High Wind in Washington, January 17 to 18, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
902 PM PST SAT JAN 17 2015

.SYNOPSIS...A WARM FRONT WILL CONTINUE TO MOVE SLOWLY N INTO
WASHINGTON OVERNIGHT. A COLD FRONT WILL MOVE ASHORE A LITTLE BEFORE
MIDNIGHT...AND THEN REACH THE CASCADES OVERNIGHT. A COUPLE OF
UPPER LEVEL DISTURBANCES WILL MOVE ACROSS THE REGION SUNDAY. HIGH
PRESSURE STARTS TO BUILD OVER THE AREA MON. HIGHER PRESSURE DEVELOPS
OVER EXTREME ERN WASHINGTON AND OREGON TUESDAY RESULTING IN THE
RETURN OF OFFSHORE LOW-LEVEL FLOW. THIS PATTERN SHOULD HOLD WEDNESDAY
AND THURSDAY.
&&

.SHORT TERM...A WARM FRONT CONTINUES TO GRADUALLY DRIFT N OVER THE
AREA THIS EVENING. THE WARMER AIR HAD REACHED THE WEST SIDE OF THE N
WILLAMETTE VALLEY AS OF 03Z...WITH KHIO AT 55 DEG. COOLER AIR
REMAINED TRAPPED ON THE EAST SIDE OF THE N VALLEY WITH TEMPS IN THE
MID TO UPPER 40S. KTTD-KDLS GRADIENT WAS AT -5.5 MB JUST BEFORE 04Z
WITH GUSTS TO 25 MPH AT KTTD. KRTX DUAL-POL DOPPLER RADAR SHOWING
HEAVIER RETURNS ALONG THE COAST ASSOCIATED WITH THE LEADING EDGE OF
THE COLD FRONT. INFRA-RED SATELLITE LOOP WITH NAM 12 SFC PRES
OVERLAID SHOWED A NEAR 990 MB LOW PRES CENTER AT 47N 129W MOVING TO
THE NE. TRAILING END OF THE COLD FRONT LOOKED TO BE NEAR 125W AT
0330Z. FRONT MAY MOVE ASHORE A LITTLE QUICKER THAN THE NAM INDICATED.
KRTX VELOCITY DISPLAY INDICATED 60-65 KT S-SW WIND ABOUT 5000 FT MSL.
STRONGEST WIND GUSTS EARLY THIS EVENING HAVE BEEN AT GARIBALDI...
AROUND 55 MPH...WITH A COUPLE ISOLATED GUSTS 55 TO 60 MPH. THE PEAK
WIND PERIOD STILL LOOKS TO BE THROUGH ABOUT 07Z.

SOME RATHER IMPRESSIVE RAINFALL TOTALS FOR PORTIONS OF THE N OREGON
CASCADES AND IN THE OREGON COAST RANGE. NEARLY 3.5 INCHES OF RAIN HAD
FALLEN AT THE 5880 FT TIMBERLINE SENSOR...WITH RAINFALL RATES UP TO
0.5 INCHES PER HR THIS AFTERNOON. AROUND 1.5 TO 3 INCHES HAVE FALLEN
IN THE OREGON COAST RANGE. FORTUNATELY...THE HEAVIER RAIN RATES HAVE
PUSHED INTO WASHINGTON. THERE WILL BE ANOTHER 3-6 HR PERIOD TONIGHT
OF HEAVIER RAINFALL WITH THE COLD FRONT. ADDED A SLIGHT CHANCE OF
TSTMS FOR THE COASTAL WATERS 03Z-06Z AS THE HRRR MODEL WAS HINTING AT
THE POTENTIAL FOR POTENTIAL CONVECTIVE DEVELOPMENT ALONG THE COLD
FRONTAL BOUNDARY AS IT MOVED TOWARD THE COASTLINE. DID NOT INCLUDE
THE COASTAL ZONES AT THIS TIME. NAMM SOUNDING FOR KAST NOT ALL THAT
IMPRESSIVE WITH CONVECTIVE POSSIBILITIES...BUT SOMETHING THAT WILL
NEED TO BE CLOSELY MONITORED AS THE FRONT MOVES ASHORE.

ONCE THE COLD FRONT MOVES INLAND...AIR MASS TRANSITIONS TO A COOLER
MORE UNSTABLE AIR MASS. MODEL SOUNDINGS INDICATE THE POST FRONTAL
UNSTABLE LAYER IS LIMITED VERTICALLY BY SOME SUBSIDENCE ALOFT...SO
CONVECTION IS NOT EXPECTED TO BE TERRIBLY DEEP...PROBABLY UP TO
AROUND 15K FT. A SERIES OF SHORTWAVES ON SUN WILL PROVIDE SOME
DYNAMIC LIFT FOR POST FRONTAL SHOWERS...WITH OROGRAPHIC LIFT AIDING
THE WINDWARD SIDE OF MOUNTAINS. WEST FLOW ALOFT COMING IN OFF THE
PACIFIC WILL KEEP SNOW LEVELS ELEVATED A BIT...BUT BY LATE SUN ENOUGH
COOLING OCCURS TO DROP THE SNOW LEVEL DOWN BELOW MOST CASCADE PASSES.
CHANCES FOR SHOWERS WILL DROP OFF FROM S TO N SUN NIGHT INTO MON AS A
SURFACE HIGH BUILDS NORTHWARD. MODELS CONTINUE TO SHOW SOME DEGREE OF
THERMALLY-INDUCED SURFACE TROUGHING ALONG THE COAST MON NIGHT AND
TUE. COUPLED WITH STRENGTHENING HIGH PRES OVER THE NRN ROCKIES
CONFIDENCE IS HIGH THAT OFFSHORE LOW-LEVEL FLOW WILL RETURN MON NIGHT
AND PERSIST TUE. WEISHAAR

