348  
FXUS65 KTFX 152329  
AFDTFX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREAT FALLS MT  
429 PM MST SUN DEC 15 2024  
 
AVIATION SECTION UPDATED.  
   
KEY MESSAGES  
 
- NEXT ROUND OF IMPACTFUL SNOWFALL BEGINS MONDAY AFTERNOON AND  
ENDS ON TUESDAY MORNING.  
- STRONG WINDS ARE LOOKING VERY LIKELY WEDNESDAY ALONG THE EAST  
SLOPES OF THE ROCKIES.  
- DRIER AND WARMER CONDITIONS EXPECTED BY THE END OF THE WEEK AND  
CONTINUING INTO NEXT WEEKEND.  
 
 
   
DISCUSSION  
 
/ISSUED 153 PM MST SUN DEC 15 2024/  
 
- METEOROLOGICAL OVERVIEW:  
AN UPPER LEVEL TROF IS EXITING THE CWA THIS AFTERNOON, RESULTING  
IN THE WIDESPREAD LIGHT SNOW FROM EARLIER TODAY TO DIMINISH. THUS  
ALL WINTER STATEMENTS THAT WERE IN EFFECT FOR TODAY HAVE NOW  
ENDED. SKIES WILL BE MOSTLY CLOUDY TONIGHT, BUT A FEW BREAKS COULD  
ALLOW FOR SOME PATCHY FOG TO DEVELOP OVER SOUTHWEST MT AND ALSO  
OVER THE NORTHERN PORTIONS OF HILL/BLAINE COUNTIES. ON MONDAY, THE  
NEXT UPPER LEVEL TROF WILL MOVE INTO WESTERN MT BY THE LATE  
AFTERNOON HOURS. THIS WILL RESULT IN ANOTHER ROUND OF LIGHT SNOW  
OVER A GOOD PORTION OF THE CWA. WINTER WEATHER STATEMENTS HAVE  
BEEN ISSUED FOR THE MOST LIKELY AREAS TO RECEIVE A FEW INCHES OR  
MORE OF SNOWFALL WITH THIS EVENT.  
 
MOST OF THE SNOWFALL DIMINISHES BY TUESDAY MORNING, BUT SCATTERED  
SNOW SHOWERS ARE LIKELY TO CONTINUE INTO WEDNESDAY FOR MOUNTAIN  
AREAS. BY WEDNESDAY AFTERNOON, A STRONG WESTERLY FLOW DEVELOPS  
ALOFT. THIS WILL RESULT IN THE POTENTIAL FOR STRONG WINDS ALONG  
THE EAST SLOPES OF THE ROCKIES AND ACROSS CENTRAL MT. HIGH WIND  
STATEMENTS WILL LIKELY BE NEEDED FOR THIS EVENT.  
 
AN UPPER LEVEL RIDGE OF HIGH PRESSURE IS EXPECTED TO BUILD OVER  
THE CWA BY THE END OF THE WEEK AND INTO THE WEEKEND. THIS WILL  
RESULT IN MOSTLY DRY CONDITIONS, ALONG WITH MILD TEMPERATURES  
MOVING INTO THE CWA FOR LATE DECEMBER.  
 
- FORECAST CONFIDENCE & SCENARIOS:  
SNOWFALL FOR MONDAY AFTERNOON AND TUESDAY MORNING WILL BE MOST  
IMPACTFUL OVER THE NORTHERN ROCKY MOUNTAIN FRONT AND THEN ACROSS  
THE MOUNTAIN AREAS OF CENTRAL MT AND SOUTHWARD THROUGH THE  
BRIDGER, BIG SKY AND WEST YELLOWSTONE AREAS. SNOWFALL AMOUNTS OF 2  
TO 4 INCHES ARE LIKELY IN MANY OF THESE AREAS, WITH ISOLATED  
HIGHER AMOUNTS AT RIDGE TOPS. THE PROBABILITY OF 1 INCH OF  
SNOWFALL AT LOWER ELEVATIONS IS GENERALLY LESS THAN 30 PERCENT, SO  
NO WINTER STATEMENT IS PLANNED FOR AT THIS TIME. HOWEVER, THE  
SNOWFALL WILL IMPACT THE EVENING RUSH HOUR ON MONDAY. IF SNOW  
AMOUNTS INCREASE A BIT, THERE IS THE POTENTIAL A WINTER STATEMENT  
MIGHT BE NEEDED FOR SOME LOWER ELEVATION LOCATIONS ON MONDAY.  
 
