Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 020946
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
346 AM MDT SAT MAY 2 2015

.DISCUSSION...
TODAY THRU MONDAY...A CANADIAN COOL FRONT WILL MOVE SOUTHWARD
THROUGH THE REGION TODAY. AS OF 3 AM...THE COOL FRONT WAS SOUTH OF
CUT BANK ALREADY...AND SHOULD MOVE THROUGH THE GREAT FALLS AREA BY
8 AM OR SO. THE MAIN EFFECTS FROM THIS FRONT WILL BE A WIND SHIFT
TO THE NORTHWEST...THEN EVENTUALLY TO THE NORTHEAST THIS EVENING.
THERE IS A SMALL CHANCE FOR A PASSING SHOWER/THUNDERSTORM OVER
FAR SOUTHWEST MONTANA LATER TODAY/THIS EVENING AS THE BOUNDARY
WORKS IT WAY SOUTH INTO A SLIGHTLY UNSTABLE AIRMASS. TEMPERATURES
WILL BE COOL TONIGHT...WITH OVERNIGHT LOWS JUST A BIT BELOW
FREEZING IN SOME AREAS. FOR SUNDAY...IT WILL BE A TOUCH
COOLER...WITH A CHANCE FOR MAINLY ISOLATED SHOWERS AGAIN OVER
SOUTHWEST MONTANA. ON MONDAY...THE FLOW ALOFT SHIFTS BACK TO THE
SOUTHWEST...ALLOWING WARMER AIR TO MOVE BACK INTO THE REGION. THE
AIRMASS WILL ALSO BECOME A BIT UNSTABLE...ESPECIALLY ALONG A LINE
FROM BOZEMAN TO LEWISTOWN. ISOLATED THUNDERSTORM ACTIVITY IS
POSSIBLE OVER PORTIONS OF SOUTHWEST/CENTRAL MT ON MONDAY...WITH
AFTERNOON HIGHS CLIMBING INTO THE 70S FOR MANY AREAS ON MONDAY.
BRUSDA

MONDAY NIGHT THROUGH SATURDAY...MEDIUM RANGE FORECAST MODELS ARE IN
MUCH BETTER AGREEMENT TONIGHT AS THE ECMWF HAS TRENDED TOWARD THE
GFS SOLUTION. MAIN CHALLENGE CONTINUES TO BE THE EVOLUTION OF AN
UPPER LEVEL LOW THAT STARTS OFF THE PERIOD ALONG THE SOUTHERN
BRITISH COLUMBIA COAST. MODELS ARE NOT IN COMPLETE AGREEMENT BUT
THEY BOTH MOVE THIS SYSTEM INLAND OVER THE PACIFIC NORTHWEST AND
THEN SOUTHWARD THROUGH CALIFORNIA BEFORE HOOKING EASTWARD INTO
NEVADA BY THE END OF THE WEEK. TUESDAY IS EXPECTED TO BE THE WARMEST
DAY OF THE WEEK WITH HIGH TEMPERATURES ABOUT 10 DEGREES ABOVE
SEASONAL AVERAGE. HIGH TEMPERATURES COOL OFF BY 10 TO 15 DEGREES
EACH DAY THROUGH THURSDAY WITH HIGHS ON THURSDAY TOPPING OUT IN THE
MID 40S TO MID 50S. SCATTERED SHOWERS AND A FEW THUNDERSTORMS WILL
BE CONFINED TO SOUTHWEST MONTANA MONDAY EVENING BUT WILL LIKELY
SPREAD ACROSS MUCH OF THE FORECAST AREA TUESDAY THROUGH THURSDAY.
THERE IS ALSO A POSSIBILITY THAT WIDESPREAD WETTING RAINS COULD
DEVELOP WEDNESDAY NIGHT AND THURSDAY BUT WILL HOLD OFF ON ADDING
THIS TO THE FORECAST AT THIS TIME AND WILL WAIT TO SEE WHAT MODELS
DO IN THE COMING 24 HOURS OR SO. MODELS SUGGEST THAT THE UPPER LOW
WILL WEAKEN INTO AN OPEN WAVE AND BEGIN TO LIFT TO THE NORTHEAST
KEEPING UNSETTLED CONDITIONS BUT NOT AS COOL CONDITIONS IN THE
FORECAST THROUGH NEXT WEEKEND. MPJ

&&

.AVIATION...
UPDATED 0530Z.
A WEAK CANADIAN COLD FRONT WILL SLIDE SOUTHWARD THRU THE REGION
TODAY. THE MAIN EFFECTS WILL BE A WIND SHIFT TO THE NORTHWEST THEN
TO THE NORTHEAST BEHIND THE FRONT. MID/HIGH LEVEL CLOUDS WILL RESIDE
OVER THE REGION THRU 01Z SUNDAY...THEN GRADUALLY DIMINISH AS DRIER
AIR MOVES IN ALOFT. AN ISOLATED SHOWER IS POSSIBLE MAINLY OVER THE
MOUNTAINS...AND MAINLY OVER FAR SOUTHWEST MT THIS AFTERNOON/EVENING.
BRUSDA

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  70  36  65  39 /  10  10  10  10
CTB  57  31  62  36 /  10  10  10  10
HLN  73  36  71  43 /  10  10  10  10
BZN  71  34  69  36 /  20  10  10  10
WEY  68  31  67  30 /  20  20  30  20
DLN  72  37  70  40 /  20  10  20  10
HVR  67  34  64  38 /  10  10  10  10
LWT  71  34  63  40 /  10  10  10  10

&&

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

&&

$$

WEATHER.GOV/GREATFALLS


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