Strong Wind in Oregon, February 25, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
208 AM PST TUE FEB 25 2014

.SYNOPSIS...HIGH PRESSURE ALOFT CENTERED OVER THE PACIFIC NORTHWEST
WILL STRENGTHEN TODAY AS A DEEP LOW PRESSURE SYSTEM REMAINS WELL
OFFSHORE AND MUCH COLDER NORTH FLOW ALOFT RESIDES OVER THE NORTHERN
ROCKIES. OFFSHORE LOW-LEVEL FLOW THROUGH THE COLUMBIA GORGE WIL
CONTINUE THROUGH TONIGHT...THEN GRADUALLY WEAKEN WEDNESDAY. RESIDUAL
COLD AIR NEAR HOOD RIVER AND IN THE UPPER HOOD RIVER VALLEY TODAY
WILL MAINTAIN THREAT OF MIXED PRECIPITATION THIS MORNING. THE RIDGE
SHIFTS TO THE EAST WEDNESDAY AS AN UPPER LOW SWINGS TOWARD SOUTHWEST
OREGON. RAIN SPREADS INTO THE SOUTH ZONES WEDNESDAY EVENING THEN
EXPANDS NORTH WEDNESDAY NIGHT. A LOW PRESSURE AREA REMAINS PARKED OFF
THE NRN CALIFORNIA COAST THURSDAY AND FRIDAY WITH THE BEST THREAT OF
PRECIPITATION OVER THE SOUTH. UNSETTLED AND POSSIBLY QUITE COOL
WEATHER WILL RETURN FOR THE COMING WEEKEND.
&&

.SHORT TERM...TUESDAY THROUGH THURSDAY...A RATHER COMPLEX LARGE-SCALE
PATTERN CONTINUES OVER THE PAC NW TODAY. THE MAIN FEATURES OF NOTE
EARLY THIS MORNING INCLUDE AN ELONGATED FRONTAL ZONE ASSOCIATED WITH
A LOW OUT NEAR 44N 145W AND A 500 MB RIDGE AXIS CENTERED OVER WRN
WASHINGTON AND OREGON. HOWEVER...THE RIDGE IS NOT STRONG ENOUGH TO
PREVENT MOISTURE FROM SPREADING NWD IN THE SLY FLOW ALOFT. WATER
VAPOR IMAGERY SHOWS A CONVERGENT BAND OF MOISTURE OVER NRN OREGON AND
SRN WA. COMPLICATING MATTERS IS COLD NLY FLOW DIVING INTO ERN WA. THE
END RESULT IS OFFSHORE LOW-LEVEL FLOW THROUGH THE COLUMBIA GORGE. A
SENSOR IN CORBETT REGISTERED WIND GUSTS TO NEAR 70 MPH BETWEEN 9 AND
10Z. TEMPERATURES IN THE UPPER HOOD RIVER VALLEY WERE RUNNING CLOSE
TO FREEZING JUST BEFORE 10Z.

THE 03Z RUN OF THE HRRR SHOWS THE MOISTURE BAND DRIFTING N  OF THE
COLUMBIA RIVER BY 14Z. WILL NEED TO KEEP A MENTION OF MIXED PRECIP
NEAR K4S2 AND IN THE UPPER HOOD RIVER VALLEY THIS MORNING. NAM
SOUNDING FOR A POINT NEAR K4S2 SHOWS A FREEZING-RAIN PROFILE AT 17Z.
HOWEVER...IT APPEARS THE MODEL IS TOO COLD AT THE SURFACE COMPARED TO
CURRENT READINGS. ALL IN ALL...PRECIP IS EXPECTED TO DIMINISH ACROSS
THE NRN ZONES AS THE DAY PROGRESSES. NAM MAINTAINS ABOUT -8 TO -10 MB
KTTD-KDLS GRADIENT TODAY. LOCAL WIND STUDY SUGGESTS WIND GUSTS 65-75
MPH ARE LIKELY AT THE MOST WIND-PRONE AREAS AT THE WEST END OF THE
COLUMBIA GORGE WITH THAT GRADIENT MAGNITUDE. QUITE A CONTRAST IN HIGH
TEMPS TODAY AS WELL. K4S2 WILL BE LUCKY TO REACH 40 DEG WHILE THE SRN
INTERIOR VALLEYS WILL BE IN THE LOW 60S.

