Flash Flood Warning 42, NWS Grand Junction, CO

223 
WGUS75 KGJT 270325
FFSGJT

Flash Flood Statement
National Weather Service Grand Junction CO
925 PM MDT Mon Jul 26 2021

UTC037-270335-
/O.EXP.KGJT.FF.W.0042.000000T0000Z-210727T0330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
San Juan UT-
925 PM MDT Mon Jul 26 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 930 PM MDT THIS EVENING FOR 
NORTHEASTERN SAN JUAN COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

A Flash Flood Watch remains in effect until 1000 PM MDT for a 
portion of southeast Utah.

LAT...LON 3830 10933 3825 10929 3822 10928 3820 10936
      3819 10943 3828 10945 3830 10939

$$

NL

Area Forecast Discussion
National Weather Service Grand Junction CO
535 PM MDT Mon Jul 26 2021

.SHORT TERM...(Tonight through Tuesday night)
Issued at 104 PM MDT Mon Jul 26 2021

PWAT on the sounding last evening was the lowest it has been in a
few days, but is still riding close the 90th percentile for late
July. Surface dewpoints were in the low 60s at the office this
morning, which is particularly modest. Models show this slightly
anomalous moisture remaining in place until further notice thus
the threat of afternoon storms with heavy rainfall continues. The
area most probable for runoff threats will continue to be across
the plateau and canyon regions of southwest Colorado and Southeast
Utah. This will be where the axis of high PWAT values will exist
and where there will still be a weakness in the atmosphere aloft.
Winds aloft remain weak so slow storm motion is a threat along
with storms forming on outflow boundaries or ahead of embedded
mesoscale features such as those last night. Several runs of the
latest high-res models show that one of these mesoscale features
develops over the northwest San Juans and moves to the northwest
and perhaps something in the central mountains that moves
westward. Localized flooding will once again be the primary threat
with burn scars and flashy terrain the most vulnerable. If you
plan on outdoor recreation today be prepared for quickly changing
conditons and the monsoonal threats of heavy rainfall and runoff
especially if you're located in a watch.

By tomorrow high pressure will have moved out of the northern Great
Basin into the Central Plains, and will bring somewhat of a tougher
atmosphere to pop stronger storms..including our northeast CWA.
Given the placement of the high storm coverage will increase from
east to west. Storm motion will be more from the south-southeast,
which is not a prevailing direction and could result in atypical
evolution off the higher terrain. There is very little change in
the moisture so localized flash flooding will again be possible
over many of the same areas as the last few days.

.LONG TERM...(Wednesday through Monday)
Issued at 104 PM MDT Mon Jul 26 2021

The high's center will settle over the Central and Southern Plains
on Wednesday, resulting in a surge of monsoonal moisture into our
forecast area by late afternoon. Even though we will still be
positioned underneath the ridge, this additional moisture push will
lead to numerous showers and thunderstorms across the region.
PWATs will increase to 150 to 200% of normal in response with Bufkit
soundings continuing to show a well saturated profile. Light
steering winds will exacerbate the potential for flooding as heavy
rain will be a threat with the stronger storms. Similar conditions
are expected through the end of the week as the high wobbles
slightly to the east. PWATs look to increase even more during this
time as a remnant tropical low pressure from Mexico looks to be
advected in the flow. Regardless, the atmosphere will remain primed
for heavy rain and anyone planning to travel should stay up-to-date
on the latest forecast and road conditions before heading out.

The high will begin to track southwest as a Pacific midlevel trough
lifts across the northwestern CONUS during the weekend. The base of
this shortwave will brush our CWA early next week, providing
additional lift for showers and storms. Beyond that, drier air looks
to push into the region. Until that time, cool and unsettled
conditions will prevail.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 535 PM MDT Mon Jul 26 2021

Showers and thunderstorms will continue, generally over the
southern and central zones, through this evening. Apart from KVEL
and KHDN all other terminals will see the threat of a thunderstorm
in the vicinity or impacting the airfield with gusty outflow winds
and heavy rainfall. In stronger storms, expect reduction to MVFR.
Once again the radar should quiet down by the early morning hours.
Similar conditions are expected on Tuesday with showers and storms
redeveloping over the higher terrain by 18Z.

