge remains over the region under WNW flow aloft.
The upper jet remains draped across the state of Colorado with model
guidance showing a weak disturbance moving through the flow. 0-6km
bulk shear 35-45 kts and MLCAPE 1000-1500 J/kg over the east plains
will provide favorable conditions for scattered storms in the
afternoon and early evening, with a few strong to severe possible.

Tuesday through the end of the work week the flattened ridge ridge
stays put over the region. Ensembles show a drying and warming trend
with highs returning to the upper 80s and low 90s. Ensemble and
deterministic guidances shows a shortwave trough just brushing the
northeast corner on Tuesday. It stays a bit too east to provide
ideal conditions for more widespread severe, but if it shifts, it
may pose a threat to the east plains. Otherwise, expect lesser
coverage in afternoon/showers and thunderstorms during this period.

Ensemble guidance shows a signal for drying and warming early
next week through the latter part of the week with ridging aloft
and zonal flow. Monday remains sufficiently below normal in the
low 80s across the plains. There will be enough moisture around to
support shower/storm chances as well. Temperatures eventually
warm back toward normal in the upper 80s by mid-week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1113 PM MDT Fri Aug 4 2023

A boundary has moved across the area early this evening with
NE winds behind it.  Winds will gradually go light south
in the next hour or so. By 16Z winds will go variable in
direction in advance of a cold front which will move across
by 21z with gusty NNE winds.  Widely sct tstms will be possible
behind this front after 21z.

&&

.HYDROLOGY...
Issued at 242 PM MDT Fri Aug 4 2023

There is a limited threat of flash flooding on the burn areas for
a couple hours early this evening, then again on Saturday
afternoon. Saturday storms should be moving fairly quickly.

Chances for scattered showers and thunderstorms Sunday and Monday
with some storms capable of localized heavy rainfall. Threat for
flash flooding over the burn areas will remain "limited" with
quicker storm motions anticipated. Remainder of the week trend drier
which will reduce the threat for flash flooding.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

UPDATE...Cooper
SHORT TERM...RJK
LONG TERM....Mensch
AVIATION...RPK
HYDROLOGY....RJK/Mensch

Hazardous Weather Outlook
National Weather Service Denver/Boulder CO
1147 AM MDT Fri Aug 4 2023

COZ030>051-051800-
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-
1147 AM MDT Fri Aug 4 2023

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

.DAY ONE...Today and Tonight

Isolated to scattered showers and thunderstorms are expected over
the plains and foothills this afternoon, with the highest coverage
over the northern border areas. A few of the storms, mainly east
of Fort Morgan and Limon could produce wind gusts to 70 mph, golf
ball sized hail, and heavy rainfall. The rest of the plains could
see wind gusts to 50 mph. The threat of burn area flooding is low.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Thunderstorm coverage will be less through the weekend.  A few
severe storms will be possible mainly over the Palmer Divide on
Saturday. There will be a limited threat of flash flooding in
the burn scars this weekend. Storm motions will be quick enough to
keep storms from staying over the burn areas for long durations.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today and tonight.

Special Weather Statement
National Weather Service Denver CO
1110 PM MDT Fri Aug 4 2023

COZ046-050545-
North and Northeast Elbert County Below 6000 Feet/North Lincoln
County CO-
1110 PM MDT Fri Aug 4 2023

...A strong thunderstorm will impact portions of northeastern Lincoln
County through 1145 PM MDT...

At 1109 PM MDT, Doppler radar was tracking a strong thunderstorm 9
miles north of Arriba, or 16 miles northwest of Flagler, moving east
at 15 mph.

HAZARD...Penny size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

This storm will remain over mainly rural areas of northeastern
Lincoln County.

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 3950 10345 3952 10315 3933 10316 3932 10336
TIME...MOT...LOC 0509Z 273DEG 14KT 3942 10333

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...<30 MPH

RPK

Special Weather Statement
National Weather Service Denver CO
1123 PM MDT Fri Aug 4 2023

COZ049-050615-
Washington County CO-
1123 PM MDT Fri Aug 4 2023

...A strong thunderstorm will impact portions of southwestern
Washington County through 1215 AM MDT...

At 1123 PM MDT, Doppler radar was tracking a strong thunderstorm 4
miles southeast of Last Chance, or 29 miles north of Limon, moving
east at 10 mph.

HAZARD...Penny size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

Locations impacted include...
Woodlin School, Last Chance and Lindon.

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 3957 10333 3957 10350 3956 10350 3958 10371
      3963 10371 3981 10362 3979 10326
TIME...MOT...LOC 0523Z 271DEG 11KT 3968 10355

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...<30 MPH

RPK

Preliminary Local Storm Report...Summary
National Weather Service Denver CO
1227 AM MDT Sat Aug 5 2023

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

0530 PM     Tstm Wnd Dmg     3 SW Highland Center    40.50N 102.62W
08/04/2023                   Phillips           CO   Public

            Irrigation Equipment destroyed.

0526 PM     Tstm Wnd Gst     2 SE Julesburg          40.97N 102.25W
08/04/2023  M59 MPH          Sedgwick           CO   Mesonet

            Mesonet station CO034 I-76 Julesburg.

0516 PM     Tstm Wnd Gst     2 SE Julesburg          40.97N 102.25W
08/04/2023  M73 MPH          Sedgwick           CO   Mesonet

            Mesonet station CO034 I-76 Julesburg.

&&

Special Weather Statement
National Weather Service Denver CO
124 AM MDT Sat Aug 5 2023

COZ049-050800-
Washington County CO-
124 AM MDT Sat Aug 5 2023

...A strong thunderstorm will impact portions of southwestern
Washington County through 200 AM MDT...

At 124 AM MDT, Doppler radar was tracking a strong thunderstorm near
Woodlin School, or 27 miles southwest of Akron, moving east at 20
mph.

HAZARD...Penny size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

Locations impacted include...
Woodlin School and Lindon.

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 3972 10356 3992 10356 3992 10320 3972 10324
TIME...MOT...LOC 0724Z 269DEG 18KT 3982 10348

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...<30 MPH

RPK