647
FXUS65 KGJT 131159
AFDGJT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
559 AM MDT SUN SEP 13 2026
KEY MESSAGES
- SHOWER AND STORM CHANCES INCREASE SUNDAY, AND PEAK IN COVERAGE
BY MONDAY, BRINGING IN WIDESPREAD COOL, WET, AND UNSETTLED
WEATHER.
- THERE IS A CHANCE FOR STRONG STORMS OVER THE NEXT FEW DAYS
CAPABLE OF PRODUCING HAIL, GUSTY WIND AND HEAVY RAINFALL.
- DAYTIME HIGHS ON SUNDAY WILL BE 5 TO 10 DEGREES ABOVE NORMAL,
BEFORE A SHIFT TO COOLER TEMPERATURES BY MONDAY.
DISCUSSION
ISSUED AT 917 PM MDT SAT SEP 12 2026
SCATTERED STORMS SUNDAY:
SHOWER AND STORM COVERAGE INCREASES TOMORROW AS THE NEXT STRONG
PUSH OF MOISTURE BEGINS TO MOVE IN. PWATS CONTINUE TO CLIMB,
WITH VALUES UPWARDS OF 200% OF NORMAL, WITH THE LIKELY CHANCE OF
EXCEEDING THE 75TH PERCENTILE AND APPROACHING, IF NOT
SURPASSING THE MAX VALUES FOR MID SEPTEMBER.
COOLER AND WETTER PATTERN MONDAY AND BEYOND:
BY MONDAY, A DEEP TROUGH BEGINS TO PUSH INTO THE PACNW. DUE TO
CYCLONIC FLOW AROUND A LOW, SOUTHWESTERLY FLOW WILL BE FAVORED
OVER THE SOUTHWESTERN CONUS. THIS MEANS SUBTROPICAL MOISTURE
WILL BE PUSHED FURTHER INLAND, CENTERING THE STRONG PLUME OF
MOISTURE OVER OUR CWA. PWATS CONTINUE TO BE FORECASTED OVER THE
75TH PERCENTILE FOR THIS TIME OF YEAR, WHICH WILL BE ENOUGH TO
PROMPT OUR NEXT CHANCE FOR WIDESPREAD SHOWERS AND STORMS.
MONDAY IS THE PEAK OF THE MOISTURE, BUT IT MAY BE SO MUCH THAT
WE END UP CLOUDY THEREFORE INHIBITING INSTABILITY. IF THAT
HAPPENS WE WILL SEE MORE STRATIFORM SHOWERS. HOWEVER, IT IS
WORTH CONSIDERING THE DYNAMIC FORCING AT PLAY DURING THIS TIME
PERIOD. FIRSTLY, SUNDAY NIGHT INTO MONDAY WILL SEE A COLD
FRONTAL PASSAGE WHICH WILL INCLUDE POCKETS OF FRONTOGENESIS.
SECONDLY, BY MONDAY WE ARE EXPECTED TO BE UNDER THE RIGHT
ENTRANCE REGION OF AN UPPER LEVEL JET. THIS MAY ENHANCE THE LIFT
ACROSS THE AREA. ALSO, THE JET MAY PROVIDE WIND SHEAR THAT
COULD SUPPORT STRONG TO SEVERE STORMS CAPABLE OF HAIL AND
DAMAGING WINDS. GIVEN THE MOISTURE THERE IS THE POTENTIAL FOR
HEAVY RAINFALL AS WELL. CELL TRAINING AND OR ANY SEVERE STORM
COULD LEAD TO LOCALIZED FLASH FLOODING.
DESPITE THE SHORTWAVE EJECTING OUT OVER THE NORTHERN PLAINS THE
MODELS SHOW A TROUGH REMAINING IN PLACE ACROSS THE PACNW AS
WELL AS THE UPPER LEVEL JET OVERHEAD. THE HIGHLY ANAMOLOUS
MOISTURE ALSO PUSHES EAST, BUT THERE IS STILL SUFFICIENT
MOISTURE LINGERING ACROSS THE AREA. THE SHEAR AND MOISTURE MAY
ONCE AGAIN COULD SUPPORT STRONG STORMS. THE COVERAGE IS MORE
UNCERTAIN WITH THE LACK OF FORCING, SO THE CONVECTION MAY BE
MORE TERRAIN DRIVEN. CONFIDENCE DECREASES MID WEEK AS THE SECOND
PACNW TROUGH EITHER SWINGS THROUGH OR BECOMES A CUT OFF LOW TO
OUR WEST.
LOOK FOR DAYTIME HIGHS TO COOL DOWN MONDAY AND BEYOND DUE TO
THAT AFOREMENTIONED FRONTAL PASSAGE AS WELL AS THE CLOUD COVER
AND POTENTIAL SHOWERS.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 557 AM MDT SUN SEP 13 2026
STORMS DEVELOP AROUND 17Z, INCREASING IN COVERAGE BY MID
AFTERNOON. BRIEF DROPS IN VIS AND CIG ARE EXPECTED BELOW
STRONGER STORMS, WITH CEILINGS LOWERING OVERNIGHT AS WIDESPREAD
RAIN SHOWERS BECOME MORE PROBABLE. OTHERWISE, GUSTS OF 20-28
KTS ARE EXPECTED TO DEVELOP THIS AFTERNOON FOR MOST, IF NOT ALL
TERMINALS.
GJT WATCHES/WARNINGS/ADVISORIES
CO...NONE.
UT...NONE.
DISCUSSION...BS
AVIATION...TGJT
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