Area Forecast Discussion
Issued by NWS Glasgow, MT

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FXUS65 KGGW 211639
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
939 AM MST SUN DEC 21 2014

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH TUESDAY...

MORNING UPDATE...
RAIN AND FREEZING RAIN IS PROGRESSING EAST ACROSS A LINE FROM
MALTA TO JORDAN. CURRENT POPS SEEM TO BE HANDLING THIS HIT AND
MISS PRECIPITATION PRETTY WELL. SPOTTER REPORTS ARE ALSO MATCHING
UP WELL WITH QPF FIELDS IN PLACE. WINDS AND WEATHER TYPES WERE
TWEAKED SLIGHTLY TO MATCH NEW MODEL FIELDS AND SPOTTER REPORTS
MOVING INTO THE AFTERNOON. TEMPERATURES SHOULD RISE THROUGH THIS
AFTERNOON AROUND THE WARM FRONT GENERATING RAIN FOR MOST AREAS...
BUT WOULD NOT BE SURPRISED IF FREEZING RAIN AND POSSIBLE SLEET
HOLDS ON IN THE NORTHEAST ACROSS DANIELS AND SHERIDAN COUNTY
DURING THE AFTERNOON HOURS. GAH


PREVIOUS SHORT TERM DISCUSSION..,.
LOW PRESSURE SYSTEM CURRENTLY OVER ALBERTA WILL MOVE SOUTHEAST
ACROSS NORTHEAST MONTANA TODAY. SHORTWAVE TROUGH THAT IS ENTERING
WESTERN MONTANA AT 09Z WILL MOVE THROUGH EASTERN MONTANA THIS
AFTERNOON. PRECIPITATION ASSOCIATED WITH THIS SYSTEM WILL ENTER
THE WESTERN ZONES OF THE FORECAST AREA THIS MORNING. AIRMASS WILL
BE WARM ENOUGH ALOFT FOR RAIN. HOWEVER... CURRENT (2 AM MST)
SURFACE TEMPERATURES ARE IN THE 20S OVER MOST OF THE AREA WITH
UPPER TEENS IN SOME LOW LYING AREAS. ONLY SOME RIDGETOP AREAS AND
WINNETT ARE IN THE 30S. SURFACE TEMPERATURES WILL STILL BE COLD
ENOUGH BY THE TIME THE RAIN ARRIVES THIS MORNING IN THE WEST FOR
FREEZING RAIN. WILL MAINTAIN FREEZING RAIN ADVISORY IN THE WESTERN
HALF OF THE FORECAST AREA. BY NOON... MOST AREAS WILL BE WARM
ENOUGH FOR RAIN. SOME AREAS IN THE NORTHEAST CORNER OF THE STATE
MAY STAY COLD ENOUGH FOR FREEZING RAIN.

THE SURFACE LOW MOVES INTO THE DAKOTAS THIS EVENING AND BRING A
COLD FRONT THROUGH THE AREA. EXPECT GUSTY NORTHWEST WINDS TO
DEVELOP BEHIND THE FRONT. MEANWHILE...THE SHORTWAVE TROUGH WILL
DIG A DEEPER TROUGH IN THE PLAINS STATES AND TURN THE FLOW ALOFT
TO THE NORTHWEST OVER MONTANA. COLD AIR ADVECTION WILL TURN THE
RAIN TO SNOW TONIGHT. A SHORTWAVE IN THE NORTHWEST FLOW ALOFT WILL
MOVE THROUGH EASTERN MONTANA LATE TONIGHT AND MONDAY MORNING WITH
DEEP MOISTURE. AT THIS POINT... EXPECT ACCUMULATING SNOW OVER THE
EASTERN HALF OF THE FORECAST AREA WITH 1 TO 4 INCHES AND AREAS OF
BLOWING AND DRIFTING SNOW POSSIBLE. THE SYSTEM MAY NEED A WINTER
WEATHER ADVISORY TONIGHT AND MONDAY. WILL HOLD OFF ON ISSUING
ADVISORY FOR NOW WITH THE FREEZING RAIN ADVISORY CURRENTLY IN
EFFECT.

THE SHORTWAVE MOVES TO THE SOUTHEAST MONDAY AFTERNOON DIMINISHING
THE SNOW. HIGH PRESSURE SYSTEM AND BUILDING RIDGE FROM THE WEST
WILL BRING MAINLY DRY AND SEASONABLY COLD WEATHER FOR MONDAY NIGHT
AND TUESDAY. FORRESTER


.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...

