Napavine Weather Discussion

000
FXUS66 KSEW 090436
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
836 PM PST WED FEB 8 2012

.SYNOPSIS...A WARM FRONT WILL SPREAD LIGHT RAIN ACROSS WESTERN
WASHINGTON LATE TONIGHT AND THURSDAY MORNING. AFTER A LULL IN THE
RAIN THURSDAY AFTERNOON AND NIGHT...A LOW PRESSURE SYSTEM WILL MOVE
UP OVER THE AREA FROM THE SOUTHWEST BRINGING MORE LIGHT RAIN ON
FRIDAY. THE LOW WILL STALL OVER THE AREA AS IT WEAKENS...ALLOWING
PERIODS OF LIGHT RAIN TO CONTINUE THROUGH SATURDAY. WEAK HIGH
PRESSURE WILL BRING A SHORT BREAK IN THE RAIN SATURDAY NIGHT AND
SUNDAY MORNING...THEN A FRONTAL SYSTEM WILL ARRIVE LATE SUNDAY.
ANOTHER FRONTAL SYSTEM MAY REACH THE AREA AROUND TUESDAY.

&&

.SHORT TERM...RADAR SHOWS RAIN HAS ENDED ACROSS JUST ABOUT ALL OF W
WA THIS EVENING...BUT THE PORTLAND RADAR SHOWS WARM FRONTAL RAIN
SPREADING NORTHWARD ACROSS NW OREGON. NO ARGUMENT WITH THE MODELS
WHICH BRING RAIN NORTHWARD ACROSS THE AREA AFTER MIDNIGHT. 00Z NAM
HAS RAIN AT SEATTLE AFTER 09Z. MODELS ALSO AGREE ON DECREASING THE
RAIN BEHIND THE WARM FRONT OVER SW WA BY 18Z THURSDAY...WITH THE
WARM FRONT CLEARING THE NW INTERIOR BY 00Z. PUGET SOUND SHOULD BE
PRETTY MUCH DONE WITH THE RAIN SOMETIME BETWEEN 18Z-21Z.

PER THE 00Z NAM THE LULL IN THE RAIN WILL LAST THURSDAY AFTERNOON
AND THURSDAY NIGHT...HOWEVER THE COARSER GFS KEEPS THE RAIN GOING
OVER THE COAST AND NW INTERIOR AHEAD OF THE NEXT SYSTEM.

GFS/NAM/ECMWF ALL AGREE THAT RATHER THAN A WEAKENING COLD FRONT
MOVING ACROSS THE AREA FRIDAY...AN UPPER LEVEL SHORTWAVE TROUGH AND
SURFACE LOW MOVE UP OVER THE AREA FROM THE SW INSTEAD...ALONG THE
COLD FRONT BOUNDARY. THERE IS SUFFICIENT WARM ADVECTION AHEAD OF THE
LOW TO WIPE OUT THE COLD FRONT. ALL MODELS STALL THE SYSTEM OVER THE
AREA LATE FRIDAY...WITH PERIODS OF LIGHT RAIN LASTING OVER THE AREA
THROUGH JUST ABOUT ALL SATURDAY AS IT WEAKENS. IT LOOKS LIKE THE 00Z
NAM HAS COME OVER TO THE EARLIER GFS/ECMWF SOLUTIONS. NAM BUFR
SOUNDINGS SHOW THE AIR MASS WILL BE PRETTY STABLE DURING THIS
PERIOD. KAM

.LONG TERM...PREVIOUS DISCUSSION FROM THE 3 PM AFD...A FRONT IS
LIKELY LATER IN THE DAY ON SUNDAY...THE 500MB HEIGHT FALLS ARE
PRETTY DECENT AND ALTHOUGH IT LOOKS LIKE THE STRONGEST PORTION OF
THE FRONTAL SYS WILL MOVE THROUGH ORE AND NRN CALIF SUN NITE RAIN IS
STILL LIKELY FOR WRN WA. THE CURRENT TIMING OF THE GFS IS FOR WEAK
RIDGE MONDAY NIGHT FOLLOWED BY ANOTHER TROUGH ON TUE WHICH MAY AGAIN
DO MORE FOR NRN CALIF THAN WRN WA. THE ECMWF AND GFS ARE COMPLETELY
DIFFERENT SOLUTIONS BY THAT TIME AND I HAVE MAINLY JUST PUSHED THE
POPS AROUND A BIT AND CHANGED SOME PERIODS TO SHOWERS. THE EXTENDED
FCST IS PRETTY LOW SKILL TODAY. 19

&&

.HYDROLOGY...NO FLOODING IS EXPECTED IN THE FORECAST AREA DURING THE
NEXT 7 DAYS.

&&

.AVIATION...A WARM FRONT WILL LIFT N ACROSS WRN WA THURSDAY MORNING.
LIGHT SSW FLOW ALOFT WILL BECOME STRONG AFTER 16Z. LOW LEVEL FLOW
WILL REMAIN OFFSHORE. RAIN WILL SPREAD OVER WESTERN WASHINGTON AFTER
12Z THIS MORNING...THEN CHANGE TO SCATTERED SHOWERS IN THE
AFTERNOON...EXCEPT RAIN LINGERING FAR N. THE AIR MASS IS MOIST AND
STABLE.

KSEA...RAIN WILL INCREASE BY 12Z. MAINLY MVFR CIGS/VIS WITH THE WARM
FRONTAL RAINFALL. CIGS IMPROVING TO VFR BY AFTERNOON AS THE FRONT
LIFTS INTO NRN WA. WIND WILL BE E/SE 4-8 KT...BECOMING S AFTER 18Z.

&&

.MARINE...SMALL CRAFT ADVISORIES REMAIN IN EFFECT FOR SOUTHERLY WIND
OVER ALL WATERS EXCEPT PUGET SOUND/HOOD CANAL AND THE CENTRAL
STRAIT. MODERATE OFFSHORE FLOW WILL CONTINUE TONIGHT. A WARM FRONT
WILL LIFT ACROSS THE WATERS ON THURSDAY. STRONGER SE FLOW BEHIND THE
WARM FRONT WILL BRING LOW-END GALE FORCE WINDS TO THE COASTAL WATERS
ON THURSDAY. BRIEF ONSHORE FLOW WILL DEVELOP ON FRIDAY BEHIND A COLD
FRONT. DTM/CHB

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY COAST THROUGH 4 AM THURSDAY.
     GALE WARNING COAST 4 AM THURSDAY THROUGH 4 PM THURSDAY.
     SMALL CRAFT ADVISORY WEST/EAST STRAIT OF JUAN DE
     FUCA...NORTHERN INLAND WATERS AND ADMIRALTY INLET THROUGH 4 PM
     THURSDAY.
     SMALL CRAFT ADVISORY GRAYS HARBOR BAR FOR ROUGH CONDITIONS.

$$

YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML.


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