TONIGHT AND WED LOOK TO BE DRY AS THE H5 RIDGE STRENGTHENS A BIT IN
RESPONSE TO THE DEEPENING LOW PRES OUT NEAR 140W. THE AIR MASS WILL
BE RATHER MILD AND MOIST IN THE LOWER LEVELS...LEADING TO LOWLAND FOG
TONIGHT. THE OFFSHORE LOW-LEVEL FLOW STARTS TO WANE WED AS THE COLDER
AIR IS FORCED FURTHER EAST. THE NEXT BATCH OF PRECIP ENTERS SW OREGON
WED AFTERNOON AND REACHES THE SWRN ZONES LATE WED AFTERNOON OR WED
EVENING. MODELS DIFFER ON THE UPPER LOW PLACEMENT ...WITH THE ECMWF
FURTHER N...OFF THE SRN OREGON COAST...COMPARED TO THE GFS. MODELS
ARE DEPICTING SOME SORT OF DEFORMATION ZONE SETTING UP WED NIGHT THEN
DRIFTING N INTO SRN WA BY 18Z THU. BUMPED UP POPS WED NIGHT...
ESPECIALLY OVER THE SRN HALF OF THE AREA. MAY NEED TO INCREASE THEM
EVEN MORE SHOULD MODELS MAINTAIN THEIR CURRENT TRENDS. WEISHAAR

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
THURSDAY NIGHT THROUGH MONDAY...SPLIT FLOW WILL PREVAIL THROUGH THE
PERIOD. EXPECT NEAR NORMAL TEMPERATURES AND PRECIPITATION THROUGH
FRIDAY AS A WEAK UPPER LEVEL LOW PRESSURE SYSTEM MOVES INTO THE
REGION AND DISSIPATES THURSDAY NIGHT. A MORE ORGANIZED UPPER LOW
OFFSHORE WILL APPROACH THE AREA FRIDAY...HOWEVER IT LOOKS TO BE
PUSHED SOUTHWARD INTO SOUTHWESTERN OREGON/NORTHERN CALIFORNIA BY A
DEVELOPING UPPER TROUGH/SHORT WAVE THAT WILL DIVE SOUTH OUT OF
CANADA. THIS UPPER TROUGH WILL NEED TO BE MONITORED. AT THIS TIME
MODELS ARE IN FAIR AGREEMENT THAT THE UPPER TROUGH WILL BRING A SURGE
OF COLD AIR INTO THE CWA VIA THE COLUMBIA GORGE LATE FRIDAY INTO
SATURDAY. IN ADDITION...BOTH THE ECMWF AND TO A LESSER EXTENT THE GFS
DEVELOP A SURFACE LOW OFFSHORE FRIDAY NIGHT...FURTHER INDUCING COLD
OFFSHORE FLOW AND POTENTIALLY ENTRAINING MOISTURE FROM THE
AFOREMENTIONED UPPER LOW TO THE SOUTH AND ADVECTING IT NORTHWARD. ALL
IN ALL...THERE IS POTENTIAL FOR SNOW OR FREEZING RAIN SATURDAY
THROUGH MONDAY FROM PDX EAST INTO THE GORGE. HOWEVER... PLENTY OF
UNCERTAINTY REMAINS. FORECASTER CONFIDENCE IS VERY LOW AT THIS TIME
ABOUT WHETHER TEMPERATURES WILL IN FACT BE COLD ENOUGH... OR IF THE
COLD AIR AND MOISTURE WILL BE COINCIDENT. BB
&&

