000 FXUS65 KTFX 220832 AFDTFX SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST NATIONAL WEATHER SERVICE GREAT FALLS MT2 215 AM MDT THU AUG 21 2003 .DISCUSSION... TODAY...SATELLITE IMAGERY DEPICTING ALL SORTS OF CLOUDINESS OVER THE WESTERN CONUS. SOUTHWEST FLOW WILL PUSH DEEP MOISTURE OVER THE GREAT BASIN INTO SOUTHWEST MONTANA TODAY. SOUTHERN STREAM OF JET WILL PUNCH INTO THE SOUTHERN ZONES THIS AFTERNOON. WHILE AIR MASS IS NOT TERRIBLY UNSTABLE...DYNAMICS AND INSTABILITY COMBINED WILL HAVE LITTLE TROUBLE WRINGING SOME MOISTURE FROM THE ATMOSPHERE. HIGHEST POPS ARE IN BEAVERHEAD COUNTY. POPS OVER THE PLAINS HAVE BEEN KEPT LOW...ESPECIALLY CLOSER TO THE ROCKIES...DUE TO A VERY DRY SURFACE LAYER. DEW POINTS GENERALLY IN THE 30S OVER THE PLAINS...WHILE NEAR 60 IN PARTS OF IDAHO. THIS WILL LEAD TO VERY HIGH CLOUD BASES OVER THE PLAINS IF ANYTHING DOES DEVELOP...SO STORMS WILL BE MOSTLY DRY. WHILE OVER THE SOUTHWEST STORMS WILL ALMOST CERTAINLY BE WET. SOME POSSIBILITY OF SEVERE WEATHER IN THE SOUTHWEST. AT THIS POINT I THINK SEVERE WEATHER WILL BE ISOLATED BASED ON A GENERAL LACK OF SUNSHINE TODAY. TONIGHT...PATTERN CHANGES LITTLE. CLOUD BASES WILL LOWER OVER THE PLAINS AS NIGHT PROGRESSES...HOWEVER DOWNSLOPE WINDS DEVELOP LATE IN THE EVENING. SO I AM NOT TOO THRILLED ABOUT PLAINS PRECIP CHANCES. LOW PRESSURE WILL MOVE EAST ACROSS THE HI-LINE IN THE EVENING DRAGGING A WEAK COLD FRONT THROUGH THE AREA. WINDOW OF OPPORTUNITY WILL BE IN THE EVENING FOR THE 3-4 HOURS THAT WINDS ARE NORTHWEST BEHIND THE FRONT. ONCE THE WINDS BACK TO THE SOUTHWEST SHORTLY BEFORE MIDNIGHT...SKIES WILL CONTAIN MAINLY VIRGA. THIS WILL BE THE START OF THE FIRST PROLONGED CHINOOK EVENT IN A WHILE. SATURDAY AND SATURDAY NIGHT...WINDS WILL BE GUSTY ON THE ROCKY MOUNTAIN FRONT RIGHT THROUGH SATURDAY EVENING. SO WILL CONTINUE THE THEME OF HAVING POPS IN THE SOUTHWEST AND ALONG THE CONTINENTAL DIVIDE AND GOING MAINLY DRY OVER THE PLAINS. MOISTURE AND INSTABILITY IN PLACE AGAIN SATURDAY AND SATURDAY NIGHT. SOME COLD AIR ADVECTION BEHIND THE WEAK FRONT FOR COOLER TEMPS. FIRE WEATHER WATCH WILL BE UPGRADED TO WARNING WITH HIGH CONFIDENCE OF WIND EVENT BEGINNING TONIGHT. POMEROY SUNDAY THROUGH MONDAY...MODELS CONTINUE TO SUGGEST THAT ANOTHER UPPER TROUGH WILL PROGRESS THROUGH THE STATE. THIS FEATURE WILL BE ACCOMPANIED BY A SURFACE FRONT THAT WILL TRIGGER SCATTERED CONVECTION AND INCREASE WINDS SUNDAY NIGHT FOR ANOTHER POSSIBLE FIRE WEATHER EVENT. DRY WEATHER IS FORECAST FOR MONDAY AND MODELS COOL THE AIRMASS AS NORTHWEST FLOW ALOFT SETS UP OVER THE STATE. WILL KEEP TEMPERATURES ABOVE GUIDANCE FOR NOW...BUT IF MODELS REMAIN CONSISTENT WITH THIS TREND MAY NEED TO DROP TEMPS 5 TO 10 DEGREES. TUESDAY THROUGH FRIDAY...MODELS DISAGREE ON SOLUTION IN THIS TIME FRAME. HAVE MADE ONLY COSMETIC CHANGES TO GOING FORECAST IN ORDER TO KEEP OUR GRIDS CONSISTENT WITH NEIGHBORING OFFICES. TREND IS FOR A SLOW WARMING TREND AND A DRY FORECAST. MPJ .CCF NUMBERS GTF EB 090/058 081/052 083 19130 BUUUB 048/077 046/080 050/083 052/084 051 10200000000 CTB EN 085/054 077/050 079 19-20 BBBBB 047/072 045/075 050/078 051/079 049 00200000000 HLN EB 091/058 085/054 084 19332 BUUUB 045/082 044/084 055/085 053/087 052 10000000000 BZN EB 090/054 084/050 084 19331 BUUUB 047/083 043/084 050/085 053/086 052 20000000000 WEY EB 082/045 078/042 080 19442 BUUUB 039/078 040/078 041/078 042/079 038 20000000000 DLN TB 087/056 086/053 085 19642 BUUUB 044/083 043/084 051/085 052/086 051 20000000000 HVR EB 092/060 086/054 084 19130 BBBBB 052/079 047/082 053/083 054/085 052 00300000000 LWT EB 090/056 082/053 082 19330 BUUUU 049/077 046/080 048/080 051/081 051 10300000000 .TFX...RED FLAG WARNING FOR ALL FIRE ZONES THIS AFTERNOON THROUGH SATURDAY. $$