123
FXUS65 KGJT 111720
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1120 AM MDT THU SEP 11 2025
KEY MESSAGES
- WIDESPREAD TO NUMEROUS SHOWERS AND STORMS ARE EXPECTED TODAY
THROUGH FRIDAY. SOME STORMS COULD BE STRONG TO SEVERE THIS
AFTERNOON AS WELL AS FRIDAY 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 BOTH TODAY
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 TODAY AND BEYOND WITH FALL-
LIKE CONDITIONS EXPECTED AND DRIER CONDITIONS RETURNING SUNDAY.
SHORT TERM /THROUGH FRIDAY/
ISSUED AT 356 AM MDT THU SEP 11 2025
SHOWER AND THUNDERSTORM ACTIVITY IS STILL ONGOING EARLY THIS
MORNING WITH RATHER ROBUST STORM MOTION OF 40 TO 50 MPH.
COVERAGE AT THIS TIME REMAINS ISOLATED TO WIDELY SCATTERED BUT
IS EXPECTED TO BECOME MORE WIDESPREAD TO NUMEROUS LATE THIS
MORNING THROUGH THE AFTERNOON AND EVENING. SATELLITE IMAGERY IS
SHOWING SOME CLEARING WORKING INTO EASTERN UTAH AND PORTIONS OF
NORTHWEST AND WEST-CENTRAL COLORADO, SO IT APPEARS LIKE WE WILL
SEE ENOUGH SURFACE HEATING FROM THE SUN TO REALIZE THE
INSTABILITY WITH DEEP MOISTURE IN PLACE TO GET CONVECTION GOING
THIS MORNING. THE LATEST HI-RES CAMS INDICATE STORMS STARTING TO
DEVELOP SOMETIME AFTER 10 AM WHICH IS ALSO WHEN THE INSTABILITY
INCREASES. CAPE WILL BE IN THE REALM OF 600 TO 1000 J/KG,
POTENTIALLY HIGHER WITH SHEAR OF 40 TO 50 KTS WHICH IS
INDICATIVE OF STRONG TO SEVERE THUNDERSTORM POTENTIAL. WHILE,
DAMAGING WINDS LOOK TO BE THE PRIMARY CONCERN WITH STRONGER
STORMS...GIVEN THE SHEAR, LARGE HAIL ALSO REMAINS A POSSIBILITY.
DYNAMIC FORCING IS ALSO PRESENT WITH OUR CWA IN FAVORABLE
PROXIMITY TO A 100 KT JET STREAK ACROSS UTAH TO PROVIDE
SUFFICIENT LIFT FOR THUNDERSTORM DEVELOPMENT. ALSO, WE REMAIN
RELATIVELY CIN FREE, MEANING THAT THERE IS NOT MUCH TO INHIBIT
THUNDERSTORM DEVELOPMENT.
