244 FXUS65 KTFX 030153 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 753 PM MDT MON AUG 2 2010 .UPDATE...HAVE PUT OUT AN EARLY UPDATE TO IN ORDER TO INCREASE POPS ALONG EASTERN PORTIONS OF THE HI-LINE. RADAR IMAGERY IS SHOWING A LARGE AREA OF SHOWERS AND THUNDERSTORMS TRACKING EAST THROUGH TOOLE AND LIBERTY COUNTIES. HAVE INCREASED POPS AT HAVRE TO BE LIKELY THIS EVENING AS IT APPEARS THAT THIS PRECIPITATION WILL AFFECT HILL COUNTY OVER THE NEXT HOUR OR TWO. WILL POSSIBLY UPDATE AGAIN BEFORE 9:30 PM MDT IF WARRANTED. MPJ && .AVIATION... UPDATED 2355Z. SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO AFFECT THE WESTERN PORTIONS OF NORTH CENTRAL AND CENTRAL MONTANA THROUGH THE EVENING HOURS. OVERALL...VFR CONDITIONS WILL PREVAIL...BUT MVFR CONDITIONS CAN BE EXPECTED IN THUNDERSTORMS. A WEAK SURFACE WIND SHIFT IS MOVING SOUTHWARD THROUGH THE REGION AS WELL. EXPECT A GRADUAL SHIFT IN SURFACE WIND DIRECTION THIS EVENING TO THE NORTH...THEN TO THE NORTHEAST. STABLE AIR SHOULD MOVE INTO THE REGION BY 06Z TONIGHT...ENDING THE THUNDERSTORM ACTIVITY...HOWEVER...THE AIR MASS BECOMES UNSTABLE AFTER 20Z TUESDAY SOUTH OF A LINE FROM GREAT FALLS TO LEWISTOWN. THUS ANOTHER PERIOD OF THUNDERSTORMS IS POSSIBLE OVER MUCH OF SOUTHWEST AND CENTRAL MONTANA ON TUESDAY AFTERNOON...WITH MVFR CONDITIONS POSSIBLE IN/NEAR THUNDERSTORMS. BRUSDA && .PREV DISCUSSION... /ISSUED 555 PM MDT MON AUG 2 2010/ TONIGHT THROUGH WEDNESDAY...SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP ALONG THE ROCKY MOUNTAIN FRONT AND ADJACENT PLAINS AS A WEAK COOL FRONT MOVES THROUGH THE AREA. SOME STORMS MAY CONTAIN SMALL HAIL AND GUSTY WINDS. ADDITIONAL SHOWERS AND THUNDERSTORMS ARE EXPECTED ON TUESDAY AS THE FRONT SLOWLY MOVES SOUTHWARD INTO CENTRAL AND SOUTHWEST MONTANA...GUSTY WINDS AND SMALL HAIL ARE POSSIBLE ONCE AGAIN AND THUNDERSTORM ACTIVITY WILL BE MORE WIDESPREAD THAN ON MONDAY SO INCREASED POPS TO CHANCE WITH SLIGHT CHANCE OVER THE SOUTHWEST MONTANA VALLEYS. AN UPPER-LEVEL RIDGE WILL BUILD LATE TUESDAY NIGHT INTO WEDNESDAY SO DECREASED POPS FOR THIS TIME PERIOD WITH THE EXCEPTION OF THE HIGHER TERRAIN WHERE AN ISOLATED TERRAIN-INDUCED SHOWER OR THUNDERSTORM IS POSSIBLE. TEMPERATURES WILL BE SLIGHTLY BELOW AVERAGE FOR TUESDAY AND THEN NEAR AVERAGE FOR WEDNESDAY. MLS WEDNESDAY NIGHT THROUGH MONDAY NIGHT...MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT AGAIN THROUGH THE PERIOD. AN UPPER LEVEL TROUGH OF LOW PRESSURE WILL REMAIN ALONG THE PACIFIC NORTHWEST COAST WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. THE SOLUTION TONIGHT HAS THE TROUGH A BIT FARTHER WEST THAN LAST NIGHT...WHICH WOULD KEEP AN UPPER LEVEL RIDGE OF HIGH PRESSURE OVER MONTANA. THEREFORE...HAVE DECREASED THE CHANCE OF SHOWERS/THUNDERSTORMS FOR THIS TIMEFRAME AND WARMED TEMPERATURES TO 4 TO 8 DEGREES ABOVE NORMAL BY FRIDAY. ON FRIDAY...A SHORTWAVE TROUGH WILL EJECT FROM THE MAIN TROUGH AND BRING A SLIGHTLY BETTER CHANCE FOR SHOWERS/THUNDERSTORMS DURING THE AFTERNOON/EVENING HOURS. AN UPPER LOW PRESSURE AREA WILL THEN MOVE SOUTH OUT OF THE GULF OF ALASKA TO REINFORCE THE UPPER TROUGH ALONG THE PACIFIC NORTHWEST COAST OVER THE WEEKEND INTO THE EARLY PART OF NEXT WEEK. THIS WILL RESULT IN A WARM AND SOMEWHAT UNSTABLE WEST-SOUTHWEST FLOW ALOFT OVER THE TFX CWA. THE MAIN ENERGY AND ASSOCIATED MOISTURE THAT WILL MOVE THROUGH THIS FLOW ALOFT WILL MAINLY BRING ISOLATED/SCATTERED SHOWERS/THUNDERSTORMS TO THE MOUNTAINS OF WESTERN AND SOUTHWEST MONTANA WITH WESTERLY DOWNSLOPE WINDS OVER THE PLAINS. HOWEVER...SOME STORMS THAT GENERATE OVER THE SOUTHWEST MOUNTAINS MAY MOVE INTO CENTRAL MONTANA. DURING THIS TIME...TEMPERATURES WILL REMAIN AT LEAST A FEW DEGREES ABOVE NORMAL. COULSTON && .PRELIMINARY POINT TEMPS/POPS... GTF 52 78 50 81 / 20 30 30 10 CTB 50 71 47 76 / 20 40 30 10 HLN 53 82 52 84 / 10 20 20 10 BZN 51 87 50 89 / 20 20 20 10 WEY 37 79 38 82 / 10 20 20 10 DLN 49 81 46 82 / 10 20 20 10 HVR 53 78 50 82 / 70 30 30 10 LWT 53 76 49 76 / 20 40 30 10 && .TFX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ WEATHER.GOV/GREATFALLS