AREA FORECAST DISCUSSION

 
 FXUS65 KMSO 150324
 AFDMSO
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE MISSOULA MT
 924 PM MDT SAT MAR 14 2009
 
 ...MODERATE TO HEAVY SNOW TO IMPACT MOUNTAIN PASSES LATE TONIGHT
 THROUGH MONDAY...
 
 .DISCUSSION...FORECAST UPDATE THIS EVENING IS BASED UPON ADJUSTMENT
 OF THE ONSET OF SNOW IMPACTING THE AREA MAINLY LATER THAN SOONER AS
 A STRONG JET STREAM ENTERING THE PACIFIC NORTHWEST CONTINUES TO
 DIG TO THE SOUTHEAST INTO OREGON. THIS DIGGING JET IS SLOWING THE
 PROGRESS OF PRECIPITATION INTO IDAHO AND WESTERN MT. ANOTHER ISSUE
 TO COMPLICATE WINTER WEATHER HIGHLIGHTS TONIGHT THROUGH SUNDAY
 EVENING IS SNOW LEVELS. WITH THE EXCEPTION OF EXTREME NORTHWEST MT
 WHERE ENOUGH COLD AIR EXISTS TONIGHT TO HAVE SNOW IN THE LOWER
 VALLEYS THROUGH MIDDAY SUNDAY...ELSEWHERE SNOW LEVELS WILL HOVER
 AROUND 4500 TO 5000 FEET WITH LITTLE SNOW ACCUMULATIONS EXPECTED.
 GUSTY SOUTHERLY WINDS ARE EXPECTED TO DEVELOP SUNDAY AS THE JET
 STREAM BEGINS TO CROSS OVER IDAHO AND WESTERN MT. LASTLY...AS THE
 STRONG COLD FRONT PUSHES THROUGH THE AREA SUNDAY NIGHT INTO
 MONDAY...WINTER WEATHER CONDITIONS WILL DEVELOP IN ALL AREAS.
 MARIAS PASS LOOKS TO GET THE BRUNT OF THIS SYSTEM WITH VERY STRONG
 WESTERLY WINDS AND HEAVY SNOW. HOWEVER...LOOKOUT AND LOLO PASSES
 ALSO HAVE THE POTENTIAL TO SEE HEAVY SNOW AS WELL. STAY TUNED AS
 THIS SYSTEM IS STRONG ENOUGH TO IMPACT ALL MOUNTAIN PASSES OF
 NORTH CENTRAL IDAHO AND WESTERN MONTANA THROUGH MONDAY.
 
 &&
 
 .AVIATION...CONSISTENT MID LEVEL CEILINGS AND SOME LIGHT
 PRECIPITATION WILL DEVELOP BY EARLY THIS EVENING ACROSS NORTHERN
 IDAHO AND FAR NORTHWEST MONTANA. LOWERING CEILINGS...TERRAIN
 OBSCURATION...AND OCCASIONAL MVFR VISIBILITIES WILL CONTINUE
 OVERNIGHT...PERSISTING THROUGH SUNDAY AS A MOIST SYSTEM PUSHES
 THROUGH THE AREA. IN ADDITION...STRONG WINDS WILL DEVELOP
 THROUGHOUT THE DAY SUNDAY IN ADVANCE OF A STRONG COLD FRONT
 APROACHING FROM WASHINGTON.
 
