000 FXUS66 KPQR 300428 AFDPQR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PORTLAND OR 830 PM PST MON DEC 29 2003 .SYNOPSIS...HIGH PRESSURE BUILDS OVER AREA TONIGHT BRINING COLD DRY AIR MASS TO AREA. HIGH PRESSURE MOVES TO IDAHO TUESDAY AS PACIFIC FRONT APPROACHES LATE IN THE DAY. HIGH PRESSURE CONTINUES OFFSHORE LOW LEVEL FLOW AS MOISTURE FROM FRONT OVERRIDES LOW LEVEL AIR. OVERRUNNING CONTINUES THROUGH WED MORNING UNTIL FRONT MOVES EAST OF CASCADES AROUND MIDDAY. SHOWERY WEATHER WITH ONSHORE FLOW BEHIND FRONT WEDNESDAY AFTERNOON DECREASES WED NIGHT AS OFFSHORE AHEAD OF NEXT SYSTEM APPROACHING FROM THE SOUTHWEST. THIS SYSTEM MOVES INTO SOUTHERN OREGON THURSDAY AND MAY EFFECT PARTS OF THE AREA. && .DISCUSSION... .SHORT TERM...GFS/ETA VERY CLOSE THROUGH WED. HIGH PRES BUILDS OVER ERN ORE TONIGHT GIVING COLD DRY AIR MASS TO AREA. DEW POINTS DROPPING STEADILY WILL GIVE VERY COLD NIGHT TO AREA WITH ALL TEMPS WELL BELOW FREEZING AND SOME TEENS LOWER ELEVATIONS ESPECIALLY SNOW COVERED AREAS. HIGH PRES SHIFTS INTO IDA TUE AS NEXT PAC SYSTEM APPROACHES. CLOUDS FROM SYSTEM WILL INCREASE NRN COAST TUE MORNING AND MOST OF N PART OF AREA DURING THE AFTERNOON. THIS WILL CAP TEMPS SOME IN AFTERNOON LEAVING MOST INLAND AREAS IN THE 30S TO AROUND 40. AS SYSTEM APPROACHES TUE NIGHT OFFSHORE LOW LEVEL FLOW INCREASES. THIS FORCES MOISTURE FROM SYSTEM TO OVERRUN LOW LEVEL AIR MASS SETTING UP GOOD SNOW SITUATION AS LEVEL AIR STILL HAS LOW DEW POINTS. COAST MAINLY RAIN WITH INTERIOR MAINLY SNOW EXCEPT SRN WILL VALLEY. MAIN VERT MOTION PUSHES IN WED MORNING. LOW LEVEL FLOW REMAINS OFFSHORE UNTIL FRONT MOVES BY WITH FRONT TO CASCADES BY MIDDAY. STICKING SNOW LIKELY MOST INLAND AREAS WITH AMOUNTS APPROACHING WARNING LEVELS COAST MOUNTAINS...CASCADE FOOTHILLS AND COL GORGE AND SOLID ADVY AMOUNTS LIKELY FOR HIGHER CASCADES. NRN VALLEYS A LITTLE MORE OF A QUESTION THOUGH STICKING SNOW LIKELY MOST AREAS. WILL NOT GO WITH ANY WATCHES AND FEEL BEST WAY IS FOR LATER SHIFTS TO ISSUED ANY NEEDED WARNING OR ADVISORIES. AS FRONT PASSES AND FLOW TURNS ONSHORE INLAND VALLEY AREAS MIX OUT AND SNOW LEVEL RISES TO ABOUT 1500 TO 2000 FEET WED AFTERNOON. SHOWERY WEATHER BEHIND FRONT WED AFTERNOON DECREASES WED NIGHT AS ONSHORE FLOW DECREASES WITH HIGH PRES BUILDING INLAND AHEAD OF NEXT SYSTEM. GFS FASTER THEN ETA WITH THIS SYSTEM WITH BOTH ETA/GFS NOW FAVORING MORE SRN TRACK. THIS MAY GIVE LESS PRECIPITATION TO AREA THU BUT DONT WANT TO BET ON THIS SOLUTION YET SO WILL HAVE NO CHANGES TO FORECAST FOR THU. KOSOVITZ .LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS... GENERAL TREND FOR THE EXTENDED PERIOD CONTINUES TO BE A COLD UPPER TROUGH PARKED OVER THE PACIFIC NW. MODELS CONTINUE TO VARY IN TIMING AND TRACK OF SMALLER SCALE FEATURES. IN PARTICULAR...THE LAST TWO MRF RUNS HAVE VARIED CONSIDERABLY WITH TRACK OF THE LOW PRESSURE AREA ASSOCIATED WITH A PROSPECTIVE WEATHER SYSTEM SAT/SUN. SNOW LEVELS WILL FLUCTUATE DURING THE EXTENDED PERIOD BUT ARE EXPECTED TO REMAIN QUITE LOW...AROUND 500 TO 1000 FEET. GIVEN MODEL INCONSISTENCIES WENT WITH THE BROAD BRUSH. && .PRELIMINARY POINT POPS AST 039966 PDX 017846 SLE 017846 EUG 014846 && .PQR WATCHES/WARNINGS/ADVISORIES... .WA/OR......SMALL CRAFT ADVISORY CASCADE HEAD TO FLORENCE. $$