Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 051640
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1040 AM MDT TUE MAY 5 2015

.UPDATE...
NO SIGNIFICANT UPDATE TO THE FORECAST THIS MORNING. SLIGHTLY
TWEAKED CLOUD COVER AND WINDS AHEAD OF THE FRONTAL PASSAGE OVER
CENTRAL MONTANA THIS AFTERNOON AND EVENING. OTHERWISE FORECAST
APPEARS ON TRACK. SUK


&&

.AVIATION...
UPDATED 1148Z.
UPPER LEVEL TROUGH OVER PACIFIC NORTHWEST WITH INCREASINGLY MOIST
AND UNSTABLE SOUTHWEST FLOW ALOFT OVER MONTANA. A FEW WEAK CELLS
WILL BRING VIRGA AND VARIABLY GUSTY WINDS TO NORTH CENTRAL MONTANA
THIS MORNING. BY 21Z SCATTERED SHOWERS AND THUNDERSTORMS DEVELOP
OVER SOUTHWEST MONTANA. PRECIPITATION COVERAGE INCREASES BECOMING
NUMEROUS TO WIDESPREAD FROM SOUTHWEST MONTANA THROUGH EASTERN
PORTIONS OF NORTH CENTRAL MONTANA AFTER 00Z. VFR CONDITIONS PREVAIL
BUT MVFR CONDITIONS POSSIBLE IN HEAVY RAIN THROUGH 06Z. AREAS OF
LIGHT RAIN WITH MVFR CONDITIONS COULD LINGER THROUGH 12Z WEDNESDAY
NEAR KLWT TERMINAL. MPJ

&&

.PREV DISCUSSION...
/ISSUED 548 AM MDT TUE MAY 5 2015/
TODAY THROUGH THURSDAY...A FEW SHOWERS WILL DRIFT NORTHEASTWARD
THRU NORTH CENTRAL MT THIS MORNING...BUT DOWNSLOPE WINDS WILL
LIMIT PRECIP INTENSITY. HOWEVER...A PACIFIC COOL FRONT WILL
APPROACH THE REGION THIS AFTERNOON...AND GENERALLY MOVE THROUGH
THE AREA EARLY THIS EVENING. EXPECT WIDESPREAD SHOWERS AND
THUNDERSTORMS TO DEVELOP AHEAD/ALONG THE COOL FRONT. SOME STORMS
COULD PRODUCE BRIEF HEAVY RAINS/GUSTY WINDS/FREQUENT LIGHTNING.
THIS PRECIP THIS EVENING WILL BE THE BEST CHANCE FOR PRECIPITATION
OVER NORTH CENTRAL MT FOR THE NEXT FEW DAYS...AS PRECIPITATION
CHANCES HAVE BEEN REDUCED OVER THE NORTH FOR WED/THU. THE REASON
IS THE UPPER LEVEL LOW CONTINUES TO DIG FURTHER SOUTH...KEEPING
ANY PRECIPITATION CHANCES MAINLY SOUTH OVER SOUTHWEST MT FOR
WED/THU. THUS RAIN CHANCES REDEVELOP LATE WEDNESDAY INTO THURSDAY
OVER SOUTHWEST MONTANA...BUT THE MAJORITY OF THE PRECIP ACTIVITY
WILL STAY SOUTH OF THE I-90 CORRIDOR FOR WED/THU. TEMPERATURES
WILL BE MILD TODAY BUT COOL TO BELOW NORMAL READINGS FOR WED/THU.
ADDITIONALLY OVERNIGHT LOWS WILL FALL TO NEAR/BELOW FREEZING IN
MANY AREAS LATER THIS WEEK. BRUSDA

THURSDAY NIGHT THROUGH TUESDAY...FORECAST MODELS CONTINUE TO SHOW A
LOT OF VARIABILITY AND REMAIN RATHER UNHELPFUL DURING THE MEDIUM
RANGE TIME FRAME. LATEST RUNS START OFF THE PERIOD SHOWING SPLIT
FLOW ALOFT WITH A CLOSED LOW ALONG THE CENTRAL CALIFORNIA COAST AND
AN OPEN WAVE EXTENDING NORTH-NORTHEASTWARD THROUGH MONTANA. MAIN
ENERGY WITH THIS OPEN WAVE REMAINS IN CENTRAL CANADA SO THAT ONLY A
SLIGHT CHANCE TO CHANCE FOR SHOWERS CAN BE EXPECTED IN MONTANA WITH
THE BEST CHANCES EXPECTED IN SOUTHWEST PORTIONS OF THE STATE. IT
SHOULD ALSO BE NOTED THAT CONFIDENCE IN THIS FORECAST REMAINS
EXTREMELY LOW. MODELS ARE CURRENTLY SUGGESTING THAT THE CLOSED LOW
OVER CALIFORNIA WILL SWEEP ACROSS THE FOUR CORNERS REGION BY
SATURDAY BUT DIVERGE IN THEIR SOLUTIONS FOR THE REMAINDER OF THE
FORECAST PERIOD. HAVE OPTED TO TREND THE FORECAST TOWARD
CLIMATOLOGICAL HIGHS AND LOWS WHILE KEEPING POPS GENERALLY BELOW
CLIMATOLOGY. MPJ

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  75  40  58  33 /  20  60  10  10
CTB  69  33  55  28 /  20  30  10  10
HLN  74  39  62  37 /  50  60  10  10
BZN  72  40  61  38 /  60  60  20  30
WEY  66  32  59  31 /  50  40  40  40
DLN  71  40  61  39 /  60  40  30  30
HVR  79  43  61  31 /  20  60  10  10
LWT  75  43  58  32 /  20  60  10  10

&&

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

$$

WEATHER.GOV/GREATFALLS


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