FXUS65 KGGW 201528 AFDGGW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GLASGOW MT 928 AM MDT SAT MAR 20 2010 .SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH MONDAY... NO UPDATE TO GOING FORECAST. UPPER RIDGE BUILDING INTO THE NORTHERN ROCKIES...WITH CLEARING SKIES AND WARM AIR ADVECTION EXPECTED. COLD START TO THE MORNING WILL CAP MAXIMUM TEMPERATURES BUT GOOD MIXING ANTICIPATED. EBERT PREVIOUS SHORT TERM DISCUSSION...UPPER RIDGE CURRENTLY OVER THE PACIFIC COAST WILL MOVE INLAND TODAY AND ACROSS MONTANA TONIGHT AND SUNDAY. THIS WILL BRING CLEAR SKIES AND A WARMING TREND TO THE FORECAST AREA. WHILE THERE WILL BE A COOLER NE TO WARMER SW TEMPERATURE PATTERN TODAY AND SUNDAY...IT WILL BE DUE TO WARMER AIR OVER THE SW. SNOW COVER HAS DISAPPEARED OVER MOST OF THE REGION THIS WEEK SO IT IS NO LONGER MUCH OF A FACTOR IN COOLING TEMPERATURES. UPPER TROUGH AND COLD FRONT MOVES INLAND FROM THE PACIFIC ON SUNDAY. THE COLD FRONT WILL PASS THROUGH NORTHEAST MONTANA MONDAY MORNING FOLLOWED BY THE UPPER TROUGH IN THE AFTERNOON AND EVENING. ENOUGH MOISTURE...INSTABILITY AND UPPER LEVEL DYNAMICS ACCOMPANIES THIS SYSTEM FOR A CHANCE OF SHOWERS. TEMPERATURES WILL BE WARM ENOUGH ON MONDAY FOR ALL RAIN. FORRESTER .LONG TERM...MONDAY NIGHT THROUGH SATURDAY... THE POLAR VORTEX STARTS OUT OVER THE YUKON TERRITORY AND JUST TO THE WEST OF THE HUDSON BAY. PIECES OF SHORTWAVE ENERGY ROTATE AROUND THE POLAR VORTEX AND ARE EJECTED SOUTH SOUTHEASTWARD TOWARDS THE NORTHERN HIGH PLAINS AND GREAT LAKES REGION. THE GFS ECMWF AND THE GEM ARE SHOWING THIS PATTERN THROUGHOUT THE EXTENDED. AS THE SHORT WAVE ENERGY ROUNDS THE POLAR VORTEX IT WILL PICK UP THE ARCTIC AIR AND TRYS TO PUSH IT SOUTHWARD TOWARDS THE LOWER 48. AS IT LOOKS NOW THE BRUNT OF THE ARCTIC AIR WILL REMAIN NORTH OF THE INTERNATIONAL BORDER. THIS PATTERN COULD CHANGE WITH FUTURE MODEL RUNS BUT THE TIME OF YEAR AND THE DWINDLING SNOW PACK ACROSS SOUTHERN CANADA IS WORKING AGAINST THE REALLY COLD AIR MAKING IT TO FAR SOUTH. SO WITH THIS IN MIND THE MODELS SHOW THE ARCTIC FRONTAL BOUNDARY WAVERING IN AND OUT OF THE NORTHEAST ZONES. DID NOT CHANGE TEMPERTURES VERY MUCH AT ALL IN THE EXTENDED BUT DID TWEAK A FEW DAY TIME HIGHS DURING THE UP COMING WEEK. EPICALLY FOR NEXT FRIDAY AS THIS LOOKS LIKE THE BEST CHANCE FOR A GLANCING BLOW OF THE ARCTIC AIR. BEING THIS FAR OUT THE PRECIPITATION IS TOUGH TO CALL BUT A MIX OF RAIN AND SNOW WITH MOSTLY SNOW DURING THE OVERNIGHT HOURS IS POSSIBLE. OF COURSE IF THE MODELS CHANGE AND SEND THE BLAST OF ARCTIC AIR THROUGH SOUTHERN MONTANA...THE PRECIPITATION TYPE WOULD BE ALL SNOW. MODELS HAVE BEEN FAIRLY CONSISTENT LATELY IN SHOWING A SHORTWAVE MOVING ACROSS WESTERN MONTANA ON MONDAY NIGHT AND TUESDAY WITH ENOUGH INSTABILITY AND COLD AIR WORKING IT WAY INTO THE CWA FOR SNOW SHOWERS MONDAY NIGHT AND THEN A MIX OF RAIN AND SNOW SHOWERS FOR TUESDAY. THIS WILL COME TO AN END AS BOTH MODELS SHOW AN UPPER RIDGE BUILDING IN FROM THE WEST TUESDAY NIGHT INTO WEDNESDAY TO PUT AN END TO THE MIXED PRECIPITATION THROUGH THURSDAY MORNING. BY THURSDAY AFTERNOON ONE OF THOSE EARLIER MENTIONED SHORTWAVES ROTATING AROUND THE POLAR VORTEX AND MOVE SOUTHEAST WARD ACROSS SOUTHERN CANADA. THIS WILL DROP AN ARCTIC FRONT INTO THE NORTHEASTERN ZONES BY THURSDAY EVENING. AT THE SAME TIME AN UPPER LOW MOVES ONSHORE AND BRING PACIFIC MOISTURE TO NORTHERN MONTANA. THE UPPER LOW OVERRUNS THE ARCTIC FRONT WHICH WILL PRODUCE PRECIPITATION. AGAIN DEPENDING ON HOW MUCH OF THE ARCTIC AIR MASS MAKES IT INTO NEMONT WILL DETERMINE IF WE ARE DEALING WITH ALL SNOW OR A RAIN SNOW MIX. LEFT THE SOUTHERN ZONES WITH A RAIN SNOW MIX AND THE NORTHERN TO NORTHEAST ZONES AS ALL SNOW ON FRIDAY. RSMITH && .AVIATION... EXPECT VFR CONDITIONS TO PREVAIL THE REST OF TODAY THROUGH TONIGHT AT ALL TERMINALS. SCATTERED HIGH CIRROSTRATUS CLOUDS AROUND 20 KFT ARE LIKELY. THE WINDS WILL BE SOUTHWEST AT 10 TO 15 KTS TODAY AND THEN BACK SLIGHTLY TO THE SOUTH AT UNDER 10 KTS OVERNIGHT. GHICKS/RSMITH && .GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ WEATHER.GOV/GLASGOW