Willamette Aviation | NWS Forecast Discussion



000
FXUS66 KPQR 111645
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
844 AM PST THU MAR 11 2010

.SYNOPSIS...THE NEXT FRONTAL SYSTEM WILL IMPACT THE FORECAST AREA
THROUGH FRIDAY. THE WARM FRONTAL PART WILL STALL ACROSS WESTERN
WASHINGTON AND NW OREGON TODAY. A SECONDARY WAVE WILL REINFORCE THE
FRONTAL ZONE TONIGHT. THE COLD FRONT FINALLY MOVES INLAND FRIDAY.
THIS SYSTEM WILL BRING SIGNIFICANT RAINFALL TO THE COAST AND COAST
RANGE. AFTER THE UPPER TROUGH MOVES THROUGH FRIDAY NIGHT...A WARM
FRONT WILL BRUSH THE AREA SATURDAY. HIGH PRESSURE TAKES OVER SUNDAY
THROUGH EARLY NEXT WEEK.

&&

.SHORT TERM...A MOIST BAROCLINIC ZONE SPREADING PRECIPITATION ACROSS
THE AREA TODAY WITH THE MAIN FOCUS OVER THE NORTHERN ZONES. A LONG
MOISTURE FETCH EXTENDS ALL THE WAY BACK BEYOND 170W. AMSU SATELLITE
TOTAL PRECIPITABLE WATER FOR THIS MORNING SHOWING .75 TO 1.00 INCHES
IN THIS MOISTURE FETCH. THIS LOOKS TO BE ONE OF THE MORE SIGNIFICANT
WEATHER SYSTEMS WE HAVE SEEN IN QUITE AWHILE. THE FRONT PASSED
THROUGH ABOUT 630 AM ON THE SOUTH WASHINGTON COAST AND WILL SLOWLY
SAG SOUTH TODAY. BREEZY TO WINDY CONDITIONS ALSO TODAY WITH GFS
SHOWING 40-50 KT SWLY 850 MB WIND INTO THE COAST RANGE. THIS WILL
ALSO YIELD SUBSTANTIAL OROGRAPHIC PRECIPITATION...WITH WETTEST AREAS
LOOKING TO BE OVER THE NW HALF OF THE FORECAST AREA. SNOW LEVELS AND
OROGRAPHICS FAVOR GOOD SNOWS IN THE S WA CASCADES...WITH CURRENT SNOW
ADVISORY THERE LOOKING GOOD. SHOULD ALSO BE GOOD SNOW AMOUNTS IN THE
N OREGON CASCADES BUT MAINLY AT HIGHER ELEVATIONS.

A STRONGER WAVE LATER TONIGHT LIFTS AND TURNS THE FRONT MORE N-S
WHILE ALSO BACKING UP THE FRONT CLOSER TO THE COAST. OVER THE PAST
DAY MODELS HAVE SLOWED AND WEAKENED THE STRENGTH OF THIS WAVE. 850 MB
WINDS NEAR 70 KNOTS APPROACH THE SOUTH SOUTH COAST EARLY FRI MORNING
BUT QUICKLY EASE AFTER THAT. STILL WILL BE WINDY ON THE COAST BUT
WITH THIS CHANGE IN MODELS...PUTS HIGH WIND WATCH IN A DIMMER LIGHT.
WILL KEEP WATCH FOR NOW AND WAIT FOR FULL WRF RUN BEFORE MAKING ANY
CHANGES.

MODELS CONSISTENT SHOWING THE FRONTAL BAND PUSHING INLAND LATER FRI
MORNING MOVING INTO THE CASCADES BY EARLY IN THE AFTERNOON. WILL NEED
TO MONITOR FOR ANY HYDROLOGIC ISSUES BUT PRESENTLY DO NOT EXPECT
RIVER FLOODING. SNOW LEVELS WILL BE FAIRLY HIGH TONIGHT AND
EARLY FRI...BUT WILL COME CRASHING DOWN FRI AFTERNOON. HOWEVER MODEL
QPF AND 850 MB OROGRAPHIC COMPONENT NOT ALL THAT FAVORABLE FOR SNOW
ADVISORY AMOUNTS. THE UPPER TROUGH MOVES THROUGH LATER FRI NIGHT WITH
DECREASING SHOWERS SAT AS THE MOIST LOW LEVEL AIR MASS STABILIZES. RW

