FXUS65 KGGW 272203
AFDGGW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
303 PM MST FRI NOV 27 2009

.SHORT TERM...FOR NORTHEAST MONTANA...TONIGHT THROUGH SUNDAY...
A LITTLE COOLER WEATHER THRU THE WEEKEND. SATELLITE CHANNELS SHOW
A FAIRLY MOIST STREAM ALOFT FROM THE SW ASSOCIATED WITH UPPER
TROUGH MOVING E ACROSS PACIFIC NW INTO W MT. GENERALLY CLOUDY
SKIES OVER NE MT ASSOCIATED WITH THIS...BUT THIS IS MID/HIGH
CLOUDS WITH FAIRLY WEAK DYNAMICS SO MAYBE A FEW FLURRIES OF SNOW
IN OUR N AT BEST FROM IT THIS AFTERNOON AND EARLY EVE. COOL
ADVECTION FROM THE NW AT LOWER LEVELS HAS COMBINED WITH THE CLOUDY
SKIES TO PRODUCE HIGHS 15F OR SO COOLER THAN YESTERDAY.

MODELS SHOW THE UPPER TROUGH TO BE SPLITTING AS IT APPROACHES OUR
AREA LATE TONIGHT. MAIN PART CLOSES OFF AND MOVES SE THRU CA.
WEAKER N PART PASSES THRU OUR N LATE TONIGHT/SAT MORN. THIS PROVIDES
THE BEST CHANCE OF ANY SNOW SHOWERS AS LOW LEVELS MOISTEN UP
ENOUGH AND UPPER LEVEL MOIST STREAM IS STILL IN PLACE. 20 POPS
LOOK ADEQUATE AND THOSE PLACES THAT DO RECEIVE ACCUMS WILL BE
QUITE LIGHT. THIS ALL SHIFTS TO OUR E BY SAT AFTERNOON WITH MODELS
SHOWING MEAN RH DROPPING BELOW 40 PCT FOR CLEARING SKIES.

UPPER RIDGING ALONG THE W COAST SUNDAY WITH A SURFACE HIGH MOVING
FROM OFF THE COAST INTO THE GREAT BASIN. THIS WILL BRING DRY
WEATHER. MODELS INDICATE QUITE A BIT OF WARM ADVECTION MID/HIGH
CLOUDS LATE SAT NIGHT AND SUN...BUT LITTLE LIFT FOR ANY PRECIP.
SIMONSEN

.LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...
EXTENDED PERIOD BEGINS WITH A REX BLOCKING PATTERN OVER THE WESTERN
US. UPPER RIDGE OVER THE WEST COAST PUSHING INTO MONTANA WITH A
CUT OFF UPPER LOW OVER THE DESERT SOUTHWEST. THIS WILL KEEP THINGS
DRY AND MILD FOR MONDAY. 

THIS PATTERN WILL BEGIN TO BREAK DOWN AS A SHORTWAVE DIVES SOUTHEAST
OUT OF THE GULF OF ALASKA. THIS SHORTWAVE WILL COMBINE WITH ANOTHER
SHORTWAVE OVER THE YUKON TERRITORY AND DRIVE A CONTINENTAL POLAR
AIR MASS SOUTHWARD INTO THE NORTHERN PLAINS MONDAY NIGHT INTO
TUESDAY. AGREEMENT BETWEEN MODELS IS SOMEWHAT HARD TO COME BY WITH THIS
SYSTEM. THE GFS AND ECMWF BOTH HAVE THIS SHORTWAVE PUSHING A COLD
FRONT THROUGH THE REGION MONDAY NIGHT INTO TUESDAY. THAT IS WHERE
THE SIMILARITIES END. THE GFS KEEP THE BRUNT OF THE POLAR AIR MASS
EAST OF MONTANA. THE ECMWF BRING THE POLAR AIR MASS DOWN ON TOP OF
NEMONT. THE GFS IS ALSO MUCH DRIER THEN THE ECMWF...ALTHOUGH
NEITHER 12Z MODELS IS PRODUCING MUCH QPF AT ALL. HARD TO DISAGREE
WITH THE QPF FORECAST SINCE BOTH MODELS HAVE THE CUT OFF LOW OVER
THE SOUTHWESTERN US. IT IS HARD FOR ANY MOISTURE TO MAKE IT NORTH
OF THIS FEATURE AND WILL LIKELY HAVE TO BE TRANSPORTED WITH THE
WAVE FROM THE NORTH. DON'T EXPECT MUCH PRECIPITATION IF ANY WITH THE
PASSING OF THIS SHORTWAVE TUESDAY MORNING/AFTERNOON. SINCE THE
ECMWF IS STILL INDICATING A CHANCE OF LIGHT SNOW WILL LEAVE A
SLIGHT CHANCE OF LIGHT SNOW ACROSS THE REGION IN THE FORECAST FOR
TUESDAY MORNING AND TUESDAY AFTERNOON. 

