913
FXUS65 KGGW 152014
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
214 PM MDT SUN SEP 15 2024
DISCUSSION
KEY MESSAGES:
1) WARM TEMPERATURES WILL CONTINUE THROUGH TUESDAY.
2) ISOLATED SHOWERS MONDAY MORNING, THEN ISOLATED THUNDERSTORMS
MONDAY AFTERNOON AND TUESDAY AFTERNOON.
3) COOLER TEMPERATURES MOVE IN TUESDAY NIGHT WITH WIDESPREAD RAIN
IN THE WEST THROUGH WEDNESDAY EVENING.
WEATHER PATTERN OVERVIEW:
A SHORTWAVE RIDGE TODAY, AND THEN A SLOW MOVING WARM FRONTAL
PASSAGE WITH AN ONCOMING LOW PRESSURE WILL HELP WARM TEMPERATURES
REMAIN OVER THE AREA THROUGH TUESDAY EVENING. THEN THE COLD FRONT
WILL PASS THROUGH BY WEDNESDAY MORNING TO KEEP TEMPERATURES NEAR
AVERAGE FOR THE REMAINDER OF THE WEEK. THE SLOW MOVING LOW WILL
DRAG GULF AND PACIFIC MOISTURE INTO NORTHEAST MONTANA TO BRING
PWATS ABOVE 1". THERE IS DISAGREEMENT AMONG THE NAM, ECMWF, AND
GFS ON EXACTLY HOW LONG THIS LOW WILL REMAIN OVER THE AREA. A
SLOWER MOVING LOW MAY RESULT IN RAINFALL TOTALS IN THE WEST OF UP
TO 2", BUT A FASTER LOW MAY KEEP THE AMOUNTS TO BELOW 0.5".
ANYWAY, ISOLATED THUNDERSTORMS ASSOCIATED WITH THE WARM FRONT ARE
EXPECTED MONDAY AFTERNOON. AS THE TROUGH GETS CLOSER ON TUESDAY,
THERE IS MODERATE (50 PERCENT) CONFIDENCE OF STRONG TO SEVERE
THUNDERSTORMS OCCURRING IN THE AFTERNOON/EVENING.
THE NBM 48 HOUR PROBABILITY OF 1 INCH OF RAIN REMAINS AT 60 TO 70
PERCENT FOR PHILLIPS COUNTY FROM TUESDAY NIGHT THROUGH WEDNESDAY
NIGHT AND DROP QUICKLY SOUTH AND EAST OF THERE. CLOSER TO THE
MT/ND BORDER, PROBABILITY OF AN INCH OF RAIN IS ONLY AROUND 10
PERCENT WHILE THE PROBABILITY OF 0.25 INCH OF RAIN IS 10 TO 30
PERCENT. DRY SLOTTING IS EXPECTED AT TIMES ALONG THE MT/ND BORDER
WHICH WILL RESULT IN LOWER RAINFALL AMOUNTS.
WHILE THE UPPER LOW MOVES NORTH WEDNESDAY NIGHT, VARYING DEGREES
OF UPPER TROUGH REMAINS OVER THE AREA INTO NEXT WEEKEND WITH
CHANCES OF SHOWERS AT TIMES.
FORECAST CONFIDENCE & DEVIATIONS:
HIGH CONFIDENCE EXISTS ON WARM AND DRY WEATHER TODAY, MONDAY, AND
TUESDAY. COMPRESSIONAL HEATING AHEAD OF THE COLD FRONT MAY ALLOW
TEMPERATURES TO TICK A FEW DEGREES WARMER, BUT CONFIDENCE IS LOW
ON THIS SOLUTION.
LOW TO MEDIUM CONFIDENCE EXISTS ON THUNDERSTORMS MONDAY GIVEN THE
MODEST SETUP.
CONFIDENCE FOR RAIN IS HIGH WEST AND LOW TO MEDIUM EAST FOR
TUESDAY AND WEDNESDAY WITH DECENT SUPPORT FOR COOLER AND WETTER
WEATHER UNFOLDING. CONSENSUS CONTINUES TO INDICATE WIDESPREAD
RAIN IN THE WEST BUT THERE REMAINS UNCERTAINTIES IN THE COVERAGE
AND AMOUNT OF PRECIPITATION DUE TO DRY SLOTTING AT TIMES,
ESPECIALLY FOR EASTERN AREAS. HAVE OPTED TO KEEP THE FORECAST IN
LINE WITH NBM OVERALL FOR NOW, WHICH HANDLES THE BIG PICTURE WELL.
AVIATION
LAST UPDATED: 2045Z
CATEGORY: VFR, POSSIBLE MVFR MONDAY AFTERNOON.
DISCUSSION: WITH A RIDGE OVERHEAD, VFR CONDITIONS WITH CLEAR
SKIES WILL GIVE WAY TO HIGH CLOUDS OVERNIGHT. A WARM FRONT MAY AID
IN ISOLATED SHOWERS LATE MONDAY MORNING BEFORE ISOLATED
THUNDERSTORMS MOVE IN LATE MONDAY AFTERNOON. BRIEF REDUCTIONS TO
MVFR ARE EXPECTED IN THUNDERSTORMS.
WINDS: LIGHT AND VARIABLE BECOMING EAST NORTHEAST AT 8 TO 17
KNOTS AFTER 00Z MONDAY, BECOMING SOUTHEAST AT 6 TO 14 KNOTS AFTER
18Z. ERRATIC AND SHIFTING WINDS NEAR THUNDERSTORMS.
GGW WATCHES/WARNINGS/ADVISORIES
NONE.
WEATHER.GOV/GLASGOW
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