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...MODELS IN
REASONABLY GOOD AGREEMENT LATE THIS WEEKEND THROUGH MON...SHOWING A
RIDGE HOLDING IN OVER THE INTERIOR PAC NW...WITH A DEEP TROUGH
PROGRESSING SLOWLY FROM 150W TO 140W. LATEST MODELS RUNS ALL KEEP THE
BAROCLINIC ZONE OFFSHORE THROUGH MON...SO WILL GO A WITH
PREDOMINANTLY DRY AND MILD FORECAST SUN AND MON. GENERAL TREND FOR
TUE ON SHOWS A SHORTWAVE AND COLD FRONT LIFTING NE AND PUSHING
INLAND...BUT TIMING BECOMES AN ISSUE WITH GFS THE MOST PROGRESSIVE
WITH THE SYSTEM. GIVEN THE DEVELOPING MODEL DISCREPANCIES...WILL
TREND FORECAST TOWARD CLIMATOLOGY AFTER TUE.

&&

.AVIATION...COASTAL TAF SITES SHOULD CONTINUE MVFR CONDITIONS...
OTHERWISE EXPECT MOSTLY VFR THROUGH EARLY AFTERNOON. DECREASING
WIND AND MORE MOISTURE THU AFTERNOON MAY ALLOW MVFR AND
OCCASIONALLY IFR CIGS OR VIS TO DEVELOP. WINDS INCREASE AND BECOME
OFFSHORE FRI WHICH IS LIKELY TO LEAD TO IMPROVEMENT -VFR CIGS AND
VIS- BY MID AFTERNOON.

KPDX AND APPROACHES...VFR THROUGH ABOUT 18Z TODAY...THEN EXPECT
MVFR CONDITIONS AS MOISTURE INCREASES AND WINDS DECREASE. IMPROVEMENT
AGAIN FRIDAY WITH DEVELOPING OFFSHORE FLOW AND INCREASING PRES
GRADIENTS.

&&

.MARINE...GALES ALL WATERS THROUGH LATER THIS MORNING...THEN ENDING
NORTHERN MARINE ZONES. GALES ENDING SOUTH MARINE ZONES LATE
AFTERNOON. SWELL AROUND 18 TO 21 FT THROUGH FRI NIGHT...THEN DROPS
TO LOW TEENS OVER WEEKEND. GALES LIKELY FRI MORNING WITH
BORDERLINE GALE/STORM FORCE GUSTS. HIGH SURF ADVISORY FOR LATE
THIS MORNING THROUGH LATE FRI EVENING...THOUGH APPEARS TO BE
MARGINAL CASE WITH SWELL PERIOD AND COMBINED SEAS BOTH BARELY
MEETING CRITERIA.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY FROM 1 PM THIS AFTERNOON TO MIDNIGHT PST
     TONIGHT FOR CENTRAL OREGON COAST-NORTH OREGON COAST.

     HIGH WIND WATCH FROM LATE TONIGHT THROUGH FRIDAY MORNING FOR
     CENTRAL OREGON COAST-NORTH OREGON COAST.

WA...HIGH SURF ADVISORY FROM 1 PM THIS AFTERNOON TO MIDNIGHT PST
     TONIGHT FOR SOUTH WASHINGTON COAST.

     HIGH WIND WATCH FROM LATE TONIGHT THROUGH FRIDAY MORNING FOR
     SOUTH WASHINGTON COAST.

     WINTER WEATHER ADVISORY UNTIL 8 PM PST THIS EVENING FOR SOUTH
     WASHINGTON CASCADES.

PZ...GALE WARNING UNTIL 10 AM PST THIS MORNING FOR COASTAL WATERS
     FROM CAPE SHOALWATER WA TO CASCADE HEAD OR FROM 10 TO 60 NM.

     GALE WARNING FROM 4 PM PST THIS AFTERNOON THROUGH NOON PST
     FRIDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE
     OR FROM 10 TO 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 10 AM
     PST FRIDAY FOR COLUMBIA RIVER BAR.

&&

$$

MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.
Weather information courtesy of NOAA and AviationWeather.gov