Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 301634
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1034 AM MDT SUN AUG 30 2015

.DISCUSSION...

AHEAD OF THE MAIN UPPER LEVEL TROUGH...NOW MOVING INTO WA/OR...A
LEAD SHORTWAVE IS JUST ABOUT TO MOVE OUT OF CENTRAL MONTANA. SHOWER
AND THUNDERSTORM ACTIVITY ASSOCIATED WITH THE LEAD WAVE WILL EXIT
EASTERN SECTIONS OF CENTRAL MONTANA BY 18Z. IN ITS WAKE...SKIES ARE
QUICKLY CLEARING FROM WEST TO EAST AT THIS TIME. WITH DAYTIME
HEATING...EXPECT THE ATMOSPHERE TO DESTABILIZE THIS AFTERNOON AHEAD
OF THE NEXT PACIFIC COLD FRONT WITH WEAK TO MODEST INSTABILITY
DEVELOPING. AT THE SAME TIME...THE APPROACHING UPPER LEVEL TROUGH
WILL PROVIDE MORE THAN SUFFICIENT WIND SHEAR ALOFT FOR STORM
ORGANIZATION. THINKING ISOLATED TO WIDELY SCATTERED SHOWERS AND
THUNDERSTORMS WILL DEVELOP EARLY TO MID-AFTERNOON AS THE FRONT
APPROACHES FROM THE WEST. HIGHEST COVERAGE OF STORMS IS EXPECTED
ACROSS CENTRAL MONTANA. STORMS EARLIER THIS MORNING WERE FAIRLY
EFFICIENT IN MIXING DOWN STRONGER WIND GUSTS WITH SEVERAL REPORTS OF
40-50 MPH ACCOMPANYING THE SHOWERS. BASED ON THIS AND THE ABOVE-
MENTIONED SHEAR/INSTABILITY...THE STRONGEST STORMS THIS AFTERNOON
COULD PRODUCE STRONG GUSTY WINDS IN EXCESS OF 55 MPH. OUTSIDE OF THE
THUNDERSTORM ACTIVITY...STRONG WINDS ARE STILL EXPECTED TO DEVELOP
ALONG AND JUST EAST OF THE NORTHERN ROCKY MOUNTAIN FRONT AREA THIS
AFTERNOON AND EVENING SO THE HIGH WIND WARNING STILL LOOKS GOOD.
MARTIN

&&

.AVIATION...
UPDATED 1146Z.

MOIST AND UNSTABLE SOUTHWEST FLOW ALOFT WILL CONTINUE TO BRING
SCATTERED SHOWERS AND THUNDERSTORMS TO THE FORECAST AREA THIS
MORNING. ANOTHER PACIFIC COLD FRONT WILL PUSH THROUGH THE STATE
TODAY WITH GUSTY WESTERLY WINDS DEVELOPING BEHIND THE FRONT. VFR
CONDITIONS ARE EXPECTED TO PREVAIL BUT AREAS IFR/MVFR VISIBILITIES
IN SMOKE REMAIN LIKELY THROUGH MONDAY MORNING. GUSTY WESTERLY WINDS
EXPECTED TO DISSIPATE BY 06Z MONDAY WITH SKIES CLEARING FROM WEST TO
EAST. MPJ

&&

.FIRE WEATHER...
COOLER TEMPERATURES AND HIGHER HUMIDITY VALUES ON SUNDAY WILL
PROVIDE A BRIEF BREAK IN CRITICAL FIRE WEATHER CONDITIONS BUT A
SECOND COLD FRONT IS FORECAST TO ARRIVE SUN AFTERNOON BRINGING
ANOTHER ROUND OF STRONG WINDS THAT WILL LAST THROUGH SUN EVENING
ESPECIALLY ACROSS FIRE WEATHER ZONE 112 WHERE A HIGH WIND WARNING
IS IN EFFECT FROM NOON UNTIL MIDNIGHT SUNDAY. WARANAUSKAS/SUK

