Area Forecast Discussion
Issued by NWS Glasgow, MT

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000
FXUS65 KGGW 222250
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
350 PM MST MON DEC 22 2014

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

SYNOPTIC SET UP... A LARGE TROUGH OF COLD AIR RUSHES DOWN FROM
THE CANADIAN PLAINS THROUGH THE GREAT PLAINS OF THE US AND IS
SMASHED UP AGAINST THE FRONT RANGE. A SHORTWAVE IS EMBEDDED IN THE
FLOW AND CURRENTLY EXISTS OVER NORTHEAST MONTANA. FARTHER WEST
NORTHWEST FLOW RESIDES OVER THE WESTERN THIRD OF THE US AND
BLOSSOMS INTO A RIDGE OFF THE COAST OF THE PACIFIC NORTHWEST.

THIS AFTERNOON THROUGH TONIGHT... RADAR ECHOS AND SATELLITE ARE
SHOWING THE SHORTWAVE BEGINNING TO DIMINISH ACROSS THE CWA. THERE
ARE STILL LARGE AREAS OF ONGOING SNOW... BUT A FEW LOCATIONS SUCH AS
PRAIRIE COUNTY AND MOST OF VALLEY COUNTY HAVE RECEIVED LITTLE
SNOW THUS FAR OR EXITED THE SNOW LINE ALTOGETHER. SNOW WILL
CONTINUE TO DIMINISH INTO THE EVENING HOURS AS MOISTURE BECOMES
MORE LIMITED.

TUESDAY THROUGH TUESDAY NIGHT... RIDGE WILL MOVE ON SHORE AND MAKE
FLOW ACROSS NORTHEAST MONTANA MORE NORTHERLY UNTIL THE RIDGE HAS
TOTAL INFLUENCE OVERNIGHT. CONDITIONS WILL REMAIN DRY AND BRIEF
CHINOOK WARMING IS EXPECTED TUESDAY NIGHT AS THE RIDGE HEAD EXITS
THE FRONT RANGE.

GAH


.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...
A COUPLE OF STORM SYSTEMS AFFECT THE AREA DURING THIS PERIOD. NOT
GOOD TIMING FOR HOLIDAY TRAVELERS. MODELS DID COME IN A BIT QUICKER
WITH THE FIRST SYSTEM ON WEDNESDAY...SPREADING A MIXED AREA OF
PRECIPITATION...MAINLY ALONG HIGHWAY 2. SYSTEM THEN PUSHES THROUGH
SOUTHERN MONTANA WEDNESDAY NIGHT AND THURSDAY. RAISED POPS/QPF A BIT
FOR THE SOUTHERN BORDER LOCATIONS. WEEKEND SYSTEM WAS TOO FAR INTO
THE FUTURE TO MAKE ANY CHANGES. REST OF FORECAST WAS LEFT UNTOUCHED.
TFJ


PREVIOUS DISCUSSION...
UPPER TROUGH MOVES INLAND WEDNESDAY NIGHT AND SPLITS BY THE TIME
IT REACHES MONTANA ON THURSDAY. THE SOUTHERN BRANCH DIGS INTO FOUR
CORNERS REGION OF THE DESERT SW WHILE THE NORTHERN BRANCH WILL BE
ACROSS SOUTHERN CANADA AND MAYBE AS FAR SOUTH AS NORTHERN MONTANA.
THE NORTHERN BRANCH IS DRY WHILE THE SOUTHERN BRANCH IS VERY
MOIST. IT IS WHERE THE MODELS FORECAST THE NORTHERN EDGE OF THE
MOISTURE THAT HAS THE MOST IMPACT ON HOW MUCH SNOW NORTHEAST
MONTANA RECEIVES FROM THIS SYSTEM. THE SURFACE LOW DEVELOPMENT IS
FORECASTED TO BE IN COLORADO WHICH IS FREQUENTLY FAR ENOUGH SOUTH
TO LIMIT THE SNOW AMOUNTS IN THE FORECAST AREA. AT THIS POINT...
IT LOOKS LIKE THE BEST CHANCE OF PRECIP FROM THIS SYSTEM FOR
NORTHEAST MONTANA WILL BE ALONG AND JUST NORTH OF THE COLD FRONT
THAT WILL DROP SOUTH THROUGH THE FORECAST AREA WEDNESDAY EVENING.
THE GFS IS SLOWER THAN THE ECMWF AND CMC WITH THIS FRONT AND WANTS
TO KEEP SNOW OVER THE FORECAST AREA THROUGH THURSDAY WHILE THE
ECMFW AND CMC GENERALLY LIMIT THE SNOW TO WEDNESDAY NIGHT AND KEEP
IT MAINLY SOUTH OF THE MISSOURI RIVER. WILL FOCUS THE FORECAST
CLOSER TO THE MOST CONSISTENT ECMWF FOR NOW BUT ALLOW FOR CHANCES
OF SNOW TO THE NORTH GIVEN THE MODEL DIFFERENCES. WILL CONTINUE TO
MENTION THIS SYSTEM IN THE HWO.

BY THURSDAY NIGHT... HIGH PRESSURE BUILDS INTO THE AREA ENDING THE
CHANCES FOR SNOW. THE SURFACE HIGH REMAINS OVER THE AREA ON FRIDAY
WITH DRY AND SEASONABLY COLD TEMPERATURES.

DRY WEATHER CONTINUES ON SATURDAY WITH A SHORTWAVE RIDGE.

THE NEXT UPPER TROUGH MOVES INTO THE AREA ON SUNDAY WITH A COLD
FRONT. THE SYSTEM HAS LIMITED MOISTURE. WILL MENTION A SLIGHT
CHANCE OF SNOW FOR NOW. SYSTEM COULD LINGER INTO MONDAY WILL
MAINTAIN A SLIGHT CHANCE OF SNOW MAINLY SOUTH. FORRESTER


&&

.AVIATION...
FLIGHT CATEGORY: IFR TO MVFR

SYNOPSIS: STORM SYSTEM/DISTURBANCE MOVING ACROSS NORTHEAST MONTANA
HAS BEGUN TO WANE IN INFLUENCE. WHILE A FEW TERMINALS ARE STILL
IN IFR CONDITIONS... THE OVERALL TREND IS EXPECTED TO IMPROVE OVER
THE NEXT 6 TO 12 HOURS. KGGW CONTINUES TO REMAIN OUTSIDE THE
STORMS INFLUENCE WITH ONLY MVFR CEILINGS ANTICIPATED.

CIGS: MAINLY 1 TO 2 KFT IN FUEL LOADING TODAY IMPROVING THROUGH THE
LATE EVENING HOURS.

VSBY: VISIBILITY WILL VARY DUE TO CHANGING INTENSITY OF SNOW AND
POSSIBLY BLOWING SNOW. HEAVIER SNOW BANDS HAVE BEEN MAINTAINING 1
TO 2 SM IN IFR.

WIND: NORTHWEST 15 TO 25 KNOTS AND GUSTY THROUGH MIDNIGHT... THEN
CALMING TO 10 TO 15 KTS.

GAH


&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR CENTRAL
AND SOUTHERN VALLEY...DANIELS...DAWSON...EASTERN ROOSEVELT...
MCCONE...NORTHERN VALLEY...RICHLAND...SHERIDAN...WESTERN
ROOSEVELT...WIBAUX.


&&

$$

WEATHER.GOV/GLASGOW




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