Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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FXUS66 KSEW 011640
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
840 AM PST SUN FEB 1 2015

.SYNOPSIS...A WEAK COLD FRONT WILL MOVE THROUGH TODAY FOR RAIN AT
TIMES. A BRIEF AND WEAK RIDGE WILL GIVE A DECREASING CHANCE OF
SHOWERS TONIGHT. ANOTHER FRONTAL SYSTEM WILL MOVE THROUGH THE AREA
ON MONDAY...WITH MORE LIGHT RAIN LIKELY. SOME LIGHT SHOWERS WILL
LINGER TUESDAY INTO WEDNESDAY AS WEAK DISTURBANCES MOVE THROUGH THE
AREA. A TRANSITION TO A FAIRLY WET AND MILD PATTERN WILL BEGIN
THURSDAY AND CONTINUE THROUGH NEXT WEEKEND.

&&

.SHORT TERM...SATELLITE IMAGERY AND RADARS SHOW A WEAK FRONT OVER
THE OUTER COASTAL WATERS THIS MORNING MOVING SLOWLY EAST. THE FRONT
WILL SLOW AND WEAKEN AS IT MOVES ONSHORE THIS AFTERNOON. TODAY WILL
BE A CLOUDY DAY WITH OCCASIONAL LIGHT RAIN AND TEMPERATURES IN THE
MID 40S TO NEAR 50 DEGREES.

THE AIR MASS BEHIND THIS FRONT IS NOT PARTICULARLY COOL OR UNSTABLE
ALOFT...SO EXPECT SHOWER ACTIVITY TO DIMINISH BEHIND THE FRONT THIS
EVENING. THE LATE EVENING THROUGH PRE DAWN HOURS MAY BE DRY ACROSS
THE AREA...JUST CLOUDY...BETWEEN THE FIRST FRONT AND THE NEXT
INCOMING SYSTEM THAT IS NOW ALONG ABOUT 142W. WITH ALL THE CLOUD
COVER AROUND...TEMPERATURES WILL HOLD MAINLY IN THE LOWER 40S
TONIGHT.

ANOTHER WEAK FRONT WILL MOVE ACROSS THE AREA ON MONDAY. THE 12Z NAM
AND 12Z GFS SOLUTIONS BOTH SHOW THE RAIN MOVING INTO THE AREA FROM
THE SOUTHWEST DURING THE MORNING HOURS ON THE COAST AND THE SOUTHERN
HALF OF THE INTERIOR THEN THROUGH THE AREA DURING THE AFTERNOON
HOURS. THIS FRONTAL FEATURE WILL BE LOSING ITS IDENTITY AS IT MOVES
ACROSS THE AREA LATER IN THE DAY.

TUESDAY AND TUESDAY NIGHT WILL LIKELY SEE SHOWERS AT TIMES. A WARM
FRONT IN THE SOUTHERN STREAM WILL AFFECT EXTREME NORTHERN CALIFORNIA
INTO CENTRAL OREGON GIVING STEADIER RAIN DOWN THERE. BUT THE
REMNANTS OF A WRAP AROUND FEATURE THAT IS SEEN MOVING AROUND THE
DEEP AND MATURE LOW NOW CENTERED NEAR 46N 158W WILL SPLIT OFF AND
MOVE ACROSS ESPECIALLY THE NORTHERN HALF OF WESTERN WASHINGTON
ENHANCING SHOWER ACTIVITY AND POSSIBLY CONVERGENCE ZONE ACTIVITY
INITIATED BY WNW FLOW ALOFT.

SHOWER ACTIVITY WILL LIKELY COME TO AN END EARLY WEDNESDAY...BUT THE
INCOMING GFS DOES SHOW WARM ADVECTION PRECIPITATION MOVING INTO THE
SOUTHERN PORTIONS OF WESTERN WASHINGTON LATE WED AFTERNOON OR
EVENING.

CURRENT FORECASTS APPEAR TO BE GENERALLY ON TRACK. NO MORNING UPDATE
IS PLANNED. ALBRECHT

.LONG TERM...FROM THE PREVIOUS LONG TERM SOLUTION...MODEL SOLUTIONS
FOR WEDNESDAY CONTINUE TO SHOW A LACK OF CONSISTENCY AMONG THE
MODELS. THE ECMWF HAS A WARM FRONT OVER OREGON TRYING TO LIFT NORTH
INTO WESTERN WASHINGTON. THE GFS HAS A WEAK SHORTWAVE RIDING BY TO
THE NORTH OF THE AREA. GFS ENSEMBLES SHOW LITTLE VARIATION IN THEIR
SOLUTION ON WEDNESDAY WHICH LENDS SOME CONFIDENCE TO THE GFS
SOLUTION BUT WITH THE LACK OF MODEL CONSENSUS WILL KEEP THE CHANCE
POPS IN THE FORECAST. WHILE THERE ARE SOME DIFFERENCES IN THE TIMING
OF THE SYSTEMS BEGINNING THURSDAY THE EXTENDED MODELS ARE IN MUCH
BETTER AGREEMENT IN REGARD TO THE OVERALL PATTERN TURNING WARMER AND
WETTER BEGINNING THURSDAY AND CONTINUING THROUGH NEXT WEEKEND.
TIMING OF THE INDIVIDUAL FEATURES IS TOUGH AT THIS POINT SO A BROAD
BRUSH RAIN LIKELY/RAIN AT TIMES FORECAST LOOKS GOD THURSDAY THROUGH
SATURDAY. FELTON

