Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 250255
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
855 PM MDT FRI JUL 24 2015

.DISCUSSION...
THE CURRENT FORECAST IS IN GOOD SHAPE AND THE ONLY CHANGE WAS TO
ADD A MENTION OF ISOLATED SHOWERS AND THUNDERSTORMS OVER MORE OF
CENTRAL MONTANA FOR THE REST OF THIS EVENING. THE FORECAST OF
SCATTERED SHOWERS AND THUNDERSTORMS FOR THIS EVENING OVER FAR
SOUTHWEST MONTANA STILL LOOKS GOOD. SOME GUIDANCE INDICATES THAT
ISOLATED SHOWERS COULD LINGER OVER CENTRAL MONTANA AFTER MIDNIGHT
BUT DO NOT HAVE ENOUGH CONFIDENCE THAT THIS WILL HAPPEN TO CHANGE
THE CURRENT DRY FORECAST. BLANK

&&

.AVIATION...
UPDATED 2350Z.

EXPECT VFR CONDITIONS. ISOLATED SHOWERS AND THUNDERSTORMS WILL
AFFECT CENTRAL AND SOUTHWEST MONTANA THIS EVENING AND AGAIN SATURDAY
AFTERNOON. OTHERWISE EXPECT MOSTLY CLEAR SKIES. GUSTY WESTERLY WINDS
OVER THE PLAINS WILL DIMINISH EARLY THIS EVENING THEN PICK UP AGAIN
SATURDAY AFTERNOON. BLANK

&&

.FIRE WEATHER...
HAVE CANCELLED THE RED FLAG WARNING FOR THIS FRIDAY EVENING AS
WINDS HAVE DIMINISHED. OVERNIGHT HUMIDITY RECOVERIES WILL BE
GOOD. WIND SPEEDS ARE NOT AS EXPECTED TO BE AS STRONG AS THEY WERE
ON FRIDAY BUT THEY WILL STILL BE GUSTY AND THEY MIGHT STILL BE
HIGH ENOUGH THAT COMBINED WITH MINIMUM HUMIDITIES NEAR TO BELOW 20
PCT RED FLAG CONDITIONS COULD BE MET ONCE AGAIN. WILL CONTINUE TO
CLOSELY MONITOR THE SITUATION OVERNIGHT.

&&

.PREV DISCUSSION...
/ISSUED 550 PM MDT FRI JUL 24 2015/

TONIGHT THROUGH SUNDAY...THE REGION IS UNDERNEATH A BROAD RIDGE WITH
NEARLY ZONAL FLOW ALOFT. THE PATTERN WILL GRADUALLY CHANGE AS A LOW
PRESSURE TROF OVER THE BRITISH COLUMBIA COAST WILL BRING COOLER,
MORE MOIST CONDITIONS THE THE LOCAL BY THE END OF THE WEEKEND. VERY
WEAK INSTABILITY WILL ONCE AGAIN DEVELOP SATURDAY ACROSS THE
SOUTHWEST ZONES AND NORTHEASTWARD TOWARDS FERGUS COUNTY. HOWEVER,
THE AIRMASS WILL BE QUITE DRY AND CONVECTION SHOULD GENERALLY REMAIN
ISOLATED. BREEZY AND GUSTY SURFACE WINDS ACROSS THE PLAINS WILL
CAUSE CRITICAL FIRE WEATHER CONDITIONS INTO THE EARLY EVENING. THE
LOW PRESSURE TROF WILL MOVE ACROSS THE WEST COAST SATURDAY. THE
APPROACH OF THIS UPPER LEVEL TROF WILL BEGIN TO LOWER HEIGHTS ALOFT
SUNDAY AS WELL AS BRING AN INCREASE OF MOISTURE INTO THE AREA.
INSTABILITY WILL DEVELOP FARTHER NORTH, SPREADING INTO THE CENTRAL
ZONES, AND SHOWER AND THUNDERSTORM ACTIVITY WILL BE MORE WIDESPREAD.
TEMPERATURES WILL REMAIN ABOVE SEASONAL NORMALS SATURDAY BUT BEGIN
TO TREND LOWER FROM THE NORTHWEST BY SUNDAY. ZELZER

SUNDAY NIGHT THROUGH FRIDAY...MEDIUM RANGE MODELS IN FAIRLY DECENT
AGREEMENT TO START THE PERIOD. THE PERIOD STARTS WITH AN UPPER TROF
DIGGING ALONG THE WEST COAST. SHORT WAVE ENERGY THAT IS EJECTED FROM
THE BASE OF THE TROF MOVES INTO SOUTHWEST MONTANA EMBEDDED WITHIN
THE SOUTHWEST FLOW ALOFT. SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS
NORTH CENTRAL AND NORTHERN MONTANA OVERNIGHT SUNDAY AND INTO MONDAY
MORNING. THE UPPER TROF CROSSES THE CONTINENTAL DIVIDE MONDAY
AFTERNOON. THE BEST CHANCE FOR WIDESPREAD SHOWER AND ISOLATED
THUNDERSTORM ACTIVITY WILL BE MONDAY AFTERNOON THROUGH MONDAY
EVENING. HOWEVER, THE FORECAST MODELS ARE A BIT SLOWER WITH THE
PROGRESSION OF THE TROF, SO HAVE KEPT A GOOD CHANCE FOR SHOWERS AND
ISOLATED THUNDERSTORMS THROUGH MONDAY NIGHT AS WELL. A PACIFIC COLD
FRONT WILL MOVE ACROSS THE AREA ON MONDAY WITH GUSTY WEST TO
NORTHWEST WINDS ACCOMPANYING THE FRONTAL PASSAGE ALONG WITH MUCH
COOLER TEMPERATURES. IN FACT, SOME LIGHT ACCUMULATING SNOW MAY FALL
ABOVE 8500 FEET IN THE MOUNTAINS MONDAY NIGHT. BY TUESDAY EVENING,
THE TROF WILL HAVE MOVED TO EASTERN MONTANA, BRINGING AN END TO THE
PRECIPITATION FROM WEST TO EAST. RISING 500MB HEIGHTS WEDNESDAY AND
THURSDAY WILL ALLOW DRIER AND WARMER CONDITIONS TO RETURN. THE
MODELS DIVERGE WITH THEIR SOLUTIONS FOR THE END OF THE PERIOD. THE
GFS MAINTAINS GENERALLY DRY WESTERLY FLOW OVER THE AREA WITH A WEAK
UPPER TROF MOVING ALONG THE INTERNATIONAL BORDER. AT THE SAME TIME,
THE ECMWF MODEL MAINTAINS AN UPPER RIDGE OVER THE AREA. EITHER WAY,
DRY CONDITIONS SHOULD CONTINUE FRIDAY. TEMPERATURES WILL GENERALLY
BE 20 DEGREES BELOW SEASONAL AVERAGES MONDAY BUT WILL BEGIN A
WARMING TREND TUESDAY. AFTERNOON READINGS WILL BE NEAR TO SLIGHTLY
BELOW SEASONAL AVERAGES WEDNESDAY THROUGH FRIDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  56  84  56  77 /   0  10  30  40
CTB  53  79  51  72 /   0  10  10  40
HLN  57  85  57  81 /  10  20  20  30
BZN  54  85  52  87 /  20  20  10  20
WEY  42  74  42  76 /  40  20  10  20
DLN  51  82  51  83 /  20  10  10  20
HVR  56  89  57  82 /   0  10  30  20
LWT  55  86  53  82 /  20  20  20  30

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

WEATHER.GOV/GREATFALLS



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