000
FXUS65 KMSO 051211
AFDMSO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
611 AM MDT FRI SEP 5 2008

.UPDATE...ADDED PATCHY VALLEY FOG TO POTIONS OF NORTH CENTRAL
IDAHO...THE BITTERROOT VALLEY...AND LOCATIONS ALONG THE INTERSTATE
90 CORRIDOR FOR THIS MORNING.

&&

.DISCUSSION...SOME PATCHY FOG HAS FORMED THIS MORNING IN LOW LYING
AREAS OF WEST CENTRAL MONTANA AND NORTH CENTRAL IDAHO. CLOUD COVER
DISPERSED ENOUGH IN THESE AREAS TO ALLOW FOR SUFFICIENT COOLING OVERNIGHT.
EXPECT FOG TO BE SHORT LIVED HOWEVER AS CLOUD COVER WILL INCREASE
OVER THE NEXT COUPLE OF HOURS.


&&

.AVIATION...CLOUD COVER WILL BEGIN TO INCREASE THROUGHOUT THE DAY
AS A SHORTWAVE ENTERS THE REGION FROM BRITISH COLUMBIA. THIS
SHORTWAVE WILL BRING AN INCREASING CHANCE FOR RAIN SHOWERS THROUGH
FRIDAY EVENING TO ALL MONTANA TERMINAL SITES...THOUGH SHOWERS ARE
MOST LIKELY ALONG THE CONTINENTAL DIVIDE. MOUNTAIN OBSCURATIONS
AND LOWERED CEILINGS ARE EXPECTED UNDER HEAVIER SHOWERS THIS
EVENING AND OVERNIGHT.


&&

.PREV DISCUSSION... /ISSUED 336 AM MDT FRI SEP 5 2008/

DISCUSSION...NORTHWEST FLOW ALOFT WILL PREVAIL OVER THE NORTHERN
ROCKIES FOR THE NEXT 48 TO 72 HOURS...ALLOWING WEAK IMPULSES OF
ENERGY TO IMPACT THE REGION. DUE TO THE SUBTLE NATURE OF THESE
FEATURES...TIMING WILL BE DIFFICULT TO PINPOINT EXACTLY.
HOWEVER...FORECAST MODELS ARE IN FAIRLY GOOD AGREEMENT IN BRINGING
THE FIRST FEATURE THROUGH THIS EVENING AND OVERNIGHT. SHOWERS WILL
FORM ACROSS WESTERN MONTANA WITH THE GREATEST COVERAGE ALONG THE
CONTINENTAL DIVIDE. ANOTHER SIMILAR FEATURE IS EXPECTED LATE
SATURDAY NIGHT INTO SUNDAY. LOCATIONS IN IDAHO WILL LIKELY AVOID
THE BRUNT OF THIS PRECIPITATION AS MOST OF THE MOISTURE AND ENERGY
SKIRTS TO THE EAST. TEMPERATURES WILL GENERALLY REMAIN BELOW
NORMAL FOR THIS TIME OF YEAR THROUGH THE PERIOD AS CLOUD COVER
LIMITS SURFACE HEATING.

MONDAY THROUGH FRIDAY...THE BEGINNING OF THE WORK WEEK SHOULD BE
FAIRLY TAME THROUGH THE DAY ON TUESDAY. DURING THIS TIME THE
NORTHERN ROCKIES WILL BE UNDER THE INFLUENCE OF A VERY WEAK AND
FLAT RIDGE WHICH WILL ALLOW TEMPERATURES TO WARM TO MORE
SEASONABLE DAYTIME HIGHS ACROSS THE REGION. THIS BRIEF REPRIEVE
WILL END WITH THE PASSAGE OF THE NEXT SHORTWAVE ON WEDNESDAY.
NEWEST MODEL RUNS HAVE SEEMED TO FLIP FLOP IN THEIR HANDLING OF
THIS SYSTEM...NOW LOOKING TO DIG A CUTOFF LOW PRESSURE SYSTEM WELL
INTO NORTHERN NEVADA AND UTAH BEFORE SKIRTING IT EASTWARD. CANT
HELP BUT WONDER IF THE MODELS ARE HAVING A DIFFICULT TIME WITH
RECENT HURRICANE ACTIVITY AND THIS CHANGE IN THE FORECAST IS A
RESULT OF IT. BECAUSE OF THIS QUANDARY...DECIDED TO KEEP
PRECIPITATION IN LINE WITH PREVIOUS FORECAST FOR WEDNESDAY INTO
THURSDAY BUT HAVE INCREASED THE CHANCE FOR SHOWERS INTO THE LEMHI
COUNTY REGION TO ACCOUNT FOR POSSIBLE MODEL SHIFT WITH THIS LOW
PRESSURE SYSTEM. STILL PRETTY FAR OUT IN THE EXTENDED PERIOD TO
MAKE ANY TRUE JUDGMENT CALLS...SO WILL HAVE TO MONITOR AS TIME
PROGRESSES.


&&

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

$$

SHORT TERM...VIA
LONG TERM....ALLEGRETTO
AVIATION...ALLEGRETTO