&&

.HYDROLOGY...FLOODING IS NOT EXPECTED THROUGH AT LEAST THURSDAY.

A SERIES OF SYSTEMS MOVING THROUGH THE AREA THURSDAY NIGHT THROUGH
SATURDAY WILL CAUSE RIVERS TO RISE BUT WITH A FEW BREAKS IN THE
STEADY PRECIPITATION THE ONLY THREAT OF FLOODING IN THIS SCENARIO
LOOKS TO BE ON THE SKOKOMISH RIVER NEXT WEEKEND. FELTON/ALBRECHT

&&

.AVIATION...MOIST WESTERLY FLOW ALOFT PREVAILS OVER WESTERN
WASHINGTON THIS MORNING...AS A WEAK FRONT MOVES INLAND FROM THE
OFFSHORE WATERS. THE FRONT WILL MOVE EAST OF THE CASCADES THIS
EVENING...BUT THE AIR MASS WILL REMAIN MOIST AT LOWER LEVELS. A FLAT
UPPER RIDGE WILL REMAIN OVER THE PACIFIC NORTHWEST.

CEILINGS ACROSS THE FORECAST AREA ARE MAINLY 6000 FT OR ABOVE AT
PRESENT...BUT THERE IS SPOTTY LIGHT RAIN AND AREAS OF VISIBILITY
3-5SM -RA BR. CONDITIONS WILL DETERIORATE DURING THE NEXT FEW HOURS
AS PRECIPITATION INCREASES...AND WIDESPREAD 3-5SM -RA BR AND CEILING
BKN-OVC025 IS LIKELY LATE THIS MORNING AND AFTERNOON. RAIN WILL
MOSTLY END OVER THE LOWLANDS THIS EVENING...BUT CEILINGS WILL
PROBABLY REMAIN LOW THROUGH TONIGHT AND MONDAY MORNING WITH
WIDESPREAD STRATUS.

KSEA...SOUTHERLY WIND 6-10 KT. CEILING WILL FALL OVER THE NEXT FEW
HOURS AS RAIN INCREASES...AND VISIBILITY 3-5SM -RA BR SEEMS LIKELY
AT TIMES. RAIN WILL END LATE TODAY OR THIS EVENING...BUT STRATUS
WILL PROBABLY CONTINUE TONIGHT AND MONDAY MORNING.   MCDONNAL

&&

.MARINE...A WEAK FRONT WILL MOVE THROUGH THE COASTAL WATERS OF
WESTERN WASHINGTON THIS MORNING AND THEN INLAND THIS AFTERNOON. THIS
FEATURE IS PRODUCING SMALL CRAFT ADVISORY SOUTHERLIES OVER THE
COASTAL WATERS FROM AROUND DESTRUCTION ISLAND NORTHWARD...AND THESE
SHOULD CONTINUE INTO THE AFTERNOON. THE FRONT WILL PROBABLY ALSO
PRODUCE MARGINAL SMALL CRAFT ADVISORY WINDS OVER THE EAST ENTRANCE
STRAIT OF JUAN DE FUCA...ADMIRALTY INLET...AND NORTHERN INLAND
WATERS THIS AFTERNOON.

A NEGATIVELY TILTED FRONT WILL MOVE THROUGH THE FORECAST AREA MONDAY
AFTERNOON AND EVENING. THIS WILL ALSO BE A RELATIVELY WEAK
FEATURE...BUT IT SHOULD RESULT IN SMALL CRAFT ADVISORY WINDS OVER
MOST OF THE MARINE ZONES. WEAK HIGH PRESSURE WILL BE OVER THE REGION
TUESDAY AND WEDNESDAY...AND A STRONGER FRONTAL SYSTEM WILL ARRIVE
THURSDAY.   MCDONNAL

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY TODAY COASTAL WATERS ZONES 150 153 170 173.
     SMALL CRAFT ADVISORY THIS AFTERNOON EAST ENTRANCE STRAIT OF
       JUAN DE FUCA...ADMIRALTY INLET...NORTHERN INLAND WATERS.

&&

$$

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