.LONG TERM...MODELS IN PRETTY GOOD AGREEMENT IN BEGINNING THE
EXTENDED PERIOD WITH AN UPPER RIDGE AT MID WEEK...WHICH SHOULD
RESULT IN DRY WEATHER BUT WITH PLENTY OF VALLEY FOG UNDER A
SUBSIDENCE INVERSION. MODELS AGREE IN WEAKENING THE RIDGE THU AND
FRI...ALTHOUGH HEIGHTS REMAIN HIGH. LOOKS LIKE WHATEVER SYSTEMS
BREAK THROUGH WILL BE ON THE WEAK SIDE...SO OVERALL WILL TEND TO
KEEP POPS ON THE LOW SIDE...PEAKING WITH SOME LIKELY POPS ACROSS THE
N ON FRI WHEN MODELS APPEAR TO BE IN BEST AGREEMENT WITH RAIN
POTENTIAL. WILL THEN TREND BACK TO DRIER CONDITIONS FOR NEXT WEEKEND
AS BOTH GFS AND ECMWF SUGGESTING A STRENGTHENING RIDGE AGAIN.
&&

.AVIATION...COASTAL SITES REMAINING MVFR WITH WINDS GUSTING TO 40
KTS AT KONP. EXPECT WINDS TO RAMP UP TO GUSTS NEAR 50 KT JUST
AHEAD OF FRONTAL PASSAGE. INTERIOR VALLEY SITES PRIMARILY
MVFR...WITH OCCASIONAL BREAKS TO VFR CIGS AS WINDS ARE RAMPING UP
OUT OF THE SOUTH. SO FAR KPDX AND KTTD STILL HAVE SOLID EASTERLY
WINDS WITH A TTD-DLS GRADIENT OF -4.6 KEEPING WINDS OUT OF THE
EAST. AS THE WARM FRONT PUSHES FURTHER NORTH OVER THE NEXT COUPLE
HOURS...EXPECT WINDS TO TURN SOUTHERLY AND RAMP UP LATER TONIGHT.
UNTIL THEN...WIND SHEAR OF 30-35 KTS FROM SFC TO FL020 IS BEING
OBSERVED VIA AMDAR SOUNDING DATA OUT OF PDX...WITH EASTERLY WINDS
AT THE SURFACE AND SOUTHERLY WINDS ALOFT. EXPECT MVFR CONDITIONS
TO CONTINUE AT INTERIOR VALLEY SITES UNTIL THE COLD FRONT MOVES
THROUGH AROUND 9-10Z. WINDS WILL EASE BEHIND THE FRONT...VEERING
WINDS MORE WESTERLY BY DAYBREAK SUNDAY. CIGS MAY RISE A LITTLE AT
THIS TIME...BUT STAY SOMEWHERE BETWEEN 015 AND 025 AGL. EXCEPTIONS
WILL LIKELY BE KONP AND KEUG WHERE IFR COULD PREVAIL ALL DAY.

KPDX AND APPROACHES...MVFR CONDITIONS TO CONTINUE THROUGH MOST OF
TONIGHT...WITH LLWS UNTIL WINDS VEER TO SOUTH AROUND 06Z. WINDS
AFTER 06Z WILL INCREASE TO 20 TO 25 KT WITH GUSTS NEAR 35 KT
LIKELY. WINDS EASE AFTER 09Z BEHIND COLD FRONT...FALLING BELOW 20
KT BY 10Z. CIGS LIFT SOME AROUND 12-14Z...BUT LIKELY WILL STAY
BELOW FL040 ALL DAY THUS LIMITING VISUAL APPROACHES. -MCCOY/JBONK

&&

.MARINE...WINDS AROUND 30 KT GUSTING TO 40 KT AT BUOY 29.
SOUTHERLY WINDS LIKELY WILL CONTINUE TO INCREASE...GUSTING TO 45 KT
AS FRONT APPROACHES THE COAST. SEAS NOT INCREASING AT RATE
EXPECTED...SO SEAS LIKELY TO PEAK A BIT LOWER AROUND 16 FT AFTER
MIDNIGHT...AND STAY UP IN THE LOW TO MIDDLE TEENS THROUGH SUNDAY.
WINDS VEER TO THE WEST-SOUTHWEST EARLY SUNDAY BEHIND THE
FRONT...AND REMAIN ABOVE 20 KT IN THE NORTHERN WATERS THROUGH MOST
OF THE DAY. WINDS LOOK TO WEAKEN OVER SOUTHERN WATERS SUNDAY
MORNING...DROPPING BELOW 20 KTS BY THE AFTERNOON.

HIGH PRESSURE BUILDS IN LATE SUNDAY BEHIND THE FRONT...STAYING IN
PLACE THROUGH EARLY THIS WEEK. THIS WILL ALLOW SEAS TO GRADUALLY
SUBSIDE UNTIL DROPPING BELOW 10 FT TUESDAY. -MCCOY

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH WIND WARNING UNTIL 3 AM PST SUNDAY FOR CENTRAL OREGON
     COAST-NORTH OREGON COAST.

WA...HIGH WIND WARNING UNTIL 6 AM PST SUNDAY FOR SOUTH WASHINGTON
     COAST.

PZ...GALE WARNING UNTIL 7 AM PST SUNDAY FOR COASTAL WATERS FROM CAPE
     SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     GALE WARNING UNTIL 4 AM PST SUNDAY FOR COASTAL WATERS FROM
     CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 4 PM
     PST SUNDAY.

&&

INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/NWSPORTLAND
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.