Gale Warning 41, NWS Seattle, WA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PDT MON APR 3 2012...CORRECTED TIME

.SYNOPSIS...A COLD FRONT WILL MOVE THROUGH WESTERN WASHINGTON TODAY.
A COOL UPPER TROUGH WILL MOVE OVER THE REGION WEDNESDAY THROUGH
FRIDAY PRODUCING A FEW SHOWERS. DRY WEATHER IS LIKELY THIS WEEKEND
ALONG WITH WARMER HIGH TEMPERATURES.

&&

.SHORT TERM...A LARGE UPPER TROUGH DEVELOPING OVER THE ERN PAC
CONTINUES TO DIG SWD AND BECOME MORE N/S ORIENTED. THIS HAS CAUSED
AN APPROACHING FRONT TO STALL ALONG THE WA COAST AS WAVES ALONG THE
FRONT ALSO HOLD UP EWD PROGRESS. MODELS SO FAR HAVE BEEN WAY TO FAST
WITH THIS SYSTEM BUT THE ECMWF APPEARS TO HAVE THE BEST HANDLE ON
THE DETAILS WITH A LATER ARRIVAL OF THE FRONT. THE 00Z NAM-12 STILL
PUSHES THE FRONT THROUGH RATHER QUICKLY WITH A QUICK FEW HOURS OF
RAIN SWITCHING TO SHOWERS THIS AFTERNOON. THE ECMWF AND THE GFS ARE
SLOWER AND SHOW THE HIGHER QPF AMOUNTS DURING THE AFTERNOON TIME
FRAME WHICH IMPLIES A LATER FRONTAL PASSAGE. THE LATEST RADAR LOOPS
SHOWS STEADY RAIN ALONG THE COAST STILL YET TO REACH THE W PORTION
OF PUGET SOUND. BEST GUESS IS THAT RAIN WILL DEVELOP OVER THE PUGET
SOUND REGION BY MID-LATE MORNING THEN TAPER TO SHOWERS LATER THIS
AFTERNOON. THE HIGHEST QPF SHOWN BY ANY MODELS IS AROUND A HALF INCH
OVER THE N CASCADES. THIS COULD GIVE 6 INCHES AT MOUNT BAKER BUT THE
ADVISORY LOOKS IFFY. DECIDED TO UPDATE THE ADVISORY AND LOWER
AMOUNTS AND INDICATE THE HIGHEST AMOUNTS MORE LOCALIZED TO MOUNT
BAKER. SINCE THE FRONT IS STRETCHING OUT AND GRADIENTS NOT AS STRONG
AS EXPECTED...WINDS SHOULD JUST BE BREEZY OVER THE N INTERIOR AND
COAST. THE WIND ADVISORY WAS APPROPRIATELY DROPPED BY THE PREVIOUS
SHIFT.

THE BROAD UPPER TROUGH MOVES OVER THE PAC NW ON WEDNESDAY WITH ALL
THE ENERGY MOVING THROUGH THE BASE OF THE TROUGH. MOISTURE WILL
GRADUALLY DECREASE OVER WA ALTHOUGH THE COOLER AIR ALOFT WILL CREATE
SOMEWHAT UNSTABLE CONDITIONS. EXPECT SOME SHOWERS AROUND...MAINLY IN
THE AFTERNOON/EVENING AND OVER HIGHER TERRAIN. POPS ARE HIGHER IN
THE MOUNTAINS BUT WERE DECREASED OVER THE LOWLANDS TO JUST A CHANCE.
THERE WAS A MENTION OF THUNDERSTORMS IN THE FORECAST BUT I COULD NOT
FIND MUCH JUSTIFICATION FOR KEEPING THEM IN GIVEN THE LACK OF
MOISTURE AND ANY ORGANIZED SHORT WAVES. INSTEAD...I WOULD EXPECT LOW
TOPPED CU AND A FEW SHOWERS ALONG WITH PARTIAL SUNSHINE.

.LONG TERM...THE TROUGH STARTS TO MOVE EWD ON FRIDAY WITH RIDGING
SHOWN BY MODELS OVER THE AREA OVER THE WEEKEND. THIS WILL LIKELY BE
A DRY PERIOD WITH TEMPERATURES WARMING TO ABOVE AVERAGE FOR THIS
TIME OF YEAR. HIGH TEMPERATURES ARE LIKELY TO REACH THE LOW 60S BY
SUNDAY AND MONDAY WITH MOSTLY SUNNY SKIES.

AN UPPER LEVEL SHORT TROUGH WILL WEAKEN ON MONDAY AND EJECT NE INTO
WA. THIS MAY OCCUR LATER MONDAY OR TUESDAY. EXPECT A CHANCE OF
SHOWERS TO RETURN WITH THIS SYSTEM.