TEMPERATURES WILL PROBABLY START OFF WARMER TUESDAY MORNING THEN
THEY WILL BE TUESDAY EVENING. MORNING WILL PROBABLY SEE HIGHS IN
THE MID TO UPPER 30S WITH TEMPERATURES FALLING INTO THE UPPER 20S
BY TUESDAY EVENING. IF THE GFS IS RIGHT MOST OF THIS COLD AIR
WILL MOVE INTO THE DAKOTAS FOR THE REMAINDER OF THE WEEK AND TEMPS
WILL BE AT OR SLIGHTLY ABOVE NORMAL. IF THE ECMWF IS CORRECT THEN
NEMONT WILL BE DEALING WITH MUCH COLDER AIR THE REST OF THE WEEK.
THIS IS WHERE THE INCONSTANCY IN THE MODELS COMES IN SO SPLIT THE
DIFFERENCE AND KEPT HIGHS SLIGHTLY BELOW NORMAL OR IN THE UPPER
20S. RSMITH

PREVIOUS DISCUSSION...THE EXTENDED FORECAST PERIOD BEGINS ON
MONDAY WITH A RIDGE OVER THE WEST COAST ROLLING OVER A UPPER LOW
IN THE BAJA REGION. SOMEWHAT OF A SPLIT FLOW PATTERN STILL EXISTS.
WESTERLY FLOW UNDER THE RIDGE ON MONDAY WILL PROVIDE MAX TEMPS
SLIGHTLY ABOVE NORMAL. THE RIDGE BREAKS DOWN AS A TROUGH MOVES IN
FROM CANADA IN NORTHWEST FLOW.

THE FRONT MOVES IN ON TUESDAY AFTERNOON. AT THIS POINT THE GFS
SEEMS TO HAVE THE BETTER HANDLE ON IT AND HAS BEEN MORE
CONSISTENT. IN PAST RUNS THE EC HAS TRIED TO MATCH UP WITH THE GFS
MORE. THE GFS IS DRIER THAN THE EC AND TRACKS THE LOW MORE EAST
RATHER THAN SE SPARING OUR FORECAST AREA THE BRUNT OF THE ARCTIC
AIRMASS. THE BEST CHANCE FOR PRECIP IS TUESDAY AFTERNOON FOR THE
CWA BUT EVEN AT BEST IS A SLIGHT CHANCE POPS FOR THE AREA. NOT
MUCH IN THE WAY OF MEASURABLE PRECIP IS EXPECTED AT THIS POINT. THE
ARCTIC AIRMASS WILL PUSH THROUGH TUESDAY EVENING AND BRING MAX
TEMPS FOR WED AND THU BACK TO NORMALS. THE PASSAGE OF THE FRONT
TUESDAY EVENING WILL BRING A CONCERN FOR STRONG NW WINDS TUE NIGHT
AND WED.

AFTER WED THE CONSISTENCY IN THE MODELS DROP AS THE GFS WANTS TO
DROP A CLOSED LOW DOWN THE EAST COAST AND KEEP THE FORECAST AREA
ON THE OUTER EDGE OF THE ARCTIC AIR. THE EC WANTS TO BRING A RIDGE
ASHORE AND WARM THE AREA UP. THE ENSEMBLES ALSO SHOW MUCH
UNCERTAINTY. FELT THE BEST CONFIDENCE IS TO STAY CLOSE TO
CLIMATOLOGY FOR FRI AND INTO NEXT WEEKEND. SHALLENBERGER

&&

.AVIATION...
VFR CONDITIONS EXPECTED TO CONTINUE THIS EVENING ACROSS NORTHEAST MONTANA.
EXPECT THE CEILINGS TO REMAIN ABOVE 5,000 FT AGL THIS EVENING ...BUT
WILL START TO DROP OVERNIGHT AS AN UPPER WAVE CROSSES THE REGION. THIS
WILL CAUSE POSSIBLE LIGHT RAIN AND OR SNOW SHOWERS ACROSS THE REGION
OVERNIGHT AND COULD LEAD MVFR CONDITIONS AT TIMES ACROSS THE TERMINALS
DUE TO LOWER CEILINGS. RSMITH

&&

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

&&

$$

WEATHER.GOV/GLASGOW