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