Heavy Snow in Washington, November 1 to 2, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
930 PM PDT SAT OCT 31 2015

.SYNOPSIS...A STRONG TROUGH WILL BRING SHOWERS AND WINDY
WEATHER TO THE AREA THROUGH SUNDAY. SNOW WILL FALL AT THE HIGHER
PASSES ON SUNDAY. SHOWERS WILL DECREASE MONDAY AND TUESDAY WITHDRY
WEATHER ON WEDNESDAY. WEAK FRONTS WILL BRING A CHANCE OF RAIN AT
TIMES LATE IN THE WEEK.

&&

.SHORT TERM...SHOWERS AND THUNDERSTORMS ARE ON THE NORTH COAST OF WA
AS A TROUGH MOVES INTO THE AREA. THERE WILL BE A CHANCE OF TSTMS
LATER IN THE INTERIOR OF WRN WA AS THE COOL AIR ALOFT WORKS OVER THE
AREA. A SURFACE LOW PRESSURE CENTER WILL TRACK ALONG VANCOUVER
ISLAND AND THEN FILL OVER NW WA MIDDAY SUNDAY...GIVING A RATHER
BLUSTERY DAY. THE SNOW LEVEL WILL BE AROUND 4000 FEET SUNDAY AND
SNOW SHOWERS WILL BE HEAVY AT TIMES ON THE HIGHER PASSES. THE
SHOWERS WILL DECREASE MONDAY AS FLOW ALOFT TURNS NORTHERLY AND THE
ONSHORE FLOW EASES.  A WEAK DISTURBANCE WILL KEEP A CHANCE OF
SHOWERS IN THE FORECAST TUESDAY.

.LONG TERM...AN UPPER RIDGE WILL MOVE ACROSS THE AREA WEDNESDAY
GIVING DRY CONDITIONS BUT AREAS OF LATE NIGHT AND MORNING FOG.

THERE WILL BE A CHANCE OF PRECIPITATION OVER THE AREA THURSDAY INTO
THURSDAY NIGHT AS A WEAK FRONT MOVES INTO THE AREA FROM THE WEST.
A TROUGH OF LOW PRESSURE ALOFT AND ASSOCIATED FRONTAL SYSTEM
WILL BRING A GOOD CHANCE OF PRECIPITATION TO THE INTERIOR WHILE
PRECIPITATION IS LIKELY ON THE COAST FRIDAY INTO SATURDAY.
TEMPERATURES ARE EXPECTED TO BE NEAR NORMAL FOR EARLY NOVEMBER.
ALBRECHT

&&

.AVIATION...STRONG MOIST SOUTHWEST FLOW ALOFT CONTINUES OVER WESTERN
WASHINGTON AHEAD OF A DEEP UPPER LOW OFF THE CENTRAL COAST OF
BRITISH COLUMBIA. THE FRONTAL WAVE NEARING THE COAST THIS
EVENING WILL MOVE ACROSS WESTERN WASHINGTON TONIGHT. THE UPPER LOW
WILL MOVE ACROSS VANCOUVER ISLAND INTO SOUTHWEST BRITISH COLUMBIA
SUNDAY...WITH ITS TROUGH MOVING ACROSS WESTERN WASHINGTON. THE AIR
MASS WILL REMAIN MOIST AND BE UNSTABLE.

THERE IS A MIX OF MAINLY HIGH-END MVFR AND LOW END VFR CONDITIONS
ACROSS THE FORECAST AREA THIS EVENING WITH SCATTERED SHOWERS.
CONDITIONS WILL LOWER TONIGHT AS THE FRONTAL WAVE OFFSHORE MOVES
INLAND WITH HEAVIER PRECIPITATION AND POSSIBLE THUNDERSTORMS. THERE
COULD BE SOME IMPROVEMENT SUNDAY MORNING...BUT CONDITIONS WILL
LIKELY DETERIORATE AGAIN DURING THE DAY AS THE UPPER LOW AND ITS
TROUGH MOVE INTO THE AREA. IT COULD ALSO PRODUCE SOME THUNDERSTORMS.
IN ADDITION THERE SHOULD BE LOCAL SUSTAINED SURFACE WINDS OF 25 KT AT
TIMES...MAINLY AFTER MIDNIGHT TONIGHT AND AGAIN SUNDAY AFTERNOON.

SEA...SOUTH TO SOUTHWEST WINDS 8-14 KT GUSTING 22 KT RISING TO 15-22
KT GUSTING 30 KT AFTER MIDNIGHT...PROBABLY EASING TO 8-14 KT SUNDAY
MORNING AND THEN RISING AGAIN SUNDAY AFTERNOON. THERE WILL BE MAINLY
A MIX OF HIGH-END MVFR AND LOW-END VFR CONDITIONS IN SHOWERS. THERE
IS ALSO A 20 PERCENT CHANCE OF THUNDERSTORMS IN THE VICINITY OF
KSEA. MOST LIKELY TIMES OF OCCURRENCE ARE PROBABLY MIDNIGHT TO 4 AM
TONIGHT AND AGAIN SUNDAY AFTERNOON. MCDONNAL

.MARINE...A VIGOROUS FRONTAL WAVE EXTENDING SOUTHWEST FROM CENTRAL
VANCOUVER ISLAND ACROSS THE WASHINGTON COASTAL WATERS WILL MOVE INTO
WESTERN WASHINGTON TONIGHT. THIS FEATURE WILL PROBABLY BRING
SOUTHERLY GALES TO ALL THE MARINE ZONES EXCEPT THE CENTRAL STRAIT
OF JUAN DE FUCA...WHERE GALE WESTERLIES ARE LIKELY IMMEDIATELY IN THE
WAKE OF THE FRONT LATE TONIGHT.