THE NEXT MAIN CONCERN IS THE POTENTIAL FOR STRONG WINDS ON  
WEDNESDAY. RIGHT NOW THERE IS AN 80 PERCENT CHANCE OR HIGHER OF  
WINDS OVER 60 MPH IN THE CUT BANK AND BROWNING AREAS BY WEDNESDAY  
EVENING. THUS HIGH WIND STATEMENTS ARE LOOKING LIKELY FOR THIS  
AREA. OVER CENTRAL MT, THE PROBABILITY IS 70 PERCENT FOR WINDS  
OVER 58 MPH. THE NORTHERN ROCKIES ALSO HAVE OVER AN 80 PERCENT  
CHANCE OF WIND GUSTS OVER 75 MPH, THUS THIS IS LOOKING LIKE A  
RATHER STRONG WIND EVENT. BRUSDA  
 
 
   
AVIATION  
 
16/00Z TAF PERIOD  
 
SURFACE AND UPPER LEVEL LOW PRESSURE CONTINUES TO MOVE OFF TO THE  
EAST OF THE AREA THIS EVENING WITH GUSTY WEST WINDS AT MOST  
TERMINALS GRADUALLY DIMINISHING THROUGH THE OVERNIGHT PERIOD. A  
FEW SNOW SHOWERS LINGER NEAR THE CONTINENTAL DIVIDE THIS EVENING  
WITH LOCAL MOUNTAIN OBSCURATION BUT OTHERWISE CLOUDS ALSO DECREASE  
THROUGH TONIGHT WITH VFR CONDITIONS PREVAILING AT ALL TERMINALS  
THROUGH MONDAY MORNING. CLOUDS INCREASE AGAIN ON MONDAY AS THE  
NEXT WEATHER SYSTEM MOVES IN FROM THE WEST WITH LIGHT SNOW  
DEVELOPING FROM SOUTH TO NORTH ACROSS THE AREA MONDAY AFTERNOON  
THROUGH MONDAY EVENING. HOENISCH  
 
REFER TO WEATHER.GOV/ZLC FOR MORE DETAILED REGIONAL AVIATION  
WEATHER AND HAZARD INFORMATION.  
 
 
   
PRELIMINARY POINT TEMPS/POPS  
 
GTF 20 36 21 32 / 0 30 70 40  
CTB 15 30 13 22 / 0 10 60 30  
HLN 20 33 23 38 / 0 70 70 40  
BZN 14 33 21 37 / 0 60 70 40  
WYS 6 26 15 29 / 20 90 90 80  
DLN 15 34 20 37 / 0 40 30 20  
HVR 13 28 12 22 / 0 0 60 60  
LWT 15 34 19 32 / 0 20 80 70  
 
 
   
TFX WATCHES/WARNINGS/ADVISORIES  
 
WINTER WEATHER ADVISORY FROM 2 PM MONDAY TO 9 AM MST TUESDAY FOR  
BIG BELT, BRIDGER AND CASTLE MOUNTAINS-EAST GLACIER PARK REGION-  
GALLATIN AND MADISON COUNTY MOUNTAINS AND CENTENNIAL MOUNTAINS-  
LITTLE BELT AND HIGHWOOD MOUNTAINS.  
 
 
 
 
HTTP://WWW.WEATHER.GOV/GREATFALLS  
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