.AVIATION...MOSTLY VFR CONDITIONS EARLY THIS MORNING EXCEPT FOR
PATCHY MVFR TO IFR CIGS IN THE CENTRAL AND SOUTHERN WILLAMETTE
VALLEY AND ALONG THE COLUMBIA RIVER NEAR KKLS. THE IFR CONDITIONS
HAVE BEEN FAIRLY ISOLATED TO VCNTY OF KEUG SO FAR. EXPECT IFR
CONDITIONS TO CONTINUE THERE THROUGH THIS MORNING. DEW POINT
DEPRESSIONS SUGGEST THAT OTHER VALLEY LOCATIONS WILL SEE SOME FOG
AND HAVE TEMPORARY MVFR-IFR CONDITIONS THIS MORNING...ESPECIALLY
WHERE THERE IS CALM WINDS. HIGH CLOUDS STREAMING OVER SHOULD
MINIMIZE RADIATION COOLING AND DO NOT EXPECT THE FOG TO BE
WIDESPREAD.

EAST WINDS WILL DOMINATE TODAY AND TONIGHT WITH
NORTHERLY WINDS THROUGH THE CENTRAL WILLAMETTE VALLEY. THE WINDS
WILL BE GUSTY NEAR KTTD WITH GUSTS OF 40 KT LIKELY THIS AFTERNOON
AND EVENING. THE WINDS SHOULD KEEP MOST AREAS VFR EXCEPT FOR THE
MORE SHELTERED AREAS LIKE KEUG...KHIO AND KKLS WHERE THERE WILL BE
PERIODS OF REDUCED VSBYS DUE TO FOG THIS MORNING AND POSSIBLY
AGAIN LATE TONIGHT.

KPDX AND APPROACHES...VFR CONDITIONS EXPECTED TODAY. EAST WINDS AT
THE AIRPORT TODAY WITH POSSIBLE GUSTS UP TO 25 KT THIS AFTERNOON
AND EVENING. HARTLEY

&&

.MARINE...HIGH PRESSURE INLAND COMBINED WITH LOW PRESSURE OVER THE NE
PACIFIC HAS RESULTED IN EAST TO SOUTHEAST WINDS OVER THE WATERS.
THE OFFSHORE WINDS ARE STRONGEST TO THE NORTH ESPECIALLY NEAR THE
ENTRANCE OF THE COLUMBIA RIVER. THE SURFACE PRESSURE GRADIENT WILL
CONTINUE TO STRENGTHEN TODAY AND AREAS NORTH OF CANNON BEACH MAY
HAVE AN OCCASIONAL GUST TO 25 KT. DO NOT THINK THAT THESE GUSTS
WILL BE WIDESPREAD OR FREQUENT ENOUGH TO WARRANT AN ADVISORY..BUT
WILL MONITOR THE WINDS CLOSELY IN CASE AN UPDATE IS NECESSARY.

SEAS BECOME COMPLICATED TUESDAY THROUGH THURSDAY AS MULTIPLE LOWS
WEST AND SOUTHWEST OF THE WATERS WILL GENERATE A VARIETY OF SWELL
TRAINS THROUGH THE WATERS. THE SWELL HEIGHTS OF THE INDIVIDUAL
TRAINS ARE GENERALLY LESS THAN 5 FEET. OVERALL WAVE HEIGHTS WILL
GENERALLY BE BETWEEN 6 AND 9 FEET TONIGHT THROUGH THURSDAY
COMPILED BY A LONG PERIOD SW SWELL AND A SHORTER PERIOD W SWELL.
THE SEAS IN THE SOUTHERN WATERS MAY BE SLIGHTLY STRONGER AND AN
ADVISORY FOR SEAS MAY BE NECESSARY FOR AREAS SOUTH OF CASCADE HEAD
WEDNESDAY AND WEDNESDAY NIGHT. HARTLEY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...NONE.

&&

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

INTERACT WITH US VIA SOCIAL MEDIA
    WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
    WWW.TWITTER.COM/NWSPORTLAND

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.