FXUS65 KGGW 071612
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
912 AM MST MON DEC 7 2009

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH WEDNESDAY...
VERY COLD START TO THE DAY WITH SOME CLEARING OCCURING OVER THE
NORTHERN ZONES. EXPECTING SOME CLOUDS TO MOVE BACK INTO THE REGION
LATER TODAY FROM THE NORTH WHILE CLOUDS WILL PERSIST ACROSS THE
SOUTH. WITH THE CLOUDS IN THE SOUTH...COULD STILL HAVE SOME
FLURRIES THROUGH THE DAY SO LEFT THAT IN THE FORECAST. ONLY OTHER
CHANGE TO THE FORECAST OTHER THAN SKY COVER WAS TO LOWER HIGH
TEMPERATURES FOR TODAY SLIGHTLY. EBERT

PREVIOUS SHORT TERM DISCUSSION...THE FORECAST STARTS WITH A LARGE
AMPLIFIED RIDGE OF HIGH PRESSURE/OMEGA BLOCK WELL INTO NORTHERN
ALASKA. MONTANA SITS IN THE MIDDLE OF A STRETCHED OUT UPPER LEVEL
TROF...FROM CENTRAL CANADA TO THE CALIFORNIA COASTLINE...WITH THE
JET STREAM REMAIN SOUTH ACROSS SOUTHERN WYOMING. A COLD ARCTIC
SURFACE HIGH NUDGING SOUTH OUT OF CANADA AND INTO CENTRAL MONTANA.
THIS WILL KEEP WEATHER CONDITIONS DRY AND CALM OVER THE NEXT FEW
DAYS. THINGS WILL STAY DRY AT THE SURFACE BUT WITH RIGHT ABOVE
THIS ARCTIC AIR MASS IS ENOUGH MOISTURE TO KEEP CONDITIONS PARTLY
TO MOSTLY CLOUDY OVER THE NEXT FEW DAYS.

THIS UPPER TROF WILL START TO SPREAD EASTWARD INTO THE CENTRAL
PLAINS AND BECOME A LARGER FEATURE. THIS WILL FLATTEN THE EASTERN
SIDE OF THE OMEGA BLOCK OUT AND SET THE STAGE FOR MUCH COLDER AIR
TO ENTER THE NORTHERN ROCKIES WEDNESDAY. EXPECT A CHANCE OF
POSSIBLE FLURRIES AND LIGHT SNOW ACROSS THE SOUTHERN ZONES...WHILE
THE UPPER TROF STARTS TO SPREAD EASTWARD. THE CHANCE OF SNOW WILL
CONTINUE INTO TUESDAY AFTERNOON BEFORE COMING TO AN END AND THERE
WILL BE LITTLE TO NO ADDITIONAL ACCUMULATION IN AREAS THAT DO SEE
ADDITIONAL SNOWFALL.

CLOUD COVER WILL CONTINUE THE TREND OF THINNING DURING THE DAY AND
GROWING DENSER AFTER SUNSET. THIS WILL HELP KEEP THE TEMPERATURES
FROM REALLY DROPPING. THIS PATTERN WILL CONTINUE TO BE THE NORM
UNTIL CHANGE ARRIVES TUESDAY NIGHT INTO WEDNESDAY AS 850 MB TEMPERATURES
DURING THIS GROUP OF PERIODS CONTINUES TO STAY IN A RANGE OF -17*C
TO -23*C. ALSO WIND CHILLS WILL BE CLOSE TO ADVISORY CRITERIA BUT
WITH THE RELATIVELY LIGHT WIND EXPECTED OVER THE NEXT FEW NIGHTS
NOT ANTICIPATING ANY NEED FOR AN ADVISORY. RSMITH

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...
WILL CONTINUE TO HOLD THE PREVIOUS COURSE OF A MAINLY DRY AND COLD
FORECAST. POLAR VORTEX CENTERED NORTH OF SASKATCHEWAN WEDNESDAY
NIGHT THRU THURSDAY NIGHT KEEPS COLD NORTH TO NORTHWEST FLOW ACROSS THE
AREA. THERE MAY BE SOME FLURRIES AT TIMES BUT NOT SEEING ANY BIG
REASONS FOR ANY SNOW DEEMED SIGNIFICANT. ECMWF AND GFS MODELS
BEGIN TO DRIFT APART A BIT AFTER THAT AND GFS ENSEMBLE MEMBERS
BEGIN TO SHOW MORE SPREAD. OPERATIONAL GFS SEEMS A BIT SUSPECT IN
ITS RATHER FAST MOVEMENT OF THE CANADIAN LOW COMPARED WITH THE
ECMWF AND THE BULK OF THE ENSEMBLE MEMBERS. WILL CONTINUE TO RIDE
ALONG WITH A COLD FORECAST AS LOW LEVEL COLD AIR REMAINS IN THE
WAKE OF THE CANADIAN LOW FINALLY ROTATING CYCLONICALLY AND KICKING
EAST TO HUDSON BAY BY SATURDAY AFTERNOON. SURFACE HIGH EXPECTED
OVER NORTHEAST MONTANA SHOULD NOT ALLOW FOR MUCH IN THE WAY OF
MIXING WHICH LOOKS TO BE FORTUNATE AS COLD AIR REMAINS IN THE
LOWER LEVELS ANYWAY. UPPER FLOW BECOMES ZONAL FOR SUNDAY AND
MONDAY BEFORE PERHAPS SOME WEAK AND VERY WEAK UPPER RIDGING MOVES
IN FOR TUESDAY. 

&&

.AVIATION...
VFR CONDITIONS SHOULD PREVAIL FOR MUCH OF TODAY BEFORE GIVING WAY
TO MORE LOW CLOUDS COMING IN FROM THE NORTH DROPPING CONDITIONS TO
MAINLY MVFR BY THE EARLY EVENING WITH SOME OCCASIONAL FLURRIES.
WINDS SHOULD REMAIN LIGHT AND VARIABLE TODAY...AND LESS THAN 10KTS
OUT OF THE EAST TONIGHT. GAH

&&

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

&&

$$

WEATHER.GOV/GLASGOW