451
FXUS65 KGJT 152137
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
337 PM MDT WED JUL 15 2026
KEY MESSAGES
- EXPECT TERRAIN-BASED SHOWERS AND THUNDERSTORMS EACH AFTERNOON
THIS WEEK, FAVORING THE SAN JUANS, BUT SPREADING NORTH BY THE
WEEKEND.
- LOCALIZED HEAVIER SHOWERS AND STORMS CREATE A RISK OF FLASH
FLOODING AND DEBRIS FLOWS IN VULNERABLE TERRAIN, INCLUDING
AREAS NEAR AND DOWNSTREAM OF BURN SCARS.
- DAYTIME HIGHS COOL THROUGHOUT THE WEEK, RETURNING TO NEAR-
NORMAL FOR MOST AREAS BY FRIDAY.
DISCUSSION
ISSUED AT 1235 PM MDT WED JUL 15 2026
DAILY SHOWERS AND THUNDERSTORMS:
PERSISTENT HIGH PRESSURE ALOFT KEEPS A PLUME OF MOISTURE OVER
MUCH OF THE WEST THROUGH AT LEAST THIS WEEKEND, POTENTIALLY
BEYOND. GUIDANCE KEEPS THE MOST MOISTURE RICH PART OF THIS
PLUME (IN TERMS OF PWAT ANOMALIES) TO OUR WEST, BUT ENSEMBLES
PLACE PWATS OF 130-200% OF NORMAL OVER OUR CWA THIS WEEK. THE
ECMWF ENS AND GFS ENS HAVE CONSISTENTLY SHOWN DIFFERENCES IN THE
MAGNITUDE OF THE ANOMALIES, WITH ECMWF ENS FAVORING A MUCH MORE
MOIST SETUP WITH MAX PWATS CLOSER TO 200% AT TIMES. THIS
MOISTURE BRINGS DAILY CHANCES OF SHOWERS AND THUNDERSTORMS IN
THE AFTERNOON AND EVENING. THESE CHANCES FAVOR SOUTH OF I-70
TODAY, BUT OVER THE NEXT FEW DAYS COVERAGE OF CHANCES SPREAD
NORTH ACROSS THE CWA. STORMS MOVING ACROSS THE SAN JUAN
MOUNTAINS THIS AFTERNOON HAVE PRODUCED MEASURABLE PRECIPITATION
AND WETTING RAIN, BUT MORE NORTHERN AREAS RECEIVING THEIR FIRST
PUSH OF MOISTURE COULD INITIALLY SEE A MIX OF RAIN REACHING THE
GROUND AND VIRGA/GUSTY OUTFLOW WINDS. WHILE MOISTURE IS A
RELIEF FOR DROUGHT CONDITIONS, IT ALSO CREATES A RISK OF FLASH
FLOODING AND DEBRIS FLOWS, INCLUDING OVER THE BURNS SCARS OF THE
GOLD MOUNTAIN, FERRIS, AND BABYLON FIRES. THE HYDROLOGY SECTION
BELOW DISCUSSES THIS RISK IN GREATER DETAIL. THESE STORMS CAN
DEVELOP QUICKLY, SO BE SURE TO MONITOR THE FORECAST AND HAVE A
WAY TO RECEIVE WEATHER ALERTS, ESPECIALLY IF YOU ARE VISITING OR
RESIDE BELOW TERRAIN THAT IS VULNERABLE TO FLASH FLOODING,
INCLUDING DOWNSTREAM OF ACTIVE FIRES.
TEMPERATURES SHOULD FALL BY AT LEAST A FEW DEGREES DURING THE
REMAINDER OF THIS WEEK THANKS TO INCREASED CLOUD COVER DURING
PEAK HEATING. GUIDANCE CONTINUES TO FAVOR ANOTHER DROP IN
TEMPERATURES NEXT WEEK, POTENTIALLY LEADING TO WIDESPREAD BELOW
NORMAL TEMPERATURES. HOWEVER, THIS IS LARGELY DEPENDENT ON HOW
THE HIGH PRESSURE ALOFT SHIFTS.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1143 AM MDT WED JUL 15 2026
EXPECT MOSTLY VFR CONDITIONS THROUGH THE TAF PERIOD, THE
EXCEPTION WILL BE BRIEF PERIODS OF MVFR ASSOCIATED WITH
THUNDERSTORMS AT TAF SITES ALONG AND SOUTH OF I-70 BETWEEN
ABOUT 20Z AND 03Z. WINDS IN THE VICINITY OF ANY SHOWERS OR
THUNDERSTORMS WILL BE VARIABLE GUSTING 35 TO 50 KTS. OTHERWISE,
LOOK FOR LIGHT WINDS GENERALLY WESTERLY TO NORTHERLY THROUGH
THE AFTERNOON BECOMING LIGHT DRAINAGE WINDS AFTER 03Z.
