Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 021626
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1026 AM MDT SAT MAY 2 2015

.DISCUSSION... UPDATE FORTHCOMING. HAVE MAINLY ADJUSTED SKY GRIDS TO
BETTER REFLECT CURRENT CONDITIONS. COLD FRONT HAS MOVED SOUTH OUT OF
CANADA THIS MORNING AND IS MOVING SOUTH ALONG THE FRONT RANGE AT
THIS TIME. SURFACE OBSERVATIONS INDICATE THE FRONT HAS PUSHED
THROUGH CHOTEAU. WINDS SHIFT TO THE NORTHWEST AND THEN NORTH AS THE
FRONT MOVES THROUGH. VERY LITTLE MOISTURE IS ASSOCIATED WITH THE
FRONT AND THAT IS SEEN IN THE 12Z GREAT FALLS SOUNDING WHICH CLEARLY
SHOWS A VERY DRY LOWER ATMOSPHERE. SOME ISOLATED CONVECTIVE ACTIVITY
IS POSSIBLE LATER THIS AFTERNOON OVER SOUTHWEST MONTANA WHERE THE
AIRMASS IS A BIT MORE UNSTABLE.

&&

.AVIATION...
UPDATED 1135Z.
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. SCATTERED TO
BROKEN MID AND HIGH LEVEL CLOUDS WILL PREVAIL OVER THE REGION WITH
WIDESPREAD VFR CONDITIONS ANTICIPATED THROUGH SUNDAY MORNING. AN
ISOLATED SHOWER IS POSSIBLE OVER THE MOUNTAINS THIS
AFTERNOON/EVENING. MPJ

&&

.PREV DISCUSSION...ISSUED 346 AM MDT SAT MAY 2 2015

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

&&

.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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