Area Forecast Discussion
Issued by NWS Great Falls, MT

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FXUS65 KTFX 271750
AFDTFX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1150 AM MDT THU AUG 27 2015

UPDATED AVIATION SECTION

.DISCUSSION...
UPDATE FORTHCOMING. HAVE MADE MINOR ADJUSTMENTS TO THE POP AND
WEATHER GRIDS. RADAR RETURNS INDICATE WEAK SHOWERS OVER PORTIONS OF
SOUTHWEST MONTANA AT THIS TIME AS WELL AS ISOLATED SHOWERS MOVING
ACROSS THE HI-LINE. HAVE LOW CONFIDENCE IN WIND FORECAST FOR FIRE
ZONE 114 AND HAVE CANCELED THE FIRE WEATHER WATCH. THE RED FLAG
WARNING WILL CONTINUE. TEMPERATURES LOOK GOOD.

&&

.AVIATION...
UPDATED 1750Z.
WEST TO SOUTHWEST FLOW ALOFT CONTINUES. SCATTERED
SHOWERS AND THUNDERSTORMS WILL DEVELOP AFTER 18Z OVER SOUTHWEST
MONTANA AND MOVE SLOWLY NORTH AND EAST. CONVECTIVE ACTIVITY SHOULD
END BY 06Z WITH PARTIAL CLEARING  VFR CONDITIONS PREVAIL THOUGH
AREAS OF MVFR WILL PERSIST DUE TO SMOKE AND REDUCED VISIBILITIES.
MVFR CONDITIONS ARE ALSO POSSIBLE IN THE VICINITY OF THUNDERSTORMS
ALONG WITH GUSTY ERRATIC WINDS. MOUNTAINS OBSCURED AT TIMES.

&&

.PREV DISCUSSION...ISSUED 339 AM MDT THU AUG 27 2015

THURSDAY THROUGH SATURDAY...FIRE WEATHER CONCERNS
WILL BE THE MAJOR IMPACT THIS THROUGH THE FIRST PART OF THE WEEKEND
AS GUSTY WINDS AND LOW RELATIVE HUMIDITY LEVELS ON THE LEE SIDE OF
THE ROCKY MOUNTAIN FRONT WILL CREATE CRITICAL AND NEAR CRITICAL FIRE
WEATHER CONCERNS TODAY. MONSOONAL MOISTURE WILL CONTINUE TO MOVE
INTO THE AREA TODAY BRINGING AN INCREASE POTENTIAL FOR THUNDERSTORMS
AND AN INCREASE IN FIRE STARTS FROM LIGHTNING AND GUSTY WINDS NEAR
THUNDERSTORMS. DRY AND WARM CONDITIONS WILL CONTINUE THROUGH THE DAY
SATURDAY WITH WINDS INCREASING AHEAD OF A DRY COLD FRONT THAT WILL
MOVE THROUGH THE AREA BRINGING GUSTY WINDS AND LOW HUMIDITY VALUES
AHEAD OF THE FRONT. THE LACK OF MOISTURE WITH THE FRONTAL PASSAGE
WILL LIMIT SHOWER AND THUNDERSTORM DEVELOPMENT...BUT THERE IS ALMOST
NO SIGNIFICANT PRECIPITATION EXPECTED WITH THIS FRONTAL PASSAGE.
ADDITIONAL FIRE WEATHER HIGHLIGHTS MAY BECOME NECESSARY AS THIS FRONT
APPROACHES. SUK

SATURDAY NIGHT THROUGH THURSDAY...MEDIUM RANGE MODEL SOLUTIONS
REMAIN IN RELATIVELY GOOD AGREEMENT THROUGH MUCH OF THE FORECAST
PERIOD. HOWEVER, BOTH HAVE TRENDED TOWARD A SOMEWHAT DRIER FORECAST
SO HAVE AGREED WITH SURROUNDING OFFICES TO PULL BACK POPS A BIT. AS
NOTED YESTERDAY, THE MAIN PLAYERS IN THE FORECAST ARE AN UPPER LEVEL
TROUGH OVER THE GULF OF ALASKA/SOUTHEAST ALASKA AND RIDGING OVER THE
HIGH PLAINS. MONTANA REMAINS BENEATH AN SOMEWHAT UNSTABLE SOUTHWEST
FLOW ALOFT THROUGH THE PERIOD AND BOTH MODELS ATTEMPT TO SLOWLY
PROGRESS THE UPPER TROUGH INTO WESTERN CANADA. THE ECMWF IS A BIT
MORE AGGRESSIVE WITH THIS THAN THE GFS BUT IT APPEARS THAT BOTH
MODELS MAY BE OVERDOING HOW FAR EASTWARD THIS FEATURE CAN MOVE GIVEN
THE UPPER RIDGE AND THE VERY WARM LATE SUMMER TEMPERATURES THAT WILL
TEND TO SUPPORT RIDGE STABILITY OVER THE PLAINS. HAVE MADE ONLY
MINOR CHANGES TO THE GOING FORECAST PACKAGE, MAINLY TO EASE BACK ON
POPS AND SURFACE WIND SPEEDS. TEMPERATURES FROM MONDAY ONWARD ARE
EXPECTED TO BE NEAR OR SLIGHTLY ABOVE SEASONAL AVERAGES AS GUIDANCE
FROM BOTH MODELS SUPPORT COOLER TEMPERATURES THAN THOSE OF THIS
WEEK. MPJ

&&

.FIRE WEATHER...
WARM AND DRY CONDITIONS WILL CONTINUE THROUGH
SATURDAY. WINDY CONDITIONS ARE EXPECTED ALONG THE ROCKY MOUNTAIN
FRONT AND ADJACENT HIGH PLAINS. A RED FLAG WARNING IS IN EFFECT FOR
FIRE WEATHER ZONE 112. FURTHER SOUTH IN FIRE WEATHER ZONE 114 THERE
IS NOT AS MUCH CONFIDENCE THAT STRONG GUSTY WINDS WILL EXIST FOR A
SIGNIFICANT PERIOD OF TIME THIS AFTERNOON. MONSOONAL MOISTURE WILL
MOVE INTO THE REST OF THE AREA AND COULD PRODUCE SOME ISOLATED
SHOWERS AND THUNDERSTORMS THIS AFTERNOON. A MIXTURE OF WET AND DRY
THUNDERSTORMS ARE EXPECTED. SATURDAY WILL BE ANOTHER NEAR CRITICAL
FIRE WEATHER DAY AS AN APPROACHING DRY COLD FRONT WILL CREATE THE
POTENTIAL FOR GUSTY WINDS WITH LITTLE TO NO MOISTURE ASSOCIATED WITH
THE FRONT ADDITIONAL HIGHLIGHTS MAY BECOME NECESSARY AHEAD OF THE
COLD FRONT. SUK

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  90  58  90  64 /  20  10  10  10
CTB  87  53  87  57 /  10  10  10  10
HLN  89  53  89  55 /  30  20  10  10
BZN  86  50  88  53 /  50  20  10  10
WEY  76  37  80  41 /  70  40  10  10
DLN  84  48  86  54 /  40  20  10  10
HVR  91  57  90  58 /  20  10   0  10
LWT  87  56  88  59 /  40  10  10  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM NOON TODAY TO 9 PM MDT THIS EVENING FOR
MTZ112.

&&

$$

WEATHER.GOV/GREATFALLS


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