FXUS65 KMSO 292146
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
246 PM MST SUN NOV 29 2009

.DISCUSSION...

TONIGHT THROUGH TUESDAY...NORTHWESTERLY FLOW WILL CONTINUE TO BRING 
CLOUDS AND A VERY MINOR THREAT OF SNOW TO NORTH CENTRAL IDAHO AND 
WESTERN MONTANA THROUGH THE OVERNIGHT TONIGHT. SNOW WILL BE MOSTLY 
LOCKED TO HIGH TERRAIN...WITH LITTLE ACCUMULATION EXPECTED. HIGH 
PRESSURE DEVELOPING TO THE WEST OF THE REGION WILL ALLOW 
TEMPERATURES AT HIGH ELEVATIONS TO INCREASE THROUGH EARLY TUESDAY. 
THE PORTION OF THE PACIFIC JET STREAM RESPONSIBLE FOR THE CURRENT 
CLOUDY SCENARIO IS ANTICIPATED TO WEAKEN AND MOVE NORTH OF THE 
CANADIAN BORDER DURING THIS EVENING AND OVERNIGHT...WITH HIGH 
PRESSURE SLOWLY BECOMING MORE DOMINANT AND CLOUDS DISSIPATING. THE 
HIGH PRESSURE...COMBINED WITH RESIDUAL LOW LEVEL ATMOSPHERIC 
MOISTURE WILL ALLOW PATCHY FOG TO DEVELOP IN THE FOG PRONE VALLEYS 
OF NORTH CENTRAL IDAHO AND NORTHWEST MONTANA. A SLIGHT THREAT OF FOG 
ALSO EXISTS NEAR KALISPELL AND MISSOULA. BY EARLY MORNING 
TUESDAY...MODELS DEPICT AN ARCTIC AIRMASS MOVING QUICKLY SOUTH 
THROUGH CENTRAL MONTANA. THE DEPTH OF THE COLD AIR IS BELIEVED TO BE 
MINIMALLY SUFFICIENT FOR INTRUSION INTO AREAS WEST OF THE 
CONTINENTAL DIVIDE. THE COLD AIR ARRIVAL WILL BE EVIDENCED BY
EASTERLY FLOW INTENSIFYING FOR A TIME IN THE FLATHEAD AND MISSOULA
VALLEYS...AS WELL AS THE TERRAIN GAPS EAST OF THESE VALLEYS. THE
COOLING EFFECT OF THIS SCENARIO WILL BE MOST NOTABLE IN THE HIGH
TERRAIN...WITH SNOW DEVELOPING ALONG AND BEHIND THE MID LEVEL
FRONTAL FEATURE. NO SIGNIFICANT SNOW ACCUMULATIONS ARE ANTICIPATED
DURING TUESDAY.

WEDNESDAY THROUGH THURSDAY...A RIDGE OF HIGH PRESSURE WILL BUILD
OVER THE NORTHERN ROCKIES CAUSING A DRYING TREND. TOWARDS THE END
OF THE WEEK THE MODELS ARE COMING MORE IN LINE WITH A SOLUTION
FAVORING A DISTURBANCE SLIDING THROUGH THE NORTHERN ROCKIES ON
FRIDAY...INCREASING PRECIPITATION CHANCES FOR THE AREA. THEN A TROUGH
APPEARS TO SETTLE OVER THE REGION WITH THE POTENTIAL OF
SIGNIFICANT COOLING AND UNSTABLE ATMOSPHERIC CONDITIONS.

&&

.AVIATION...TERRAIN LOCKED SHOWERS AND LIGHT DIURNAL WINDS WILL
CONTINUE OVERNIGHT SUNDAY OVER THE NORTHERN ROCKIES. BREEZY
CONDITIONS CAN BE EXPECTED ACROSS THE GREAT DIVIDE...KEEPING SOME
STRONGER SUSTAINED WINDS AT KBTM THROUGH THE AFTERNOON.
OVERNIGHT...PATCHY FOG DEVELOPMENT WILL BE POSSIBLE ACROSS
NORTHWEST MONTANA AND ALSO THE SALMON RIVER VALLEY. DENSITY AND
LOCATION OF THE FOG WILL DEPEND OF SKY COVER...BUT MODEL SOUNDINGS
INDICATE A MOIST TEMPERATURE PROFILE SATURATING THE LOWER LEVELS
SUPPORTING FOG DEVELOPMENT. A BUILDING HIGH PRESSURE RIDGE WILL
CONTINUE AND INCREASE THE FOG CHANCES THROUGH THE BEGINNING OF THE
WEEK.

&&

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

$$

SHORT TERM...ZUMPFE
LONG TERM....SMITH
AVIATION...NOLTE