Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 292123
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
323 PM MDT SAT AUG 29 2015

.DISCUSSION...

TONIGHT THROUGH SUNDAY...SCATTERED THUNDERSTORMS WILL CONTINUE TO
DEVELOP OVER SOUTHWEST MONTANA AND MOVE TOWARD THE NORTHEAST.
RAPID CELL MOTION WILL LIMIT ANY RAINFALL...BUT A FEW OF THESE
STORMS COULD PRODUCE DAMAGING WIND GUSTS DUE TO STEEP LOW LEVEL
LAPSE RATES AND INCREASING MID LEVEL WINDS. THE ADVERTISED COLD
FRONT IS PRESENTLY LOCATED FROM NORTHERN ID TO NORTHEAST OR.
PRESSURE FALLS EAST OF THE CONTINENTAL DIVIDE ARE CRANKING UP THE
WINDS AS EXPECTED OVER PORTIONS OF NORTH CENTRAL MT. THE RED FLAG
WARNING REMAINS IN EFFECT THROUGH THIS EVENING FOR LOW HUMIDITY
AND STRONG WINDS. VISIBILITY HAS IMPROVED IN SOME AREAS AS WIND
BEGINS TO MIX OUT THE SMOKE. THE PASSING COLD FRONT THIS EVENING
SHOULD ALLOW A PERIOD OF RELIEF FROM SMOKE FOR MOST AREAS...BUT
CONFIDENCE IS LOW AS TO HOW QUICKLY THE SMOKE WOULD RETURN. COOLER
AND MORE HUMID CONDITIONS ARRIVE FOR SUNDAY WITH TEMPERATURES
FINALLY RETURNING TO NEAR SEASONAL AVERAGES. ATTENTION THEN TURNS
TO ANOTHER PACIFIC FRONT CROSSING THE NORTHERN ROCKIES SUNDAY
EVENING. STRONG SUBSIDENCE BEHIND ITS ASSOCIATED UPPER TROUGH
COULD GENERATE HIGH WINDS ALONG THE NORTHERN ROCKY MOUNTAIN FRONT
AND ADJACENT PLAINS. A HIGH WIND WATCH IS POSTED TO COVER THE
HAZARD WITH MODERATE CONFIDENCE. ALTHOUGH HUMIDITY WILL BE ABOVE
CRITICAL FIRE WEATHER CRITERIA...CONTINUED STRONG WINDS COULD HELP
MAINTAIN EXTREME BEHAVIOR ON EXISTING FIRES IN THE AREA WITH THE
ABSENCE OF WETTING RAINFALL. PN

MONDAY NIGHT THROUGH SATURDAY...MODELS CONTINUE TO SHOW THAT THE
MAIN INFLUENCE ON MONTANA WEATHER DURING THE MEDIUM RANGE PERIOD
WILL BE AN UPPER LEVEL TROUGH THAT STARTS OFF THE PERIOD OVER
CANADA`S WEST COAST. DIFFERENCE TONIGHT IS THAT BOTH THE ECMWF AND
THE GFS HAVE EVOLVED THEIR SOLUTIONS OVER THE LAST 24 HOURS TO
SUGGEST THAT THIS FEATURE WILL DEEPEN OVER THE PACIFIC NORTHWEST AND
PROGRESS INLAND AS FAR AS THE NORTHERN ROCKIES. AS A RESULT, BOTH
MODELS ARE NOW TRENDING TO A COOLER AND SOMEWHAT WETTER SOLUTION FOR
WEDNESDAY NIGHT THROUGH SATURDAY. THIS NEW SOLUTION DEVELOPED WITH
THE FRIDAY 12Z MODEL RUN AND CONTINUES TO APPEAR TONIGHT. WHILE
CONFIDENCE IN THIS EVOLUTION IS NOT ABSOLUTE, IT IS ENCOURAGING THAT
BOTH MODELS HAVE TRENDED THIS WAY. CURRENT FORECAST PACKAGE KEEPS
TUESDAY/WEDNESDAY TIME FRAME SIMILAR TO WHAT HAS BEEN FORECAST FOR
SEVERAL DAYS NOW. FOR THURSDAY AND BEYOND, I HAVE TAKEN THE FIRST
STEPS TO BEGIN INCREASING POPS AND COOLING TEMPERATURES TOWARD THIS
NEW SOLUTION. HAVE ALSO OPTED TO REMOVE MENTION OF SMOKE FOR
THURSDAY AND BEYOND. WHILE THIS MODEL TREND STILL DOES NOT INDICATE
A SEASON-ENDING EVENT FOR WESTERN WILDFIRES, IT WOULD APPEAR THAT
SOME RAIN AND A MORE NORTHERLY WIND DIRECTION SHOULD REDUCE SMOKE
COVERAGE. MPJ

&&

.AVIATION...
UPDATED 1755Z.