 
 &&
 
 .PREV DISCUSSION... /ISSUED 239 PM MDT SAT MAR 14 2009/ 
 
 DISCUSSION...A VIGOROUS PACIFIC STORM IS APPROACHING THE NORTHERN
 ROCKIES...BUT MAY BE PROGRESSING JUST A LITTLE SLOWER THAN WAS
 PREVIOUSLY EXPECTED. CLOUD COVER AND LIGHT PRECIPITATION ON THE
 LEADING EDGE OF THE SYSTEM IS STARTING TO SHOW UP IN EASTERN
 WASHINGTON AND THE PANHANDLE...BUT WILL NOT INTENSIFY MUCH UNTIL
 THE THE SURFACE FRONT APPROACHES. THAT FEATURE IS STILL WEST OF
 THE CASCADES. THE MOUNTAINS OF THE PANHANDLE AND FAR NORTHWEST
 MONTANA WILL BEGIN SEEING MORE PERSISTENT SNOW EARLY THIS
 EVENING...BUT WARM STARTING TEMPERATURES WILL KEEP ACCUMULATING SNOW
 OUT OF THE VALLEYS UNTIL LATER TONIGHT. PRECIPITATION WILL SAG
 SOUTH THROUGH THE EVENING...AND BEGIN TO ACCUMULATE IN THE
 CLEARWATER AND CENTRAL BITTERROOT MOUNTAINS AROUND DARK.
 OROGRAPHIC LIFT WILL SPREAD LIGHT SNOW TO THE MOUNTAINS ALONG THE
 NORTHERN DIVIDE TONIGHT...BUT THE LARGE SCALE LIFT WILL REMAIN
 CLOSER TO THE MONTANA/IDAHO BORDER. HOWEVER...THE LIFT THROUGH
 THE EARLY PART OF THE EVENT DOES NOT LOOK LIKE A HEAVY SNOW
 PRODUCER...BUT MORE OF A STEADY LIGHT TO MODERATE SNOWFALL.
 
 A SECONDARY FRONT AND UPPER JET WILL MOVE OVER THE REGION SUNDAY
 AFTERNOON. THIS COULD FURTHER INTENSIFY THE SNOW...AS WELL AS
 INCREASE MOUNTAIN WINDS. THIS IS OF PARTICULAR CONCERN OVER THE
 HIGHER IMPACT AREAS OF THE GLACIER PARK REGION...NAMELY HIGHWAY 2
 FROM NEAR ESSEX TO MARIAS PASS. A WINTER STORM WATCH HAS BEEN
 ISSUED FOR THAT AREA. IN THE WAKE OF THIS SECOND FRONT...THE FOCUS
 OF THE PRECIPITATION WILL SLOWLY SAG SOUTH WITH THE UPPER LEVEL
 JET. BY MONDAY...BEST CHANCES WILL BE OVER THE MOUNTAINS OF LEMHI
 COUNTY AND SOUTHWEST MONTANA.
 
 TUESDAY THROUGH SATURDAY...A PROGRESSIVE WESTERLY FLOW ALOFT WILL
 BRING UNSETTLED WEATHER TO THE NORTHERN ROCKIES THROUGH NEXT
 WEEKEND. NUMEROUS DISTURBANCES WILL COMBINE WITH PACIFIC MOISTURE
 UNDER THIS FLOW PATTERN BRINGING ALMOST CONTINUOUS SNOW SHOWERS TO
 THE HIGHER TERRAIN. IT WILL TAKE STRONGER SHORTWAVE TROUGH
 FEATURES TO ALLOW FOR SHOWERS TO REACH MANY OF THE LARGER VALLEY
 FLOORS...SO WILL CONTINUE TO MONITOR LATEST MODEL RUNS TO BETTER TIME
 AND EVALUATE EACH FEATURE.
 
 
 
 &&
 
 .MSO WATCHES/WARNINGS/ADVISORIES...
 MT...WINTER WEATHER ADVISORY UNTIL 3 PM MDT SUNDAY FOR 
      KOOTENAI/CABINET REGION-LOWER CLARK FORK REGION.
 
      WINTER STORM WARNING FROM 6 AM SUNDAY TO 6 AM MDT MONDAY FOR 
      WEST GLACIER REGION.
 
      WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO MIDNIGHT MDT 
      SUNDAY NIGHT FOR BITTERROOT/SAPPHIRE MOUNTAINS.
 
 ID...WINTER WEATHER ADVISORY FROM 5 PM SUNDAY TO 11 AM PDT MONDAY FOR 
      NORTHERN CLEARWATER MOUNTAINS.
 
      WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 11 PM PDT 
      SUNDAY FOR SOUTHERN CLEARWATER MOUNTAINS.
 
 &&
 
 

 
 SHORT TERM...FELSCH
 LONG TERM....KITSMILLER
 AVIATION...DICKERSON