Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 301709
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1009 AM PDT THU OCT 30 2014

.SYNOPSIS...AFTER A FEW LIGHT SHOWERS TODAY...STEADIER RAIN WILL
SHIFT OVER THE REGION THIS EVENING AND LINGER INTO FRIDAY MORNING AS
A COLD FRONT SLOWLY PUSHES THROUGH THE AREA. EXPECT SHOWERS
CONTAINING BRIEF HEAVY RAIN...SMALL HAIL AND POSSIBLY SOME THUNDER
FRIDAY AFTERNOON. SHOWERS SHOULD QUICKLY BECOME ISOLATED DURING THE
EVENING HOURS FOR THOSE TRICK OR TREATING. HIT OR MISS SHOWERS MAY
LINGER INTO SATURDAY...BEFORE LIGHT RAIN SPREADS BACK ACROSS OUR
NORTHERN ZONES SUNDAY WITH ANOTHER WET SYSTEM ON TAP FOR LATE MONDAY
AND TUESDAY OF NEXT WEEK.

&&

.UPDATE...NATIONAL WEATHER SERVICE RADAR DEPICTS RAIN SHOWERS...SOME
LOCALLY HEAVY...CONTINUING ACROSS PORTIONS OF THE FORECAST AREA THIS
MORNING...PREDOMINATELY NORTH OF A LINCOLN CITY TO MT HOOD LINE.
SATELLITE IMAGERY DEPICTS A BREAK IN RAIN ACTIVITY BETWEEN THE
LIFTING WARM FRONT AND ADVANCING COLD FRONT OVER THE SOUTHERN
PORTIONS OF THE AREA...AND SURFACE OBSERVATIONS SUPPORT THIS.
THEREFORE LOWERED POPS A BIT THROUGH THIS MORNING FOR LINN AND
INTERIOR LANE COUNTIES.

MEANWHILE...CAMERAS AND OBSERVATIONS INDICATE THAT SOME LOCALLY DENSE
FOG HAS DEVELOPED IN THE CENTRAL AND SOUTH WILLAMETTE VALLEY. IMAGES
DEPICT A RELATIVELY SHALLOW LAYER AND EXPECT THIS TO MIX OUT BY
MIDDAY. OTHERWISE...FORECAST REMAINS ON TRACK AND DETAILS IN PREVIOUS
DISCUSSION REMAIN VALID.  CULLEN

PREVIOUS DISCUSSION... /ISSUED 237 AM PDT THU OCT 30 2014/

SHORT TERM...TODAY THROUGH SUNDAY...WATER VAPOR SATELLITE IMAGERY
REVEALS A LARGE DIGGING SHORTWAVE TROUGH NEAR 140W. AHEAD OF THIS
SYSTEM...AN OLD BAROCLINIC ZONE IS BEING RE-ENERGIZED AND LIFTING
BACK NORTHWARD ACROSS THE AREA IN THE FORM OF A WARM FRONT. THIS
SYSTEM HAS TAPPED INTO PRECIPITABLE WATER VALUES IN EXCESS OF 1 TO
1.25 INCHES. LIGHT RAIN SHOWERS HAVE BROKEN OUT ACROSS WESTERN
OREGON AND WASHINGTON EARLY THIS MORNING...BUT HAVE ONLY RESULTED IN
A COUPLE HUNDREDTHS OF AN INCH OF RAIN OR LESS EARLY THIS MORNING.
WITH CLOUD TOPS CONTINUING TO COOL TO OUR SOUTH...EXPECT OFF AND ON
LIGHT SHOWERS TO CONTINUE ACROSS MOST OF THE AREA TODAY WITH PERHAPS
A MORE EXTENDED BREAK IN THE RAIN TOWARDS LANE AND LINN COUNTIES
LATER THIS MORNING. A MORE CONSOLIDATED REGION OF RAIN IS CURRENTLY
LIFTING NORTHWARD OFF THE NORTH OREGON AND SOUTH WASHINGTON
COAST...A PRELUDE OF THINGS TO COME TONIGHT.

A COLD FRONT CURRENTLY NEAR 130W WILL PUSH EASTWARD TOWARDS THE COAST
THIS AFTERNOON AND EVENING. WITH GOOD LOW AND MID LEVEL
SUPPORT...EXPECT A SOUTH-SOUTHWEST TO NORTH-NORTHEAST BAND OF RAIN TO
SHIFT EASTWARD TOWARDS THE COAST TODAY...BEFORE PUSHING INTO THE
INTERIOR THIS EVENING AND OVERNIGHT. ONE TO TWO INCHES OF RAIN
APPEAR LIKELY ALONG THE COAST AND ACROSS THE HIGHER TERRAIN...WITH
RAIN TOTALS IN THE 0.50 TO 1.00 RANGE FOR MANY VALLEY LOCATIONS.
THIS FRONT MAY HAVE A TENDENCY TO SLOW DOWN LATE TONIGHT INTO FRIDAY
MORNING MORE THAN CURRENT MODEL GUIDANCE SUGGESTS DUE TO A 120 KT
JET DIGGING DOWN THE BACKSIDE OF THE UPPER LEVEL TROUGH.

