Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 060304 CCA
AFDTFX

AREA FORECAST DISCUSSION...CORRECTED POPS
NATIONAL WEATHER SERVICE GREAT FALLS MT
900 PM MDT THU MAY 5 2016

.UPDATE...

900 PM MDT UPDATE...SHOWERS AND THUNDERSTORMS ARE SLOWER TO SPREAD
OUT ONTO THE PLAINS OF NORTH CENTRAL MONTANA THAN PREVIOUSLY
EXPECTED, BUT AM EXPECTING AT LEAST SCATTERED COVERAGE OF SHOWERS BY
MIDNIGHT. A FEW STORMS MAY STILL DEVELOP THIS EVENING OVER NORTH
CENTRAL MONTANA, BUT THE LOSS OF DAYTIME HEATING AND THE DEEPENING
OF THE COOLER AIRMASS WILL HINDER SIGNIFICANT DEVELOPMENT. THE
BETTER CHANCE FOR STRONGER STORMS WILL REMAIN ALONG THE CONTINENTAL
DIVIDE THROUGH MIDNIGHT, BASED UPON THE STRONG STORMS MOVING NORTH
ACROSS THE PART OF THE STATE WEST OF THE DIVIDE. THE DEEPENING
UPSLOPE FLOW WILL BRING MORE WIDESPREAD SHOWERS TO NORTH CENTRAL
MONTANA AFTER MIDNIGHT. HAVE ALSO TRIED TO FOCUS THE BEST CHANCE FOR
SHOWERS FROM EASTERN PONDERA AND EASTERN TETON COUNTIES EAST INTO
THE HAVRE AREA BASED UPON THE NEWEST SHORT TERM MODEL FORECASTS. THE
COLD FRONT HAS ALSO MOVED THROUGH THE REMAINDER OF NORTH CENTRAL
MONTANA AND PAST HELENA. THIS WILL CONTINUE THE GUSTY NORTHERLY
WINDS OVERNIGHT, BUT IT WILL DIMINISH THE CHANCE FOR OVERNIGHT
THUNDERSTORMS FOR MOST OF THE AREA, EXCEPT IN SOUTHWEST MONTANA
WHERE THE COLD FRONT WILL MOVE THROUGH OVERNIGHT. TEMPERATURES
APPEAR TO BE ON TRACK, SO HAVE LEFT THEM AS IS.
COULSTON

708 PM MDT UPDATE...MADE AN ADJUSTMENT TO THE CURRENT WIND FORECAST
FOR TONIGHT THROUGH FRIDAY. NORTH WINDS ARE BLOWING A BIT STRONGER
THAN PREVIOUSLY FORECAST, SO HAVE INCREASED THEM TO GIVE 25 TO 35
MPH WIND GUSTS. SOME GUSTS COULD BE STRONGER, ESPECIALLY WITH
THUNDERSTORMS. WILL DETERMINE LATER IF FURTHER FORECAST ADJUSTMENTS
ARE NEEDED.  COULSTON

&&

.AVIATION...
UPDATED 2330Z.
FRONTAL BOUNDARY DRAPED FROM KHVR TO JUST NW OF KGTF AND EXTENDING
WEST ACROSS WESTERN MT INTO CENTRAL ID THIS AFTERNOON WILL PUSH
SOUTH THROUGH CENTRAL MT THIS EVENING AND CONTINUE SOUTH THROUGH SW
MT OVERNIGHT. WINDS WILL SHIFT TO THE NORTH AND INCREASE SOME AS THE
FRONT PASSES WITH SHOWERS ALSO DEVELOPING ALONG AND N/W OF THE
FRONTAL BOUNDARY AS MOISTURE IN THE MID-UPPER LEVELS SPREADS NORTH
INTO THE REGION. SOME POTENTIAL FOR THUNDERSTORMS THIS EVENING
MAINLY NORTH AND WEST OF A LINE FROM KHLN TO KGTF TO KHVR. SHOWERS
WILL BECOME MORE WIDESPREAD LATER TONIGHT AS FLOW ALOFT BECOMES
EASTERLY. PERIOD OF MVFR/IFR CONDITIONS ARE LIKELY AT MOST TERMINALS
LATER TONIGHT ACROSS NORTH-CENTRAL AND CENTRAL MT AND LATE TONIGHT
THROUGH FRIDAY MORNING AT SW MT TERMINALS. SHOWERS WILL END FROM
NORTH TO SOUTH FRIDAY AFTERNOON. HOENISCH

