194  
FXUS65 KTFX 192337  
AFDTFX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREAT FALLS MT  
537 PM MDT TUE SEP 19 2017  
 
UPDATED AVIATION DISCUSSION  
   
SYNOPSIS
 
 
MOIST WESTERLY FLOW ALOFT WILL CONTINUE TO BRING CLOUDS AND  
SHOWERS TO THE WESTERN AND SOUTHWEST MONTANA MOUNTAINS. BREEZY  
CONDITIONS AND CONTINUED COOL TEMPERATURES WITH ISOLATED SHOWERS  
ARE EXPECTED OVER THE PLAINS. THIS PATTERN IS EXPECTED TO  
CONTINUE TONIGHT THROUGH FRIDAY.  
 

 
   
DISCUSSION
 
 
TONIGHT THROUGH THURSDAY...AN UPPER LEVEL TROUGH OF LOW PRESSURE  
WILL REMAIN OVER SOUTHWESTERN CANADA THROUGH THURSDAY. THIS  
PATTERN WILL ALLOW COOL TEMPERATURES TO CONTINUE ACROSS THE  
REGION, WHILE WEST TO SOUTHWEST FLOW ALOFT WILL BRING ABUNDANT  
PACIFIC MOISTURE TO THE REGION. PERIODS OF RAIN AND SNOW ARE  
EXPECTED OVER THE MOUNTAINS OF SOUTHWEST MONTANA AND ALONG THE  
CONTINENTAL DIVIDE THROUGH THE SHORT TERM. MEANWHILE, MOSTLY DRY  
CONDITIONS ARE ANTICIPATED OVER THE PLAINS WITH ONLY AN ISOLATED  
SHOWER OR TWO MOVING OFF THE MOUNTAINS. SURFACE LOW PRESSURE  
SYSTEM CURRENTLY IN SOUTHERN ALBERTA WILL REMAIN IN PLACE TONIGHT  
AND WEDNESDAY BEFORE EJECTING EASTWARD WEDNESDAY NIGHT AND  
THURSDAY. AS A RESULT, TIGHT PRESSURE GRADIENTS WILL FUEL GUSTY  
WEST TO SOUTHWEST WINDS ALONG THE EAST SLOPES OF THE ROCKY  
MOUNTAINS AND THROUGH THE HIGHER TERRAIN OF SOUTHWEST MONTANA.  
BREEZY TO WINDY CONDITIONS ARE ALSO ANTICIPATED OVER THE PLAINS,  
ALTHOUGH THEY ARE NOT EXPECTED TO BE AS STRONG AS IN THE HIGHER  
TERRAIN. AT THIS TIME, IT DOES NOT APPEAR THAN ANY HIGHLIGHTS WILL  
BE NECESSARY BUT THIS WILL CONTINUE TO BE MONITORED. MPJ  
 
FRIDAY THROUGH TUESDAY...THOUGH THERE ARE STILL DISCREPANCIES TO  
RESOLVE BETWEEN THE VARIOUS GLOBAL MODELS AND THEIR ENSEMBLES, THERE  
IS MODERATE CONFIDENCE THAT AN AREA OF DEFORMATION COMBINED WITH A  
STRONG SURFACE FRONT OVER SOUTH-CENTRAL AND NORTHEASTERN MONTANA  
WILL RESULT IN A POTENTIALLY WIDESPREAD AREA OF RAIN AND HIGH-  
ELEVATION SNOW. THE LESS-CONFIDENT ASPECT OF FORECASTING THIS EVENT  
AT THIS POINT IS JUST HOW WIDESPREAD THE PRECIPITATION IS, WITH  
LOWERING CONFIDENCE AS ONE MOVES NORTH AND WEST THROUGH OUR CWA.  
WITHIN THE REGION OF WIDESPREAD PRECIPITATION, THERE WILL BE THE  
POTENTIAL FOR SIGNIFICANT SNOW ACCUMULATIONS ABOVE 5500-FT  
ELEVATION. THIS SYSTEM WILL FINALLY BEGIN TO SLOWLY EXIT THE REGION  
TO THE EAST LATE FRIDAY INTO SATURDAY, WITH JUST RESIDUAL RAIN AND  
MOUNTAIN SNOW SHOWERS REMAINING BEHIND. A QUIETER WEATHER PATTERN  
WITH PERIODS OF SUN AND CLOUDS AND PERHAPS A STRAY SHOWER OR TWO CAN  
BE EXPECTED EARLY NEXT WEEK AS NORTHWESTERLY FLOW INCREASES ACROSS  
THE REGION AHEAD OF A POTENTIALLY ROBUST UPPER LEVEL RIDGE MOVING  
ONTO THE PACNW COAST. CC  
 

 
   
AVIATION
 
 
UPDATED 2337Z.  
 
UPPER LEVEL TROUGH/LOW CENTERED OVER AB/BC WILL MAINTAIN FAST AND  
UNSETTLED WESTERLY FLOW ALOFT ACROSS THE NORTHERN ROCKIES AND MT  
WITH SEVERAL EMBEDDED DISTURBANCES PASSING EAST ACROSS SW MT THROUGH  
WEDNESDAY. SHOWERS WILL PRIMARILY AFFECT WESTERN AND SW MT WITH  
DRIER CONDITIONS PREVAILING ACROSS THE PLAINS. OCCASIONAL MVFR  
CONDITIONS CAN BE EXPECTED AT SW MT TERMINALS ALONG WITH MOUNTAIN  
OBSCUREMENT. THE MOST WIDESPREAD PRECIPITATION AND LOWEST CEILINGS  
ARE ANTICIPATED ON WEDNESDAY ACROSS FAR SW MT.  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
GTF 42 54 35 53 / 10 30 20 20  
CTB 39 52 33 47 / 10 10 10 30  
HLN 37 52 35 53 / 30 40 30 30  
BZN 34 51 34 49 / 50 50 40 30  
WEY 25 41 25 39 / 60 60 70 60  
DLN 34 51 30 44 / 20 50 30 40  
HVR 41 59 36 56 / 10 0 10 10  
LWT 38 51 36 52 / 30 40 20 10  
 

 
   
TFX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
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