IN TERMS OF MOISTURE, WE REMAIN UNDERNEATH A RELATIVELY DEEP
PLUME OF MONSOONAL MOISTURE AS WE SIT BETWEEN A STRONG CLOSED
LOW TO OUR WEST AND HIGH PRESSURE TO OUR SOUTHEAST, ALLOWING FOR
THIS FAVORABLE MOISTURE RETURN. MIXING RATIOS INCREASE TO AROUND
8 G/KG ACCORDING TO THE LATEST HRRR WITH VALUES BETWEEN 7 AND 9
G/KG. THE POTENTIAL FOR HEAVY RAIN AND FLASH FLOODING IS THERE,
WITH AN ELEVATED DEBRIS FLOW/FLASH FLOODING RISK ACROSS OUR
RECENT BURN SCARS, SO A FLOOD WATCH REMAINS IN EFFECT STARTING AT
6 AM THIS MORNING AND CONTINUING THROUGH MIDNIGHT FRIDAY NIGHT.
DECIDED TO EXTEND THIS FLOOD WATCH THROUGH FRIDAY EVENING SINCE
SIMILAR CONDITIONS WITH JET PLACEMENT, INSTABILITY AND SHEAR AS
WELL AS DEEP MOISTURE REMAINS IN PLACE. IT DOESN'T LOOK LIKE WE
WILL HAVE MUCH OF A BREAK AS CONVECTION CONTINUES OVERNIGHT
TONIGHT AND INTO FRIDAY. THE JET STREAK MOVES DIRECTLY OVERHEAD
THOUGH ON FRIDAY WITH EMBEDDED SHORTWAVES MOVING THROUGH WHICH
SHOULD GENERATE MORE CONVECTION DESPITE MORNING CLOUD COVER WITH
POTENTIAL FOR HEAVY RAIN. GIVEN QUICK STORM MOTIONS, THE THING TO
WATCH FOR IS TRAINING STORMS FOR ANY FLASH FLOODING POTENTIAL,
WHICH IS WHEN STORMS MOVE OVER THE SAME LOCATION IN SUCCESSION.
STRONG TO SEVERE STORMS ARE POSSIBLE ONCE AGAIN ON FRIDAY, FOCUSED
MORE ON SOUTHWEST COLORADO AS THE BETTER INSTABILITY AND SHEAR
REMAIN PRESENT THERE WITH UP TO 800 J/KG OF CAPE AND 40 TO 50 KTS
OF SHEAR. IF THE INSTABILITY CAN BE REALIZED THEN STRONG TO SEVERE
STORMS ARE CERTAINLY POSSIBLE. HOWEVER, EXCESSIVE CLOUD COVER
COULD RESULT IN MORE POCKETS OF STRATIFORM WITH EMBEDDED LIGHTNING
AS OPPOSED TO WIDESPREAD STORMS.
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
ISSUED AT 259 PM MDT WED SEP 10 2025
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 /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1117 AM MDT THU SEP 11 2025
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BE WIDESPREAD TO
NUMEROUS THIS AFTERNOON AND EVENING SO MOST TAF SITES WILL CARRY
VCTS AND PROB30 GROUPS FOR POTENTIAL REDUCED VSBY AND LOWER
CIGS DUE TO HEAVIER RAIN RATES. WINDS IN EXCESS OF 45 KNOTS,
HAIL AND HEAVY RAIN BURSTS WILL BE THE PRIMARY THREATS OF
STRONGER STORMS THAT DEVELOP NEAR THE TERMINALS. A FEW STORMS
WILL CONTINUE TO IMPACT TAF SITES THROUGH THE EVENING AND
OVERNIGHT, 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 WIDELY SCATTERED SO LEFT PROB30
GROUPS IN PLACE.
HYDROLOGY
ISSUED AT 356 AM MDT THU SEP 11 2025
WITH MULTIPLE ROUNDS OF CONVECTION AND HEAVY RAIN RATES UNDER
STRONG TO SEVERE THUNDERSTORMS THIS AFTERNOON AS WELL AS FRIDAY
AFTERNOON, THE FLASH FLOOD WATCH FOR TODAY HAS BEEN EXTENDED
THROUGH FRIDAY EVENING AS THE LATEST HI-RES CAMS INDICATE
WIDESPREAD TO NUMEROUS STORM COVERAGE CONTINUING THROUGH THE
OVERNIGHT HOURS AND INTO FRIDAY WITH POTENTIAL FOR HEAVY RAIN.
THIS FLOOD WATCH IS IN EFFECT FROM 6 AM THIS MORNING THROUGH
MIDNIGHT FRIDAY NIGHT 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 TERRAIN. STORM MOTIONS ARE EXPECTED TO BE
HIGHER THAN NORMAL SO TRAINING STORMS WILL BE A KEY INGREDIENT
FOR FLASH FLOODING TODAY THROUGH FRIDAY EVENING.
GJT WATCHES/WARNINGS/ADVISORIES
CO...FLOOD WATCH THROUGH FRIDAY EVENING FOR COZ003-006>014-017>023.
UT...FLOOD WATCH THROUGH FRIDAY EVENING FOR UTZ027-028.
SHORT TERM...MDA
LONG TERM...KJS
AVIATION...TGJT
HYDROLOGY...TGJT
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