Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000
FXUS66 KSEW 142303
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
300 PM PST FRI NOV 14 2014

.SYNOPSIS...HIGH PRESSURE ALOFT AND DRY LOW LEVEL OFFSHORE FLOW
WILL PROVIDE CLEAR SKIES AND VERY COOL TEMPERATURES THROUGH THE
WEEKEND. THE UPPER LEVEL RIDGE WILL MIGRATE OVER WASHINGTON ON
MONDAY AND TUESDAY MAINTAINING THE DRY WEATHER PATTERN BUT WITH
SLOWLY MODERATING TEMPERATURES. A WEAK SYSTEM WILL BRING A CHANCE OF
RAIN BACK INTO THE AREA BY MID WEEK.

&&

.SHORT TERM...NORTHERLY FLOW ALOFT BEHIND A TROUGH DIGGING SWD OVER
THE INTERIOR WEST WILL USHER IN A -30C COLD POOL AT 500 MB OVER THE
PAC NW TONIGHT. A 1040 MB SURFACE HIGH OVER SRN B.C. WILL ALSO
MAINTAIN DRY LOW LEVEL OFFSHORE FLOW. GRADIENTS WILL WEAKEN
OVERNIGHT SO WINDS CURRENTLY GUSTING TO 35 MPH ACROSS THE N INTERIOR
WILL GRADUALLY DIMINISH. THE COMBINATION OF VERY LOW DEW
POINTS...LIGHT FLOW...AND CLEAR SKIES...WILL RESULT IN COLD
TEMPERATURES THIS WEEKEND. MOS GUIDANCE IS IN BETTER AGREEMENT
INDICATING LOWS IN THE 20S FOR MOST PLACES BUT SHELTERED COLD
POCKETS LIKE OLYMPIA FALLING TO THE UPPER TEENS. AREAS THAT HAD SOME
WIND TODAY LIKE BELLINGHAM WILL PROBABLY BE A FEW DEGREES COLDER
WITH LESS MIXING BY SATURDAY MORNING. ANOTHER HARD FREEZE WILL IS
EXPECTED SUNDAY AS WELL WITH LITTLE CHANGE IN THE PATTERN. HIGH
TEMPERATURES WILL WARM A FEW DEGREES ON SUNDAY AS THE UPPER RIDGE
OFFSHORE SHIFTS EWD DIRECTLY OVER OUR REGION.

UPPER LEVEL HIGH PRESSURE WILL BRING MILDER AIR ALOFT WHICH WILL
GRADUALLY HELP MODIFY THE LOW LEVELS. HIGH TEMPERATURES BY MONDAY
COULD REACH NEAR 50. IT WILL REMAIN DRY AND MORNING LOWS WILL
STILL FALL BELOW FREEZING IN MANY SPOTS. FOG IS UNLIKELY THE NEXT
FEW DAYS GIVEN HOW DRY THE AIR MASS IS WITH NO INFLUX OF MOISTURE OR
RESIDUAL MOISTURE IN PLACE.

.LONG TERM...MODELS AGREE THAT HIGH PRESSURE WILL HOLD OFF PACIFIC
MOISTURE THROUGH TUESDAY. THE UPPER FLOW WILL SPLIT TUESDAY NIGHT AS
SRN STREAM SYSTEMS EVENTUALLY UNDERCUT THE HIGH. THERE IS GOOD
AGREEMENT THAT THE INITIAL SYSTEM BREAKING THROUGH THE RIDGE WILL
SPREAD LIGHT RAIN OVER THE AREA LATE TUESDAY NIGHT AND WEDNESDAY.
THE TROUGH WILL DAMPEN OUT RAPIDLY AND THE DRY AIR MASS IN PLACE
WILL NEED TO MOISTEN UP SO RAINFALL AMOUNTS SHOULD BE RATHER LIGHT.

RAIN WILL CHANGE OVER TO SHOWERS AS THE SYSTEM DISSIPATES OVER THE
AREA WEDNESDAY NIGHT AND THURSDAY. THE GFS/ECMWF DIFFER SLIGHTLY ON
HOW MUCH OF A BREAK WILL OCCUR UNTIL THE NEXT SYSTEM ARRIVES. FRIDAY
COULD BE DRY BUT THE NEXT SYSTEM MAY BE STRONGER AND COULD ARRIVE BY
LATE IN THE DAY IF THE GFS IS CORRECT. WILL KEEP THE CHANCE POPS IN
PLACE WITH HIGHER POPS TOWARD THE COAST. BY MID WEEK...TEMPERATURES
WILL MODERATE CONSIDERABLY WITH HIGHS IN THE LOW 50S AND LOWS ABOVE
FREEZING. MERCER

&&

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

&&

.AVIATION...CLEAR COOL DRY AIR IS OVER WRN WA WITH LOW LEVEL
OFFSHORE FLOW AND NLY FLOW ALOFT.

KSEA...CLEAR WITH A NNE BREEZE.

&&

.MARINE...NE FLOW WITH A SURFACE HIGH OVER B.C. EXTENDING SOUTH INTO
ERN WA. THE BREEZIEST NE WIND IS IN THE NORTH CLOSER TO THE FRASER.
THE OFFSHORE FLOW WILL BECOME LIGHTER BY EARLY NEXT WEEK. A FRONT
WILL REACH THE REGION NEXT WED.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...NONE.
PZ...SMALL CRAFT ADVISORY NORTHERN INLAND WATERS.

&&

$$

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