719 FXUS65 KTFX 231726 AFDTFX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 1126 AM MDT THU JUL 23 2015 .DISCUSSION... TODAY...UPDATE TO ZONES NOT PLANNED...AN UPPER LEVEL LOW PRESSURE TROF WILL KEEP THE AIRMASS MOIST AND UNSETTLED ACROSS CENTRAL AND SOUTHERN PORTIONS OF THE CWA. COOLER AIR ASSOCIATED WITH THIS SYSTEM WILL KEEP TEMPERATURES MODERATE AND BELOW SEASONAL NORMALS. AFTERNOON THUNDERSTORM ACTIVITY WILL BE CONCENTRATED OVER EXTREME SOUTHWEST MONTANA. MAIN THREAT WILL BE LOCAL HEAVY RAIN ALTHOUGH STRONG WINDS AND SMALL HAIL ARE ALSO POSSIBLE. ZELZER && .AVIATION... UPDATED 1725Z. AN UPPER LEVEL LOW PRESSURE TROF WILL CROSS CENTRAL MONTANA TONIGHT. UNSTABLE CONDITIONS WILL CONTINUE ACROSS THE CENTRAL AND SOUTHERN PORTIONS OF THE REGION AND SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED MAINLY ACROSS SOUTHWEST MONTANA. THE AIRMASS WILL DRY OVERNIGHT WITH MOST PRECIPITATION ENDING DURING THE EVENING HOURS. LOCAL MVFR CONDITIONS ARE POSSIBLE NEAR SHOWERS AND THUNDERSTORMS. ELSEWHERE VFR CONDITIONS WILL PREVAIL THROUGH THE NEXT 24 HOURS. && .FIRE WEATHER... AFTERNOON HUMIDITY WILL LIKELY FALL TO NEAR OR JUST BELOW 20% TODAY ACROSS NW PORTIONS OF THE NORTH CENTRAL MT PLAINS WHERE A DRIER AIRMASS WILL REMAIN IN PLACE. AFTERNOON MIXING AND A SURFACE PRESSURE GRADIENT ACROSS THE NORTHERN ROCKIES WILL ALLOW BREEZY WINDS TO DEVELOP THIS AFTERNOON WITH WIND GUSTS OF 25-30MPH POSSIBLE ACROSS PORTIONS OF GLACIER COUNTY, CREATING A PERIOD OF CRITICAL FIRE WEATHER CONDITIONS ACROSS FIRE WEATHER ZONE 112. CENTRAL MT FIRE DISTRICTS SHOULD AGAIN SEE SHOWERS AND THUNDERSTORMS, SOME OF WHICH WILL PROVIDE WETTING RAINS BUT ALSO THE THREAT OF GUSTY AND ERRATIC WINDS. && .PREV DISCUSSION... /ISSUED 550 AM MDT THU JUL 23 2015/ TODAY THROUGH SATURDAY...AREA REMAINS BENEATH A SW FLOW ALOFT DOWNSTREAM OF AN UPPER LEVEL TROUGH MOVING ONTO THE WEST COAST TODAY. A SHORTWAVE AHEAD OF THE MAIN TROUGH LOCATED OVER SW MT THIS MORNING WILL LIFT NE TODAY. SHOWERS AND A FEW ISOLATED THUNDERSTORMS IN ASSOCIATION WITH THIS INITIAL WAVE WILL SPREAD NE ACROSS CENTRAL AND EASTERN PORTIONS OF NORTH CENTRAL MT THIS MORNING WITH MORE WIDESPREAD THUNDERSTORM DEVELOPMENT EXPECTED THIS AFTERNOON OVER SW MT, WHERE A BREAK IN CLOUD-COVER BEHIND THE INITIAL SHORTWAVE SHOULD ALLOW FOR BETTER SURFACE HEATING/DESTABILIZATION. A FEW STORMS OVER SW MT THIS AFTERNOON COULD PRODUCE STRONG WINDS AND SMALL HAIL. THE MAIN UPPER LEVEL TROUGH AXIS CONTINUES EAST TOWARDS THE NORTHERN ROCKIES TONIGHT AND WEAKENS AS IT CONTINUES EAST ACROSS THE STATE FRIDAY. FLOW ALOFT BECOMES MORE WESTERLY FRIDAY AND FRIDAY NIGHT BEFORE TUNING BACK TO THE