058 FXUS65 KTFX 081103 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 403 AM MST SUN JAN 8 2012 .DISCUSSION... TODAY THROUGH TUESDAY...INCREASING MID-HIGH LEVEL CLOUDINESS IS EXPECTED TODAY AS WEAK ENERGY ROTATES ON THE LEE-SIDE OF UPPER- LEVEL RIDGE. GUSTY WINDS ARE ALSO OCCURRING ALONG THE ROCKY MOUNTAIN FRONT...HOWEVER WINDS HAVE STAYED BELOW HIGH WIND CRITERIA SO WILL HOLD OFF ON A HIGH WIND WARNING THIS MORNING BUT CONTINUE TO MONITOR. RIDGE FLATTENS OUT TODAY SO BREEZY WEST-NORTHWEST WINDS WILL BE FELT ACROSS NORTH-CENTRAL MONTANA. IN ADDITION...LIMITED PACIFIC MOISTURE AND ISENTROPIC LIFT ASSOCIATED WITH WEAK SHORTWAVES MAY BE ENOUGH TO ALLOW FOR A SLIGHT CHANCE OF SNOW IN THE MOUNTAINS THOUGH ANY ACCUMULATIONS WOULD BE LESS THAN AN INCH. OTHERWISE CONTINUED DRY WITH ABOVE AVERAGE TEMPERATURES ARE ANTICIPATED THROUGH MONDAY. THE MAIN CONCERN IS REGARDING A FAST- MOVING PACIFIC STORM SYSTEM AND ASSOCIATED COLD FRONT WHICH SHOULD AFFECT THE FORECAST AREA ON TUESDAY. INCREASING MOISTURE AND A COLDER CANADIAN AIRMASS WITH A COLD FRONTAL PASSAGE MAY BRING WIDESPREAD LIGHT SNOW TO NORTH-CENTRAL AND SOUTHWEST MONTANA. INITIALLY...A BRIEF PERIOD OF A RAIN/SNOW MIX IS POSSIBLE THOUGH ONCE THE COLD FRONT PASSES PRECIPITATION SHOULD QUICKLY CHANGE TO ALL SNOW. MODELS CONTINUE TO SHOW DIFFERENCES REGARDING TIMING AND SNOW AMOUNTS BUT AS OF NOW...THIS SYSTEM SEEMS TO BE MOVING TOO QUICKLY TO BE CONCERNED ABOUT HEAVY SNOW AMOUNTS AND ADVISORY CRITERIA SNOWFALL IS PROBABLE. TIMING OF THE FRONT SHOULD BE TUESDAY MORNING OVER NORTH-CENTRAL MONTANA AND TUESDAY AFTERNOON IN SOUTHWEST MONTANA. OVER THE PLAINS AND VALLEYS...SNOW ACCUMULATIONS OF 2 TO 5 INCHES ARE POSSIBLE WITH HIGHER AMOUNTS IN THE MOUNTAINS...ESPECIALLY ON NORTH-FACING SLOPES. TEMPERATURES WILL QUICKLY FALL INTO THE 20S BY TUESDAY AFTERNOON WITH GUSTY NORTHERLY WINDS. MLV TUESDAY NIGHT THROUGH SUNDAY...FAST MOVING WEATHER SYSTEM MOVING THROUGH MY FORECAST AREA ON TUESDAY WILL LEAVE RESIDUAL SHOWERS ACROSS MUCH OF THE AREA TUESDAY EVENING. THIS SYSTEM MOVES EAST OF THE FORECAST AREA ON WEDNESDAY. MEDIUM RANGE MODELS CONTINUE TO INDICATE THAT THE UPPER AIR PATTER WILL RETURN TO A WEAK POSITIVE TILT RIDGE OVER THE PACIFIC NORTHWEST AND WESTERN MONTANA WITH THE REMAINDER OF THE WEEK EXPECTED TO SEE A RETURN TO WARMER TEMPERATURES AND BREEZY CONDITIONS FOR THURSDAY THROUGH SATURDAY. MODEL SOLUTIONS DIVERGE AGAIN ON SUNDAY WITH THE GFS BRINGING ANOTHER COLD SHORTWAVE THROUGH THE STATE WHILE THE ECMWF KEEPS A LESS AMPLIFIED NORTHWESTERLY FLOW ALOFT OVER MONTANA. HAVE TRENDED TOWARD CLIMATOLOGY DUE TO THE UNCERTAINTY. MPJ && .AVIATION... UPDATED 0535Z. WIDESPREAD VFR CONDITIONS EXPECTED FOR THE OVERNIGHT PERIOD INTO SUN MORNING AS HIGH PRESSURE RIDGE KEEPS CONDITIONS QUIET. BAND OF MOISTURE CROSSING OVER THE TOP OF THE RIDGE WILL BRING IN MID-LEVEL CEILINGS (AROUND FL100) BUT ANY PRECIPITATION WILL BE CONFINED TO THE ROCKY MTN FRONT WHERE ISOLATED -SHSN WILL OCCUR. WINDS WILL GENERALLY BE LIGHT ACROSS THE REGION TONIGHT WITH A FEW GUSTS NEAR 30 KT VCNTY KCTB. TIGHTENING PRESSURE GRADIENT WILL PRODUCE GUSTY WEST-SOUTHWEST WINDS FROM KGTF TO KCTB STARTING AROUND MIDDAY TOMORROW...WITH GUSTS OF 30-40 KTS LIKELY. WARANAUSKAS && .PRELIMINARY POINT TEMPS/POPS... GTF 46 38 53 33 / 10 0 0 10 CTB 47 37 51 30 / 10 0 0 30 HLN 41 24 47 24 / 10 0 0 10 BZN 39 15 45 20 / 10 0 0 10 WEY 23 -1 28 11 / 40 0 0 10 DLN 38 20 43 21 / 10 0 0 10 HVR 50 34 56 31 / 0 0 0 10 LWT 45 32 53 32 / 10 0 0 10 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ WEATHER.GOV/GREATFALLS