EXPECT WIDESPREAD MVFR VISIBILITIES IN SMOKE WITH IFR
VISIBILITIES/MVFR CEILINGS CLOSE TO WILDFIRES. A COLD FRONT WILL
SWEEP THROUGH THE AREA LATE THIS AFTERNOON AND COULD BRING SOME
IMPROVEMENT IN VISIBILITIES BUT CONFIDENCE IN WHAT WILL HAPPEN WITH
VISIBILITIES AFTER THE PASSAGE OF A COLD FRONT IS LOW. SPEAKING OF
THE COLD FRONT IT IS EXPECTED TO REACH KCTB BY 00Z...KGTF/KHLN
AROUND 03Z...AND KHVR/KLWT/KBZN AROUND 06Z. GUSTY SOUTHERLY WINDS
WILL DEVELOP IN ADVANCE OF THE FRONT AND WINDS SHOULD DIMINISH AFTER
THE PASSAGE OF THE FRONT. CONFIDENCE IN WIND DIRECTIONS AFTER THE
PASSAGE OF THE FRONT IS LOW. CONFIDENCE IS HIGHER THAT GUSTY
SOUTHWEST WINDS WILL DEVELOP OVER THE PLAINS NEAR THE END OF THE
PERIOD AT 18Z SUNDAY. EXPECT A FEW SHOWERS AND THUNDERSTORMS THIS
AFTERNOON INTO THIS EVENING. GUSTY WINDS TO NEAR 40 KTS WILL BE A
RISK WITH THUNDERSTORMS MAINLY OVER SOUTHWEST MONTANA LATE THIS
AFTERNOON AND EARLY EVENING. LATE TONIGHT INTO SUNDAY MORNING A BAND
OF SHOWERS IS EXPECTED TO MOVE EAST THROUGH THE AREA AND CAN NOT
RULE OUT AN ISOLATED THUNDERSTORM. OTHER THAN THE MVFR/IFR
CONDITIONS WITH SMOKE CONDITIONS WILL BE VFR. BLANK

&&

.FIRE WEATHER...RED FLAG WARNING REMAINS IN EFFECT UNTIL 9 PM
TONIGHT.  PACIFIC COLD FRONT STILL EXPECTED TO CROSS THE CONTINENTAL
DIVIDE BY EARLY THIS EVENING AND SWEEP THROUGH CENTRAL/SOUTHWEST MT
BY MIDNIGHT. GUSTY SOUTHWEST WINDS AHEAD OF THE FRONT WILL TURN TO
WEST-NORTHWEST AFTER FRONTAL PASSAGE WITH WIND GUSTS OF 25 TO 35 MPH
LIKELY THROUGH MID-LATE EVENING. THOUGH A FEW SHOWERS AND
THUNDERSTORMS MAY PRECEDE THE FRONT, THEIR COVERAGE WILL BE SPOTTY
AND RAINFALL AMOUNTS GENERALLY 0.05 INCH OR LESS. 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. WARANAUSKAS

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  61  78  49  74 /  20  30  20   0
CTB  54  72  46  69 /  20  20  10  10
HLN  56  78  44  75 /  20  20  10   0
BZN  54  81  42  77 /  30  30  10   0
WEY  45  71  30  69 /  30  20  10   0
DLN  54  76  41  75 /  40  30  10   0
HVR  59  81  48  76 /  30  30  30   0
LWT  58  79  44  74 /  20  50  30   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING FOR MTZ112-114-
116>118.

HIGH WIND WATCH FROM SUNDAY AFTERNOON THROUGH SUNDAY EVENING FOR
MTZ009-010.

&&

$$

WEATHER.GOV/GREATFALLS


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