Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 202153
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
253 PM MST THU NOV 20 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SATURDAY...

THE EFFECTS OF THE LINGERING COLD AIR MASS THAT NORTHEAST MONTANA
HAS BEEN ENDURING THE LAST FEW WEEKS IS FINALLY EXITING TOWARD THE
EAST...ALLOWING WARMER TEMPERATURES TO ARRIVE FROM THE WEST BY WAY
OF A SHORT-WAVE RIDGE OF HIGH PRESSURE EMERGING OVER THE
CONTINENTAL DIVIDE TODAY. NORTHWEST FLOW ALOFT TODAY WILL BECOME
MORE WESTERLY TONIGHT AS LOW-LEVEL CLOUDS ACROSS THE AREA GIVE WAY
TO MID AND UPPER-LEVEL CLOUDS.

EARLY FRIDAY MORNING...THIS SHORT-WAVE RIDGE WILL BE QUICKLY
FOLLOWED BY A SHORT-WAVE TROUGH WHICH SHOULD ONLY RESULT IN SOME
SCATTERED MID-LEVEL CLOUDS AND SOME LIGHT PRECIP NORTH OF THE
INTERNATIONAL BORDER THROUGH FRIDAY EVENING.

EARLY SATURDAY...THE NEXT ORGANIZED STORM SYSTEM EMERGES OVER THE
NORTHERN ROCKIES AND BEGINS TO SPREAD EASTWARD OVER THE NORTHERN
HIGH PLAINS. IF PRECIP GET STARTED EARLY ENOUGH ON
SATURDAY...TEMPERATURES JUST MIGHT BE COLD ENOUGH OVER OUR WESTERN
ZONES TO ALLOW SOME MIXED PRECIPITATION TO FALL - COULD BE SOME
LIGHT FREEZING RAIN. DAYTIME TEMPERATURES WILL THEN WARM ENOUGH TO
CHANGE MOST PRECIP TO RAIN EXCEPT FOR JUST ALONG THE INTERNATIONAL
BORDER WHERE SOME MIXED PRECIP MAY LINGER DURING THE DAY. USED
SOME NEW WEATHER TOOLS TO REPRESENT THE EXPECTED PRECIP TYPES ON
SATURDAY. RESULTED IN SOME HOURLY WEATHER GRIDS WHICH THE GFE
FORMATTER HANDLED FAIRLY WELL IN THE TEXT ZONE FORECAST.

LATE SATURDAY...A COLD FRONT WILL QUICKLY ALLOW PRECIP TO CHANGE
OVER TO SNOW AS THE BACKSIDE OF THIS STORM SYSTEM PUSHES THE NEXT
ROUND OF PRECIP THROUGH THE CWA JUST BEYOND THE END OF THIS
FORECAST PERIOD. BMICKELSON

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
12Z MODELS ADDED SOME MORE SPECIFIC INFORMATION MAINLY IN REGARDS
TO TEMPERATURE AND WINDS...SO TWEAKS GRIDS TOWARDS THESE
SOLUTIONS. ALSO TWEAKED QPF AND SNOW AMOUNTS A BIT MAINLY FOR
SATURDAY NIGHT...SUNDAY AND WEDNESDAY. TFJ

PREVIOUS DISCUSSION...

MODELS IN QUITE GOOD AGREEMENT THROUGH MUCH OF THE PERIOD WITH
DIFFERENCES ONLY DEVELOPING BY THE MIDDLE OF NEXT WEEK. CLIPPER
SYSTEM FOR THIS WEEKEND WILL TRANSITION FROM A WINTRY MIX TO ALL
SNOW SATURDAY NIGHT AS COLDER AIR IS PULLED INTO THE REGION BEHIND
THE STORM. SNOW AMOUNTS ON SUNDAY EXPECTED TO BE GENERALLY LIGHT
WITH THE TRACK OF THE STORM JUST CLIPPING MONTANA.

MONDAY AND TUESDAY THE COLD HIGH PRESSURE PUSHES INTO THE NORTHERN
PLAINS WITH BOUNDARY ALONG THE FRONT RANGE. AS ANOTHER SHORTWAVE
BEGINS DROPPING OUT OF THE GULF OF ALASKA...UPPER FLOW TURNS A
LITTLE TO THE WEST...ALLOWING WARM AIR ACROSS THE DIVIDE TO BEGIN
SHALLOWING THE COLD AIR BY WEDNESDAY. MAIN MODEL DIFFERENCE IS HOW
FAR EAST DOES THE WARM AIR MIX BEFORE THE WAVE PULLS ANOTHER SURGE
OF ARCTIC AIR INTO THE NORTHERN PLAINS. SIGNIFICANT OVERRUNNING
PRECIPITATION ALSO POSSIBLE FOR WEDNESDAY AND THURSDAY AND
POSITIONING WILL RELY ON LOCATION OF THE ARCTIC BOUNDARY. EBERT

&&

.AVIATION...

PATCHY LOW STRATUS MAY MAKE A RETURN TONIGHT BUT STRONG WEST
WINDS A FEW HUNDRED FEET OFF THE GROUND WILL LIKELY KEEP IT FROM
BECOMING WIDESPREAD AND LONG LIVED. THESE WINDS MAY ALSO BRING
BRIEF LOW-LEVEL WIND SHEAR CONDITIONS. TFJ


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

WEATHER.GOV/GLASGOW




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