&&

.PREV DISCUSSION...
/ISSUED 530 PM MDT THU MAY 5 2016/

TONIGHT THROUGH SATURDAY...WARM AND DRY CONDITIONS CONTINUE AHEAD
OF A CANADIAN COLD FRONT THAT IS SLOWLY PUSHING SOUTH. THE FRONT IS
CURRENTLY JUST SOUTH OF CUT BANK AND SHOULD MAKE IT TO GREAT FALLS
BY LATE AFTERNOON. NORTH WINDS BEHIND THE FRONT WILL ALSO BECOME
GUSTY AT TIMES. THE AIRMASS AHEAD OF THE FRONT WILL CONTINUE TO
DESTABILIZE AS LAPSE RATES STEEPEN AND CAPE VALUES CLIMB TO 400 TO
500 J/KG ALONG WITH BULK SHEAR VALUES OF 40 KTS. SCATTERED
THUNDERSTORMS ARE POSSIBLE LATE THIS AFTERNOON AND INTO THE EVENING.
SEVERE THUNDERSTORMS ARE NOT EXPECTED BUT SOME STORMS COULD BE
STRONG. CONVECTIVE ACTIVITY SHOULD DIMINISH BY LATE EVENING FOLLOWED
BY A PERIOD OF STRATIFORM RAIN OVERNIGHT. SCATTERED SHOWERS WILL BE
CONFINED TO MOSTLY CENTRAL AND SOUTHERN MONTANA FRIDAY AND THEN
JUST SOUTHERN MONTANA SATURDAY AS THE FRONT CONTINUES TO PUSH
FURTHER SOUTH. TEMPERATURES WILL BE NEAR SEASONAL AVERAGES FRIDAY
BUT WARM SOME 10 DEGREES ABOVE AVERAGE TO START THE WEEKEND.

SATURDAY NIGHT THROUGH THURSDAY...SOUTHWEST MONTANA WILL STILL BE
MOIST SATURDAY NIGHT AND UNDER THE INFLUENCE OF THE LOW PRESSURE TO
THE SOUTH. HOWEVER, THE NORTHERN ZONES WILL BE DRIER AND UNDERNEATH
WEAK HIGH PRESSURE ALOFT. THE CHANCE OF PRECIPITATION WILL INCREASE
OVER THE REGION SUNDAY AS THE TROF DIGS INTO THE PACIFIC NORTHWEST.
THE APPROACHING TROF WILL CAUSE THE AIRMASS TO BECOME QUITE UNSTABLE
SUNDAY AFTERNOON WITH SCATTERED SHOWERS AND THUNDERSTORMS. ALSO, AS
THIS TROF APPROACHES, AN ASSOCIATED COLD FRONT WILL CROSS THE
ROCKIES SUNDAY NIGHT AND BRING COOLER AIR INTO THE REGION. THE
AIRMASS WILL REMAIN VERY MOIST WITH PERIODS OF WIDESPREAD
PRECIPITATION UNDER THE INFLUENCE OF THIS TROF UNTIL DRYING SOMEWHAT
WEDNESDAY NIGHT AS THE TROF MOVES EAST. THE REGION WILL REMAIN
UNSETTLED, HOWEVER, AS A SHORTWAVE MOVING THROUGH THE NORTHWEST FLOW
ALOFT CROSSES THE ZONES. THIS WILL BRING ANOTHER PUSH OF COOLER
CANADIAN AIR INTO THE REGION AND SLOW DOWN ANY QUICK TEMPERATURE
RECOVERIES. TEMPERATURES WILL BE WELL ABOVE SEASONAL NORMALS SUNDAY
BUT COOL TO NEAR AND BELOW SEASONAL AVERAGES MONDAY THROUGH THE END
OF THE PERIOD. ZELZER

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  60  40  72 /  70  50  20  10
CTB  40  62  37  72 /  70  30   0   0
HLN  47  60  42  74 /  50  50  30  20
BZN  45  60  40  68 /  20  50  40  30
WEY  42  57  39  56 /  30  60  50  50
DLN  47  59  44  66 /  30  60  40  40
HVR  47  69  38  75 /  80  30   0   0
LWT  47  61  40  69 /  60  40  20  10

&&

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

$$

WEATHER.GOV/GREATFALLS



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