226
FXUS65 KGJT 110619
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1219 AM MDT THU SEP 11 2025
KEY MESSAGES
- ISOLATED STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE TOMORROW
AFTERNOON. LARGE HAIL, DAMAGING WINDS, AND FLASH FLOODING WILL
BE THE PRIMARY THREATS OF THE STRONGEST STORMS.
- THERE WILL BE AN ELEVATED THREAT OF FLASH FLOODING ON THURSDAY
AND FRIDAY, ESPECIALLY IF MULTIPLE ROUNDS OF STORMS TRACK OVER
THE SAME AREAS. FRESH BURN SCARS WILL BE ESPECIALLY CONDUCIVE
TO FLASH FLOODING AND DEBRIS FLOWS
- TEMPERATURES WILL TREND COOLER THURSDAY AND BEYOND WITH FALL-
LIKE CONDITIONS EXPECTED.
SHORT TERM /THROUGH FRIDAY/
ISSUED AT 259 PM MDT WED SEP 10 2025
THE TROUGH CURRENTLY CENTERED OVER NORTHERN CALIFORNIA TAKES ON
A POSITIVE TILT OVER THE NEXT 12-24 HOURS, ALTERING THE JET
STREAM ENOUGH TO POSITION MUCH OF THE FORECAST AREA UNDER THE
RIGHT EXIT REGION OF A HEALTHY JET STREAK. THIS PROVIDES BOTH
SHEAR AND INSTABILITY TO SUPPORT THE POTENTIAL FOR MORE ROBUST
THUNDERSTORM ACTIVITY TOMORROW AFTERNOON AND EVENING. STORMS
THAT ARE ABLE TO SUSTAIN A STRONGER UPDRAFT WILL BE CAPABLE OF
PRODUCING LARGE HAIL, DAMAGING WINDS, AND LOCALIZED FLASH
FLOODING. AS IS THE NORM WITH THUNDERSTORM ACTIVITY THESE DAYS,
THERE WILL ALSO BE AN ELEVATED DEBRIS FLOW/FLASH FLOODING RISK
OVER THIS YEAR'S BURN SCARS WITH HEAVY RAIN RATES EXPECTED.
DIFFERENTIAL MOISTURE ADVECTION ALSO ENTERS THE CHAT
COMPLICATING TOMORROWS FORECAST. ALONG THE MOISTURE GRADIENT,
THUNDERSTORMS ARE EXPECTED TO DEVELOP FROM SOUTHWEST COLORADO UP
ALONG THE DIVIDE AND ADJACENT VALLEYS TOMORROW MORNING. THIS
COULD EITHER HELP OR HURT THE AFTERNOON SEVERE WEATHER THREAT
DEPENDING ON HOW MUCH CLEARING OCCURS BETWEEN ROUNDS OF
CONVECTION. IF THERE'S ENOUGH CLEARING TO TAP INTO DAYTIME
HEATING, HIGHER DEWPOINTS AND ENHANCED HEATING WILL INCREASE THE
INSTABILITY/CAPE LEADING TO A HIGHER POTENTIAL FOR SEVERE
WEATHER. CLOUDY SKIES WILL CREATE A MORE STABLE ATMOSPHERE AND
THEREFORE DECREASE THE SEVERE THUNDERSTORM THREAT. ONLY TIME
WILL TELL WHICH SCENARIO WINS OUT.
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
ISSUED AT 259 PM MDT WED SEP 10 2025
ON FRIDAY, THE EXPANSIVE LOW PRESSURE WILL BE LOCATED TO OUR
WEST AND NORTH WITH THE ASSOCIATED JET ABOVE US. A PLUME OF
ANAMOLOUS MOISTURE (MIXING RATIOS 7 G/KG) WILL BE IN PLACE
ESPECIALLY THE SOUTHEAST PORTION OF THE CWA. ALSO, LAPSE RATES
LOOK TO BE STEEP ENOUGH FOR MODEST INSTABILITY ALTHOUGH SOME OF
THAT MAY DEPEND ON CLOUD COVER. MODELS ARE SHOWING CONVECTION IN
THE MORNING HOURS, WHICH HAS IMPLICATIONS ON THE AFTERNOON.
