Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 201559
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
859 AM MST SAT DEC 20 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH MONDAY...
UPDATE...THE SHORTWAVE FEATURE OVER NORTHEAST MONTANA HAS WRAPPED
UP TO THE POINT WIDESPREAD FREEZING RAIN IS NO LONGER A THREAT FOR
SHERIDAN COUNTY...THUS ENDED THE WINTER WEATHER ADVISORY THERE.
PATCHY FREEZING RAIN WILL REMAIN A POSSIBILITY NORTH OF THE
MISSOURI RIVER THROUGH THE MORNING...WITH DRY CONDITIONS
ANTICIPATED FOR THE AFTERNOON. GILCHRIST

PREVIOUS DISCUSSION...PRECIP TYPE FORECAST WILL BE A CHALLENGE
TODAY THROUGH SUNDAY AS WARM AIR ALOFT AND A MIX OF ABOVE AND
BELOW FREEZING SURFACE TEMPERATURES WILL PROVIDE A VARIETY OF
PRECIP TYPES.

A SHORTWAVE TROUGH AND WARM FRONT WILL MOVE THROUGH NORTHEAST
MONTANA THIS MORNING. A BAND OF MIXED PRECIPITATION IS CURRENTLY
MOVING THROUGH THE FORECAST AREA NORTH OF THE MISSOURI RIVER. WITH
SURFACE TEMPERATURES IN THE 20S AND WARMER AIR ALOFT... AT LEAST
SOME OF THE PRECIP IS FREEZING RAIN. HOWEVER... THERE IS A
POSSIBILITY THAT EVAPORATIVE COOLING COULD RESULT IN A MIX OF
FREEZING RAIN... SLEET AND LIGHT SNOW. GIVEN THAT ANY AMOUNT OF
FREEZING RAIN WILL MAKE ROADS VERY SLIPPERY... WILL ISSUE A WINTER
WEATHER ADVISORY FOR NORTH OF THE MISSOURI RIVER THIS MORNING.

THAT SYSTEM WILL MOVE TO THE EAST THIS AFTERNOON. THE NEXT
SHORTWAVE TROUGH MOVES INTO CENTRAL MONTANA LATE TONIGHT WITH A
LOW PRESSURE SYSTEM AND WARM FRONT. MOISTURE ALONG AND AHEAD OF
THE FRONT WILL MOVE INTO NORTHEAST MONTANA SUNDAY MORNING.
TEMPERATURES IN MOST AREAS WILL BE BELOW FREEZING FOR AT LEAST
PART OF THE MORNING WITH WARMER AIR ALOFT WHICH WILL MAKE
CONDITIONS FAVORABLE FOR FREEZING RAIN OR SLEET WHICH WILL BE
MIXED WITH OR CHANGE TO RAIN AS TEMPERATURES WARM ON SUNDAY. A COLD
FRONT WILL FOLLOW THE SURFACE LOW PASSAGE IN THE AFTERNOON OR
EVENING WHICH WILL CHANGE ANY PRECIP THAT LINGERS INTO SNOW BY
SUNDAY NIGHT.

ZONAL FLOW ALOFT TURNS TO THE NORTHWEST SUNDAY NIGHT AND ANOTHER
SHORTWAVE MOVES SOUTHEAST ALONG THE MT/ND BORDER ON MONDAY WITH
COLDER TEMPERATURES. MODELS ARE INCREASINGLY SHOWING ENOUGH MOISTURE FOR A
CHANCE OF ACCUMULATING SNOW MAINLY ALONG THE NORTH DAKOTA BORDER.
WILL HIGHLIGHT THE POSSIBILITY OF SNOW IN A HAZARDOUS WEATHER
OUTLOOK FOR NOW. FORRESTER

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...

THE PERIOD BEGINS MONDAY NIGHT WITH A LONG-WAVE TROUGH CENTERED
OVER THE MIDDLE OF THE COUNTRY AND A LARGE RIDGE OFF THE WEST
COAST. THIS PATTERN WILL GENERATE A NORTHWEST FLOW ALOFT FOR
NORTHEAST MONTANA. THE COLD AIR BOUNDARY WILL BE LOCATED WELL TO
THE SOUTH. THEREFORE TEMPERATURES WILL BEGIN CLOSE TO NORMAL.

ON TUESDAY THE WEST COAST RIDGE SHIFTS EAST AND BEGINS TO NUDGE TO
BOUNDARY TOWARDS MONTANA AS A WARM FRONT. THE RIDGE AXIS THEN
LEANS OVER TO THE EAST ON WEDNESDAY. THE FLOW ALOFT WILL BE
DIRECTLY FROM THE OCEAN OFF THE COAST OF WASHINGTON AND BC WHICH
WILL PICK UP MOISTURE. THE COLD AIR BOUNDARY WILL ONCE AGAIN BE
PUSHED SOUTH AROUND WEDNESDAY AND THURSDAY. THE MOISTURE AND THE
FRONT COULD BRING RAIN AND/OR SNOW INTO NORTHEAST MONTANA POSSIBLY
WEDNESDAY AFTERNOON AND EVENING. FROM THIS POINT ON THE EC AND GFS
DIFFER IN STORM LOCATION. SO THERE IS UNCERTAINTY CONCERNING SNOW
LOCATION. THE EC SENDS IT MORE TO THE SOUTH...WHEREAS THE GFS
SPREADS SNOW MAINLY SOUTH OF THE MISSOURI RIVER.

BY 00Z THURSDAY AN ENERGETIC TROUGH MOVES INTO THE PAC-NW AND
PUSHES ACROSS THE DIVIDE WEDNESDAY NIGHT AND THURSDAY. WITH THE
COLD FRONT PUSHED WELL TO THE SOUTH THE DISTURBANCE WILL LIKELY BE
ALL SNOW. WHILE NORTHEAST MONTANA WILL END UP WITH AN INCH OR
TWO...MOST QPF TRENDS SOUTH...GENERATING AREAS OF HEAVY SNOW FOR
OUR NEIGHBORS LATE IN THE WEEK. SCT


&&

.AVIATION...
FLIGHT CATEGORY: MAINLY VFR... IFR LATE IN CYCLE.

MORNING SHOWERS: WEAK SHORTWAVE WILL EXIT THE AREA THIS MORNING. SOME
ISOLATED SHOWERS ARE POSSIBLE WITH THE EXIT OF THIS SYSTEM.
CONDITIONS SHOULD REMAIN VFR.

FOG: RADIATION FOG IS ANTICIPATED ALONG THE MISSOURI AND MILK
RIVER VALLEY TONIGHT AFTER MIDNIGHT. MVFR VISIBILITY IS POSSIBLE
BUT NOT VERY LIKELY.

STORM AND FREEZING RAIN: AFTER 12Z LATE IN THE CYCLE KGGW
EXPERIENCE DETERIORATING CONDITIONS TO IFR AS A WINTER STORM SYSTEM
MOVES THROUGH THE AREA. OTHER TERMINALS WILL DROP JUST BEYOND THE CYCLE
PRECIPITATION SHOULD BEGIN AS SLEET OR FREEZING RAIN INT EH MORNING BUT
TRANSITION TO ALL RAIN AS CONDITIONS WARM THROUGH THE AFTERNOON.

AREA WIND: OUT OF THE WEST AROUND 10 KTS DURING THE AFTERNOON... VEERING TO
THE SOUTH OVERNIGHT.

GAH


&&

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

&&

$$

WEATHER.GOV/GLASGOW






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