725 FXUS65 KTFX 042043 AFDTFX SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 245 PM MDT SUN MAY 4 2003 .SHORT TERM...ACTIVE WEATHER PATTERN TO PERSIST THROUGH MONDAY MORNING. LOW PRESSURE OVER THE WESTERN DAKOTAS WILL CONTINUE TO SLOWLY PUSH WEST OVERNIGHT. A DEFORMATION ZONE HAS SET UP OVER THE EASTERN PART OF THE FORECAST AREA AND WILL PERSIST THROUGH MUCH OF THE NIGHT. COOLER AIR CONTINUES TO FILTER INTO THE AREA AND BY 06Z 850MB TEMPS ARE BELOW ZERO. SNOW ALREADY FALLING AT ABOUT 4000 TO 4500 FEET AND EXPECT SNOW TO MAKE DOWN TO THE PLAINS AROUND SUNSET. EXPECT QUITE A BIT OF SNOW TO FALL BUT WITH THE WARM TEMPERATURES AND WARM GROUND GETTING HIGH ACCUMULATIONS WILL BE HARD. PLAN ON GOING WITH A WINTER WEATHER ADVISORY FOR HILL... FERGUS...BLAINE AND EASTERN CHOUTEAU COUNTIES. WILL CALL AROUND TO IF ANY SNOW IS ACCUMULATING YET...MAY HAVE TO GO WITH A WARNING IF WE FIND SIGNIFICANT TOTALS. PARTIAL CLEARING OVER SOUTHWEST MONTANA THIS AFTERNOON HAS LEAD TO SOME DESTABILIZATION OVER THE AREA. SHOWERS AND THUNDERSTORMS WILL CONTINUE TO INCREASE OVER THE REGION INTO THE EARLY EVENING. WIDESPREAD PRECIPITATION WILL DEVELOP THIS EVENING AS A SHORT WAVE TRACKS OVER THE AREA. CURRENTLY A LARGE TEMPERATURE-DEW POINT SPREAD EXIST AND ONCE THE PRECIPITATION STARTS TEMPERATURES WILL QUICKLY DROP TO NEAR FREEZING. WILL HAVE RAIN CHANGING TO SNOW OVERNIGHT EVEN AT THE VALLEY FLOOR. RIGHT NOW IT LOOKS LIKE SNOWFALL AMOUNTS JUST FALL SHORT OF ADVISORY CRITERIA. THINGS QUIET DOWN FOR MONDAY. SOME SNOW WILL LINGER INTO THE MORNING ACROSS THE FAR EASTERN ZONES. CAN EXPECT SOME SCATTERED AFTERNOON AND EVENING INSTABILITY SHOWERS DUE TO THE COLD AIR ALOFT AND A SHORT WAVE SLIDING OVER THE REGION. AN UPPER LEVEL LOW MOVES INTO NORTHWEST MONTANA TUESDAY AFTERNOON FOR ANOTHER ROUND OF SHOWERS. MODELS HINTING AT ANOTHER COLD PLUNGE ALONG EAST SLOPES LATE TUESDAY SO CANT RULE OUT THE CHANCE FOR SOME SNOW AROUND THE CUT BANK AREA AND GLACIER PARK TUESDAY NIGHT. MEIER .EXTENDED...WEDNESDAY THROUGH SUNDAY. EXPECT MORE UNSETTLED WEATHER WITH THE POTENTIAL FOR A SPRING STORM LATE NEXT WEEK INTO THE WEEKEND SOMEWHERE OVER THE PLAINS. UPPER TROUGH OVER THE PAC NW WILL SWING THROUGH THE AREA TUE/TUE NIGHT AND BE EAST OF AREA BY WEDNESDAY. BEST BET FOR DRY WEATHER APPEARS TO BE WED AS AREA WILL BE IN BETWEEN SYSTEMS. COULD SEE SOME CONVECTIVE ACTIVITY OVER SW MT THAT DAY. MODELS DIFFER ON TRACK OF NEXT UPPER LOW. GFS HAS BEEN GOING BACK AND FORTH BETWEEN A SOLUTION WITH A TRACK FROM THE PAC NW ACROSS MT TO ONE WITH A TRACK A LITTLE S OF MT. CMC IS THE FARTHEST S WHILE ECMWF IS FARTHEST N. LATEST GFS/UKMET FAVOR A TRACK S OF MT. HAVE RAISED POPS LATE IN THE WEEK INTO THE WEEKEND BUT STILL KEPT THEM IN THE CHANCE CATEGORY TO LINE UP WITH SURROUNDING OFFICES. WILL ALSO UNDERCUT GUIDANCE TEMPERATURES FOR SAT. MODELS SEEM TO BE POINTING TOWARDS DRIER CONDITIONS BY LATE IN THE WEEKEND SO WILL DROP POPS FOR SUN AND WARM TEMPERATURES. BLANK .CCF NUMBERS GTF EE 033/050 030/052 033 12732 BECRB 056/035 059/037 055/033 048/030 055 33123335551 CTB EE 030/045 029/045 028 12732 BECCB 052/032 055/035 051/028 046/026 050 33124434441 HLN EB 036/053 032/052 033 12632 BECCB 060/036 060/039 055/035 050/036 058 33224444441 BZN EB 032/052 028/052 028 12+32 BECOB 058/032 059/035 055/032 050/034 055 33223445551 WEY EB 027/040 017/040 020 12+42 BETSB 050/024 050/030 049/025 038/028 042 23333555551 DLN EB 032/048 026/048 028 12632 BECCB 055/030 057/035 053/031 045/033 049 33224555441 HVR OE 031/048 032/054 032 12+62 BECRB 058/035 063/038 057/036 052/033 057 32-22335551 LWT EE 030/048 029/051 030 12+42 BECOB 056/036 058/037 055/035 048/032 053 23122445551 .TFX...WINTER WEATHER ADVISORY TONIGHT FOR HILL...BLAINE...FERGUS AND CHOUTEAU COUNTIES. $$