FXUS65 KGGW 042200
AFDGGW
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
300 PM MST THU DEC 4 2008
.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SATURDAY...
HIGH CLOUDS ARE INCREASING ACROSS THE TREASURE STATE AS STRATUS
ALONG THE NORTH DAKOTA BORDER CONTINUES TO BREAK UP AND MOVE TO
THE SOUTHEAST. EXPECT THE HIGH CLOUDS TO BE JOINED BY SOME MID
LEVEL CLOUDS AS CEILNGS LOWER A BIT INTO THE OVERNIGHT HOURS. A
LEE SIDE TROUGH WILL ALSO DEVELOP ALONG THE ROCKY MOUNTAIN FRONT AS
AN ALBERTA CLIPPER SYSTEM SPINS UP TO THE NORTH. THE POLAR SURFACE
HIGH THAT HAS DOMINATED OVER THE LAST TWO DAYS WILL ALSO MOVE INTO
THE GREAT PLAINS...ALLOWING WARMER AIR TO MOVE IN BEHIND IT. THAT
BEING SAID NO WARMING WILL BE REALIZED TONIGHT AS COLD AIR AT THE
SURFACE WILL HOLD TIGHT. FRIDAY THE CLIPPER SYSTEM WILL DROP
SOUTHEASTWARD INTO NORTH DAKOTA/MINNESOTA...BRINGING WITH IT SOME
POTENTIAL FOR LIGHT SNOW ACROSS MUCH OF NORTHEAST MONTANA. WEST
WINDS IN THE LOW LEVELS WILL SERVE TO SCOUR OUT MUCH OF THE
LINGERING POLAR AIRMASS ON FRIDAY AS WELL...WHICH WILL MAKE FOR
WARMER TEMPERAUTRES. THE WINDS WILL ALSO BE IN THE 15 TO 25 MPH
RANGE...WHICH WILL NEED TO BE MONITORED FOR A POSSIBLE LAKE WIND
ADVISORY FOR FORT PECK LAKE. FRIDAY EVENING WILL SEE A COLD FRONT
STALL OUT ACROSS EASTERN MONTANA. MOISTURE WILL RIDE ALONG THIS
BOUNDARY...KEEPING SOME POTENTIAL FOR -SN IN THE FORECAST INTO
SATURDAY. SATURDAY ACTUALLY LOOKS TO HAVE THE BEST POTENTIAL FOR
SNOWFALL AS MOISTURE AVAILABILITY INCREASES...AND THERE COULD EVEN
BE SOME RAIN MIXED WITH THE SNOW ACROSS THE SOUTHEAST ZONES. GILCHRIST
.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
THE EXTENDED PERIOD IS TRENDING TOWARD COLDER CONDITIONS AS A
STRONG UPPER LEVEL RIDGE BUILDS NORTH INTO THE GULF OF ALASKA AND
A LARGE TROUGH DEVELOPS OVER THE EASTERN TWO THIRDS OF NORTH
AMERICA WITH A POLAR VORTEX OVER THE HUDSON BAY REGION SENDING
ARCTIC AIR SOUTHWARD. THE END RESULT FOR THE LOCAL FORECAST AREA
WILL BE UNSETTLED NORTHWEST FLOW ALOFT WITH THE ARCTIC BOUNDARY
OSCILLATING BACK AND FORTH ACROSS THE REGION.
12Z ECMWF...GFS...CANADIAN...AND GFS ENSEMBLES ARE DEMONSTRATING
DECENT AGREEMENT THROUGH EARLY NEXT WEEK. SATURDAY NIGHT...A WARM
FRONT CROSS THE AREA WITH THE POTENTIAL FOR A WARM AIR ADVECTION
DRIVEN BAND OF LIGHT SNOW OVERNIGHT. TEMPERATURES WILL WARM
SUNDAY...BUT MEANWHILE A PACIFIC SHORTWAVE WILL MOVE INTO THE
PACIFIC NORTHWEST...WHICH WILL ACT TO DEEPEN THE LONGWAVE
TROUGH...AND PULL A COLD FRONT SOUTH THAT WILL CROSS THE AREA IN
THE SUNDAY NIGHT TIME-FRAME. ANOTHER ROUND OF LIGHT SNOW IS
POSSIBLE WITH THE COLD FRONT. THE FRONT REVERSES COURSE AND MOVES
NORTHEAST AS A WARM FRONT MONDAY NIGHT. GFS AND ECMWF DIVERGE
WITH THE FRONTAL POSITION BY TUESDAY...WITH THE ECMWF FARTHER
NORTH AND EAST WITH THE POSITION...AND HENCE WARMER. THIS IS
FOLLOWED BY ANOTHER PUSH OF COLD AIR WEDNESDAY.
