621
FXUS65 KGJT 121213
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
613 AM MDT WED AUG 12 2026
KEY MESSAGES
- MOISTURE INCREASES THROUGH THE WEEK WITH AN UPTICK IN STORM
COVERAGE AND INTENSITY EXPECTED WEDNESDAY ONWARDS.
- LOCALIZED HEAVY RAINFALL MAY PROMPT FLASH FLOODING AND DEBRIS
FLOWS, ESPECIALLY AROUND BURN SCARS.
- TEMPERATURES COOL DOWN NOW THROUGH THE WEEKEND.
DISCUSSION
ISSUED AT 1038 PM MDT TUE AUG 11 2026
A TROUGH MOVING ONTO THE WEST COAST HAS DISPLACED THE HIGH PRESSURE
DOME EASTWARD. THIS HAS ALLOWED FLOW ALOFT OVER THE DESERT
SOUTHWEST AND SOUTHERN GREAT BASIN TO SHIFT TO MORE SOUTHERLY-
SOUTHWESTERLY, WHICH IS ADVECTING IN MONSOONAL MOISTURE. PWATS ON
THIS EVENING'S 00Z KGJT SOUNDING ARE ROUGHLY THE SAME AS AT 00Z
YESTERDAY, HOWEVER THE PROFILE IS SATURATED TO A LOWER LEVEL IN THE
ATMOSPHERE. THIS INCREASED LEVEL OF SATURATION WAS EVIDENT IN MORE
PRECIPITATION REACHING THE GROUND TODAY, WITH WETTING RAINS OBSERVED
ACROSS AND SOUTH OF THE SAN JUANS. BY WEDNESDAY, SATURATION DOWN TO
THE SURFACE IS EXPECTED, WITH WIDESPREAD SHOWERS AND THUNDERSTORMS
IN THE AFTERNOON, AND WETTING RAIN ACROSS THE HIGHER ELEVATIONS.
THIS WILL LEAD TO AN INCREASED THREAT FOR FLASH FLOODING AND BURN
SCAR DEBRIS FLOWS AS WE MOVE INTO WEDNESDAY AND THURSDAY.
PER ENSEMBLE FORECASTS, MOISTURE, AND THEREFORE SHOWER AND STORM
COVERAGE, IS EXPECTED TO PEAK ON THURSDAY, WITH BOTH WEDNESDAY AND
FRIDAY SEEING WIDESPREAD SHOWERS AND STORMS AS WELL. THIS MEANS THAT
THURSDAY HAS THE HIGHEST THREAT FOR HEAVY RAINS, FLASH FLOODING, AND
DEBRIS FLOWS. HOWEVER, THERE COMES THE QUESTION OF MORNING CLOUD
COVER. HI-RES GUIDANCE IS FAVORING A VERY MONSOONAL PATTERN OF
OVERNIGHT CONVECTION THE NEXT SEVERAL NIGHTS, WITH CLOUD COVER
LINGERING INTO THE MORNING HOURS. SHOULD THIS CLOUD COVER BE
PARTICULARLY DENSE AND LONG-LASTING, IT WILL IMPACT HOW MUCH
INSTABILITY CAN DEVELOP OVER EASTERN UTAH AND WESTERN COLORADO, AND
THEREFORE HOW MUCH PRECIPITATION WILL BE CONVECTIVE VERSUS
STRATIFORM. THIS WILL ALSO IMPACT TIMING OF STORM DEVELOPMENT, WITH
LINGERING CLOUD COVER DISPLACING INITIATION LATER INTO THE
AFTERNOON. THIS WILL BE SOMETHING TO KEEP AN EYE ON, ESPECIALLY WHEN
MOISTURE IS MAXIMIZED ON THURSDAY. THE OTHER QUESTION IS THAT OF A
SOURCE OF LIFT. TERRAIN IS A BIG ONE, WITH AFTERNOON SHOWERS AND
STORMS EXPECTED TO FORM FIRST OVER THE RIDGES. HOWEVER, THERE ARE
ALSO SUBTLE WAVES ROTATING AROUND THE EDGE OF THE HIGH THAT COULD
GIVE SOME EXTRA LIFT OVER THE NEXT SEVERAL DAYS, AS WELL AS
BOUNDARIES LEFT OVER FROM THE PREVIOUS DAY'S CONVECTION. THERE IS
LESS CERTAINTY IN THE IMPACT FROM THE SHORTWAVES AND THE LINGERING
BOUNDARIES, WHICH DOES THROW SOME UNCERTAINTY OVER WHERE CONVECTION
WILL DEVELOP ONCE IT'S MOVED OFF THE RIDGES. SO WHILE DETAILS ARE
STILL A BIT MURKY, CONFIDENCE IS HIGH THAT WE'RE MOVING INTO A
WETTER PERIOD FOR THE SECOND HALF OF THIS WORK WEEK, AND EVEN INTO
THE WEEKEND.
TEMPERATURES WILL COOL THROUGH THE BACK HALF OF THE WEEK AS SHOWERS,
STORMS, AND CLOUD COVER RULE THE DAY. NEAR-NORMAL HIGHS ON WEDNESDAY
WILL COOL TO CLOSE TO TEN DEGREES BELOW NORMAL BY FRIDAY. OVERNIGHT
LOWS WILL ALSO COOL TO NEAR-NORMAL LEVELS, WHICH WILL BE A WELCOME
RELIEF.
AVIATION /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 604 AM MDT WED AUG 12 2026
LIGHT RAIN SHOWERS ARE LINGERING IN EASTERN UTAH AND
NORTHWESTERN COLORADO. SHOWERS WILL PERSIST THROUGH THE MORNING
AND THUNDERSTORM ACTIVITY WILL BEGIN AROUND 18Z, BECOMING
WIDESPREAD THROUGH THE AFTERNOON. PROB30 HAS BEEN INCLUDED AT
ALL SITES FOR CHANCES OF IMPACTS, INCLUDING GUSTY OUTFLOW WINDS,
PERIODS OF HEAVY RAINFALL, AND LOWERED CEILINGS. BRIEF DROPS TO
MVFR CONDITIONS ARE POSSIBLE FROM SHOWERS AND THUNDERSTORMS,
BUT OTHERWISE VFR CONDITIONS WILL PREVAIL. AFTER SUNSET
THUNDERSTORM COVERAGE WILL GRADUALLY DECREASE, BUT SOME LIGHT
SHOWERS WILL PERSIST OVERNIGHT.
GJT WATCHES/WARNINGS/ADVISORIES
CO...NONE.
UT...NONE.
DISCUSSION...BGB
AVIATION...TGJT
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