Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 282105
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
305 PM MDT THU AUG 28 2014

.DISCUSSION...A PASSING WEATHER FEATURE NORTH OF THE BORDER HAS
PRODUCE SOME IMPRESSIVE CONVECTION OVER SE BRITISH COLUMBIA AND SW
ALBERTA. THERE IS THE CHANCE THAT A FEW STRAY SHOWERS OR EVEN A
THUNDERSTORM MAY DRIFT SOUTH OF THE BORDER THIS EVENING AND
OVERNIGHT. HOWEVER THESE WILL RESULT IN LITTLE PRECIPITATION.
HIGH PRESSURE WILL BRIEFLY BUILD ACROSS THE REGION FRIDAY MORNING,
BUT QUICKLY TURN TO SOUTHWESTERLY FLOW ALOFT AS A STRONGER TROUGH
APPROACHES THE WEST COAST. WINDS WILL AGAIN BE GUSTY DURING THE
AFTERNOON AS THE ATMOSPHERE STARTS TO DESTABILIZE. THIS WILL ALSO
BRING AN INCREASING CHANCE FOR SHOWERS AND THUNDERSTORMS,
ESPECIALLY ACROSS SW MONTANA.

PRECIPITATION CHANCES WILL CONTINUE THROUGH THE NIGHT AND INTO
SATURDAY MORNING AS A STRONG COLD FRONT STARTS TO PUSH THROUGH THE
NORTHERN ROCKIES. FRONTAL PASSAGE WILL LIKELY OCCUR DURING THE
EARLY MORNING HOURS, SHORTLY AFTER SUNRISE. BUT THIS WILL ONLY
MARK THE BEGINNING OF WHAT APPEARS TO BE A PERSISTENTLY BREEZY DAY
ACROSS MUCH OF WESTERN MONTANA AND PERHAPS PARTS OF CENTRAL IDAHO.
THE ATMOSPHERE WILL BE HIGHLY UNSTABLE BEHIND THE FRONT SATURDAY
AFTERNOON, ALLOWING STRONGER, MOUNTAIN TOP WINDS THE OPPORTUNITY
TO MIX TO THE SURFACE. THIS WILL ESPECIALLY BE THE CASE ACROSS
NORTHWEST MONTANA WHERE THE STRONGEST WINDS ARE CURRENTLY
FORECAST. TEMPERATURES WILL BE WELL BELOW SEASONAL NORMS THIS
WEEKEND AND LIKELY FEEL QUITE COOL CONSIDERING THE BREEZY,
SHOWERY ATMOSPHERE. BUT SHOWERS SHOULD SHOW SIGNS OF SUBSIDING
LATE SUNDAY NIGHT.

MONDAY & TUESDAY: NORTHWEST FLOW ON MONDAY WILL BE TRANSITIONING
TO MORE OF A WESTERLY FLOW BY TUESDAY. THIS WILL REDUCE THE THREAT
FOR SHOWERS AND PRODUCE A GRADUAL WARMING TREND. THERE IS SOME
DISCREPANCY BETWEEN THE ECMWF AND GFS FOR MONDAY WITH GFS BEING
MUCH WETTER. SO HAVE KEPT THE CHANCE FOR SHOWERS IN THE FORECAST
BECAUSE OF THE NORTHWEST FLOW PATTERN RECOGNITION AND ANECDOTALLY
IT SEEMS LIKE THESE TROUGHS HANG ON A LITTLE LONGER.

WEDNESDAY ONWARD: THERE ARE SOME INDICATIONS THAT A DECENT UPPER
LEVEL TROUGH WILL BEGIN TO IMPACT THE NORTHERN ROCKIES. CONFIDENCE
IS LOW ON SPECIFIC DETAILS, BUT ONE ATTRIBUTE TO THIS SYSTEM IS
THAT IT MAY DIG FURTHER SOUTH COMPARED TO THE MORE TRANSIENT,
EAST/WEST ORIENTED SYSTEM OF THIS WEEKEND. THIS WOULD LEAD TO THE
POTENTIAL FOR BELOW NORMAL TEMPERATURES, WIDESPREAD PRECIPITATION,
GUSTY WINDS AND EVEN HIGH ELEVATION SNOWFALL.

&&

.AVIATION...SHOWERS AND THUNDERSTORMS ARE PASSING ALONG THE
CANADA/MONTANA BORDER THIS MORNING OTHERWISE THE REST OF THE
REGION IS MOSTLY CLOUD FREE TO START THIS MORNING. THERE IS A
SHORTWAVE APPROACHING FROM THE WEST TODAY, SO HIGH PRESSURE OVER
THE REGION WILL FLATTEN AND WINDS WILL INCREASE. THERE WILL ALSO
BE A CHANCE FOR SHOWERS AND THUNDERSTORMS THROUGH THE GLACIER PARK
REGION AND ALONG THE CONTINENTAL DIVIDE AS THE SHORTWAVE PASSES
THIS EVENING. HIGH PRESSURE WILL REBUILD OVERNIGHT SO CLOUD COVER
AND SHOWERS WILL DECREASE.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

$$

IV/NOBLE



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