FXUS65 KMSO 102106
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
206 PM MST THU DEC 10 2009

...SIGNIFICANT SNOW POSSIBLE THIS WEEKEND...ESPECIALLY OVER NORTH
CENTRAL IDAHO AND NORTHWEST MONTANA...

.DISCUSSION...A NORTHWEST FLOW WILL PERSIST OVER THE NORTHERN
ROCKIES WITH ATMOSPHERIC MOISTURE FAVORING NORTHWEST MONTANA.
THEREFORE...THE THREAT OF SNOW WILL CONTINUE IN THIS AREA
TONIGHT...MAINLY ALONG THE DIVIDE.  NORTHERN IDAHO AND WEST
CENTRAL MONTANA FROM FROM NEAR MISSOULA SOUTH WILL SEE LITTLE
CHANCE OF SNOW AND VARYING CLOUD COVER UNDER A SOMEWHAT DRIER FLOW
ALOFT. THIS WILL ALSO CONTINUE TO BE THE COLDEST AREAS WITH BETTER
RADIATIONAL COOLING. ICE BUILDUP ON AREA STREAMS WILL CONTINUE TO
BE A CONCERN. ON FRIDAY THE NORTHERN ROCKIES WILL BE UNDER A
RELATIVELY DRY FLOW AS THE MOISTURE OVER NORTHWEST MONTANA SHIFTS
NORTH. THE GLACIER NATIONAL PARK AREA COULD STILL SEE SOME LIGHT
SNOW...BUT CHANCES WILL BE DECREASING. 

THINGS BEGIN TO CHANGE LATE FRIDAY NIGHT AND SATURDAY IN A BIG WAY WITH
A WARM FRONT SPREADING SNOW NORTHWARD ACROSS THE CLEARWATERS INTO
THE WESTERN MONTANA. AS THE UPPER FLOW INCREASES SATURDAY NIGHT
INTO SUNDAY...ADDITIONAL SURGES OF MOISTURE AND ENERGY FROM THE
EASTERN PACIFIC WILL SHIFT ACROSS THE AREA. MODEL GUIDANCE SUGGEST
THAT AN ARCTIC FRONT WILL BRIEFLY SHIFT WESTWARD ACROSS THE DIVIDE
INTO NORTHWEST MONTANA SATURDAY NIGHT AND SUNDAY. THIS FRONT
SHOULD FURTHER ENHANCE THE SNOW. AT THIS POINT THERE REMAINS
SIGNIFICANT UNCERTAINTY REGARDING THE SPECIFIC AREA WHERE ALL THE
INGREDIENTS WILL COME TOGETHER FOR HEAVY SNOW. AT THIS TIME...THE BEST
POTENTIAL FOR MODERATE TO HEAVY SNOW IS OVER THE
CLEARWATERS...LOLO PASS...LOOKOUT PASS...THE FLATHEAD
VALLEY...GLACIER PARK...AND THE SEELEY/SWAN REGION. WE ARE USING
A BLEND OF THE GFS/ECMWF/ENSEMBLE FOR THIS FORECAST PERIOD.
IF...AND THIS IS A BIG IF...THE UPPER WEATHER DISTURBANCE SHIFTS A
BIT FURTHER SOUTH AS THE 12Z OPERATIONAL GFS MODEL INDICATES...THE
MISSOULA...BITTERROOT...AND SAPPHIRES MAY ALSO COME UNDER THE SNOW
BULLSEYE. AT THE VERY LEAST MANY OF THESE OTHER AREAS MAY SEE
LIGHT TO MODERATE SNOW AMOUNTS. STAY TUNED!!!

IN THE LONGEST TERM...MODEL GUIDANCE INDICATES A FLAT RIDGE OF
HIGH PRESSURE SHOULD SHIFT OVER THE PACIFIC NORTHWEST EARLY NEXT
WEEK. THIS SHOULD SUPPORT WARMER TEMPERATURES...BUT ALSO
SIGNIFICANT MOISTURE AND LIKELY A PERIOD OF MIXED FREEZING AND
FROZEN PRECIPITATION.

&&

.AVIATION...NORTHWEST FLOW CONTINUES TONIGHT AND IS PRODUCING SOME
LIGHT SNOW MAINLY TO THE NORTHEAST AND EAST OF FLATHEAD LAKE.
THESE SHOWERS WILL LOWER VISIBILITIES AND CEILINGS. BY FRIDAY
WESTERN MONTANA WILL BE UNDER A DRIER FLOW AND EXPECT VFR
CONDITIONS.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

$$

SHORT TERM...WHITMORE
LONG TERM....BAUCK
AVIATION...KOLATA