A SURFACE LOW WILL TRACK QUICKLY EAST ACROSS CENTRAL OR SOUTHERN
VANCOUVER ISLAND ON SUNDAY AND INTO MAINLAND SOUTHWEST BRITISH
COLUMBIA SUNDAY AFTERNOON. IT SHOULD ALSO PRODUCE GALES FOR ALL
WATERS...WITH ANOTHER ROUND OF WESTERLY GALES IN THE STRAIT OF JUAN
DE FUCA.

WINDS WILL EASE SUNDAY NIGHT AND MONDAY AS HIGH PRESSURE BUILDS
INTO THE FORECAST AREA FROM THE SOUTHWEST. LIGHT ONSHORE FLOW SHOULD
PREVAIL TUESDAY AND WEDNESDAY...WITH SOUTHERLY OFFSHORE FLOW
DEVELOPING THURSDAY AHEAD OF THE NEXT APPROACHING FRONT.

WESTERLY SWELL OF 12 TO 15 FEET WILL BUILD TO 19 TO 22 FEET EARLY
SUNDAY MORNING. A HIGH SURF ADVISORY REMAINS IN EFFECT FROM 4 AM
SUNDAY THROUGH 11 PM SUNDAY NIGHT. SEAS WILL GRADUALLY SUBSIDE SUNDAY
NIGHT AND MONDAY. EXPECT SEVERE GRAYS HARBOR BAR CONDITIONS WITH
BREAKERS THE NEXT 24-36 HOURS.

&&

.HYDROLOGY...THE HEAVY RAIN IS OUT OF THE AREA NOW WITH JUST A FEW
SHOWERS THROUGHOUT AND MANY RIVERS HAVE ALREADY CRESTED. THIS WILL
END THE INFLOW TO AREA STREAMS ALLOWING THE REST OF THE RIVERS IN
THE AREA TO CREST IN THE HEADWATERS AT LEAST. THE FLOOD WAVES ON
AREA RIVERS WILL CONTINUE DOWNSTREAM AS THE LOWER REACHES OF RIVERS
CONTINUE TO RISE.

ON THE OLYMPIC PENINSULA AREA RIVERS HAVE CRESTED WITH ONLY THE
SKOKOMISH RIVER ABOVE FLOOD STAGE. THIS WILL LIKELY RECEDE SLOWLY
AND NOT DROP BELOW FLOOD STAGE UNTIL EARLY MONDAY MORNING.

IN THE NORTHWEST...SO FAR IT STILL APPEARS THE NOOKSACK AND SKAGIT
RIVERS WILL NOT FLOOD BUT THE FLOOD WATCH REMAINS FOR NOW FOR SKAGIT
COUNTY SINCE THE FORECAST CRESTS ARE CLOSE TO FLOOD STAGE.

THE HARD HIT CENTRAL WEST IS STILL QUITE ACTIVE WITH MANY RIVERS
STILL RISING. THE SKYKOMISH IS FALLING AND SOON WILL BE BELOW
MODERATE FLOOD WHILE THE LOWER SNOHOMISH IS STILL RISING AND JUST
REACHING FLOOD STAGE NOW. THE SNOQUALMIE IS ABOVE FLOOD STAGE
THROUGHOUT WITH MODERATE FLOOD CATEGORY FOR THE SNOQUALMIE FALL GAGE
AND FORECAST TO REACH MODERATE CATEGORY AT CARNATION.

FOR THE SOUTH WEST REGION...FLOODING IS ENDING ON MANY RIVERS BUT
MANY OTHERS ON THE DOWNSTREAM REACHES ARE STILL RISING WITH SOME
MORE FLOODING POSSIBLE SO THE FLOOD WATCHES REMAIN IN EFFECT.

SEVERAL ROUNDS OF SHOWERS WILL BE COMING INTO THE AREA OVERNIGHT AND
TOMORROW MORNING AND WHILE SOME WILL HAVE HEAVY RAIN THEY WILL BE OF
SHORT DURATION AND NOT CAUSE ANY ADDITIONAL RIVER FLOODING. BOWER

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WIND ADVISORY COAST AND INTERIOR LOWLANDS UNTIL 6 PM PST SUNDAY.
     WINTER STORM WARNING FOR THE CASCADES AND OLYMPICS ABOVE
      4000 FEET MIDNIGHT PDT TONIGHT THROUGH MONDAY MORNING.
     HIGH SURF ADVISORY FOR THE NORTH AND CENTRAL COAST FROM
      4 AM PST TO 10 PM PST SUNDAY.
     FLOOD WATCHES AND/OR WARNINGS FOR PORTIONS OF THE FORECAST
      AREA.
PZ...GALE WARNING ALL WATERS.
     SMALL CRAFT ADVISORY FOR SEVERE GRAYS HARBOR BAR CONDITIONS.

&&

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