Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 171606
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
858 AM PDT THU APR 17 2014

.SYNOPSIS...A DEVELOPING COLD FRONT IN THE NE PACIFIC WILL MOVE
ACROSS THE FORECAST AREA TODAY. THE COLD POOL ALOFT BEHIND THE FRONT
SETTLES OVER REGION THURSDAY NIGHT. EXPECT SNOW LEVELS TO LOWER NEAR
THE CASCADE PASSES THURSDAY NIGHT AND EARLY FRIDAY MORNING. A GRADUAL
DRYING TREND OCCURS FRIDAY...BUT WILL BE SHORT-LIVED. ANOTHER FRONT
IMPACTS SW WASHINGTON AND NW OREGON SATURDAY. AN UNSETTLED WEATHER
PATTERN RETURNS FOR THE FIRST PART OF NEXT WEEK.

&&

.MORNING UPDATE...RAIN IS INCREASING IN COVERAGE THIS MORNING TO
ENCOMPASS EVERYWHERE BUT THE LANE COUNTY CASCADES. MORNING SOUNDING
FROM SALEM INDICATED THAT SOME LOWER LEVEL SATURATION WAS STILL
NEEDED AND NOW THIS HAS OCCURRED. THERE IS A DECENT MOISTURE PLUME
THAT HAD ORIGINS IN THE SUBTROPICS FOCUSED ON NORTHERN CALIFORNIA
BUT SOME OF IT (0.90 PW ON KLSE 12Z SOUNDING) HAS BEEN ENTRAINED
THIS FAR NORTH. THIS MOISTURE COUPLED WITH SOMEWHAT WEAK ISENTROPIC
LIFT WILL MAINTAIN THE CURRENT INTENSITY OF LIGHT TO OCCASIONAL
MODERATE RAIN THROUGH EARLY AFTERNOON. LATEST RAP/HRRR PUT THE COLD
FRONT ON THE COAST AROUND 0Z...A FEW HOURS THEREAFTER IN THE
VALLEY....THOUGH MOST OF THE PRECIP IS ALONG AND AHEAD OF THE FRONT.
EXPECT SOME UPTICK IN PRECIP WITH THE FRONT BUT NOT EXPECTING A REAL
BIG KICK AS THE CORE OF THE UPPER TROUGH AND ASSOCIATED STEEPER MID
LEVEL LAPSE RATES DRAG BY TO OUR NORTH. CURRENT GRIDS HAVE A GOOD
HANDLE ON THIS.

AFTER A MOSTLY DRY FRIDAY...MODELS ARE STILL IN GOOD AGREEMENT ON A
SATURDAY BEING A WET AFTERNOON INLAND...SO EXPECT POPS TO GO UP
DURING THIS TIME. LESS IN THE WAY OF MOISTURE BUT MAYBE SLIGHTLY
BETTER DYNAMICS BUT THIS WILL BRING A SHORTER PERIOD OF LIGHTER RAIN
THAN TODAY. /KMD

&&

.SHORT TERM...THURSDAY THROUGH SATURDAY...SYNOPTIC OVERVIEW EARLY
THIS MORNING CONSISTS OF A WEAK 500 MB RIDGE CENTERED NEAR THE
WASHINGTON AND OREGON CASCADES AND AN UPPER LEVEL TROUGH OVER THE
GULF OF ALASKA AND THE BRITISH COLUMBIA COAST. WATER VAPOR IMAGERY
SHOWS A FAIRLY SHARP DEVELOPING SHORT-WAVE NEAR 46N 134W AS OF 09Z
WITH A MOISTURE FETCH ALONG 40N EXTENDING OUT BEYOND 160W. BLENDED
TOTAL PRECIPITABLE WATER IMAGE VALID 07Z INDICATED AROUND AN INCH
ALONG THE COAST AND 1 TO 1.5 INCHES WITHIN THE MOISTURE FETCH. NWS
KRTX DUAL-POL DOPPLER RADAR HAS STEADILY FILLED OVER THE PAST FEW
HOURS WITH WIDESPREAD LIGHT PRECIP ACROSS MUCH OF THE FORECAST AREA.
3-HR PRECIP AMOUNTS THROUGH 08Z HAVE BEEN ON THE ORDER OF ONE TO TWO
TENTHS OVER HIGHER TERRAIN AND A TENTH OR LESS ALONG THE COAST AND
OVER THE INLAND VALLEYS AND LOWLANDS.

