Napavine Weather Discussion
000 FXUS66 KSEW 232218 AFDSEW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SEATTLE WA 315 PM PDT THU MAY 23 2013 .SYNOPSIS...A SLOW MOVING COLD UPPER-LEVEL LOW WILL CONTINUE TO PRODUCE SHOWERS WITH ISOLATED EVENING THUNDERSTORMS MAINLY OVER THE MOUNTAINS. THE UPPER LOW WILL WOBBLE AROUND THE PACIFIC NORTHWEST INTO THE MEMORIAL DAY WEEKEND AS IT SLOWLY FILLS AND WEAKENS. THE COOL AIR MASS WILL GRADUALLY MODERATE INTO THE WEEKEND AND SHOWERS WILL GRADUALLY DIMINISH STARTING TONIGHT. && .SHORT TERM...THERE APPEAR TO BE TWO DISTINCT WEATHER REGIMES OVER WESTERN WASHINGTON THIS AFTERNOON. ONE IS SCATTERED SHOWERS OVER ABOUT THE NORTHERN THIRD OF THE AREA. THERE ARE SUN BREAKS AND HIGHS HERE WILL BE 55-60. THE OTHER IS A LARGE AREA OF THICK CLOUDS AND STEADY RAIN OVER THE SOUTHERN TWO THIRDS. THIS IS ASSOCIATED WITH THE UPPER LEVEL LOW THAT IS CENTERED ALONG THE CENTRAL WASHINGTON COAST. UNDER THIS SYSTEM CONDITIONS ARE QUITE GLOOMY WITH RAIN AND TEMPERATURES IN THE 40S AND LOW 50S. BOTH KOLM AND KHQM ARE LIKELY TO SET NEW LOW MAX RECORDS TODAY. THE UPPER LOW IS FORECAST TO MOVE SOUTHEAST TONIGHT THEN FILL AND MOVE NORTHEAST FRIDAY. AT LEAST THAT IS WHAT THE NAM AND GFS SHOW. THE EURO KEEPS THE UPPER LOW OVER THE AREA THROUGH SUNDAY. ANYWAY KEPT CHANCE POPS IN ALL PERIODS THROUGH SUNDAY...AND STILL HAVE A SLOW WARMING TREND IN THE FORECAST. HIGHS SHOULD REACH THE LOW TO MID 60S ON FRIDAY AND SATURDAY. BY SUNDAY IF THE UPPER LOW IS GONE AND THERE IS ZONAL FLOW...A BIG IF...SKIES SHOULD BE PARTLY SUNNY AND THERE COULD BE SOME LOW 70S AROUND. BURKE .LONG TERM...THE GFS CONTINUES TO BRING A WEAK SYSTEM INLAND AROUND MONDAY OR TUESDAY. THE EURO IS STARTING TO COME AROUND TO THIS IDEA EXCEPT THAT IT SENDS THE SYSTEM SOUTH INTO OREGON AND CALIFORNIA. HAVE RAIN LIKELY FOR A FEW PERIODS IN THE EXTENDED BUT AM NOT CONFIDENT IN THE DETAILS. BACK TO SCATTERED SHOWERS STARTING ABOUT WEDNESDAY. TEMPERATURES ARE LIKELY TO BE NEAR NORMAL. BURKE && .AVIATION...A DEEP UPPER LOW CENTERED OVER WESTERN WASHINGTON THIS AFTERNOON WILL REMAIN OVER THE REGION THROUGH FRIDAY...PROBABLY SHIFTING SLOWLY EASTWARD. FLOW AT THE SURFACE AND ALOFT WILL BE GENERALLY LIGHT AND VARIABLE. THE AIR MASS WILL BE MOIST AND WEAKLY UNSTABLE. FAIRLY SOLID SHOWERY PRECIPITATION COVERS THE SOUTHERN HALF OF THE FORECAST AREA THIS AFTERNOON...WITH MORE SCATTERED SHOWERS TO THE NORTH. IT WILL CONTINUE THROUGH TONIGHT ESPECIALLY OVER THE SOUTHERN TWO-THIRDS OF THE FORECAST AREA...AND SHOWERS SHOULD DECREASE SOMEWHAT FRIDAY. THERE IS ROUGHLY A 15 PERCENT CHANCE OF THUNDERSTORMS THIS AFTERNOON AND EVENING. THERE WAS AGAIN A WIDE MIX OF CONDITIONS ACROSS THE FORECAST AREA AT 2 PM. MOST OF THE AREA HAD LOW-END VFR CONDITIONS BUT THERE WERE ALSO LOCAL CEILINGS OF BKN020-030...AND MUCH OF THE COAST AND SOUTH INTERIOR IS IFR WHERE PRECIPITATION IS MORE SOLID. THIS KIND OF VARIABILITY WILL BE THE RULE THROUGH TONIGHT AND FRIDAY MORNING. BY FRIDAY AFTERNOON VFR CONDITIONS SHOULD BECOME MORE WIDESPREAD. CONFIDENCE IN FORECAST DETAILS REMAINS RATHER LOW. KSEA...MAINLY SOUTHWEST WIND 4-10 KT...EXCEPT PROBABLY LIGHT NORTHEAST FOR SEVERAL HOURS LATE TONIGHT. ROUGHLY A 10 PERCENT CHANCE OF A THUNDERSTORM THROUGH THIS EVENING. MCDONNAL && .MARINE...A 1014 MB LOW OVER THE WASHINGTON OFFSHORE WATERS WILL WEAKEN AND MOVE SOUTHEAST INTO NORTHWEST OREGON TONIGHT. WEAK ONSHORE FLOW WILL DEVELOP FRIDAY AND CONTINUE SATURDAY AND SUNDAY. SMALL CRAFT ADVISORY WESTERLIES ARE LIKELY IN THE CENTRAL STRAIT OF JUAN DE FUCA AND EAST ENTRANCE FRIDAY NIGHT...AND POSSIBLY AGAIN SATURDAY AND SUNDAY NIGHTS. A FRONT WILL APPROACH THE PACIFIC NORTHWEST FROM THE WEST MONDAY AND WEAKEN AS IT MOVES INLAND MONDAY NIGHT. AT THIS POINT IT LOOKS LIKE IT WILL PRODUCE SMALL CRAFT ADVISORY WINDS OVER THE COASTAL WATERS. WEAK ONSHORE FLOW WILL DEVELOP AGAIN TUESDAY. MCDONNAL && .SEW WATCHES/WARNINGS/ADVISORIES... WA...NONE. PZ...NONE. && $$ YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML
NWS SEw Office Area Forecast Discussion