588 FXUS65 KMSO 271014 AFDMSO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MISSOULA MT 414 AM MDT SAT MAR 27 2010 .DISCUSSION...A STRATUS DECK ASSOCIATED WITH A MID-LEVEL CIRCULATION LAST EVENING HAS PERSISTED OVER THE NORTHERN ROCKIES INTO EARLY THIS MORNING. HIGH MOUNTAIN SHOWERS ARE POSSIBLE THROUGH MID-MORNING WITH THIS DECK. OTHERWISE...CLOUD COVER IS EXPECTED TO BREAK UP LATER THIS MORNING...GIVING WAY TO MOSTLY SUNNY SKIES AS AN UPPER LEVEL RIDGE OF HIGH PRESSURE BUILDS OVER THE REGION. ALTHOUGH TEMPERATURES ARE STARTING OFF A GOOD 10 TO 20 DEGREES ABOVE NORMAL THIS MORNING DUE TO THE CURRENT CLOUD COVER...VERY LITTLE MIXING IS ANTICIPATED THIS AFTERNOON AS THE ATMOSPHERE BECOMES MORE STABLE UNDER THE RIDGE. THIS SHOULD HINDER HIGH TEMPERATURES FROM REACHING THEIR MAXIMUM POTENTIAL TODAY DESPITE THE AFTERNOON SUNSHINE. THE UPPER LEVEL RIDGE WILL BEGIN TO BREAKDOWN ON SUNDAY...ALLOWING CLOUDS TO INCREASE AND GRADUALLY LOWER THROUGH THE DAY. BY LATE SUNDAY AFTERNOON...THE FIRST OF SEVERAL WEATHER DISTURBANCES WILL PUSH INTO EXTREME NORTHWEST MONTANA...AND INTO NORTH CENTRAL IDAHO AND WESTERN MONTANA BY SUNDAY EVENING. WEST-FACING SLOPES SHOULD RECEIVE THE BULK OF MOISTURE AS WINDS ALOFT ARE PRIMARILY FROM THE WEST WHICH IS AN IDEAL WEATHER PATTERN FOR OROGRAPHICALLY- ENHANCED PRECIPITATION. SOUTHERLY SURFACE WINDS ARE ALSO EXPECTED TO INCREASE SUNDAY AFTERNOON AS THIS DISTURBANCE MOVES INTO THE REGION AND SHOULD PERSIST THROUGH SUNDAY NIGHT. MONDAY AND TUESDAY...A ROBUST JET STREAM WITH A GOOD TAP OF PACIFIC MOISTURE WILL MOVE INTO THE INTERMOUNTAIN REGION ON AN UPPER LEVEL SOUTHWEST FLOW EARLY MONDAY. A WARM AIRMASS AHEAD OF THE SYSTEM WILL KEEP SNOW LEVELS HIGH THROUGH MUCH OF MONDAY...BUT AS THE JET AND AN ASSOCIATED SURFACE COLD FRONT MOVE FROM NORTH TO SOUTH...SNOW LEVELS WILL BE FALLING AFTER MIDNIGHT MONDAY NIGHT. AT THIS TIME...GIVEN THE FORECASTED PLACEMENT OF THE SURFACE FRONT AND UPPER JET...THE PASSES ALONG THE MONTANA/IDAHO BORDERS LOOK TO BE THE MAIN AREAS IMPACTED BY MODERATE SNOW ACCUMULATIONS THROUGH TUESDAY. WITH SOME MELTING OF THE SNOW AT FIRST...THEN FREEZING WITH SNOW STICKING TO THE ROAD SURFACES...TRAVEL IMPACTS ARE ANTICIPATED. AT THIS TIME THE MAIN IMPACT DOES APPEAR TO BE RIGHT AT PASS LEVELS WITH ONLY LIGHT ACCUMULATIONS ON EITHER SIDE. SNOW TOTALS AT LOLO AND LOOKOUT PASSES ARE EXPECTED TO BE BETWEEN 5 TO 8 INCHES FROM MIDNIGHT THROUGH TUESDAY AFTERNOON. OUTSIDE OF THE PASSES...THE WESTERN MOUNTAINS OF GLACIER NATIONAL PARK...THE CLEARWATER MOUNTAINS OF IDAHO AND WESTERN BITTERROOT MOUNTAINS ARE ALSO EXPECTED TO SEE ACCUMULATING SNOW. OUTDOOR ENTHUSIASTS SHOULD BE PREPARED FOR WET AND WINTRY CONDITIONS LATE MONDAY THROUGH TUESDAY. A WEATHER STORY HIGHLIGHTING THIS WINTRY SCENARIO WILL REMAIN ON THE WWW.WEATHER.GOV/MISSOULA WEB PAGE HIGHLIGHTING THIS TIMEFRAME. WEDNESDAY THROUGH FRIDAY...THE MODELS CONTINUE TO ADVERTISE A COOL AND SHOWERY PATTERN AS THE PACIFIC TROUGH DIGS AND MOVES INLAND BY THE END OF THE WEEK. AT THIS TIME THE MODELS DO INDICATE THE PRECIPITATION FOCUS WILL SHIFT SOUTH ON WEDNESDAY...BUT ENERGY SKIRTING ALONG THE CANADIAN/MONTANA BORDER WILL KEEP SLIGHT CHANCE POPS IN THE NORTH. MODELS ARE TRYING TO INDICATE A BRIEF DRYING PERIOD/SHORTWAVE RIDGE DURING THE LATTER PART OF NEXT WEEK BUT ARE DISAGREEING ON THE TIMING OF THIS FEATURE. GIVEN THE PROGRESSIVE NATURE OF THIS PATTERN...HAVE CONTINUED THE AT TO SLIGHTLY ABOVE CLIMATOLOGICAL POPS AND NEAR TO BELOW NORMAL TEMPERATURES UNTIL BETTER CONSISTENCY IS ACHIEVED. && .AVIATION...A PERSISTENT STRATUS DECK IS EXPECTED TO LINGER OVER THE NORTHERN ROCKIES THROUGH LATE MORNING...WITH HIGH MOUNTAIN SHOWERS POSSIBLE UNTIL 27/1500Z. CLOUDS WILL BEGIN TO BREAK UP LATE THIS MORNING AS AN UPPER LEVEL RIDGE OF HIGH PRESSURE BUILDS OVER THE REGION...HELPING TO DRY AND STABILIZE THE ATMOSPHERE. STRONG WINDS ARE STILL POSSIBLE ALONG THE CONTINENTAL DIVIDE TODAY AND ARE EXPECTED TO DIMINISH BY EARLY THIS EVENING AS THE HIGH PRESSURE RIDGE FULLY STABILIZES ALL LEVELS OF THE ATMOSPHERE. && .MSO WATCHES/WARNINGS/ADVISORIES... MT...NONE. ID...NONE. && $$ SHORT TERM...DEROSA LONG TERM....MEAD AVIATION...DEROSA