795  
FXUS65 KTFX 221543  
AFDTFX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREAT FALLS MT  
840 AM MST TUE JAN 22 2019  
   
UPDATE
 
 
STRONG WEST WINDS ALONG THE ROCKY MOUNTAIN FRONT AND ADJACENT PLAINS  
ARE CAUSING AREAS OF DRIFTING AND BLOWING SNOW. A SHALLOW LAYER OF  
COLD AIR PERSISTS ALONG THE HILINE, WITH DENSE FOG ALONG THE MILD  
RIVER IN NORTHERN BLAINE COUNTY. HIGH CLOUDS ARE INCREASING OVER THE  
FORECAST AREA AS THE NEXT SYSTEM UPSTREAM ADVANCES FURTHER EAST. THE  
CURRENT FORECAST DESCRIBES THE SITUATION REASONABLY WELL, SO A  
MORNING UPDATE WILL NOT BE POSTED.  
 

 
   
SYNOPSIS
 
 
MOSTLY SUNNY SKIES THIS MORNING WILL YIELD TO INCREASING CLOUDS  
THIS AFTERNOON AND EVENING AS THE NEXT SYSTEM APPROACHES. SNOW  
WILL MOVE INTO THE MOUNTAINS WELL BEFORE DAWN TOMORROW, AND SPREAD  
TO LOWER ELEVATIONS THROUGH THE DAY WEDNESDAY. A COLD FRONT WILL  
PUSH SOUTH THROUGH THE STATE WEDNESDAY AFTERNOON AND NIGHT, AND  
SNOW WILL END OVERNIGHT. HIGH PRESSURE WILL BRING SOME CLEARING  
THURSDAY, AND ANOTHER SYSTEM MAY BRING SOME MOUNTAIN SNOW FRIDAY.  
 

 
   
DISCUSSION
 
 
TODAY THROUGH WEDNESDAY NIGHT...  
HIGH PRESSURE ACROSS THE NORTHERN ROCKIES WILL ALLOW FOR SOME  
CLEARING AND DRYING TODAY. INTERACTION BETWEEN THIS HIGH AND LOW  
PRESSURE MOVING THROUGH NORTHERN ALBERTA WILL LEAD TO A STRONG  
PRESSURE GRADIENT ALONG THE NORTHERN ROCKIES, AND A ROUND OF  
CHINOOK WINDS. AT THIS TIME, THE FORECAST HAS EASTERN GLACIER  
COUNTY GETTING SUSTAINED WINDS AROUND 25KTS WITH GUSTS NEAR 40KTS  
THIS AFTERNOON, SO NO HIGH WIND HEADLINES WERE ISSUED. HIGHS WILL  
BE IN THE LOW TO MID 30S FOR MOST LOWER ELEVATION LOCATIONS,  
EXCEPT 20S FOR THE SW VALLEYS.  
 
THE NEXT SYSTEM THEN APPROACHES TONIGHT, THOUGH NOT MUCH MOISTURE  
IS EXPECTED TO MAKE IT EAST OF THE DIVIDE UNTIL AFTER MIDNIGHT.  
SNOW SPREADS INTO THE MOUNTAINS FROM THE LITTLE BELTS DOWN TO THE  
GALLATIN AND MADISON RANGES BEFORE SUNRISE WED, AND THEN INTO  
LOWER ELEVATION LOCATIONS DURING WED MORNING AS LOW PRESSURE AND  
ASSOCIATED PACIFIC MOISTURE ARRIVE FROM THE WEST. ONE CHANGE FROM  
PREVIOUS FORECASTS IS THE EXPECTED EARLIER ARRIVAL OF A COLD FRONT  
FROM CANADA, WHICH WILL PUT MORE OF A CAP ON HIGH TEMPS, AND ALLOW  
MORE SNOW IN LOWER ELEVATIONS, ESPECIALLY ACROSS THE NORTH-CENTRAL  
PLAINS. FORECAST SNOW TOTALS OF 2 TO 5 INCHES AT SOME LOWER  
ELEVATIONS, 5 TO 10 INCHES FOR MANY PASSES, AND 10 INCHES OR MORE  
FOR MANY OF THE MOUNTAINS PROMPTED THE ISSUANCE OF ADVISORIES FOR  
THIS SYSTEM, WITH THE EXCEPTION OF THE NORTHERN TIER OF THE PLAINS  
ZONES. SNOW TAPERS OFF WED NIGHT, AND ALL ADVISORIES DROP BY 12Z  
OR EARLIER. KREDENSOR  
 