SW ON SATURDAY AS ANOTHER UPPER TROUGH MOVES TOWARDS THE WEST COAST. SHOWERS AND THUNDERSTORMS WILL BE MAINLY LIMITED TO PORTIONS OF SW MT FRIDAY AND SATURDAY AS DRIER AIR FROM THE WEST MOVES INTO THE REGION. TEMPERATURES WILL REMAIN NEAR SEASONAL AVERAGES THROUGH SATURDAY. SATURDAY NIGHT THROUGH THURSDAY...MEDIUM RANGE MODELS CONTINUE TO BE IN GOOD AGREEMENT WITH THE LARGER FEATURES DURING THIS PERIOD, BUT THEY DIFFER A BIT WITH REGARDS TO TIMING OF PRECIPITATION WITH THIS NEXT SYSTEM. AN UPPER LEVEL TROUGH OF LOW PRESSURE WILL DEEPEN OVER THE PACIFIC COAST SATURDAY NIGHT INTO SUNDAY, AND THE RESULTING MOIST AND UNSTABLE SOUTHWESTERLY FLOW ALOFT WILL BRING AN INCREASING CHANCE OF SHOWERS AND THUNDERSTORMS TO WESTERN AND CENTRAL MONTANA. FOR THIS MODEL RUN, THE GFS AND ECMWF DIFFER SOMEWHAT ON WHEN THE HEAVIER BANDS OF SHOWERS AND THUNDERSTORMS WILL MOVE OVER THE AREA. ALSO, OVER THE LAST COUPLE OF RUNS, THE MODELS HAVE CHANGED WHERE THE MOST PERSISTENT PRECIPITATION WILL OCCUR. HAVE THEREFORE CONTINUED A BROADBRUSHED GOOD CHANCE OF ACTIVITY ACROSS THE AREA SUNDAY THROUGH SUNDAY NIGHT, AND WILL FINE TUNE THE TIMING AND LOCATION OF THE BEST ACTIVITY ONCE MODELS COME INTO BETTER AGREEMENT. REGARDLESS, THOUGH, SOME OF THE STRONGER STORMS WILL LIKELY PRODUCE BRIEF HEAVY RAIN, GUSTY WINDS, AND SMALL HAIL. AS THE TROUGH MOVES ACROSS MONTANA MONDAY INTO MONDAY NIGHT, IT WILL ALSO MOVE A STRONG PACIFIC COLD FRONT ACROSS THE AREA, WHICH WILL CAUSE WESTERLY WINDS TO INCREASE ACROSS THE AREA, ESPECIALLY OVER THE PLAINS OF CENTRAL MONTANA. AS THE FLOW ALOFT SHIFTS MORE NORTHWESTERLY WITH THE PASSAGE OF THE SYSTEM, NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES THROUGH SUNDAY NIGHT WILL DROP TO BETWEEN 15 AND 20 DEGREES BELOW NORMAL FOR MONDAY. MOST LOCATIONS WILL ONLY WARM INTO THE 60S ON MONDAY, WITH SOME MOUNTAIN LOCATIONS POSSIBLY NOT GETTING OUT OF THE 40S. AS THE SYSTEM EXITS THE AREA ON TUESDAY, TEMPERATURES WILL WARM BACK TO WITHIN 10 DEGREES OF NORMAL AND THE CHANCE FOR SHOWERS AND THUNDERSTORMS WILL DIMINISH FROM THE WEST. A BROAD UPPER LEVEL RIDGE OF HIGH PRESSURE WILL THEN MOVE INTO THE REGION FOR WEDNESDAY THROUGH THURSDAY, KEEPING THE AREA DRY WITH TEMPERATURES WARMING TO JUST ABOVE SEASONAL AVERAGES BY THURSDAY. COULSTON && .PRELIMINARY POINT TEMPS/POPS... GTF 78 54 84 55 / 50 20 10 10 CTB 79 49 79 52 / 10 10 0 0 HLN 78 56 86 57 / 60 30 20 10 BZN 78 52 84 52 / 60 40 20 10 WEY 70 41 72 40 / 60 40 20 20 DLN 76 50 81 50 / 60 40 20 10 HVR 82 54 88 54 / 30 20 0 0 LWT 78 54 83 54 / 70 30 20 10 && .TFX WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR MTZ112. && $$ WEATHER.GOV/GREATFALLS