441 FXUS65 KTFX 151747 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 1045 AM MST SUN JAN 15 2012 UPDATED AVIATION DISCUSSION .UPDATE...CANADIAN COLD FRONT HAS ALREADY PUSHED THROUGH NORTH CENTRAL MONTANA AND WILL CONTINUE TO MOVE THROUGH SOUTHWEST MONTANA THIS AFTERNOON. WITH TEMPERATURES FALLING HAVE UPDATED NORTH CENTRAL ZONES TO REFLECT CURRENT TEMPERATURES AS TODAYS MAX. HAVE ALSO MADE SOME TWEAKS TO WINDS TO REFLECT CURRENT OBSERVATIONS AND ANTICIPATED PROGRESSION OF THE FRONT. FINALLY HAVE MADE SOME TWEAKS TO POPS BASED ON LATEST OBSERVATIONS AND MORNING MODEL RUNS. SURFACE OBSERVATIONS AND WEB CAMERAS INDICATE THAT SNOWFALL IS FAIRLY LIGHT AND ACCUMULATIONS WILL LIKELY NOT ADD UP TO MUCH. STILL SEE NO NEED FOR ANY WINTER WEATHER HIGHLIGHTS. MPJ && .AVIATION... UPDATED 1200Z. COLD SFC HIGH PRESSURE WILL CONTINUE TO BUILD SOUTHWARD INTO HE AREA TODAY WHILE LOW PRESSURE OVER THE DAKOTAS MOVES EAST. SECONDARY FRONTAL BOUNDARY MOVING THROUGH NORTH-CENTRAL AND CENTRAL MT TODAY WILL BRING A WIND SHIFT TO THE NORTH ALONG WITH A PERIOD OF GUSTY WINDS AND SHARPLY FALLING TEMPS. SCATTERED SNOW SHOWERS CURRENTLY FROM HLN SOUTH TO BZN AND ALSO ALONG/BEHIND THE NORTHERN FRONTAL BOUNDARY SAGGING SOUTH. SNOW IN SW MT WILL INTENSIFY SOME OVER THE MTNS SOUTH OF BZN TOWARD THE WYS AREA THIS EVENING. EXPECT LOW CLOUDS AND FLURRIES/LIGHT SNOW SHOWERS TO BECOME MORE WIDESPREAD OVER NORTH CENTRAL MT AS COLD AIR AND NW UPSLOPE FLOW DEEPENS LATER TODAY AND TONIGHT WITH SOME LOWER VISIBILITY IN HAZE AS WELL. VFR CONDITIONS WILL DEGRADE THROUGHOUT THIS AFTERNOON AND EVENING WITH MVFR AND OCCASIONAL IFR PREVAILING TONIGHT MAINLY DUE TO LOWER CLOUDS/CIGS. HOENISCH && .PREV DISCUSSION... /ISSUED 513 AM MST SUN JAN 15 2012/ TODAY THROUGH TUESDAY EVENING...LEADING EDGE OF THE DEEP AND COLD UPPER LEVEL TROF BRINGING A RETURN OF MORE TYPICAL WINTER CONDITIONS HAS REACHED WESTERN MT AND WILL GRADUALLY MAKE ITS WAY ACROSS CENTRAL AND SOUTHWEST MT OVER THE NEXT TWO DAYS. MOST SIGNIFICANT IMPACT WILL BE THE SHARP DROP IN TEMPERATURES AS CHILLY CANADIAN/ARCTIC AIRMASS WILL SETTLE OVER OUR REGION BEGINNING TODAY. THE SURFACE COLD FRONT USHERING IN THE AIRMASS PASSED THROUGH GREAT FALLS AROUND 2 AM THIS MORNING AND SHOULD MAKE IT TO THE MT/ID/WY BORDER BY AROUND MIDDAY. TEMPS WILL PEAK EARLY TODAY...THEN FALL STEADILY WITH OVERNIGHT LOWS REACHING THE SINGLE DIGITS ABOVE/BELOW ZERO TONIGHT. LESS CERTAIN PART OF THE FORECAST IS THE SNOW COVERAGE AND AMOUNT. FORECAST MODELS GENERALLY HAVE BEEN CONSISTENT IN SHOWING MOST FAVORABLE SNOW AREAS ARE THE HIGHER ELEVATIONS OF THE ROCKY MTN FRONT AND SOUTHWEST MTNS WITH 4 TO 8 INCHES POSSIBLE BETWEEN THIS MORNING AND MON EVE...WITH LESS THAN AN INCH TO A FEW SPOTS NEARING 2 INCHES OVER THE PLAINS/VALLEYS. HOWEVER...MODEL MOISTURE FIELDS FOR THIS MORNING APPEAR TO BE OVERESTIMATING THEIR COVERAGE WHEN COMPARED TO CURRENT WATER VAPOR SATELLITE IMAGERY WHICH SHOWS QUITE A