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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