&&

.HYDROLOGY...THE INCOMING FRONT THIS MORNING WILL PRODUCE LESS THAN
1 INCH OF RAIN TOTAL THE NEXT 12-18 HOURS OVER THE OLYMPICS. HYDRO
MODELS SHOW THE SKOKOMISH RIVER RISING TO ABOUT 16.0 FEET AND FLOOD
STAGE IS 16.5 FEET. LATEST MODEL RUNS SHOW LESS QPF AMOUNTS AND
HYDRO GRAPHS ARE TRENDING BELOW THE FORECAST. THEREFORE...FLOODING
IS NOT EXPECTED ON THE SKOKOMISH RIVER.

THE PATTERN BECOMES SHOWERY BY WEDNESDAY WHICH IS NOT CONDUCIVE FOR
FLOODING ON ANY AREA RIVERS. DRIER WEATHER WILL DEVELOP OVER THE
WEEKEND. FLOODING IS NOT EXPECTED ON ANY AREA RIVERS OVER THE NEXT 7
DAYS. MERCER

&&

.AVIATION...A VERY SLOW MOVING COLD FRONT WILL MOVE INTO WESTERN
WASHINGTON THIS MORNING REACHING THE CASCADES THIS AFTERNOON. STRONG
SOUTHWEST FLOW ALOFT WILL CONTINUE UNTIL THE FRONT MOVES EAST OF THE
AREA. AT 10Z THE COLD FRONT IS ABOUT 100 NM WEST OF KHQM.

RAIN BEGAN AT KHQM AROUND 08Z WITH THE CEILINGS ALREADY DOWN TO NEAR
3000 FEET AT 10Z. JUST MID AND HIGH LEVEL CLOUDS OVER THE INTERIOR
AT 10Z. CEILINGS WILL LOWER QUICKLY DOWN TO 3000 TO 4000 FEET OVER
THE INTERIOR WITH THE ONSET OF THE RAIN AROUND 15Z. CEILINGS
LOWERING DOWN TO NEAR 2000 FEET RIGHT AHEAD OF THE FRONT LATE THIS
MORNING. NOT MUCH ONSHORE FLOW BEHIND THE FRONT SO EXPECT CIGS TO
POP BACK UP INTO THE LOW END OF VFR THIS AFTERNOON. EXPECT CEILINGS
TO SLOWLY IMPROVE THIS EVENING BACK UP TO NEAR 5000 FEET.

KSEA...JUST MID LEVEL CLOUDS EARLY THIS MORNING. CEILINGS LOWERING
QUICKLY DOWN TO NEAR 3000 FEET AROUND 15Z BOTTOMING OUT NEAR 2000
FEET 18Z-21Z. CEILINGS RECOVERING BACK UP TO 3500 TO 4500 FEET BY
01Z THIS EVENING. SOUTHEAST WINDS 4 TO 8 KNOTS BECOMING SOUTHWEST 6
TO 10 KNOTS THIS AFTERNOON. FELTON

&&

.MARINE...A SLOW MOVING COLD FRONT WILL MOVE THROUGH THE WATERS THIS
MORNING. GALE FORCE WINDS OVER THE COASTAL WATERS...ENTRANCES TO THE
STRAIT AND ADMIRALTY INLET HAVE ALREADY EASED AND WILL CONTINUE TO
TREND LOWER TODAY. SMALL CRAFT ADVISORIES FOR WINDS ONLY REMAIN UP
FOR CAMANO ISLAND TO POINT ROBERTS AND THE EAST ENTRANCE OF THE
STRAIT. WINDS WILL REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA
BEHIND THE FRONT THIS AFTERNOON. SURFACE GRADIENTS WEAKENING QUICKLY
TONIGHT. A WEAK UPPER TROUGH HANGS OVER THE AREA LATER TONIGHT
THROUGH FRIDAY WITH LIGHT SURFACE GRADIENTS. DIURNAL SCA LEVEL
WESTERLIES MAY DEVELOP IN CENTRAL/EASTERN STRAIT DURING THE
AFTERNOON AND EVENING HOURS IN RESPONSE TO DAY TIME HEATING OVER THE
LAND.

A SMALL CRAFT ADVISORY IS IN EFFECT THROUGH WEDNESDAY FOR HAZARDOUS
SEAS FOR THE COASTAL WATERS AND THE WEST ENTRANCE TO THE STRAIT.
WESTERLY SWELLS IN THE 14 TO 18 FEET RANGE TODAY WILL SUBSIDE SLOWLY
TONIGHT AND BE DOWN TO 11 TO 13 FEET DURING THE DAY ON WEDNESDAY.
FELTON

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY NORTHERN CASCADES THROUGH THIS EVENING.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS COAST AND WEST ENTRANCE
     TO THE STRAIT.
     SMALL CRAFT ADVISORY CAMANO ISLAND TO POINT ROBERTS AND EAST
     ENTRANCE TO THE STRAIT.
     SMALL CRAFT ADVISORY FOR ROUGH BAR FOR GRAYS HARBOR BAR.

&&

WWW.WEATHER.GOV/SEATTLE

FOR THE GRAPHICAL AFD VISIT...
WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML