FXUS66 KSEW 061558
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PDT MON OCT 6 2008

.SYNOPSIS...A VIGOROUS FRONTAL SYSTEM WILL SWEEP THROUGH WESTERN
WASHINGTON TONIGHT. THE SNOW LEVEL WILL FALL TO 4000 FEET IN THE
MOUNTAINS ON TUESDAY BEHIND THE FRONT. UNSETTLED WEATHER WILL
PERSIST THROUGH THE MIDDLE OF THE WEEK. HIGH PRESSURE WILL BUILD FOR
NEXT WEEKEND.

&&

.SHORT TERM...A NOVEMBER FRONT...PROBABLY A NOTCH STRONGER THAN YOU
SEE TYPICALLY IN OCTOBER. THE WATER VAPOR SATIMG SHOWS A RAPIDLY
DEEPENING LOW PRESSURE SYSTEM THAT IN THE NAM DEEPENS TO ARND 990MB
AND TRACKS ACROSS THE NRN PART OF VRISL TONIGHT AROUND MIDNITE. THE
GFS IS A TAD DEEPER AND TRACKS JUST NORTH OF VRISL AT 06Z. EITHER
WAY THE FRONT PROMISES TO BRING GALES TO THE COASTAL WATERS THIS
EVENING. AREAS OF LIGHT RAIN IN THE WARM SECTOR TODAY WILL GIVE WAY
TO STEADIER RAIN WITH THE COLD FRONT TONIGHT. SNOW LEVEL IN THE
MOUNTAINS WILL BE AROUND 8000 FEET THRU THIS EVENING AND THEN FALL
TO 4000 FEET BY MIDDAY TUE. MOUNT BAKER AND THE NORTH CASCADES
HIGHWAY ABOVE 4000 FEET HAVE A GOOD CHANCE OF PICKING UP AT LEAST
SEVERAL INCHES OF SNOW TUE...AND EVEN STEVENS PASS HAS A SHOT.
PROBABLY THIS AFTERNOON I WILL ISSUE A SNOW ADVISORY FOR THE CENTRAL
AND NORTH CASCADES FOR 3-6" ABOVE THE SNOW LEVEL. I DON'T SEE SNOW
STICKING AS LOW AS SNOQUALMIE PASS AND THERE IS A GOOD CHANCE IT
STAYS RAIN AT THAT ELEVATION RIGHT THRU TUE NITE. ONSHORE FLOW AND
SHOWERS WILL BE MORE NUMEROUS IN THE CASCADES TUE NITE AND WED AND
JUST SCATTERED IN THE LOWLANDS. SNOW LEVEL SHUD STAY AROUND 3500FT
TUE NITE AND WED. 19

.LONG TERM...UPPER TROF OVER THE REGION THRU THE MIDDLE OF THE WEEK
SHIFTS INLAND TO THE ROCKIES THU. UPPER RIDGE IS OVER WA SAT. CHANCE
OF SHOWERS THRU FRIDAY LOOKS FINE AND THE PARTLY CLOUDY FCST FOR THE
WEEKEND CAN PROBABLY BE KICKED UP TO SUNNY. THE ECMWF HAS
CONSISTENTLY KEPT A MUCH DEEPER UPPER TROF OVER THE WESTERN U.S.
THRU THE END OF THE WEEK AND THE RIDGE FOR NEXT WEEKEND IS RATHER
ANEMIC...THE 06/00Z RUN OF THE ECMWF HAS NOTHING MORE THAN A NARROW
RIDGE ARTIFACT BETWEEN TWO LARGE TROFS...THE HUGE TROF/LOW CENTERED
OVER THE GREAT BASIN AND IDAHO...AND ANOTHER TROF IN THE NE PAC.
UPPER HEIGHTS DO NOT EVEN GET UP TO 570DAM AT 500MB OVER WRN WA IN
THE ECMWF. SO ALTHOUGH SOME SUNSHINE SHUD BE ON TAP NEXT WEEKEND
TEMPS WILL LIKELY BE ON THE COOL SIDE IF THE ECMWF IS RIGHT. 19

&&

.AVIATION...WEAK HIGH PRESSURE OVER EASTERN WASHINGTON WITH WEAK LOW
PRESSURE DISSIPATING ALONG THE COAST THIS MORNING. A DEEP SURFACE
LOW WILL MOVE TOWARDS NORTHERN VANCOUVER ISLAND TODAY. CEILINGS ALL
OVER THE PLACE THIS MORNING...2-4K FT AROUND KSEA...1K FT OR LESS
KTCM AND POINTS SW...AND VFR NORTH. SOME VISIBILITY RESTRICTIONS AS
WELL IN SHOWERS. WITH APPROACHING SYSTEM AM HOPING THE CEILINGS
SETTLE DOWN TO 5-6K FT MOST AREAS...FALLING TO 2-3K FT AS RAIN
COMMENCES THIS EVENING. TYPICAL VISIBILITIES DURING THE RAIN TONIGHT
WILL LIKELY BE 3-5SM. LOW LEVEL SE WIND INCREASING AFTER 00Z.

KSEA...EXPECT STRATUS CEILINGS 2-3K FT TO LIFT TO VFR MID MORNING.
THEN BACK TO MVFR OVERNIGHT IN RAIN. LIGHT WIND THIS MORNING...
BECOMING SE 4-8 KT THIS AFTERNOON...AND RISING TO SE 15G25 KT LATE
TONIGHT. CHB

&&

.MARINE...LIGHT EASTERLY FLOW THROUGH EARLY AFTERNOON. A VERY STRONG
FRONTAL SYSTEM...ASSOCIATED WITH A 994 MB LOW NEAR 45N/138W...WILL
BRING GALES TO THE COAST THIS AFTERNOON AND TO THE INLAND WATERS
THIS EVENING. GALE FORCE WESTERLIES WILL OCCUR BEHIND THE FRONT AS
THE LOW MOVES NE ACROSS NORTHERN VANCOUVER ISLAND. WINDS SHOULD STAY
SLIGHTLY BELOW GALE FORCE IN PUGET SOUND AND HOOD CANAL.

WINDS AND SEAS WILL GRADUALLY SUBSIDE TUESDAY THROUGH TUESDAY NIGHT.
HIGH PRES WILL GIVE LIGHT WINDS TO THE AREA WEDNESDAY.

ON THURSDAY SMALL CRAFT ADVISORY NORTHWEST WINDS ARE POSSIBLE AS A
TROUGH OF LOW PRESSURE SWINGS SOUTHEAST ACROSS THE AREA. THEN
SURFACE HIGH PRES WILL SHIFT EAST OF THE CASCADES FRIDAY GIVING
OFFSHORE FLOW.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER STORM WATCH IN EFFECT FOR THE NORTH CASCADES ABOVE 4000FT
ON TUE.
PZ...GALE WARNING ALL WATERS EXCEPT PUGET SOUND AND HOOD CANAL
SMALL CRAFT ADVISORY FOR PUGET SOUND AND HOOD CANAL.

$$

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