GIVEN THE SCATTERED TO WIDESPREAD COVERAGE ALL OF THE
INGREDIENTS SUPPORT THE POTENTIAL FOR HEAVY RAINFALL AND FLASH
FLOODING. ALSO, THE JET SHOULD CONTRIBUTE TO OVERALL MODEST
SHEAR. IF THE INSTABILITY CAN BE REALIZED THEN STRONG TO SEVERE
STORMS ARE CERTAINLY POSSIBLE. EXCESSIVE CLOUD COVER COULD
RESULT IN MORE POCKETS OF STRATIFORM WITH EMBEDDED LIGHTNING AS
OPPOSED TO WIDESPREAD STORMS. ON SATURDAY, THE MAIN PIECE OF
ENERGY PASSES OVER WYOMING AND MONTANA WITH THE BASE OF THE
TROUGH MOVING OVERHEAD. TEMPERATURES COOL BEHIND THE TROUGH AND
LAPSE RATES STEEPEN, SO ANY MOISTURE IN THE LOWER LEVELS COULD
RESULT IN CONVECTION. THE MODELS ARE HINTING AT THAT WITH THE
BETTER CHANCES ACROSS THE NORTH. MOISTURE VALUES DECREASE SO NOT
SURE IF THERE WILL STILL BE A POTENTIAL FOR HEAVY RAIN. ON
SUNDAY, WE LOSE THE LAPSE RATES SO OVERALL THERE WILL NOT BE AS
MUCH SHOWERS AND STORMS AROUND. MONDAY COULD ALSO BE MOSTLY DRY
AND WITH ACTIVITY PICKING UP MID WEEK AS ANOTHER LOW PRESSURE
APPROACHES FROM THE PACNW.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1216 AM MDT THU SEP 11 2025
STRONG SOUTHERLY FLOW WILL CONTINUE TO PUSH MOISTURE ACROSS THE
4 CORNERS OVER THE NEXT 24 HOURS AS WELL AS GUSTY WINDS.
SCATTERED SHOWERS AND THUNDERSTORMS CONTINUE THROUGH THE EARLY
MORNING HOURS SO TEMPO GROUPS AND VCTS/VCSH FOR AT LEAST THE
FIRST 4 HOURS. THIS COMBINATION OF WIND AND MOSITURE IS LIKELY
TO PRODUCE MORE ORGANIZED STRONG STORMS ON THURSDAY AND MOST TAF
FORECASTS WILL CARRY A PROB30 LINE WITH VCTS ESPECIALLY DURING
THE AFTERNOON. WINDS IN EXCESS OF 45 MPH, HAIL AND HEAVY RAIN
BURSTS WILL ALL BE THREATS ON THURSDAY. A FEW STORMS WILL
CONTINUE TO IMPACT TAF SITES THROUGH THE EVENING...MOST LIKELY
KDRO AND KTEX. NOCTURNAL SHOWERS AND STORMS WILL ALSO LINGER
WELL INTO THE EARLY MORNING HOURS FRIDAY MORNING, BUT
CONFIDENCE ON THE LOW SIDE ON WHEN AND WHERE AT THIS TIME AS
COVERAGE WILL BE ISOLATED TO WIDELY SCATTERED SO LEFT PROB30
GROUPS IN PLACE.
HYDROLOGY
ISSUED AT 259 PM MDT WED SEP 10 2025
WITH MULTIPLE ROUNDS OF CONVECTION AND HEAVY RAIN RATES UNDER
STRONG TO SEVER THUNDERSTORMS TOMORROW AFTERNOON, WE HAVE ISSUED
A FLASH FLOOD WATCH FOR MUCH OF WESTERN COLORADO AND PORTIONS
OF EASTERN UTAH. RECENT BURN SCARS WILL HAVE THE HIGHEST
POTENTIAL OF PRODUCING FLASH FLOODING AND DEBRIS FLOWS, BUT
HEAVY RAIN COULD LEAD TO FLASH FLOODING OVER SATURATED AREAS AND
OTHER SUSCEPTIBLE TERRAINS. STORM MOTIONS ARE EXPECTED TO BE
HIGHER THAN NORMAL SO TRAINING STORMS WILL BE A KEY INGREDIENT
FOR FLASH FLOODING TOMORROW.
ANOTHER ROUND OF SCATTERED TO WIDESPREAD STORMS WILL IMPACT THE
SAME GEOGRAPHICAL AREA ON FRIDAY. SATURATED SOILS WILL INCREASE
THE POTENTIAL FOR FLASH FLOODING UNDER STRONGER STORMS WITH
HIGH RAIN RATES. A FLASH FLOOD WATCH MAY BE NEEDED DURING THIS
PERIOD AS WELL, BUT WE WILL WAIT FOR THE HIGH-RES GUIDANCE TO
POPULATE THROUGH FRIDAY BEFORE MAKING A GO/NO-GO DECISION ON
THAT.
GJT WATCHES/WARNINGS/ADVISORIES
CO...FLOOD WATCH FROM 6 AM MDT THIS MORNING THROUGH THIS EVENING
FOR COZ003-006>014-017>023.
UT...FLOOD WATCH FROM 6 AM MDT THIS MORNING THROUGH THIS EVENING
FOR UTZ027-028.
SHORT TERM...KAA
LONG TERM...KJS
AVIATION...TGJT
HYDROLOGY...KAA
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