474
FXUS65 KGJT 010005
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
605 PM MDT MON AUG 31 2026
KEY MESSAGES
- SCATTERED TO WIDESPREAD PRECIPITATION CHANCES PERSIST TODAY,
WITH HIGHER COVERAGE OF PRECIPITATION ACROSS SOUTHEAST UT AND
SOUTHWEST CO THAN PREVIOUS DAYS.
- FLASH FLOODING WILL CONTINUE TO BE POSSIBLE AS ORGANIZED AND
TRAINING THUNDERSTORMS CAN PRODUCE HEAVY RAINFALL OVER A SHORT
PERIOD OF TIME.
- PRIMARY AREAS OF CONCERN FOR FLASH FLOODING WILL BE THOSE OF
INCREASINGLY SATURATED SOILS, RECENT BURN SCARS, AND STEEP
TERRAIN.
DISCUSSION
ISSUED AT 1203 PM MDT MON AUG 31 2026
SHOWERS AND THUNDERSTORMS TODAY:
TODAY LOOKS TO BE OUR FINAL DAY OF WIDESPREAD SHOWERS AND
THUNDERSTORMS FROM THE CURRENT PUSH OF MONSOONAL MOISTURE.
TODAY'S SOUNDING SHOWS A DECREASE IN BOTH PRECIPITABLE WATER
(PW) AND INSTABILITY. HOWEVER, THE PW VALUE OF 1.04 INCHES
EXCEEDS THE 90TH PERCENTILE FOR AUGUST 31ST AT GJT, WHICH SHOWS
THAT ATMOSPHERIC MOISTURE IS STILL ABUNDANT. THE REDUCTION IN
INSTABILITY AND PERSISTING WIDESPREAD CLOUD COVER COULD ACT TO
DAMPEN TODAY'S CONVECTION, MOSTLY DURING THE EARLY AFTERNOON.
HOWEVER, A SHORTWAVE TROUGH, IN ADDITION TO A BIT OF JET SUPPORT
AND DIFLUENCE ALOFT, WILL SUPPORT MORE STORMS THIS EVENING EVEN
DURING THE ABSENCE OF SURFACE HEATING. MANY STORMS WILL
EFFICIENTLY PRODUCE RAIN, WHICH COULD LEAD TO LOCALIZED AREAS OF
FLASH FLOODING FROM HEAVY RAINFALL. PRIMARY AREAS OF CONCERN
FOR FLOODING ARE RECENT BURN SCARS, SLOT CANYONS, SLICK ROCK
AREAS, CREEKS, STREAMS, AND OTHER LOW-LYING AND FLOOD-PRONE
LOCATIONS. MOST OF EASTERN UTAH AND WESTERN COLORADO REMAINS IN
A FLOOD WATCH THROUGH MIDNIGHT TONIGHT.
DRIER TUESDAY THROUGH FRIDAY:
ATMOSPHERIC MOISTURE WILL DECREASE TOMORROW, LEADING TO
DECREASED PRECIPITATION CHANCES. AFTERNOON CONVECTION WILL STILL
BE POSSIBLE, PARTICULARLY ON TUESDAY AND FRIDAY, BUT CHANCES
FAVOR THE HIGHER TERRAIN. HIGH TEMPERATURES WILL GRADUALLY
INCREASE THROUGH THE WORKWEEK, RETURNING TO NEAR NORMAL BY
FRIDAY.
MOISTURE RETURNS THIS WEEKEND:
GUIDANCE SUGGESTS A STRONG PUSH OF TROPICAL MOISTURE LATE IN
THE WORKWEEK AND INTO THE WEEKEND. THE ECMWF ENS AND GFS ENS
ARE PRESENTLY IN RELATIVELY GOOD AGREEMENT REGARDING THE TIMING
AND MAGNITUDE OF THIS MOISTURE. HOWEVER, CHANGES WITH THE
TROPICAL SYSTEM ACTIVITY IN THE PACIFIC COULD SUBSTANTIALLY
ALTER THIS FORECAST, SO BE SURE TO STAY TUNED FOR UPDATES ON
HOW THIS WEEKEND'S FORECAST DEVELOPS.
AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 551 PM MDT MON AUG 31 2026
ISOLATED TO SCATTERED SHOWERS WITH A FEW EMBEDDED THUNDERSTORMS
ARE MOVING TO THE NORTHEAST MOSTLY NORTH OF I-70 WILL MOVE OUT
OF THE REGION OVER THE NEXT FOUR HOURS. ANOTHER BAND OF
SCATTERED SHOWERS WITH ISOLATED THUNDERSTORM ARE MOVING INTO THE
REGION FROM THE SOUTHWEST AND SHOULD TRANSIT THE REGION THROUGH
ABOUT 09Z, EXITING TO THE NORTHEAST. PRIMARY THREATS ARE HEAVY
RAIN WITH BRIEF PERIODS OF MVFR TO IFR CONDITIONS BELOW ILS
BREAKPOINTS, LIGHTNING AND GUSTS TO 25KTS. OTHERWISE, EXPECT
CLOUDY SKIES OVERNIGHT BECOMING SCATTERED TO CLEAR AFTER 12Z AND
LIGHT WINDS ACROSS THE REGION. ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS WILL DEVELOP AFTER 18Z OVER THE HIGHER TERRAIN.
HYDROLOGY
ISSUED AT 1203 PM MDT MON AUG 31 2026
ANOMALOUS MOISTURE WILL REMAIN IN PLACE ACROSS WESTERN COLORADO
AND EASTERN UTAH THROUGH TONIGHT. TODAY'S 18Z SOUNDING FROM GJT
SHOWS THAT PRECIPITABLE WATER EXCEEDS THE 90TH PERCENTILE FOR
TODAY, AND RELATIVE HUMIDITY REMAINS ELEVATED IN THE MID AND
LOWER LEVELS OF THE ATMOSPHERE. GIVEN THE ANTECEDENT MOISTURE
FROM RAINFALL OVER PREVIOUS DAYS AND ALREADY SATURATED SOILS IN
SEVERAL SUB-BASINS, RAPID RUNOFF AND POOR INFILTRATION HAS
BECOME MORE LIKELY IN SOME AREAS. A FLOOD WATCH REMAINS IN
EFFECT THROUGH MONDAY EVENING FOR MOST LOCATIONS.
FLASH FLOODING AND DEBRIS FLOWS ARE POSSIBLE, ESPECIALLY OVER
RECENT BURN SCARS AND SUSCEPTIBLE TERRAIN. CRITICAL AREAS OF
CONCERN WITHIN THE FLOOD WATCH INCLUDE THE LEE AND ELK RX, GOLD
MOUNTAIN, ELK, FERRIS, AND BABYLON BURN SCARS, WHERE HYDROPHOBIC
SOILS HAVE THE ABILITY TO AMPLIFY PEAK FLOW UNDER MODERATE
RAINFALL RATES.
ALTHOUGH DRIER AIR MOVES INTO THE REGION TOMORROW, LINGERING
MID-LEVEL MOISTURE AND DAYTIME HEATING WILL KEEP AFTERNOON
THUNDERSTORMS IN THE FORECAST FOR THE HIGHER TERRAIN REGIONS.
HENCE, A LOCALIZED FLASH FLOODING THREAT REMAINS.
GJT WATCHES/WARNINGS/ADVISORIES
CO...FLOOD WATCH UNTIL MIDNIGHT MDT TONIGHT FOR COZ002-003-006>014-
017>023.
UT...FLOOD WATCH UNTIL MIDNIGHT MDT TONIGHT FOR UTZ022-025-027>029.
DISCUSSION...GF/TGJT
AVIATION...DB
HYDROLOGY...TGJT
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