LATEST MODEL RUNS IN REASONABLE AGREEMENT REGARDING FRONTAL TIMING.
RAIN RATES SHOULD STEADILY INCREASE THROUGH THE MORNING WITH
INCREASING INTEGRATED WATER VAPOR TRANSPORT AND STRENGTHENING 700 MB
AND 850 MB WLY WIND. GFS AND ECMWF IN A LITTLE BETTER AGREEMENT
SHOWING THE COLD FRONT REACHING THE S WA AND FAR N OREGON COAST 21Z
TO 00Z FRI. THE ECMWF HAS SLOWED A BIT...COMING MORE IN LINE WITH
PREVIOUS GFS TIMING. THE COLD FRONT REACHES THE CASCADES AROUND 06Z
FRI. EXPECT BREEZY TO WINDY CONDITIONS TO DEVELOP IN THE COLUMBIA
GORGE EAST OF KCZK LATE THIS AFTERNOON OR IN THE EVENING.
FINALLY...THE COLD POOL ALOFT ASSOCIATED WITH THE UPPER TROUGH SLIDES
OVER WRN WA AND NWRN OREGON THU NIGHT. 850 MB OROGRAPHIC WLY FLOW OF
10-20 KT INTO THE CASCADES WILL ENHANCE PRECIP RATES IN THE 00Z-06Z
FRI TIME FRAME...BUT SNOW LEVELS ARE NOT EXPECTED TO FALL TO NEAR THE
PASSES UNTIL AFTER 06Z WHEN SHOWER ACTIVITY BEGINS TO WANE.

SURFACE HIGH PRES BUILDS OVER THE FORECAST AREA FRI...BUT CANNOT RULE
OUT ISOLATED SHOWERS FOR THE S WA AND EXTREME N OREGON CASCADES AND
FOOTHILLS FRI MORNING. 850 MB TEMPS REMAIN A LITTLE ON THE COOL SIDE
FRI AFTERNOON...ABOUT +2C OVER KPDX PER THE GFS AND +3C ON THE ECMWF.
HOWEVER...HIGH SUN ANGLE FOR MID-APRIL WILL WARM THE BOUNDARY LAYER
AND ALLOW DAYTIME TEMPS TO BE AT OR JUST ABOVE NORMAL. SATURDAY
LOOKED TO BE A DRY A COUPLE DAYS AGO. HOWEVER...MODEL TRENDS HAVE
BEEN TO SPEED UP THE TIMING OF THE NEXT FRONTAL SYSTEM. THE ECMWF HAS
BEEN THE FASTEST ALL ALONG THE LATEST GFS HAS SEEMED TO CAUGHT UP
WITH IT. PRECIP EXPECTED TO REACH THE COAST BY 18Z SAT...OR EVEN A
LITTLE SOONER...AND SPREAD INLAND THEREAFTER. BOOSTED POPS
SUBSTANTIALLY SAT AFTERNOON AND LOWERED MAX TEMPS AT LEAST A FEW
DEGREES. WEISHAAR

.LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...PRECIP DIMINISHES SAT
NIGHT AS WEAK 500 MB RIDGING TRIES TO FORM OVER THE PAC NW. A
DEEPENING GULF OF ALASKA TROUGH WILL HELP AMPLIFY THE RIDGE A BIT
MORE SUN. SW WA ZONES STILL VULNERABLE TO SOME LIGHT PRECIP
SUNDAY...BUT THE MORE SOUTH ONE TRAVELS THE MORE SUNSHINE THERE
SHOULD BE. THE ECMWF AND GFS DRAG A WEAK FRONT THROUGH LATE SUN NIGHT
OR MON MORNING. BEYOND MON...THE DEEP UPPER LOW SETTLES OVER THE NE
PAC FOR MUCH OF THE WEEK. LOOKS LIKE A RETURN TO COOL...SHOWERY
CONDITIONS THE THE POTENTIAL FOR SOME ACCUMULATING SNOWS IN THE
CASCADES. WEISHAAR