HYDROLOGY
ISSUED AT 1235 PM MDT WED JUL 15 2026
AN ANOMALOUS PLUME OF MOISTURE CONTINUES TO ROTATE INTO UTAH AND
WESTERN COLORADO THIS AFTERNOON, AS AN ELONGATED AREA OF HIGH
PRESSURE SHIFTS INTO THE SOUTHWESTERN CONUS. FOR TODAY, STEERING
WINDS OVERHEAD ARE NORTHERLY, PROVIDING A UNIQUE STORM MOTION FOR
THE GJT FORECAST AREA. IN ADDITION, OUR SOUTHERN ZONES AND MOST OF
EASTERN UTAH CONTAIN HIGHER AMOUNTS OF MOISTURE, SO AS STORMS
GENERALLY BUILD AND SHIFT SOUTH, THEY'RE MOVING INTO JUICIER
ENVIRONMENTS.
EVEN THOUGH THIS SOURCE OF MOISTURE IS A GREAT RELIEF TO THE DROUGHT
STRICKEN WEST, EXCESSIVE RAINFALL RETURNS THE CONCERNS OF FLASH
FLOODING AND DEBRIS FLOWS OVER RECENT (OR EVEN ON GOING) BURN SCARS.
18Z'S SOUNDING ALSO SHOWS WEAK FLOW THROUGHOUT THE ATMOSPHERIC
COLUMN, WHICH WILL RESULT IN SLOW MOVING THUNDERSTORMS THIS
AFTERNOON. THE COMBINATION OF INCREASED MOISTURE AND SLOW STORM
MOTION FURTHER ELEVATES THE CONCERN FOR EXCESSIVE RAINFALL IN
LOCALIZED AREAS. THE SAN JUAN'S ARE A BULLSEYE IN PRECIPITATION
FORECASTS OVER THE NEXT SEVERAL DAYS, MAINTAINING FLOOD THREATS
REDEVELOPING EACH AFTERNOON. DUE TO THE PROLONGED PERIOD OF
ANOMALOUSLY HIGH MOISTURE, OVER AREAS WITH SENSITIVE BURN SCARS, WE
WANT TO EMPHASIZE THE POTENTIAL FOR FLASH FLOODING AND DEBRIS FLOWS
IN THIS REGIME. WE'RE EXPECTING AN UPTICK IN MOISTURE CONTENT ACROSS
THE ENTIRE REGION ON THURSDAY, WHICH FAVORS A HIGHER LIKELIHOOD OF
WETTING RAIN WITH BURSTS OF HEAVY RAIN IN LOCALIZED STORMS.
FOR 2026 FIRES, WE HAVE YET TO TEST THEIR SUSCEPTIBILITY TO HANDLE
RAINFALL. THEREFORE, WE WANT TO INCREASE OUR MESSAGING OF THE
POTENTIAL HAZARDS AT PLAY DOWNSTREAM NEARBY FIRES. KEEP AN EYE ON
OUR FORECASTS THROUGH THE END OF THE WEEK AND STAY TUNED FOR UPDATED
HYDRO ALERTS IF VISITING OR IF YOU RESIDE BELOW VULNERABLE TERRAIN
TO FLASH FLOODING AND/OR DEBRIS FLOWS. STORMS ACROSS THE WEST
DEVELOP QUICKLY, LEAVING LITTLE ROOM FOR LEAD TIME IN FLASHY
TERRAIN.
GJT WATCHES/WARNINGS/ADVISORIES
CO...NONE.
UT...NONE.
DISCUSSION...GF/TGJT
AVIATION...DB
HYDROLOGY...ERW
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