BY THE LATER HALF OF THE WEEK THE MEAN TROUGH POSITION IS FARTHER
WEST IN THE ECMWF...AND IT IS THEREFORE COLDER THAN THE GFS...ALTHOUGH
BOTH APPEAR COLD. DEPENDING ON THE PLACEMENT OF THE TROUGH
POSITION AND HOW MUCH SNOW IS ON THE GROUND TEMPERATURES COULD
FALL WELL BELOW NORMAL. AJZ
PREVIOUS LONG TERM DISCUSSION...
A LONG WAVE RIDGE TO THE WEST AND TROUGH TO THE EAST WILL INITIATE
THE EXTENDED PERIOD WITH NW FLOW ALOFT. THE TROUGH WILL BE
ANCHORED TO A COLD HUDSON BAY LOW. THE STATIONARY FRONT/BOUNDARY
DRAPED OVER NE MT WILL DRIFT EAST BUT OVERRIDING MOISTURE FROM WAA
SHOULD GENERATE ADDITIONAL SNOW SHOWERS SATURDAY NIGHT. A WEAK
SHORT WAVE DISTURBANCE WILL THEN MOVE INTO THE PAC NW AND MT
SUNDAY SENDING A COLD FRONT SOUTH FROM CANADA. THIS WILL GENERATE
ADDITIONAL SHOWERS THAT WILL INCLUDE RAIN DURING THE AFTERNOON IN
THE SOUTHERN ZONES. ANOTHER SHORTWAVE QUICKLY FOLLOWS SENDING A
STRONGER COLD FRONT SOUTH MONDAY FOR ANOTHER ROUND OF SNOW. THE
PATH OF PRECIPITATION SUNDAY NIGHT AND MONDAY APPEARS TO BE
ACROSS THE CENTRAL REGION INTO THE SOUTHERN REGION GIVING OUR AREA
ANOTHER GLANCING BLOW MAINLY OVER OUR SW ZONES. MONDAY NIGHT WILL
FOLLOW WITH COLD TEMPERATURES AND LOW STRATUS WITH LIGHT SNOW OR
FLURRIES. THE PICTURE BECOMES LESS CLEAR TUESDAY WITH THE GFS
SHOWING A STRONG ARCTIC LOW PUSHING ANOTHER BACK DOOR FRONT OVER
THE AREA WITH OVERRIDING MOISTURE WHILE THE ECMWF PUSHES THE FRONT
EAST OF THE AREA. THE DIFFERENCES COULD CREATE QUITE DIFFERENT
CONDITIONS FOR THE LOCAL AREA. WILL NOT MAKE MAJOR CHANGES TO
INHERITED TUESDAY/TUESDAY NIGHT GRIDS. THE EC CATCHES UP WITH THE
GFS AROUND WEDNESDAY WITH A LARGE ARCTIC AIR MASS SPREADING SOUTH
FROM HUDSON BAY...MAINTAINING THE STATIONARY FRONT NEAR EASTERN
MT. IN COORDINATION WITH SURROUNDING OFFICES DID LOWER
TEMPERATURES QUITE A BIT FOR WED AND BEYOND. SCT
&&
.AVIATION...
VFR CONDITIONS WILL PREVAIL THROUGH TOMORROW MORNING WITH
INCREASING HIGH CLOUDS OVERNIGHT AHEAD OF AN APPROACHING LOW
PRESSURE SYSTEM. CEILINGS WILL LOWER TO AROUND 6K FT TOMORROW
MORNING WITH AREAS OF LIGHT SNOW BY AFTERNOON. PERIODIC MVFR
CONDITIONS ARE POSSIBLE IN ANY AREAS OF LIGHT SNOW...AND POSSIBLY
BRIEF IFR CONDITIONS. THE WIND WILL BE LIGHT AND VARIABLE
OVERNIGHT...EXCEPT FOR A SOUTHEAST WIND AROUND 10KT AT KGGW. A
SOUTHERLY WIND AROUND 8KT WILL DEVELOP TOMORROW MORNING AND THEN
VEER TO THE WEST AT 10-15KT IN THE AFTERNOON. AJZ
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
WEATHER.GOV/GLASGOW
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