000
FXUS65 KGGW 201528
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
928 AM MDT SAT MAR 20 2010

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH MONDAY...
NO UPDATE TO GOING FORECAST. UPPER RIDGE BUILDING INTO THE
NORTHERN ROCKIES...WITH CLEARING SKIES AND WARM AIR ADVECTION
EXPECTED. COLD START TO THE MORNING WILL CAP MAXIMUM TEMPERATURES
BUT GOOD MIXING ANTICIPATED. EBERT

PREVIOUS SHORT TERM DISCUSSION...UPPER RIDGE CURRENTLY OVER THE
PACIFIC COAST WILL MOVE INLAND TODAY AND ACROSS MONTANA TONIGHT
AND SUNDAY. THIS WILL BRING CLEAR SKIES AND A WARMING TREND TO THE
FORECAST AREA. WHILE THERE WILL BE A COOLER NE TO WARMER SW
TEMPERATURE PATTERN TODAY AND SUNDAY...IT WILL BE DUE TO WARMER
AIR OVER THE SW. SNOW COVER HAS DISAPPEARED OVER MOST OF THE
REGION THIS WEEK SO IT IS NO LONGER MUCH OF A FACTOR IN COOLING
TEMPERATURES.

UPPER TROUGH AND COLD FRONT MOVES INLAND FROM THE PACIFIC ON
SUNDAY. THE COLD FRONT WILL PASS THROUGH NORTHEAST MONTANA MONDAY
MORNING FOLLOWED BY THE UPPER TROUGH IN THE AFTERNOON AND EVENING.
ENOUGH MOISTURE...INSTABILITY AND UPPER LEVEL DYNAMICS ACCOMPANIES
THIS SYSTEM FOR A CHANCE OF SHOWERS. TEMPERATURES WILL BE WARM
ENOUGH ON MONDAY FOR ALL RAIN. FORRESTER

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY...
THE POLAR VORTEX STARTS OUT OVER THE YUKON TERRITORY AND JUST TO
THE WEST OF THE HUDSON BAY. PIECES OF SHORTWAVE ENERGY ROTATE
AROUND THE POLAR VORTEX AND ARE EJECTED SOUTH SOUTHEASTWARD TOWARDS
THE NORTHERN HIGH PLAINS AND GREAT LAKES REGION. THE GFS ECMWF AND
THE GEM ARE SHOWING THIS PATTERN THROUGHOUT THE EXTENDED. AS THE
SHORT WAVE ENERGY ROUNDS THE POLAR VORTEX IT WILL PICK UP THE
ARCTIC AIR AND TRYS TO PUSH IT SOUTHWARD TOWARDS THE LOWER 48. AS
IT LOOKS NOW THE BRUNT OF THE ARCTIC AIR WILL REMAIN NORTH OF THE
INTERNATIONAL BORDER. THIS PATTERN COULD CHANGE WITH FUTURE MODEL
RUNS BUT THE TIME OF YEAR AND THE DWINDLING SNOW PACK ACROSS
SOUTHERN CANADA IS WORKING AGAINST THE REALLY COLD AIR MAKING IT
TO FAR SOUTH.

SO WITH THIS IN MIND THE MODELS SHOW THE ARCTIC FRONTAL BOUNDARY
WAVERING IN AND OUT OF THE NORTHEAST ZONES. DID NOT CHANGE TEMPERTURES
VERY MUCH AT ALL IN THE EXTENDED BUT DID TWEAK A FEW DAY TIME
HIGHS DURING THE UP COMING WEEK. EPICALLY FOR NEXT FRIDAY AS THIS
LOOKS LIKE THE BEST CHANCE FOR A GLANCING BLOW OF THE ARCTIC AIR.
BEING THIS FAR OUT THE PRECIPITATION IS TOUGH TO CALL BUT A MIX OF
RAIN AND SNOW WITH MOSTLY SNOW DURING THE OVERNIGHT HOURS IS
POSSIBLE. OF COURSE IF THE MODELS CHANGE AND SEND THE BLAST OF
ARCTIC AIR THROUGH SOUTHERN MONTANA...THE PRECIPITATION TYPE WOULD
BE ALL SNOW.

MODELS HAVE BEEN FAIRLY CONSISTENT LATELY IN SHOWING A SHORTWAVE MOVING
ACROSS WESTERN MONTANA ON MONDAY NIGHT AND TUESDAY WITH ENOUGH
INSTABILITY AND COLD AIR WORKING IT WAY INTO THE CWA FOR SNOW
SHOWERS MONDAY NIGHT AND THEN A MIX OF RAIN AND SNOW SHOWERS FOR
TUESDAY. THIS WILL COME TO AN END AS BOTH MODELS SHOW AN UPPER
RIDGE BUILDING IN FROM THE WEST TUESDAY NIGHT INTO WEDNESDAY TO
PUT AN END TO THE MIXED PRECIPITATION THROUGH THURSDAY MORNING. BY
THURSDAY AFTERNOON ONE OF THOSE EARLIER MENTIONED SHORTWAVES
ROTATING AROUND THE POLAR VORTEX AND MOVE SOUTHEAST WARD ACROSS
SOUTHERN CANADA. THIS WILL DROP AN ARCTIC FRONT INTO THE NORTHEASTERN
ZONES BY THURSDAY EVENING. AT THE SAME TIME AN UPPER LOW MOVES
ONSHORE AND BRING PACIFIC MOISTURE TO NORTHERN MONTANA. THE UPPER
LOW OVERRUNS THE ARCTIC FRONT WHICH WILL PRODUCE PRECIPITATION. AGAIN
DEPENDING ON HOW MUCH OF THE ARCTIC AIR MASS MAKES IT INTO NEMONT
WILL DETERMINE IF WE ARE DEALING WITH ALL SNOW OR A RAIN SNOW
MIX. LEFT THE SOUTHERN ZONES WITH A RAIN SNOW MIX AND THE NORTHERN
TO NORTHEAST ZONES AS ALL SNOW ON FRIDAY. RSMITH

&&

.AVIATION...
EXPECT VFR CONDITIONS TO PREVAIL THE REST OF TODAY THROUGH TONIGHT AT
ALL TERMINALS. SCATTERED HIGH CIRROSTRATUS CLOUDS AROUND 20 KFT ARE
LIKELY. THE WINDS WILL BE SOUTHWEST AT 10 TO 15 KTS TODAY AND THEN
BACK SLIGHTLY TO THE SOUTH AT UNDER 10 KTS OVERNIGHT. GHICKS/RSMITH

&&

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

&&

$$

WEATHER.GOV/GLASGOW

NWS GGW Office Area Forecast Discussion