&&

.HYDROLOGY...
Issued at 104 PM MDT Mon Jul 26 2021

Monsoonal moisture will remain entrenched over the area until
further notice. This means the threat of heavy rainfall will
remain a threat especially under stronger storms. Slow storm
motion and terrain interactions will also invite the threat of
excess runoff from storms and localized flash flooding will remain
a threat over much of the upcoming week. If recreating outdoors
it will be important to stay up to date on the latest forecasts
and know the threats during this active monsoon season.

A Flash Flood Watch was issued for the La Sal and Abajo Mountains
as well as portions of west-central Colorado until 10 PM MDT this
evening. We will continue to monitor the need for additional
highlights.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Flash Flood Watch until 10 PM MDT this evening for COZ017-020.

UT...Flash Flood Watch until 10 PM MDT this evening for UTZ028.

&&

SHORT TERM...KJS/TGJT
LONG TERM...MMS
AVIATION...TGJT
HYDROLOGY...TGJT

Hazardous Weather Outlook
National Weather Service Grand Junction CO
427 AM MDT Mon Jul 26 2021

COZ001>014-017>023-UTZ022>025-027>029-271030-
Lower Yampa River Basin-Central Yampa River Basin-
Roan and Tavaputs Plateaus-Elkhead and Park Mountains-
Upper Yampa River Basin-Grand Valley-Debeque to Silt Corridor-
Central Colorado River Basin-Grand and Battlement Mesas-
Gore and Elk Mountains/Central Mountain Valleys-
Central Gunnison and Uncompahgre River Basin-
West Elk and Sawatch Mountains-Flat Tops-
Upper Gunnison River Valley-Uncompahgre Plateau and Dallas Divide-
Northwest San Juan Mountains-Southwest San Juan Mountains-
Paradox Valley/Lower Dolores River-
Four Corners/Upper Dolores River-Animas River Basin-
San Juan River Basin-Southeast Utah-Eastern Uinta Mountains-
Eastern Uinta Basin-Tavaputs Plateau-Arches/Grand Flat-
La Sal and Abajo Mountains-Canyonlands/Natural Bridges-
427 AM MDT Mon Jul 26 2021

This hazardous weather outlook is for eastern Utah and western
Colorado.

.DAY ONE...Today and Tonight

Thunderstorm development will occur today especially over the
southern mountains by early afternoon. Lightning and heavy
rainfall will be the main threat along with gusty outflow winds. A
few storms will be capable of producing locally heavy rainfall
which could lead to flooding. The thunderstorm threat should end
during the early morning hours on Tuesday.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Daily scattered to numerous showers and thunderstorms can be
expected each day with monsoon moisture entrenched across the
area. Moderate to heavy rain and gusty winds will be the primary
threats with storms along with lightning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected today or tonight, however
spotters are encouraged to relay rainfall amounts or any observed
flooding to the National Weather Service in Grand Junction.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
530 PM MDT MON JUL 26 2021

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

0510 PM     HEAVY RAIN       4 WNW MANCOS            37.38N 108.35W
07/26/2021  U0.66 INCH       MONTEZUMA          CO   COCORAHS

&&

NL

Special Weather Statement
National Weather Service Grand Junction CO
552 PM MDT Mon Jul 26 2021

COZ001-003-006-UTZ025-270030-
Roan and Tavaputs Plateaus CO-Grand Valley CO-
Lower Yampa River Basin CO-Tavaputs Plateau UT-
552 PM MDT Mon Jul 26 2021

...SPECIAL WEATHER STATEMENT...

At 551 PM MDT, Doppler radar was tracking a strong thunderstorm 31
miles north of Fruita, or 37 miles north of Grand Junction, moving
west at 5 mph.

Frequent cloud to ground lightning, pea size hail and winds in excess
of 30 mph will be possible with this storm.

This storm will remain over mainly rural areas of west central
Garfield County.

This includes Colorado 139 between mile markers 25 and 42.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3970 10876 3953 10868 3941 10894 3966 10907
TIME...MOT...LOC 2351Z 068DEG 5KT 3960 10881

NL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
602 PM MDT MON JUL 26 2021

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

0556 PM     HEAVY RAIN       5 NNE BONDAD            37.15N 107.86W
07/26/2021  M0.61 INCH       LA PLATA           CO   TRAINED SPOTTER

            RAIN FELL IN 30 MINUTES.

&&