320 FXUS65 KTFX 162338 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 438 PM MST MON JAN 16 2012 UPDATED AVIATION .DISCUSSION... TONIGHT THROUGH WEDNESDAY...OVERALL...AN ACTIVE WEATHER PATTERN WILL RESIDE OVER THE REGION FOR THE NEXT FEW DAYS. EXPECT SCATTERED SHOWERS OVER THE ROCKY MOUNTAIN FRONT...TO BECOME MORE WIDESPREAD AND HEAVIER TOWARDS MORNING. THERE IS THE POTENTIAL FOR HEAVY SNOW OVER THIS REGION AT TIMES THEN FROM TUESDAY THROUGH THURSDAY NIGHT...SO THIS REGION HAS BEEN PLACED UNDER A WINTER STORM WATCH. ELSEWHERE OVER THE REGION TONIGHT...EXPECT SOME PASSING EVENING FLURRIES...WITH ISOLATED SNOW SHOWERS AFTER MIDNIGHT...MAINLY OVER THE NORTHERN TIER OF THE REGION. FOR TUESDAY...EXPECT THE SNOW TO CONTINUE ALONG THE FRONT RANGE...WHILE THE SNOW SHOWERS START TO SPREAD A BIT FURTHER EASTWARD OVER NORTH CENTRAL MONTANA DURING THE AFTERNOON HOURS. TEMPERATURES WILL GENERALLY REMAIN COLD. FOR TUESDAY NIGHT THE SNOW BECOMES LIKELY ACROSS MUCH OF NORTH CENTRAL/SOUTHWEST MONTANA AS THE MAIN WARM FRONT BEGINS TO DEVELOP OVER SOUTHWEST MONTANA. THIS WARM FRONT WILL BEGIN TO SLOWLY PUSH NORTHWARD WEDNESDAY...AND LOCATIONS NEAR THE MAIN FRONTAL BOUNDARY SHOULD RECEIVE THE HEAVIEST SNOWFALL. TEMPERATURES WILL REMAIN COLD OVER MUCH OF NORTH CENTRAL MONTANA...AS SEASONABLE TEMPERATURES START TO MOVE BACK INTO FAR SOUTHWEST MONTANA. BRUSDA WEDNESDAY NIGHT THROUGH MONDAY NIGHT...MEDIUM RANGE MODELS AGREE THAT THE BITTERLY COLD AIRMASS WILL BEGIN TO MODERATE WEDNESDAY NIGHT INTO THURSDAY AS THE FLOW ALOFT BECOMES MORE WESTERLY. HOWEVER...THERE ARE STILL DIFFERENCES AMONG THE MODELS IN THE EXACT POSITIONING OF THE SURFACE BOUNDARY DIVIDING THE WARM AND COLD AIRMASSES...WHICH IS RESULTING IN MODEL FORECAST TEMPERATURE DIFFERENCES OF GENERALLY 10 TO 20 DEGREES THROUGH THE END OF THIS WEEK. THEREFORE...AM ELECTING TO GO WITH MORE OF A GRADUAL MOVEMENT OF THE BOUNDARY THROUGH THE PERIOD...RESULTING IN A GRADUAL WARMING OF TEMPERATURES. HOWEVER...SNOW WILL REMAIN LIKELY FOR THE WEDNESDAY NIGHT AND THURSDAY PERIODS DUE TO CONTINUED SIGNIFICANT MOISTURE OVERRUNNING THE COLD AIRMASS STILL IN PLACE. AS HAS BEEN MENTIONED IN THE HAZARDOUS WEATHER OUTLOOK...WINTER WEATHER HIGHLIGHTS MAY BE NECESSARY FOR THIS EVENT...AS SNOWFALL WILL BE LIGHT BUT PERSISTENT. THE SURFACE BOUNDARY WILL LIFT NORTHEAST DURING THIS PERIOD...ALLOWING TEMPERATURES IN SOUTHWEST MONTANA TO WARM TO ABOVE NORMAL...CAUSING VALLEY PRECIPITATION TO LIKELY BE A RAIN/SNOW MIX. CENTRAL MONTANA (INCLUDING GREAT FALLS AND LEWISTOWN) WILL LIKELY ONLY REACH NEAR NORMAL. AS THE FLOW ALOFT BECOMES MORE WESTERLY FRIDAY AND SATURDAY...THE BOUNDARY WILL CONTINUE TO MOVE NORTHEAST...ALLOWING ABOVE NORMAL TEMPERATURES TO REACH INTO CENTRAL MONTANA WITH NEAR NORMAL TEMPERATURES AS FAR NORTH AS THE CANADIAN BORDER. THERE WILL LESS OF A THREAT OF OVERRUNNING PRECIPITATION AS THE SURFACE BOUNDARY LIFTS NORTH...BUT A DISTURBANCE IN THE FLOW ALOFT WILL CONTINUE MOUNTAIN SHOWERS AND KEEP A CHANCE OF SHOWERS OVER THE PLAINS. HOWEVER...STRONG WESTERLY WINDS BLOWING OVER RIDGE TOPS WILL CAUSE AREAS OF BLOWING SNOW THERE. THE MORE PROGRESSIVE WESTERLY FLOW ALOFT WILL BECOME LESS MOIST OVER THE WEEKEND AND KEEP TEMPERATURES CLOSE TO NORMAL...BUT DISTURBANCES IN THE FLOW WILL GENERALLY KEEP AT LEAST A SLIGHT CHANCE OF SHOWERS AROUND THROUGH THE REMAINDER OF THE PERIOD. COULSTON && .AVIATION... UPDATED 0000Z. LOW CLOUDS WILL LINGER OVER PORTIONS OF CENTRAL AND SOUTHWEST MONTANA THOUGH CLOUDS WILL GRADUALLY LIFT FROM KGTF TO KLWT AND AREAS SOUTH OF THIS LINE AS WINDS SHIFT SOUTHWEST. A COLD FRONT WILL DESCEND FROM CANADA AND BRING LIGHT SNOW TO AREAS ALONG THE HI-LINE INCLUDING KCTB AND KHVR. WINDS WILL SHIFT TO THE NORTHEAST BEHIND THE FRONT FOR KCTB AND KHVR. MVFR AND OCCASIONAL IFR CONDITIONS ARE POSSIBLE FOR THESE LOCATIONS AND WIDESPREAD MOUNTAIN OBSCURATION IS ALSO EXPECTED THROUGH TUESDAY MORNING. THE FRONT WILL GRADUALLY APPROACH CENTRAL MONTANA TOWARDS THE END OF THE CURRENT FORECAST PERIOD. MLV && .PRELIMINARY POINT TEMPS/POPS... GTF -3 13 -10 -2 / 10 30 80 90 CTB -16 -6 -21 -10 / 20 70 80 90 HLN 1 21 8 16 / 10 30 70 90 BZN 1 22 10 21 / 10 20 70 80 WEY -16 11 3 20 / 20 40 60 80 DLN -4 18 11 21 / 10 20 60 80 HVR -13 2 -18 -9 / 20 40 60 60 LWT -4 19 -8 0 / 10 20 70 80 && .TFX WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FROM LATE TONIGHT THROUGH LATE THURSDAY NIGHT NORTHERN ROCKY MOUNTAIN FRONT...SOUTHERN ROCKY MOUNTAIN FRONT. && $$ WEATHER.GOV/GREATFALLS