FXUS65 KMSO 272154
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
254 PM MST FRI NOV 27 2009

.DISCUSSION...

TONIGHT THROUGH SATURDAY NIGHT...A WEAKENING PACIFIC STORM 
SYSTEM...CURRENTLY SPLITTING INTO TWO SEPARATE SYSTEMS NORTH AND 
SOUTH...WILL CONTINUE TO BRING MOIST CONDITIONS TO NORTH CENTRAL 
IDAHO AND WESTERN MONTANA DURING THE EVENING AND OVERNIGHT TONIGHT. 
THE LOWER LEVELS OF THE ATMOSPHERE HAVE BECOME SATURATED AT MANY 
LOCATIONS...MOST NOTEWORTHY WITH FOG DEVELOPMENT ACROSS THE CAMAS
PRAIRIE IN IDAHO. AS THE UPPER LEVEL CLOUD SHIELD CONTINUES TO
MOVE EAST OVERNIGHT...HIGH CLOUDINESS WILL DIMINISH SIGNIFICANTLY
OVER IDAHO BY MIDNIGHT. GIVEN THE SLIGHTLY COOLER AIR ALOFT TO BE
PRESENT THROUGH THIS EVENING...MOST OF THE FOG IN IDAHO IS
ANTICIPATED TO LIFT TO A LOW STRATUS DECK OVERNIGHT.
HOWEVER...AREAS OF FOG ARE EXPECTED TO DEVELOP IN NORTHWEST
MONTANA DURING THIS SAME TIME WITH LOW STRATUS ALREADY IN PLACE.
GIVEN HOW WEAK THIS SYSTEM IS AND HOW LITTLE COOLING HAS BEEN
ASSOCIATED WITH ITS PRESENCE...TEMPERATURES ARE NOT EXPECTED TO
COOL SIGNIFICANTLY ACROSS THE AREA. BY MIDDAY
SATURDAY...NORTHWESTERLY FLOW WILL BECOME THE DOMINANT FEATURE
PRESENT OVER NORTHWEST MONTANA. MODELS DEPICT A RELATIVELY STRONG
PORTION OF THE PACIFIC JET STREAM OVER NORTHWEST MONTANA DURING
SATURDAY...LIKELY TO FORCE A MAINLY TERRAIN LOCKED SNOW EVENT. NO
SIGNIFICANT SNOW ACCUMULATIONS ARE EXPECTED SATURDAY.

SUNDAY 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...
A WEAK PACIFIC STORM SYSTEM WILL BE PRESENT IN THE REGION THROUGH 
28/1000Z...WITH A NORTHWESTERLY FLOW DEVELOPING THEREAFTER. TERRAIN 
OBSCURATIONS WILL CONTINUE TO BE COMMONPLACE THROUGHOUT THE 
REGION...INCLUDING KBTM...KSMN...KMSO...AND KGPI. FOG DEVELOPMENT IN 
THE VICINITY OF KGPI IS POSSIBLE BETWEEN 28/0600Z AND 28/1800Z.

&&

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

$$

SHORT TERM...ZUMPFE
LONG TERM....KITSMILLER
AVIATION...ZUMPFE