&&

.AVIATION...RAIN CONTINUES TO PUSH INLAND AND EXPECT
WIDESPREAD RAIN AND MVFR ACROSS THE AREA...FIRST WITH VIS AND
EVENTUALLY WITH CIGS. EXPECT IFR AT TIMES AS WELL.  THE COAST CAN
CONTINUE TO EXPECT OF MIX OF EVERYTHING TODAY BUT MVFR AND IFR WILL
BE PREDOMINANT...WITH PERSISTENT IFR CIGS INTO THE COAST RANGE. COLD
FRONT WITH SHIFT TO W WINDS AND WILL PUSH ONSHORE AROUND 0Z...AND
REACH THE INTERIOR BY AROUND 2-3Z FRI. MTNS WILL BE FREQUENTLY
OBSCURED THROUGH THE PERIOD. RETURNING TO VFR WITH A FEW SHOWERS
BEHIND THE FRONT FOR MOST AREAS EXCEPT THE CASCADES. CANNOT RULE OUT
SOME MVFR TOWARDS DAYBREAK AS THERE IS SOME LINGERING LOW LEVEL
MOISTURE...ESPECIALLY ALONG THE NORTH COAST AND ALONG AND NORTH OF
THE COLUMBIA RIVER...BUT LOW LEVELS REMAIN GENERALLY UNSTABLE TO
SUPPORT VFR.

KPDX AND APPROACHES...MVFR CONDITIONS AND EXPECT CIGS DOWN TO 1500 FT
OR LOWER AT TIMES AS RAIN INTENSITY REMAINS STEADY TODAY. HAVE POCKETS
OF IFR CONDITIONS AROUND THE TERMINAL AS WELL. COLD FRONT WILL LIKELY REACH
OPS AREA AROUND 03Z FRI...WITH SHIFT TO W WINDS. HEADING BACK TO VFR
BEHIND THE FRONT. /KMD

&&

.MARINE...A COLD FRONT WILL PUSH ACROSS THE COASTAL WATERS THIS
AFTERNOON. EXPECT SOUTH WINDS TO INCREASE TOWARDS MIDDAY BEFORE
TURNING W TO NW LATE THIS AFTERNOON. WIND GUSTS OF 25 TO 30 KT
SHOULD BE WIDESPREAD BOTH AHEAD AND BEHIND THE FRONT. WE WILL BE
WATCHING TRENDS CLOSELY AS THERE IS AN CHANCE WIND GUSTS COULD
PUSH 35 KT ACROSS THE NORTHERN INNER WATERS...BUT WILL HOLD OFF ON
A GALE WARNING DUE TO LOW CONFIDENCE AT THIS POINT. EITHER
WAY...SEAS SHOULD BUILD INTO THE 8 TO 10 FT RANGE THIS EVENING SO
A SMALL CRAFT FOR HAZARDOUS SEAS WAS ISSUED FOR THE NORTHERN
WATERS WHERE SEAS WILL STAND THE BEST CHANCE OF TOPPING OUT FOR
SEVERAL HOURS AROUND 10 FT.

AFTER A BRIEF BREAK FRIDAY INTO EARLY SATURDAY...ANOTHER FRONT
WILL PUSH ACROSS THE WATERS MIDDAY SATURDAY...BRINGING ANOTHER
ROUND OF 25 TO 30 KT WINDS. LIKELY THE BIGGEST STORY WITH THIS
FRONT IS THAT A LARGE WESTERLY SWELL WILL FOLLOW LATE SATURDAY
INTO SUNDAY. 15 TO 20 FT SEAS APPEAR LIKELY...WITH THE LATEST
MODEL RUN OR TWO TRENDING HIGHER. SEAS SHOULD REMAIN ABOVE 10 FT
THROUGH THE FIRST HALF OF NEXT WEEK. /NEUMAN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 PM PDT THIS EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 5 PM THIS
     AFTERNOON TO 11 PM PDT THIS EVENING FOR COASTAL WATERS FROM
     CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 9 AM
     PDT THIS MORNING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 5 PM
     THIS AFTERNOON TO 11 PM PDT THIS EVENING.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 6 AM TO
     9 AM PDT FRIDAY.

&&

$$

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..



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