FXUS65 KGGW 101124
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
424 AM MST THU DEC 10 2009

.SHORT TERM...FOR NORTHEAST MONTANA...TODAY THROUGH SATURDAY...
STRONG NW FLOW ALOFT ALOFT CONTINUING TO KEEP COLD AIR FLOWING
INTO OUR AREA. THIS ASSOCIATED WITH UNUSUALLY LARGE AND STRONG
UPPER LOW THAT DOMINATES MUCH OF CANADA AND THE U.S. LOW CENTER IS
SLOWLY MOVING S INTO N SK. SATELLITE CHANNELS INDICATE
MOISTURE/CLOUDS CONTINUING TO FOLLOW THIS FLOW CYCLONICALLY INTO
OUR AREA.

SEVERAL WEAK SHORTWAVES IN THIS FLOW...BUT OVERALL DYNAMICS WEAK
AND MOISTURE VERY LIMITED IN COLD AIRMASS...WITH CLOUDS BROKEN UPSTREAM.
00Z KGGW SOUNDING DID SHOW SLIGHT MOISTENING OF THE AIRMASS...BUT
THIS WAS ASSOCIATED WITH A LITTLE BIT STRONGER SHORTWAVE THAT
EXITED OUR AREA LAST EVE. THEREFORE...EXPECT MAINLY JUST FLURRIES
AGAIN TODAY. NOT MUCH CHANGE IN THE AIRMASS...BUT MOST HIGHS WILL
AT LEAST BE A LITTLE ABOVE ZERO...THANKS TO A LITTLE MORE MIXING
IN LOWER LEVELS. THEN...LITTLE CHANGE IN TEMPS THRU SAT.

MODELS SHOW UP TO 35 KT AT 850 MB TODAY...BUT FORECAST SOUNDINGS
DON'T QUITE SUPPORT MIXING MUCH OFF THE SURFACE. BUT WITH VWP
SHOWING 20KT AT 3K FT AGL ALL NIGHT...EXPECT WINDS A LITTLE MORE
THAN SURFACE GRADIENTS WOULD INDICATE. WIND CHILL ADVISORY IS HIT
AND MISS ON BOTH WIND SPEEDS AND TEMPS...BUT ENOUGH LOCATIONS NEAR
OR PAST CRITERIA TO LET IT CONTINUE UNTIL 10 AM EXPIRATION.

THE UPPER LOW CENTER HEADING SOUTH STALLS AND BECOMES MORE W-E
ORIENTED FRI AND SAT. WHILE THIS TURNS FLOW W ALOFT...THE ORIGIN
THOUGH REMAINS THE N BRANCH OF THE JET...WITH A 120 KT JET STREAK
HEADING S INTO MT. A SLIGHTLY MORE ACTIVE FRONTAL BOUNDARY DEVELOPS
AS A RESULT....DIVIDING COLDER ARCTIC AIR FROM THAT SOMEWHAT
MODIFIED. NE MT STAYS ON THE COLD SIDE OF THE FRONT. ONE LITTLE
STRONGER PUSH OF COLDER AIR N OF THE FRONT STARTS FRI NIGHT...BUT
THIS PUSH SLOWS UP A LOT SAT. SURFACE WAVE ALONG THE FRONT AND A
LITTLE LIFT AND VORTICITY WOULD INDICATE JUST A LITTLE BIT BETTER
CHANCE OF MEASURABLE SNOW...BUT WORD EMPHASIS ON LIGHT...NOT
MUCH MORE THAN A DUSTING. FLOW TURNING W ALOFT WOULD GIVE A LITTLE
OVERRUNNING MOISTURE TOO. MODELS KEEP QPF MOSTLY JUST A FEW
HUNDREDTHS.

ALTHOUGH MODELS SHOW THICKNESSES RISE A BIT WITH MORE WESTERLY
FLOW ALOFT...THIS IS MAINLY ALOFT WITH LITTLE REFLECTION TO
SURFACE ON COLD SIDE OF THE FRONT. NAM AND ECMWF TAKE THE WARMER
SIDE OF THIS WITH THICKNESSES INTO THE 530S DM. THESE APPEAR
RELATED TO MOVING THE CLOSED LOW NOT SO FAR S OVER CANADA. SOME
RATHER LARGE MAV/MET TEMP DIFFERENCES...WILL STAY VERY MUCH ON THE
COLD SIDE DUE TO RECENT CONDITIONS OF LATE AND SURFACE PROGS. SIMONSEN

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...
POLAR VORTEX OVER CANADA TO REMAIN THE DOMINANT FEATURE SATURDAY
NIGHT THRU MONDAY BEFORE IT FINALLY MOVES FAR ENUF EAST TO ALLOW
SOME UPPER RIDGING AND MILDER AIR TO MOVE IN. REINFORCING SHOT OF
ARCTIC AIR COMES SATURDAY NIGHT OR EARLY SUNDAY MORNING IN THE
FORM OF A COLD FRONT. THAT AIR THEN REMAINS IN PLACE UNDER A
SURFACE HIGH UNTIL A SURFACE TROF MOVES IN MONDAY NIGHT AND BRINGS
MILDER AIR FROM THE SOUTHWEST AS SOME SEMBLANCE OF AN UPPER RIDGE
DEVELOPS OVER THE INTERMOUNTAIN WEST. COULD BE SOME LIGHT
OVERRUNNING SNOW AS THIS WARM FRONT PASSES. BEHIND THAT IT APPEARS
THINGS DRY OUT AND WARM UP INTO THE MIDWEEK PERIOD. THE UPPER
RIDGE TO OUR WEST ON TUESDAY CONTINUES TO TRUNDLE EAST AND IS
EXPECTED TO BE OVER THE AREA BY WEDNESDAY NIGHT OR THURSDAY.
EXTENDED MODELS THO HAVE BEEN QUITE CHANGEABLE OF LATE...THUS
CONFIDENCE IS STILL LOW AT THIS POINT ON THE WARM SOLUTION FOR THE
MIDDLE TO END OF NEXT WEEK. WILL WARM THINGS A BIT BUT STILL PLAY
THINGS CLOSE TO THE VEST BY NOT BEING TOO LIBERAL WITH THE AMOUNT
OF WARMING. 

&&

.AVIATION...
EXPECT CEILINGS TO VACILLATE BETWEEN VFR AND MVFR TODAY AS LOW
CLOUDS CONTINUE TO COME DOWN IN THE NORTHWEST FLOW. OCCASIONAL
FLURRIES OR LIGHT SNOW MAY DROP VISIBILITIES AT TIMES TO BELOW 3
MILES BRIEFLY. EXPECT VFR CONDITIONS TO PREVAIL TONIGHT WITH
PERHAPS SHORT PERIODS OF MVFR CEILINGS. WIND TO GET A LITTLE
EXCITED TODAY FROM THE WEST NORTHWEST IN THE 10-15 KT RANGE DURING
THE EARLY AND MID AFTERNOON. WIND DROPS OFF TO LIGHT QUICKLY AFTER
SUNSET. 

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 10 AM MST THIS MORNING FOR CENTRAL AND 
SOUTHEAST PHILLIPS-CENTRAL AND SOUTHERN VALLEY-DANIELS-SHERIDAN-
WESTERN ROOSEVELT-PETROLEUM-GARFIELD-MCCONE-RICHLAND-DAWSON-
PRAIRIE-WIBAUX-NORTHERN PHILLIPS-SOUTHWEST PHILLIPS-NORTHERN 
VALLEY-EASTERN ROOSEVELT.

&&

$$

WEATHER.GOV/GLASGOW