THURSDAY THROUGH TUESDAY... NORTHWEST FLOW ALOFT DOMINATES THE  
PERIOD WITH A LARGE SCALE PATTERN FEATURING AN UPPER LEVEL RIDGE  
JUST OFF OF THE WEST COAST AND DEEP UPPER TROUGH OVER CENTRAL  
CANADA. A SURFACE TROUGH TO THE LEE/EAST OF THE ROCKIES WILL KEEP  
THE MAIN COLD AIRMASS BENEATH THE UPPER TROUGH EAST OF THE REGION  
THROUGH SATURDAY WHILE ALSO SUPPORTING BREEZY TO WINDY CONDITIONS  
AT TIMES, ESPECIALLY ACROSS WESTERN PORTIONS OF NORTH-CENTRAL MT.  
TEMPERATURES BEGIN NEAR SEASONAL AVERAGES THURSDAY, THEN WARM TO  
ABOVE SEASONAL AVERAGES BY SATURDAY. GENERALLY WEAK SHORTWAVE  
ENERGY EMBEDDED WITHIN THE NW FLOW ALOFT WILL BRING A SLIGHT  
CHANCE OF SOME MOUNTAIN SNOW SHOWERS LATE THURSDAY AND AGAIN  
SATURDAY, THOUGH CONFIDENCE IN THE TIMING OF THESE FEATURES IN NOT  
GREAT DUE TO MODEL DIFFERENCES. MODELS DO HOWEVER CONTINUE TO  
GENERALLY SUPPORT THE IDEA OF A STRONGER SHORTWAVE TO DROP SOUTH  
THROUGH THE REGION DURING THE SUNDAY/SUNDAY NIGHT TIMEFRAME, WHICH  
WOULD BRING ANOTHER ROUND OF ACCUMULATING SNOWFALL ALONG WITH A  
SURGE OF COLDER AIR. HOENISCH  
 

 
   
AVIATION
 
 
UPDATED 1230Z.  
 
MVFR TO VFR CONDITIONS PREVAIL ACROSS THE CWA THROUGH THIS EVENING.  
HIGH AND EVENTUALLY MID-LEVEL CLOUDS WILL MOVE ACROSS THE DIVIDE  
LATER THIS MORNING INTO THE EVENING. HOWEVER, OVERNIGHT CEILINGS  
WILL GRADUALLY LOWER, ESPECIALLY FOR THE CENTRAL AND WESTERN PART OF  
THE CWA. OBSCURED TERRAIN IS LIKELY IN THE MOUNTAINS TONIGHT INTO  
WEDNESDAY. SNOW WILL BEGIN IN THE MOUNTAINS TONIGHT, AND WILL  
GRADUALLY SPREAD TO LOWER ELEVATIONS LATE TONIGHT INTO WED AM. MOST  
SITES SHOW PROB30 SNOW GROUPS, IF NOT OUTRIGHT PREDOMINANT SNOW, AT  
THE END OF THE 12Z TAFS, BUT KHVR AND KLWT MAY ESCAPE SNOW UNTIL  
AFTER 12Z WED.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
GTF 34 24 36 11 / 0 40 90 70  
CTB 32 22 33 5 / 0 50 70 10  
HLN 32 20 36 14 / 0 40 70 70  
BZN 31 17 35 16 / 0 80 90 70  
WEY 21 4 23 7 / 0 90 100 80  
DLN 29 19 37 22 / 0 30 60 40  
HVR 32 17 31 1 / 0 30 70 30  
LWT 33 22 34 8 / 0 20 90 70  
 

 
   
TFX WATCHES/WARNINGS/ADVISORIES
 
 
WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 11 PM MST  
WEDNESDAY FOR BEAVERHEAD...CENTRAL AND SOUTHERN LEWIS AND  
CLARK... JEFFERSON...MADISON...NORTHERN ROCKY MOUNTAIN  
FRONT...SOUTHERN ROCKY MOUNTAIN FRONT.  
 
WINTER WEATHER ADVISORY FROM 2 AM WEDNESDAY TO 5 AM MST THURSDAY  
FOR BROADWATER...CASCADE...CHOUTEAU...FERGUS...GALLATIN...JUDITH  
BASIN...MEAGHER.  
 
FLOOD ADVISORY THROUGH 315 PM MST TUESDAY FOR A PORTION OF THE  
MISSOURI RIVER IN CASCADE COUNTY.  
 

 
 

 
 
HTTP://WWW.WEATHER.GOV/GREATFALLS  
 
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