Small Craft Advisory 1, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
328 AM PST FRI JAN 1 2016

.SYNOPSIS...A DRY AND COOL WEATHER PATTERN WILL CONTINUE OVER THE
REGION THROUGH SATURDAY. A WARMER AIR MASS WITH MORE MOISTURE WILL
ARRIVE SUNDAY AND MONDAY AND THE CHANCE OF RAIN WILL INCREASE NEXT
WEEK.

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS UPPER LEVEL RIDGE OVER
WESTERN WASHINGTON EARLY THIS MORNING. LITTLE IN THE WAY OF FOG
EVIDENT ON THE IMAGERY AT 3 AM WITH JUST SOME PATCHY FREEZING FOG
OVER THE SOUTHWEST INTERIOR. WIDE RANGE OF TEMPERATURES WITH THE
WIND SHELTERED AREAS AS COLD AS THE UPPER TEENS WHILE LOCATIONS
WITH EXPOSURE TO THE EAST WIND WERE NEAR FREEZING.

LITTLE CHANGE TO THE FORECAST TODAY WITH THE UPPER LEVEL RIDGE
OVER THE AREA AND LOW LEVEL OFFSHORE FLOW. CROSS CASCADE GRADIENT
APPROACHING -10 MB WITH THE KOLM-KBLI GRADIENTS BETWEEN -1.5 AND
-2.5 MB. EVEN WITH THE TEMPERATURE INVERSION OVER THE AREA ENOUGH
MIXING IN THE LOWER LEVELS TO CANCEL THE AIR STAGNATION ADVISORY.
HIGH TEMPERATURES TODAY WILL BE IN THE MID 30S TO MID 40S.

SMALL CHANGES IN THE PATTERN BEGIN TO TAKE PLACE OVERNIGHT WITH
LITTLE EFFECT ON THE WEATHER. UPPER LEVEL RIDGE STARTS TO DRIFT
EAST AS AN UPPER LEVEL LOW...CURRENTLY NEAR RENO...STARTS TO MOVE
NORTH. AT THE SURFACE OFFSHORE FLOW PATTERN REMAINING INTACT. THIS
WILL KEEP THE LOWER LAYERS OF THE AIR MASS DRY LIMITING THE AMOUNT
OF FOG DEVELOPMENT OVERNIGHT. LOWS WILL ONCE AGAIN BE DEPENDENT ON
WIND EXPOSURE WITH THE WIND SHELTERED AREAS DROPPING INTO THE
TEENS WHILE THE AREAS WITH EXPOSURE TO THE EAST WINDS REMAIN NEAR
FREEZING.

ANOTHER DRY DAY ON SATURDAY WITH THE UPPER LEVEL RIDGE CONTINUING TO
MOVE OFF TO THE NORTH AND EAST AND THE UPPER LEVEL LOW SLOWLY
MOVING NORTH REACHING CENTRAL OREGON BY 00Z SUNDAY. OFFSHORE FLOW
AT THE LOWER LEVELS CONTINUING. HIGH TEMPERATURES IN THE MID 30S
TO MID 40S WILL BE COMMON. LOWS SATURDAY NIGHT IN THE 20S AND
LOWER 30S.

UPPER LEVEL LOW MOVING UP OVER THE AREA ON SUNDAY WITH JUST
INCREASING MID/HIGH LEVEL MOISTURE OVER THE AREA. THE GFS AND
ECMWF BRING SOME VERY LIGHT PRECIPITATION INTO THE AREA LATE IN
THE DAY BUT WITH THE LACK OF LOW LEVEL MOISTURE AND THE OFFSHORE
FLOW PATTERN AT THE SURFACE WILL JUST GO FOR AN INCREASE IN CLOUD
COVER ON SUNDAY. LITTLE CHANGE IN THE HIGH TEMPERATURES WITH MID
30S TO LOWER 40S EXPECTED.

.LONG TERM...CONFIDENCE IN THE EXTENDED PERIOD IS LOW THIS
MORNING. EXTENDED MODELS SHOWING VERY LITTLE RUN TO RUN
CONSISTENCY. THE GENERAL IDEA IN THE MODELS IS THAT THE UPPER
LEVEL RIDGE WILL BE TO THE EAST OF THE AREA. SPLITTING SYSTEMS
EMBEDDED IN THE SOUTHWESTERLY FLOW ALOFT MOVING INTO WESTERN
WASHINGTON DURING THE PERIOD. THE MODELS HAVE SHOWN LITTLE
CONSISTENCY IN TIMING THESE FEATURES. THE 00Z RUN HAS THE BEST
CHANCES FOR RAIN ON TUESDAY WITH THE NEXT SYSTEM AFTER TUESDAY
SPLITTING AND MOVING SOUTH BEFORE IT REACHES WESTERN WASHINGTON
WEDNESDAY AND THURSDAY. WITH THE LACK OF CONSISTENCY IN THE
MODELS WILL STAY WITH THE CURRENT FORECAST THAT IS BROAD BRUSH
CHANCE OF RAIN THROUGH MOST OF THE PERIOD. FELTON

&&

.AVIATION...UPPER LEVEL HIGH PRESSURE WILL REMAIN CENTERED OVER
SOUTHERN BRITISH COLUMBIA THROUGH TONIGHT WITH EASTERLY FLOW ALOFT
AND LOW LEVEL OFFSHORE FLOW. THE AIR MASS IS DRY AND STABLE.
PATCHY FOG OR FREEZING FOG IS POSSIBLE OVER THE SOUTH INTERIOR
THIS MORNING BUT IT SHOULD BE PRETTY LIMITED.

KSEA...CLEAR SKIES. NORTHEASTERLY WIND 5-10 KNOTS. SCHNEIDER

&&

.MARINE...OFFSHORE FLOW WILL PREVAIL THROUGH EARLY NEXT WEEK WITH
SMALL CRAFT ADVISORY EAST WINDS OVER THE COASTAL WATERS AND STRAIT
OF JUAN DE FUCA AT TIMES. A FRONTAL SYSTEM WILL REACH THE AREA
AROUND TUESDAY. SCHNEIDER

&&

.HYDROLOGY...FLOODING IS NOT EXPECTED IN THE NEXT 7 DAYS.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 6 AM SATURDAY COASTAL WATERS AND
     WEST ENTRANCE STRAIT OF JUAN DE FUCA.

     SMALL CRAFT ADVISORY UNTIL 6 PM THIS EVENING FOR CENTRAL
     STRAIT OF JUAN DE FUCA.

&&

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