Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 071044
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 AM PDT TUE JUL 7 2015

.SYNOPSIS...THE UPPER RIDGE OVER THE REGION WILL BRING MORE WARM AND
GENERALLY SUNNY WEATHER TO WESTERN WASHINGTON TODAY THROUGH
THURSDAY. AN UPPER TROUGH WILL MOVE INTO THE OFFSHORE WATERS
FRIDAY...APPROACH THE COAST THIS WEEKEND...AND MOVE INLAND MONDAY.
THE RESULT WILL BE A SWITCH TO MORE TYPICAL JULY WEATHER.

&&

.SHORT TERM...NORTHWEST FLOW ALOFT CONTINUES OVER WESTERN WASHINGTON
EARLY THIS MORNING...AHEAD OF THE LARGE UPPER TROUGH OVER THE
OFFSHORE WATERS. THE AIR MASS REMAINS DRY EXCEPT FOR SHALLOW
SURFACE-BASED MARINE MOISTURE...AND MARINE STRATUS COVERS MOST OF
THE COASTAL WATERS. LOW LEVEL ONSHORE FLOW PEAKED A LITTLE
STRONGER MONDAY EVENING AND THE STRATUS PUSHED INLAND THROUGH THE
CHEHALIS GAP ALL THE WAY TO SHELTON BEFORE MIDNIGHT...BUT IT HAS
MADE LITTLE TO NO PROGRESS INLAND SINCE THEN. TEMPERATURES AT 2 AM
WERE IN THE 50S TO LOWER 60S.

MARINE STRATUS WILL PROBABLY PUSH INLAND A LITTLE FURTHER DURING THE
EARLY MORNING HOURS...BUT IT LOOKS LIKE THERE WILL BE JUST
PATCHY LOW CLOUDS FOR THE AREAS EAST OF THE PUGET SOUND. THE STRATUS
THAT IS PRESENT THIS MORNING WILL AGAIN BURN BACK TO THE COAST BY
MIDDAY. TEMPERATURES TODAY WILL PROBABLY BE ON AVERAGE JUST A
COUPLE DEGREES LOWER THAN MONDAY.

THE LARGE SCALE PATTERN WILL CHANGE LITTLE...EXCEPT THAT A WEAK
UPPER SHORTWAVE IN THE NORTHWEST FLOW ALOFT WILL MOVE INTO THE AREA
AND COME INTO PHASE WITH THE UPPER LOW OFF THE COAST OF CALIFORNIA.
THIS FEATURE COULD TRIGGER SOME CONVECTION OVER THE NORTH CASCADES
THIS AFTERNOON AND EVENING.

ONSHORE FLOW WILL BE WEAKER THIS EVENING AND TONIGHT...SO THE
STRATUS SHOULD BE LESS EXTENSIVE LATE TONIGHT AND WEDNESDAY
MORNING. THE OFFSHORE UPPER RIDGE WILL TILT INTO BRITISH COLUMBIA ON
WEDNESDAY...AND THE AIR MASS WILL BE A FEW DEGREES WARMER. SO HIGHS
WEDNESDAY SHOULD AGAIN BE IN THE 80S TO LOWER 90S ACROSS MOST OF THE
INTERIOR LOWLANDS OF WESTERN WASHINGTON UNDER SUNNY SKIES.

THE UPPER LOW OVER THE CALIFORNIA OFFSHORE WATERS WILL SLOWLY MOVE
INLAND WEDNESDAY NIGHT AND THURSDAY...AND A WEAK UPPER TROUGH WILL
EXTEND NORTHWARD FROM IT ACROSS THE PACIFIC NORTHWEST. UPPER HEIGHTS
WILL FALL A BIT AND ONSHORE FLOW WILL STRENGTHEN...SO STRATUS COULD
PUSH A LITTLE FURTHER INLAND. IN ADDITION SOME OF THE CONVECTION
THAT THE UPPER LOW HAS BEEN PRODUCING OVER THE SIERRA NEVADA AND
OREGON CASCADES COULD MOVE NORTHWARD ALONG THE WASHINGTON CASCADES.
 MCDONNAL

.LONG TERM...THE CALIFORNIA UPPER LOW WILL CONTINUE INLAND AS IT
WEAKENS THURSDAY NIGHT AND FRIDAY. ANOTHER UPPER LOW WILL MOVE
INTO THE PACIFIC NORTHWEST OFFSHORE WATERS FRIDAY AND MOVE SLOWLY
INLAND BY MONDAY. THIS WILL BE A PERIOD OF SOMEWHAT STRONGER ONSHORE
FLOW WITH AREAS OF NIGHT AND MORNING LOW CLOUDS GIVING WAY TO
AFTERNOON SUNSHINE. TEMPERATURES SHOULD BE CLOSER TO NORMAL. SOME OF
THE RECENT MODEL RUNS HAVE ALSO STARTED SHOWING AREAS OF
PRECIPITATION OVER THE MOUNTAINS ON SUNDAY AND ACROSS WESTERN
WASHINGTON MORE GENERALLY ON MONDAY AS THE TROUGH MOVES INLAND.
 MCDONNAL

&&

.AVIATION...STRATUS IS STILL ANTICIPATED TO MOVE INTO THE PUGET
SOUND REGION THIS MORNING BEFORE RETREATING BACK TO THE COAST THIS
AFTERNOON. IT DOES NOT APPEAR THAT THERE WILL BE MUCH FOG BUT IF
THERE IS...VSBYS SHOULD IN THE MVFR CATEGORY. CIGS WILL GENERALLY
BE IN THE MVFR CATEGORY /1-2K FT/ BUT THERE WILL LIKELY BE AREAS
OF IFR CIGS.

MEANWHILE...LITTLE CHANGE IS EXPECTED IN THE OVERALL PATTERN
TODAY. CONTD NLY FLOW ALOFT AND LOW LEVEL ONSHORE FLOW. SMOKE
LAYERS FROM NUMEROUS WILDFIRES OVER BRITISH COLUMBIA WILL CONTINUE
TO STREAM ACROSS THE AREA. PREDICTING WHETHER IT WILL BE DENSE
ENOUGH TO SIGNIFICANTLY IMPACT VSBYS ACROSS THE NRN PORTION OF THE
CWA WILL BE DIFFICULT.

KSEA...STILL ANTICIPATING STRATUS /CIGS NEAR 1K FT/ TO REACH THE
TERMINAL BETWEEN 1200 AND 1400 UTC. WINDS WILL BE S OR SW DURING
MUCH OF THE DAY.

&&

.MARINE...
HIGH PRES OFF THE WASHINGTON COAST WITH LOWER PRES E OF THE
CASCADES WILL RESULT IN ONSHORE FLOW OF VARYING STRENGTH THIS
WEEK.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY IN EFFECT FOR THE CENTRAL AND EASTERN
STRAIT OF JUAN DE FUCA.

&&

$$

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