372
FXUS65 KGJT 120622
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1222 AM MDT FRI SEP 12 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 SATURDAY/
ISSUED AT 139 PM MDT THU SEP 11 2025
LOW PRESSURE IS CURRENTLY CENTERED OVER NORTHERN CALIFORNIA WITH THE
ASSOCIATED JET STRETCHED OVER OUR AREA. THIS JET HAS BEEN ADVECTING
RICHER MOISTURE IN FROM THE SOUTH ALLOWING US TO DESTABILIZE.
THE LATEST 18Z SOUNDING SHOWS 500-800 J/KG OF CAPE WITH 45 KT OF
EFFECTIVE BULK SHEAR, AND 700 MB MIXING RATIOS ARE AROUND (6-8
G/KG). THIS ENVIRONMENT WILL SUPPORT STRONG TO SEVERE STORMS AS
WELL AS HEAVY RAINFALL. CONVECTION HAS ALREADY DEVELOPED AND
THERE IS LITTLE TO NO CIN IN PLACE. A FEW OF THESE STORMS HAVE
ALREADY SHOWED DECENT STRUCTURE ON SATELLITE AND THE POTENTIAL
TO PRODUCE LARGE HAIL. WITH THE PATTERN LOCKED IN WE WILL SEE
CONVECTION DEVELOP THROUGH THE AFTERNOON AND EVENING. MOISTURE
ADVECTION ALSO CONTINUES TONIGHT SO EXPECT SHOWERS AND STORMS
WILL BE POSSIBLE TONIGHT. THE HIGHEST PRECIPITATION CHANCES WILL
BE ACROSS THE SOUTHEAST TWO THIRDS OF THE CWA. HEAVY RAINFALL
RATES AND STORM TRAINING DOES POSE A RISK FOR FLASH FLOODING
ESPECIALLY FOR THE RECENT BURN SCARS. TOMORROW THE LOW PRESSURE
MOVES INLAND, BUT FOR THE MOST PART WE STAY IN THE SAME SECTOR.
MODELS ARE SHOWING SCATTERED SHOWERS TOMORROW MORNING, WHICH
MEANS CLOUD COVER AS WELL. THE BIG QUESTION WILL BE CLEARING SO
THAT SURFACE HEATING CAN HELP BUILD INSTABILITY. PLACES THAT
ARE UNABLE TO CLEAR MAY SEE MORE STRATIFORM. BREAKS IN THE
CLOUDS SUPPORT MORE CAPE AND THE POTENTIAL FOR STRONGER STORMS.
IT MIGHT BE THAT THE EDGE OF THE CLOUD SHIELD HAS THE BEST
BALANCE OF MOISTURE AND CLEARING. DESPITE THE DETAILS THERE IS
STILL A POTENTIAL FOR HEAVY RAINFALL AND FLOODING SO THE WATCH
REMAIN VALID. BY FRIDAY EVENING CONVECTION MAY TREND TO MORE
STRATIFORM, AND SOME OF THE HIGH PEAKS COULD GET A COUPLE INCHES
OF SNOW.
LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
ISSUED AT 139 PM MDT THU SEP 11 2025
ON SATURDAY, THE LOW PRESSURE PASSES OVER WYOMING AND MONTANA WITH
THE BASE OF THE TROUGH TRACKING OVERHEAD. LAPSE RATES STEEPEN IN THE
TROUGH AND WITH LOW LEVEL MOISTURE LINGERING EXPECT CONVECTION IN
THE AFTERNOON. A RIDGE BUILDS OVER THE REGION ON SUNDAY AND A CAP IN
PLACE SHOULD HOLD CONVECTION TO A MINIMUM. ATTENTION THEN TURNS TO
THE STORM OVER THE PACNW, WHICH HAS NOT BEEN HANDLED WELL BY THE
MODELS. THAT SYSTEM MAY BE ABLE TO TAP INTO THE MOISTURE TO OUR
SOUTH. IF THAT HAPPENS THEN THE CHANCES FOR SHOWERS INCREASES ON
TUESDAY AND WEDNESDAY, AND BY THURSDAY THE TROUGH CROSSES THE
DIVIDE BRINING DRY AIR IN FROM THE WEST.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 1219 AM MDT FRI SEP 12 2025
SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS WILL CONTINUE TO
IMPACT MOST TERMINALS DURING THE OVERNIGHT HOURS. SHOWERS BECOME
MORE WIDESPREAD AFTER 12Z WITH MORE MOISTURE MOVING UP FROM THE
SOUTH. THIS WILL RESULT IN AREAS OF STRATIFORM RAINFALL WITH
EMBEDDED THUNDERSTORM ACTIVITY. THUNDERSTORMS WILL DEVELOP
SATURDAY AFTERNOON ONCE AGAIN AND CONTINUE THROUGH THE EVENING,
ESPECIALLY WHERE PERIODS OF SUN BREAK OUT TO ALLOW FOR SURFACE
HEATING. EXPECT GUSTY OUTFLOW WINDS AND BRIEF HEAVY RAIN WITH
ANY CONVECTION, WITH CIGS AND VSBY REDUCTIONS TO MVFR AND BELOW
ILS BREAKPOINTS AT TIMES.
HYDROLOGY
ISSUED AT 139 PM MDT THU SEP 11 2025
SCATTERED TO WIDESPREAD STORMS ARE EXPECTED THROUGH FRIDAY
NIGHT. HEAVY RAINFALL IS POSSIBLE WITH THE STRONGER STORMS.
STORM MOTION WILL INHIBIT RESIDENCE TIME, BUT ANY CELL TRAINING
COULD LEAD TO EXCESSIVE RAIN. RECENT BURN SCARS ARE THE MOST
SUSCEPTIBLE RIGHT NOW. IF THE MOUNTAINS CAN RECEIVE MULTIPLE
ROUNDS MODERATE RAIN THEN THERE COULD BE ROCK AND DEBRIS
SLIDES. THE SOUTHERN AND CENTRAL MOUNTAINS HAVE THE HIGHEST
FORECAST RAINFALL AMOUNTS.
GJT WATCHES/WARNINGS/ADVISORIES
CO...FLOOD WATCH THROUGH THIS EVENING FOR COZ003-006>014-017>023.
UT...FLOOD WATCH THROUGH THIS EVENING FOR UTZ027-028.
SHORT TERM...KJS
LONG TERM...KJS
AVIATION...TGJT
HYDROLOGY...TGJT
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