FXUS65 KMSO 281050
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
350 AM MST SAT NOV 28 2009

.DISCUSSION...STRENGTHENING HIGH PRESSURE...CLEARING SKIES AND SUFFICIENT
LOW LEVEL MOISTURE ACROSS NORTHWEST MONTANA AND PORTIONS OF CENTRAL
IDAHO HAVE PRODUCED SOME PATCHY TO AREAS OF VALLEY FOG. THIS FOG IS
EXPECTED TO PERSIST THROUGH THE MID MORNING HOURS BUT ISN'T EXPECTED
TO LAST TOO LONG THIS MORNING AS CLOUDS AND A NORTHWEST FLOW ALOFT
ARE EXPECTED TO INCREASE. THE INCREASE IN WINDS ALOFT WITH LOW LEVEL
MOISTURE AND WEAK INSTABILITY WILL AID IN INCREASING LIFT NECESSARY
TO TRIGGER SOME MOUNTAIN SNOW SHOWERS LATE THIS AFTERNOON THROUGH
THE EVENING HOURS.

SUNDAY AND MONDAY...MODELS ARE IN AGREEMENT IN DEVELOPING A STRONG RIDGE
OF HIGH PRESSURE ACROSS WEST AND INTO THE NORTHERN ROCKIES SUNDAY AFTERNOON
INTO MONDAY. VERY STABLE CONDITIONS AND STRONG INVERSIONS ARE EXPECTED
UNDER THIS PATTERN...WHICH IS FAVORABLE FOR VALLEY FOG IN CENTRAL IDAHO
AND WESTERN MONTANA. MODEL SOUNDINGS ARE INDICATING THESE INVERSIONS
COULD LAST THROUGH MOST OF THE MORNING AND POTENTIALLY MUCH OF MONDAY
AFTERNOON. THESE STRONG INVERSIONS...IF THEY DEVELOP...MAY ALSO CREATE
SOME AIR STAGNATION ISSUES.

TUESDAY THROUGH FRIDAY...THE ECMWF REMAINS THE PREFERRED MODEL FOR THE
EXTENDED FORECAST PERIOD WITH ITS GENERAL LEVEL OF CONSISTENCY. 
A LOW PRESSURE TROUGH WILL DROP OUT OF CANADA AND THROUGH THE 
NORTHERN ROCKIES ON TUESDAY. THIS TROUGH DOES NOT LOOK AS COLD OR 
MOIST AS GUIDANCE PREVIOUSLY PROJECTED...BUT LIGHT SNOW AND COOLER 
CONDITIONS ARE POSSIBLE ON TUESDAY FROM NEAR THE MONTANA/IDAHO 
BORDER AND EASTWARD. A BROAD TROUGH OF LOW PRESSURE WILL DOMINATE THE
MAJORITY OF THE UNITED STATES AFTER TUESDAY WITH NORTH CENTRAL IDAHO 
AND WESTERN MONTANA UNDER A COOL AND POTENTIALLY ACTIVE NORTHWESTERLY
FLOW PATTERN. 

&&

.AVIATION...FOG DEVELOPMENT IS EXPECTED THIS MORNING ACROSS MUCH
OF CENTRAL IDAHO AND THE VALLEYS OF NORTHWEST MONTANA. KGPI IS
EXPECTED TO BE IMPACTED BY PATCHY FOG. FOG IS EXPECTED TO DIMINISH
THROUGH THE MID MORNING HOURS AS ANOTHER WEAK SYSTEM IS EXPECTED
TO MOVE THROUGH THIS AFTERNOON AND EVENING PRODUCING MAINLY
SCATTERED MOUNTAIN SNOW. 

&&

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

$$

SHORT TERM...RPN
LONG TERM....KOLATA
AVIATION...RPN