&&

.PREV DISCUSSION...
/ISSUED 546 AM MDT SUN AUG 30 2015/
SUNDAY THROUGH TUESDAY...AN ACTIVE WEATHER PERIOD WILL CONTINUE
SUNDAY AS SECOND COLD FRONT WILL MOVE ACROSS THE AREA BRINGING
WIDESPREAD SHOWERS AND THUNDERSTORMS THROUGHOUT THE DAY.
ATMOSPHERIC MOISTURE REMAINS HIGH FOR THIS TIME OF THE YEAR AND
HEAVY RAIN CAN BE EXPECTED BRIEFLY WITH ANY STORM THAT DOES
DEVELOP. HOWEVER WINDS ALOFT ARE RATHER STRONG AND WILL QUICKLY
TRANSPORT STORMS ACROSS THE AREA AND WILL LIMIT THE AMOUNT OF
RAINFALL THAT CAN BE EXPECTED AT A PARTICULAR LOCATION.
TEMPERATURES WILL BE COOLER THAN SATURDAY AND CLOSE TO SEASONAL
AVERAGES. SMOKE HAS RETURNED TO THE MAJORITY OF THE AREA AFTER A
BRIEF RESPITE BEHIND THE FIRST COLD FRONT. SOME CLEARING MAY BE
POSSIBLE AFTER THE SECOND COLD FRONT ON SUNDAY...HOWEVER THE SMOKE
WILL LIKELY RETURN JUST AS QUICKLY AS IT DID ON SATURDAY.

ANOTHER CONCERN WITH THE FRONTAL PASSAGE WILL BE THE EXPECTED HIGH
WINDS ALONG THE NORTHERN ROCKY MOUNTAIN FRONT AND GLACIER COUNTY.
RH VALUES HAVE RECOVERED BEHIND THE COLD FRONT AND ARE NOT
EXPECTED TO DROP LOW ENOUGH TO NECESSITATE A RED FLAG WARNING.
HOWEVER SOME LOCATIONS MAY SEE NEAR CRITICAL FIRE WEATHER MAINLY
DUE TO THE STRONG GUSTY WINDS.

MONDAY AND TUESDAY LOOK TO HAVE LESS ACTIVE WEATHER WITH DRYING
CONDITIONS EXPECTED AND TEMPERATURES REMAINING SLIGHTLY BELOW TO
NEAR SEASONAL AVERAGES. BREEZY WINDS ARE EXPECTED CONTINUE TO
TRANSPORT SMOKE FROM FIRES IN IDAHO AND WESTERN MONTANA INTO THE
AREA AND LONG TERM REDUCTIONS IN VISIBILITY FROM SMOKE ARE
EXPECTED TO CONTINUE THROUGH THE FIRST PART OF THE WORK WEEK. SUK

TUESDAY NIGHT THROUGH SUNDAY...MEDIUM RANGE MODELS CONTINUE TO
TREND TOWARD COOLER AND WETTER CONDITIONS FOR WEDNESDAY NIGHT
THROUGH SATURDAY. MODELS ARE STILL KEEPING THE SOLUTION FOR TUESDAY
NIGHT INTO WEDNESDAY RELATIVELY UNCHANGED WITH SEASONABLE OR ABOVE
TEMPERATURES AND BREEZY CONDITIONS. HOWEVER, BY THURSDAY THE UPPER
LEVEL TROUGH ALONG THE WEST COAST OF CANADA MOVES INLAND ACROSS THE
PACIFIC NORTHWEST AND INTO THE NORTHERN ROCKY MOUNTAIN REGION. THIS
PATTERN LOOKS INCREASINGLY FAVORABLE FOR SCATTERED TO NUMEROUS RAIN
SHOWERS WITH HIGH TEMPERATURES LIKELY TO TOP OUT IN THE LOW TO MID
60S FOR THURSDAY, FRIDAY AND SATURDAY. MODEL SOLUTIONS DIFFER BY
SUNDAY WITH THE ECMWF KEEPING COOLER AND WETTER CONDITIONS IN PLACE
WHILE THE GFS TRENDS DRIER AND WARMER. HAVE LEANED TOWARD THE GFS
SOLUTION FOR NOW. MPJ

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  79  49  74  52 /  30  20  10  10
CTB  72  46  69  48 /  10  10  10  10
HLN  78  45  76  46 /  20  10   0   0
BZN  82  43  77  45 /  20  10   0   0
WEY  71  32  69  34 /  20   0   0   0
DLN  77  41  76  45 /  20   0   0   0
HVR  81  49  75  50 /  30  20   0  10
LWT  80  44  74  49 /  40  50   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
HIGH WIND WARNING UNTIL MIDNIGHT MDT TONIGHT FOR MTZ009-010.

&&

$$

WEATHER.GOV/GREATFALLS


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