ONCE THE STEADIER RAIN SHIFTS EAST OF THE REGION FRIDAY...A MUCH
COOLER AND UNSTABLE AIRMASS WILL SPREAD INTO THE REGION. EXPECT
SHOWERS TO POP IN THE AFTERNOON HOURS...ALTHOUGH THIS WILL BE
SOMEWHAT DEPENDENT ON HOW QUICKLY THE AFOREMENTIONED FRONT SHIFTS
EAST OF THE AREA. BRIEF HEAVY RAIN AND SMALL HAIL WILL BE THE MAIN
THREATS WITH ANY SHOWERS THAT BUBBLE UP. OCEAN TEMPERATURES CERTAINLY
SUPPORT THUNDER NEAR THE COAST...AND DEPENDING ON CLEARING OVER THE
INTERIOR...A COUPLE RUMBLES OF THUNDER WILL BE POSSIBLE IN THE
AFTERNOON. ANY SHOWER ACTIVITY OVER THE INTERIOR SHOULD BECOME MUCH
MORE ISOLATED FRIDAY EVENING AS THE LOWER ATMOSPHERE STABILIZES.
THIS SHOULD RESULT IN MOST TRICK OR TREATERS STAYING DRY FRIDAY
EVENING.

THE AFOREMENTIONED COLD FRONT WILL ALLOW SNOW LEVELS TO LOWER INTO
THE 4500 TO 5000 FT RANGE LATE FRIDAY INTO SATURDAY. AS THE UPPER
LEVEL TROUGH DIGS...LOW LEVEL FLOW WILL WEAKEN WITH THIS SYSTEM.
THIS SHOULD RESULT IN LIMITED OROGRAPHIC PRECIPITATION ENHANCEMENT
FRIDAY NIGHT INTO SATURDAY. AS A RESULT...SNOW AMOUNTS ARE EXPECTED
TO STAY UNDER WINTER WX ADVISORY CRITERIA. NONETHELESS...HIGHER
PASSES LIKE SANTIAM PASS AND WILLAMETTE PASSES SHOULD STILL SEE
ENOUGH SNOW TO AT LEAST IMPACT TRAVEL OFF AND ON FRIDAY EVENING INTO
EARLY SATURDAY...EVEN IF ACCUMULATIONS REMAIN RELATIVELY LIGHT.

A WEAK WARM FRONT SPREADING EASTWARD MAY BRING LIGHT RAIN TO OUR
FORECAST AREA LATE SATURDAY NIGHT INTO SUNDAY...ESPECIALLY ACROSS OUR
NORTHWESTERN ZONES. /NEUMAN
&&


.LONG TERM...SUNDAY NIGHT THROUGH WEDNESDAY...LITTLE IN THE WAY OF
CHANGE IN THE EXTENDED...MODELS SEEM TO CONVERGING ON THE IDEA OF A
CONSOLIDATED...BUT TRANSIENT FRONT BRINGING A GOOD SHOT OF RAIN TO
THE AREA LATE MONDAY INTO TUESDAY. LOW END CATEGORICAL TO LIKELY POPS
WERE MAINTAINED FOR THIS PERIOD. HOWEVER...THE BRUNT OF THE QPF LOOKS
TO REMAIN ACROSS THE OLYMPIC PENINSULA AND POINTS NORTHWARD. WITH
ZONAL FLOW TO FOLLOW...POPS WERE KEPT A BIT ABOVE CLIMO IN THE FAR
EXTENDED. /NEUMAN

&&

.AVIATION...MAINLY VFR CONDITIONS ALONG THE COAST AND NORTH
WILLAMETTE VALLEY. THE CENTRAL AND SOUTH WILLAMETTE VALLEY WILL
EXPERIENCE LIFR CONDITIONS WITH LOW STRATUS AND FOG THROUGH AT
19Z. CONDITIONS LOWERING TO MVFR WITH OCCASIONAL IFR VIS AND CIGS
THIS AFTERNOON AS THE COLD FRONT MOVES ONSHORE. EXPECT FRONTAL
PASSAGE ALONG THE COAST AROUND 21Z AND INLAND AROUND 00Z.

SURFACE LOW PRESSURE DEEPENS OFF THE NORTH OREGON COAST AND WILL
INDUCE A MODERATE PRESSURE GRADIENT ACROSS THE CASCADES WITH EAST
WIND GUSTS 25 TO 30 KT POSSIBLE AT KTTD THROUGH 21Z. EXPECT
LIGHTER EASTERLY WINDS AT KPDX.

KPDX AND APPROACHES...MAINLY VFR CONDITIONS EXPECTED THROUGH
TOMORROW MORNING. CHANCE OF MVFR CIGS AND VIS TODAY AS THE COLD
FRONT MOVES THROUGH. IFR CONDITIONS ARE HIGHLY UNLIKELY BUT IF
THEY DO FORM THEY WILL LIKELY BE BRIEF IN NATURE. BREEZY EAST
WINDS WITH GUSTS 15-20 KT POSSIBLE THROUGH 02Z. /27/64

&&

.MARINE...A COLD FRONT WILL MOVE ACROSS THE WATERS TODAY. S WINDS
THIS AFTERNOON WITH GUSTS OF 25 TO 30 KT EXPECTED. THE SCA FOR
WINDS REMAINS IN EFFECT THROUGH EARLY THIS EVENING. WINDS QUIET
DOWN BEHIND THE FRONT. HOWEVER....THERE REMAINS A SLIGHT CHANCE
OF TSTMS OVER THE COASTAL WATERS FRIDAY WITH GUSTY WINDS POSSIBLE.
WINDS WILL TURN TO THE NW BY SAT...BUT SHOULD REMAIN BELOW SCA
CRITERIA.

SEAS MAY CLIMB TO 10 FT AS WINDS PEAK TODAY BUT IT SHOULD BE
BRIEF AND LOCALIZED IN NATURE. SEAS ABOVE 10 FT POSSIBLE FRI
AFTERNOON AS ANOTHER UPPER LEVEL LOW MOVES ACROSS THE WATERS WITH
A MUCH STRONGER SYSTEM EXPECTED EARLY NEXT WEEK. /27/64

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 7 PM PDT THIS EVENING FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 9 PM
     THIS EVENING TO 1 AM PDT FRIDAY.

&&

$$

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.



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