Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 011011
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
311 AM PDT MON SEP 1 2014

.SYNOPSIS...HIGH PRESSURE ALOFT WILL PREVAIL OVER THE AREA TODAY.
A STRONG AND FAST MOVING LOW PRESSURE SYSTEM WILL IMPACT THE
REGION ON TUESDAY. LOOK FOR HIGH PRESSURE ALOFT TO PREVAIL OVER
THE AREA THE REST OF THE WEEK FOR DRY AND WARMER CONDITIONS.

&&

.SHORT TERM...
AN UPPER RIDGE WILL PREVAIL OVER THE REGION TODAY AND WILL WEAKEN
TONIGHT. EXPECT DAYTIME HIGHS TO BE NEAR NORMAL FOR THIS TIME OF
THE YEAR.

A VIGOROUS LOW PRESSURE SYSTEM EMANATING FROM THE GULF OF AK WILL
IMPACT THE PACIFIC NORTHWEST ON TUE. THE BEST CHANCE OF PRECIP
WILL BE ACROSS THE NORTHERN PART OF THE CWA AND WITHIN THE PUGET
SOUND CONVERGENCE ZONE /PSCZ/. THE PSCZ SHOULD DEVELOP QUICKLY
BEHIND THE COLD FRONT LATE TUE AFTERNOON OR EARLY EVENING. WOULD
NOT BE SURPRISED IF THERE WERE ISOLATED TSTMS WITH SMALL HAIL
ASSOCIATED WITH THE PSCZ. WINDS WILL ALSO KICK UP AHEAD OF THE
COLD FRONT. HAVE A FEELING THAT THE MODELS MIGHT BE UNDER-
PREDICTING WIND SPEEDS IN SOME PLACES.

THE SNOW LEVEL WILL PLUMMET TO NEAR 6500 FEET ACROSS MUCH OF THE
CASCADES LATE TUE NIGHT IN THE WAKE OF THE COLD FRONT BUT LITTLE
/IF ANY/ SNOW ACCUMULATION IS EXPECTED SINCE THE AIR MASS WILL BE
UNDERGOING STRONG DRYING AND SUBSIDENCE AT THAT TIME.

STRONG...DRY NORTHERLY FLOW ALOFT WILL PREVAIL OVER THE REGION ON
WED. DAYTIME TEMPS WILL REBOUND SLIGHTLY BUT REMAIN BELOW NORMAL.
WED NIGHT WILL LIKELY BE THE CHILLIEST NIGHT ACROSS THE LOWLANDS
UNDER A CLOUDLESS SKY. MOST PLACES WILL EXPERIENCE MINIMUMS IN THE
40S.

.LONG TERM...
NO CHANGES WERE MADE TO THE INHERITED FORECAST EXCEPT TO BLEND
WITH ADJACENT FORECAST OFFICES. AN UPPER RIDGE WILL DOMINATE THE
WEATHER PATTERN OVER THE PACIFIC NORTHWEST DURING THIS PERIOD.

&&

.AVIATION...LIGHT NW FLOW ALOFT OVER THE REGION THROUGH TONIGHT.
STRONG WESTERLY FLOW ALOFT DEVELOPS ON TUESDAY AS A TROUGH
APPROACHES WA. THE AIR MASS IS GENERALLY MOIST AND STABLE...EXCEPT
BECOMING WEAKLY UNSTABLE THIS AFTERNOON. ONLY A SLIGHT CHANCE OF A
FEW SHOWERS...MAINLY N OF SEATTLE THIS AFTERNOON. INCREASING SHOWERS
TUESDAY. AN MVFR CEILING OVER PORTIONS OF WRN WA THIS MORNING WILL
LIFT AND SCATTER BY 18Z.

KSEA...S WIND TO 5 KT...BECOMING SLY 4-7 KT AFTER 19Z THEN SWITCHING
TO THE N AFTER 5 PM THIS AFTERNOON. MVFR CIGS THIS MORNING WILL LIFT
AND SCATTER BY 18-19Z. A BKN-OVC 4-5K FT DECK WILL FILL IN THIS
EVENING. SLIGHT CHANCE OF A SHOWER THROUGH TONIGHT. INCREASING
SHOWERS TUESDAY. DTM

&&

.MARINE...A SURFACE TROUGH WILL DISSIPATE OVER THE COASTAL WATERS BY
MIDDAY. SLY WINDS AHEAD OF THE TROUGH SHOULD REMAIN BELOW 20 KT OVER
THE COASTAL WATERS...WITH LIGHT SLY WIND OVER THE INLAND WATERS.
ANOTHER SYSTEM WILL BRING A BOUT OF STRONG ONSHORE FLOW TUESDAY
NIGHT...THEN EASING ON WEDNESDAY. THE REST OF THE WEEK WILL BE A
MORE SUMMERY WIND REGIME WITH A TYPICAL NW BREEZE EACH DAY. DTM

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...NONE.

&&

$$

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