FXUS65 KGGW 240406 AAA
AFDGGW

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GLASGOW MT
906 PM MST WED DEC 23 2009

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH FRIDAY...
SNOW HAS MOVED ON INTO THE DAKOTAS SO REMOVED MOST POPS FOR
TONIGHT. WINDS REMAIN STRONG OVER THE EASTERN ZONES BUT NOT STRONG
ENOUGH FOR BLOWING SNOW. THE WINTER WEATHER ADVISORY HAS RUN ITS
COURSE. HOWEVER WINDS AND DROPPING TEMPERATURES WILL PRODUCE WINDS
CHILLS OF LESS THAN -20*F. THEREFORE CHANGED EASTERN ZONES FROM
WINTER WEATHER ADVISORY TO A WIND CHILL ADVISORY TO RUN ALL NIGHT
CONCURRENTLY WITH THE WIND CHILL ADVISORY OVER THE WESTERN ZONES.
TEMPERATURES WILL DROP TO AS LOW AS -20*F IN NORTHERN AREAS WHILE
A SURFACE HIGH SLIDES OVER THE CWA. THIS WILL REDUCE WINDS TO LESS
THAN 10MPH IN THE WESTERN ZONES. WITH SKIES CLEARING WENT AHEAD
AND ADDED PATCHY FOG LATE TONIGHT AND THE MORNING. SCT

PREVIOUS DISCUSSION...
WITH ARCTIC FRONT SOUTH OF NORTHEAST MONTANA AND THE SNOW HEADING
INTO NORTH DAKOTA. THE SNOW HAS COME TO AN END ACROSS WESTERN
ZONES AND BREAKS IN THE CLOUD COVER ARE STARTING TO APPEAR. THE
WINDS ARE STILL DRIFTING THE SNOW AROUND IN THE WESTERN ZONES. THE
SNOW WAS STILL BLOWING AND DRIFTING AROUND IN THE CENTRAL AND
EASTERN ZONES. SINCE THE CLOUDS ARE STARTING CLEAR FROM WEST TO
EAST ACROSS THE WESTERN ZONES COMBINED WITH FRESH SNOW ON THE
GROUND. EXPECT THE OVERNIGHT TEMPERATURES TO TAKE A NOSE DIVE WITH
THE FRESH SNOW ON THE GROUND. THE WINDS WILL REMAIN UP AROUND 10
MPH UNTIL AFTER MIDNIGHT WHICH WARRANTS A WIND CHILL ADVISORIES AS
MOST PLACES ACROSS NEMONT WILL SEE WIND CHILL READING RANGING IN
BETWEEN -20 TO -30. SURFACE HIGH PRESSURE DROPS SOUTH INTO CENTRAL
MONTANA. THIS INCLUDES THE WESTERN ZONES IN NEMONT. THE UPPER LOW
SHOULD HELP MAINTAIN THE CLOUD COVER AND SNOWFALL ACROSS THE
EASTERN ZONES. LEFT THE WINTER WEATHER ADVISORY FOR SNOW AND
BLOWING SNOW ALONE FOR THOSE ZONES. WILL LET THE EVENING SHIFT
MAKE THE JUDGMENT CALL ON WHETHER TO EXTEND THE ADVISORY PAST 06Z
OR LET IT EXPIRE.

UPPER LOW MOVES TO THE SOUTH ON THURSDAY AND COLD HIGH PRESSURE
PREVAILS OVER EASTERN MONTANA THROUGH CHRISTMAS DAY. THE AREA WILL
BE IN NORTHERLY FLOW ALOFT BETWEEN AN UPPER RIDGE TO THE EAST AND
A SLOW MOVING UPPER LOW TO THE EAST. THAT UPPER LOW WILL BECOME A
MAJOR WINTER STORM WHICH WILL BE BRINGING SNOW AS FAR WEST AS THE
DAKOTAS THURSDAY AND FRIDAY OF WHICH THE WESTERN EDGE MAY CLIP FAR
EASTERN MONTANA AT THIS. WILL MENTION A SLIGHT CHANCE OF SNOW FOR
NOW. RSMITH/FORRESTER.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...
MAIN FORECAST IMPACT IN THE EXTENDED WILL BE LARGE CYCLONIC SYSTEM
ON THE EASTERN PORTIONS OF THE CWA AND TEMPS. BY 06Z SAT THE
UPPER LOW BECOMES STACKED OVER UPPER MIDWEST WITH SURFACE LOW
VCNTY OF IOWA. ECMWF LITTLE STRONGER AND FARTHER NORTH WITH LOW
PLACEMENT BUT STILL ENOUGH GRADIENT ALONG EXTREME EASTERN ZONES
FOR SOME BLOWING SNOW. WRAP AROUND PCPN DOES NOT APPEAR TO BE A
CONCERN OTHER THAN A FEW FLURRIES AS THE MODELS HAVE BEEN TRENDING
A LITTLE FASTER AND FARTHER EAST WITH THIS STORM. BY SATURDAY
NIGHT AND SUNDAY THE THICKNESS PATTERN AND 850MB TEMPS ON GFS AND
ECMWF ARE A LITTLE COOLER WITH SOMEWHAT OF A REX BLOCK/OMEGA
LOOKING PATTERN. THE GFS THEN SPLITS TROUGH ENERGY BY WEDNESDAY
AND MORE PROGRESSIVE THAN ECMWF TREND OF LAGGING A GENERAL TROUGH
ACROSS THE WEST. HAVE KEPT TEMPS IN LINE WITH BELOW NORMAL PATTERN
AND DRY INTO WED. SLA

&&

.AVIATION...
THE SKY HAS CLEARED IN THE WAKE OF THE WINTER STORM WHICH HAS NOW
MOVED EAST OF THE AREA. SURFACE HIGH PRESSURE WILL BUILD IN
TONIGHT AND RESULT IN SHIFTING A TIGHT PRESSURE CURRENTLY OVER
THE EASTERN THIRD OF THE AREA INTO NORTH DAKOTA. THIS WILL ALLOW
THE STRONG WIND CURRENTLY AFFECTING KSDY AND KGDV TO GRADUALLY
DIMINISH OVERNIGHT. SURFACE HIGH PRESSURE WILL REMAIN OVER THE
AREA THURSDAY AND KEEP WIND BELOW 10 KT. BROKEN MID CLOUDS ARE
EXPECTED TO ACCOMPANY THE UPPER LOW AS IT PASSES BUT CONDITIONS
SHOULD REMAIN VFR AT ALL SITES. LIGHT WIND AND A CLEAR SKY
TOMORROW NIGHT COULD MAKE FOR FOG FORMATION. 

&&

.GLASGOW WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 5 AM MST THURSDAY 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