FXUS65 KMSO 092104
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
204 PM MST WED DEC 9 2009

.DISCUSSION...THE NORTHERLY FLOW AND COLD AIR MASS WILL CONTINUE
TONIGHT. IN FACT...TONIGHT IS SHAPING UP SIMILAR TO LAST NIGHT
WITH RELATIVELY CLEAR SKIES TO BEGIN THIS EVENING THEN CLOUD COVER
INCREASING AFTER MIDNIGHT. THEREFORE...EXPECT ANOTHER QUICK DROP
IN TEMPERATURES EARLY...THEN A LEVELING OFF ESPECIALLY OVER
NORTHWEST MONTANA.

CLOUD COVER MOVING IN LATE TONIGHT IS ASSOCIATED WITH THE LEADING
EDGE OF A WEAK SHORTWAVE EMBEDDED IN THE FLOW. THIS COULD BE
ANOTHER WIDESPREAD LIGHT SNOW PRODUCER ACROSS WESTERN MONTANA
THURSDAY. THE FOCUS IS EXPECTED IN THE MOUNTAINS FROM NEAR
FLATHEAD LAKE TO THE CONTINENTAL DIVIDE. A COUPLE INCHES OF SNOW
ARE POSSIBLE IN THAT AREA. THIS FEATURE WILL MOVE EAST OF THE
DIVIDE THURSDAY NIGHT. THE FLOW WILL GRADUALLY SHIFT TO NORTHWEST
THROUGH FRIDAY NIGHT. MOST OF THE REGION WILL SEE CLOUD COVER
DURING THIS TIME...BUT THE MAIN THREAT OF CONTINUED LIGHT SNOW
WILL BE OVER THE MOUNTAINS OF NORTHWEST MONTANA...PARTICULARLY
ALONG THE DIVIDE. ON SATURDAY THIS FLOW BECOMES MORE WESTERLY AND
SAGS SOUTH OVER THE NORTHERN ROCKIES...BRINGING THE THREAT OF
PRECIP WITH IT. AT THE SAME TIME IT STILL APPEARS A VERY MOIST
SOUTHERN BRANCH WILL MOVE OFF THE PACIFIC INTO THE NORTHERN GREAT
BASIN. CURRENT TIMING HAS THIS MOISTURE SPREADING OVER NORTH
CENTRAL IDAHO SATURDAY.

SATURDAY NIGHT THROUGH WEDNESDAY...IT LOOKS LIKE THE MODELS HAVE 
SLOWED DOWN THE TWO AREAS OF LOW PRESSURE THAT WILL IMPACT WESTERN 
MONTANA AND NORTH CENTRAL IDAHO. THE PACIFIC LOW IS STILL DIGGING TO 
THE SOUTH OF THE REGION AND BRINGING SOME SNOW WITH IT...THE
CANADIAN LOW IS SLOWER TO DROP DOWN. BUT BY SUNDAY...THE PACIFIC LOW
IS FORECAST TO MOVE TO THE SOUTHEAST OF THE REGION AND THE
CANADIAN LOW HAS DROPPED DOWN TO SOUTHERN ALBERTA...WITH INCREASED
WINDS...COLDER TEMPERATURES AND A GOOD CHANCE OF SNOW. SUNDAY
NIGHT AND MONDAY SHOULD BE THE COLDEST PERIOD IN THE EXTENDED
FORECAST...WITH A WEAK RIDGE DEVELOPING TUESDAY BRINGING
MODERATING TEMPERATURES AHEAD OF ANOTHER PACIFIC WEATHER SYSTEM.

&&

.AVIATION...NORTHERLY FLOW SUPPORTED BY THE UPPER JET WILL KEEP SOME
CLOUDS AND MOSTLY TERRAIN LOCKED SHOWERS AROUND WESTERN MONTANA
OVERNIGHT WEDNESDAY. ANOTHER PULSE OF SHORTWAVE ENERGY WILL ENTER
THE REGION THURSDAY MORNING AND COULD SET OFF SNOW SHOWERS MAINLY
IMPACTING NORTHERN AIRFIELDS...INCLUDING KMSO AND KGPI. THE DEPTH
OF AVAILABLE MOISTURE TO ALLOW FOR SNOW DEVELOPMENT IS STILL
UNCERTAIN...HOWEVER WITH A FLOW PATTERN SIMILAR TO OBSERVED
TODAY...COULD NOT RULE OUT THE POSSIBILITY THAT SNOW SHOWERS COULD
LOWER CEILINGS AND VISIBILITIES AGAIN THURSDAY MORNING. ANY
SIGNIFICANT SNOW AND CEILING IMPACTS ARE EXPECTED TO LAST THROUGH
MIDDAY THURSDAY. OTHERWISE...MOSTLY CLEAR SKIES AND LIGHT DIURNAL
WINDS CAN BE EXPECTED.

&&

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

$$

SHORT TERM...WHITMORE
LONG TERM....KOLATA
AVIATION...NOLTE