BIT OF DRY AIR IN THE FLOW BOTH AHEAD AND BEHIND THE UPPER TROF AXIS PRESENTLY NEAR THE WA/OR COAST. THUS HAVE SLIGHTLY REDUCED PROBABILITIES AND AMOUNTS FOR SNOW IN OUR REGION TODAY AND WILL HOLD OFF ON ISSUING ANY WINTER WEATHER HEADLINES AT THIS TIME...THOUGH LATER ISSUANCES MAY BE NEEDED IF THE MODEL-EXPECTED MOISTURE FINALLY MATERIALIZES. UPPER TROF SHOULD EXIT INTO ERN MT MON NIGHT AND WEAK RIDGING WILL TRACK OVER THE STATE ON TUES. EXPECT CLOUDY BUT MOSTLY DRY CONDITIONS OVER OUR AREA EXCEPT FOR PERIODS OF LIGHT SNOW ALONG THE ROCKY MTN FRONT. HIGH TEMPS REMAIN MUCH BELOW NORMAL ON MON AND TUES WITH SINGLE DIGIT ABOVE ZERO VALUES FOR THE CENTRAL AND HILINE COUNTIES AND TEENS OVER SOUTHWEST MT. WARANAUSKAS TUESDAY NIGHT THROUGH SUNDAY NIGHT...MEDIUM RANGE MODELS CONTINUE TO INDICATE THAT THE COOL AND UNSETTLED PATTERN WILL PERSIST AT LEAST THROUGH THIS WEEK UNDER A MOIST NORTHWESTERLY FLOW ALOFT. A SURFACE BOUNDARY ALONG A KALISPELL-HELENA-BILLINGS LINE WILL DIVIDE THE TFX CWA IN HALF THROUGH WEDNESDAY. THIS WILL KEEP A VERY COLD AIRMASS ACROSS NORTH CENTRAL MONTANA WITH LIGHT NORTHERLY WINDS...WHILE A MORE MODERATE (THOUGH STILL COOLER THAN NORMAL) AIRMASS WITH BREEZY SOUTHWEST WINDS WILL REMAIN OVER SOUTHWEST MONTANA. A DISTURBANCE IN THE FLOW ALOFT WILL ALSO BRING WIDESPREAD SNOW TO THE AREA DURING THIS TIME...WITH THE BEST CHANCE FOR PERSISTENT SNOW WILL BE IN THE FAVORED UPSLOPE AREAS ALONG THE EAST SLOPES OF THE ROCKIES (INCLUDING THE CUT BANK AND GREAT FALLS AREAS). IN THE WAKE OF THIS DISTURBANCE...THE SURFACE BOUNDARY AND ITS ASSOCIATED WINDS WILL SHIFT NORTHEAST SOMEWHAT TO A GREAT FALLS-TO-LEWISTOWN LINE FOR THURSDAY AND FRIDAY...ALLOWING TEMPERATURES TO WARM NEAR/ABOVE NORMAL ALONG AND SOUTH OF THIS LINE. ALTHOUGH TEMPERATURES WILL ALSO WARM UP ABOUT 20 DEGREES NORTH OF THIS LINE...THEY WILL STILL BE BELOW NORMAL. THE MOIST FLOW ALOFT WILL KEEP A GOOD CHANCE OF PRECIPITATION ACROSS THE AREA DURING THIS TIME...ESPECIALLY IN THE MOUNTAINS. IT SHOULD BE WARM ENOUGH IN THE SOUTHWEST VALLEYS TO ALLOW RAIN TO MIX WITH THE SNOW THERE. FOR SATURDAY THROUGH SUNDAY NIGHT...THE MEDIUM RANGE MODELS DIFFER ON THE FORECAST SOLUTION. SOME TEND TO DRY OUT THE PATTERN...WHILE OTHERS KEEP IT QUITE COOL. HAVE THEREFORE COMPROMISED AND GONE WITH MORE OF A BROAD-BRUSHED CLIMATOLOGICAL SOLUTION...AS THERE IS ENOUGH EVIDENCE THAT DISTURBANCES IN THE FLOW WILL KEEP TEMPERATURES NEAR SEASONAL AVERAGES WITH AT LEAST A CHANCE OF PRECIPITATION. WILL CONTINUE TO MONITOR THIS SITUATION AND FINE TUNE THE FORECAST AS MODELS COME INTO BETTER AGREEMENT. COULSTON && .PRELIMINARY POINT TEMPS/POPS... GTF 17 -2 9 -1 / 40 50 50 30 CTB 9 -6 3 -10 / 90 50 50 50 HLN 25 5 17 5 / 50 60 40 30 BZN 32 9 17 4 / 50 60 60 20 WEY 22 -3 11 -4 / 40 60 60 20 DLN 35 6 16 1 / 50 40 30 20 HVR 22 -4 7 -4 / 30 20 20 30 LWT 22 -2 10 -1 / 50 60 60 20 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ WEATHER.GOV/GREATFALLS