THE PERIOD BEGINS TUESDAY NIGHT WITH A LONG-WAVE EAST-LEANING
RIDGE OVER THE WESTERN STATES AND A MEDIUM-WAVE TROUGH EXTENDING
FROM HUDSON BAY TO TEXAS. THIS PLACES A NORTHWESTERLY FLOW ALOFT
OVER NORTHEAST MONTANA. A SPLIT TROUGH DISTURBANCE IN NORTHWESTERN
CANADA KNOCKS DOWN THE RIDGE...SENDING A BROAD COLD FRONT SOUTH
TOWARDS THE INTERNATIONAL BORDER. THE NORTHWEST FLOW BECOMES MORE
WESTERLY. THIS WILL SEND PACIFIC MOISTURE OVER THE DIVIDE
OVERRUNNING THE COLD BOUNDARY IN MONTANA ON WEDNESDAY.

THE EC AND GFS HAVE BEEN STRUGGLING TO COME INTO SOME SORT OF
AGREEMENT AS TO WHERE THIS BOUNDARY WILL BE...WITH THE EC
FURTHER SOUTH. THE BOUNDARY LOCATION WILL DETERMINE WX TYPE AND
WHERE THAT PRECIPITATION WILL FALL. THE LATEST SOLUTIONS ARE
CLOSER TOGETHER. SO RIGHT NOW A BLENDED SOLUTION POINTS TO NEMONT
GETTING AN INITIAL SHOT OF MIXED PRECIPITATION THEN TURNING TO
SNOW BY WEDNESDAY EVENING. FOR NOW...EXPECT 1 TO 3 INCHES OF
SNOW....MAINLY SOUTH OF THE MISSOURI RIVER.

AS THE FRONT CONTINUES SOUTH...SO WILL THE PRECIPITATION. THEN
LATE WEDNESDAY NIGHT AND THURSDAY BOTH MODELS POINT TO A HEAVY
SNOW EVENT OVER CENTRAL AND SOUTHEAST MONTANA. THE ORIGINAL SPLIT
TROUGH FEATURE WILL CONTINUE TO BRING IN LIGHT SNOW SHOWERS INTO
NEMONT THROUGH THE REMAINDER OF THE PERIOD. TOWARDS THE WEEKEND
TEMPERATURES CONTINUE TO TREND LOWER AS CAA IS SUSTAINED.


&&

.AVIATION...

A WARM FRONT WILL MOVE INTO NORTHEAST MONTANA THIS MORNING AND
SPREAD NORTHEAST ACROSS THE AREA TODAY. TEMPERATURES ALOFT SUGGEST
FREEZING RAIN INITIALLY...THEN BECOMING RAIN AS SURFACE
TEMPERATURES WARM IN THE AFTERNOON...WITH THE TRANSITION TO RAIN
MOVING FROM THE SOUTHWEST TOWARDS THE NORTHEAST AS THE FRONT
PROGRESSES. THE CHANGE-OVER FROM FREEZING RAIN/DRIZZLE TO RAIN IS
EXPECTED IN THE GGW AREA AROUND 3PM. A COLD FRONT MOVES IN TONIGHT
TO CHANGE RAIN OVER TO SNOW.

EXPECT MVFR/IFR CEILINGS TODAY AND TONIGHT. ANY SNOWFALL TONIGHT
WILL CREATE LIMITED VISIBILITIES.

WIND INITIALLY WILL BE SOUTHERLY AND GENERALLY LIGHT. THEN A
CLOSED SURFACE LOW MOVES DOWN FROM CANADA TO DEVELOP NORTHWESTERLY
WINDS THAT WILL INCREASE TO 15KT TO 25KT LATE IN THE AFTERNOON AND
EVENING.


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
FREEZING RAIN ADVISORY UNTIL NOON MST TODAY FOR CENTRAL AND
SOUTHEAST PHILLIPS...CENTRAL AND SOUTHERN VALLEY...GARFIELD...
NORTHERN PHILLIPS...NORTHERN VALLEY...PETROLEUM...SOUTHWEST
PHILLIPS.

FREEZING RAIN ADVISORY UNTIL 5 PM MST THIS AFTERNOON FOR
DANIELS...EASTERN ROOSEVELT...RICHLAND...SHERIDAN...WESTERN
ROOSEVELT.


&&

$$

WEATHER.GOV/GLASGOW




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