Area Forecast Discussion
Issued by NWS Great Falls, MT

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000
FXUS65 KTFX 011835
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1235 PM MDT FRI MAY 1 2015

UPDATED AVIATION SECTION

.DISCUSSION... UPDATE FORTHCOMING. HAVE INCREASED CLOUD COVER OVER
NORTHERN PORTION OF COUNTY WARNING AREA DUE TO PRESENCE OF BROAD
CHINOOK ARCH. SAID ARCH MAY IMPACT AFTERNOON HEATING BUT HOURLY
TRENDS CONTINUE ON TRACK TO BE NEAR OR REACH FORECAST HIGHS SO WILL
NOT MAKE ANY CHANGES. MODELS CONTINUE TO INDICATE INCREASING WINDS
THIS AFTERNOON. WILL LEAVE HIGH WIND WARNING IN PLACE IN
ANTICIPATION OF THOSE WINDS EVEN THOUGH SPEEDS ALONG THE NORTHERN
ROCKY MOUNTAIN FRONT ARE LOW AT THIS TIME.

&&

.AVIATION...
UPDATED 1835Z.
STRONG WESTERLY FLOW ALOFT CONTINUES. ENOUGH MOISTURE
WITHIN THE FLOW TO PRODUCE A CHINOOK ARCH IN THE LEE OF THE ROCKIES.
SURFACE WINDS WILL BECOME GUSTY WITH THE STRONGEST GUSTS ALONG THE
THE SLOPES OF THE NORTHERN ROCKY MOUNTAIN FRONT. WINDS OVER THE
PLAINS WILL GRADUALLY DECREASE AFTER 02Z. VFR CONDITIONS PREVAIL.

&&

.PREV DISCUSSION...ISSUED 355 AM MDT FRI MAY 1 2015

TODAY THRU SUNDAY...EXPECT A BRISK WESTERLY FLOW ALOFT TO RESIDE
OVER THE REGION TODAY. AS A RESULT...WIND SPEEDS WILL BE NEAR HIGH
WIND WARNING CRITERIA AT TIMES OVER THE NORTHERN ROCKY MOUNTAIN
FRONT. EAST GLACIER PARK REPORTED A WIND GUST TO 60 MPH THIS
MORNING ALREADY. THUS A HIGH WIND WARNING IS IN EFFECT FOR THIS
REGION UNTIL 4 AM SATURDAY. ELSEWHERE IT WILL BE BREEZY BUT MILD
TODAY...WITH AFTERNOON HIGHS MOSTLY IN THE 70S. WINDS BEGIN TO
DIMINISH TONIGHT OVER THE REGION...AS A WEAK CANADIAN COLD FRONT
BEGINS TO PUSH SOUTHWARD TOWARDS NORTH CENTRAL MT. THIS COLD FRONT
WILL MOVE SOUTHWARD THRU THE REGION ON SATURDAY. SOME COOLER
TEMPERATURES AND A WIND SHIFT TO THE NORTH WILL OCCUR BEHIND THE
COLD FRONT. THERE IS A SMALL CHANCE FOR PRECIP SATURDAY AFTERNOON
THRU SUNDAY...WITH THE BEST CHANCE FOR PRECIP MAINLY IN THE WEST
YELLOWSTONE AREA ON SUNDAY. AFTERNOON HIGHS ON SUNDAY WILL BE
ABOUT 4 TO 8 DEGREES COOLER IN MANY AREAS WHEN COMPARED TO
SATURDAY. BRUSDA

SUNDAY NIGHT THROUGH FRIDAY...FORECAST MODELS START OFF THE MEDIUM
RANGE PERIOD IN GOOD AGREEMENT BUT DIVERGE SIGNIFICANTLY BY TUESDAY
EVENING. MAIN PROBLEM IN THE FORECAST CONTINUES TO BE THE EVOLUTION
OF AN UPPER LEVEL LOW THAT STARTS OFF THE PERIOD IN THE GULF OF
ALASKA. MODELS DIFFER SIGNIFICANTLY IN THE STRENGTH AND LOCATION OF
THIS FEATURE WITH THE GFS CLOSING OFF A SIGNIFICANT LOW PRESSURE
SYSTEM OVER THE PACIFIC NORTHWEST AT 00Z WEDNESDAY WHILE THE ECMWF
CLOSES OFF A WEAK UPPER LOW IN CENTRAL BRITISH COLUMBIA AND KEEP AN
OPEN WAVE OVER THE PACIFIC NORTHWEST. AS THE WEEK PROGRESSES MODEL
SOLUTIONS TREND EVEN FURTHER APART AS THE GFS MOVES THE CLOSED LOW
SOUTH TO THE CENTRAL CALIFORNIA/NEVADA BORDER REGION AND THE ECMWF
PROGRESSES THE OPEN WAVE EASTWARD THROUGH THE NORTHERN ROCKY
MOUNTAINS. BOTH MODELS INDICATE THAT PRECIPITATION WILL BE SPREAD
INTO MONTANA BUT THE DIFFERENCES IN AMOUNTS/TIMING AND LOCATIONS
CONTINUE TO CREATE A VERY LOW CONFIDENCE FORECAST FOR THE REMAINDER
OF NEXT WEEK. HAVE MADE MAINLY MINOR CHANGES TO THE GOING FORECAST
KEEPING COOL TEMPERATURES AND ISOLATED TO SCATTERED PRECIPITATION AS
THE DOMINANT WEATHER FOR WEDNESDAY THROUGH FRIDAY. IF AND WHEN
MODELS BEGIN TO AGREE ON A SOLUTION I ANTICIPATE THAT MAJOR CHANGES
COULD BE MADE TO THE FORECAST IN ORDER TO CATCH UP WITH WHATEVER
TREND APPEARS MOST LIKELY. MPJ

&&

.FIRE WEATHER...
EXPECT A BRISK WESTERLY WIND OVER MUCH OF THE REGION TODAY...WITH
THE STRONGEST WINDS EXPECTED IN THE CUT BANK AREA. WITH SURFACE
CONDITIONS STARTING TO GREEN UP...I WILL HOLD OFF ON A FIRE
WEATHER HIGHLIGHT FOR NOW...BUT CONTINUE TO MONITOR IT CLOSELY
THROUGH THE DAY. FOR SATURDAY AND SUNDAY...COOLER
TEMPERATURES...LIGHTER WINDS AND SLIGHTLY HIGHER HUMIDITIES
SHOULD DECREASE THE FIRE THREAT A BIT. BRUSDA

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  75  45  68  34 /   0   0  10  10
CTB  70  36  60  29 /   0   0  10  20
HLN  75  43  72  36 /   0   0  10  10
BZN  73  39  72  36 /   0   0  10  10
WEY  66  29  68  29 /   0   0  10  20
DLN  73  41  73  38 /   0   0  10  10
HVR  77  40  66  32 /   0   0  10  10
LWT  74  45  71  34 /   0   0  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL 4 AM MDT SATURDAY FOR MTZ009.

&&

$$

WEATHER.GOV/GREATFALLS


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