Area Forecast Discussion
Issued by NWS Portland, OR

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000
FXUS66 KPQR 311639
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
838 AM PST SAT JAN 31 2015

.SYNOPSIS...AN UPPER RIDGE AND OFFSHORE FLOW WILL REMAIN OVER SW
WASHINGTON AND NORTHWEST OREGON TODAY. THE RIDGE SHIFTS EAST SATURDAY
NIGHT AS A FRONTAL SYSTEM APPROACHES THE COAST. THE FRONT MOVES
ACROSS THE AREA SUNDAY. A STRONGER SYSTEM IS EXPECTED TO IMPACT THE
REGION LATE SUNDAY NIGHT AND MONDAY. A SERIES OF WETTER COLD FRONTS
IS LIKELY LATE NEXT WEEK INTO NEXT WEEKEND. SIGNIFICANT SNOWS AT
CASCADE PASS LEVEL APPEAR UNLIKELY DURING THE NEXT WEEK.
&&

.UPDATE...MADE NO CHANGES TO THE FORECAST WITH THE MORNING UPDATE AS
THE NEAR-TERM FORECAST IS ON TRACK. THERE IS SHALLOW FOG IN THE
INTERIOR VALLEYS...WITH VISIBILITIES BOUNCING BETWEEN A HALF OF A
MILE AND A QUARTER OF A MILE IN SOME LOCATIONS WITH OTHER LOCATIONS
HAVING UNRESTRICTED VISIBILITY. THE MORNING FOG IS HANDLED WELL WITH
THE CURRENT NOW FORECASTS. THE EASTERLY SURFACE PRESSURE GRADIENT HAS
INCREASED A LITTLE THE PAST FEW HOURS...AND WILL CONTINUE TO DO SO
THIS MORNING. EAST WINDS WILL INCREASE THROUGH THE GORGE WITH GUSTS
TO 30 MPH LATER THIS MORNING AND UP TO 50 MPH THIS AFTERNOON. THESE
WINDS WILL HELP CLEAR OUT THE FOG AND LOW CLOUDS FOR THE NORTHERN
WILLAMETTE VALLEY. A PATTERN CHANGE TO WETTER WEATHER IS EXPECTED
LATE SUNDAY. A SERIES OF STORMS THAT WILL BE INCREASINGLY WETTER WILL
MOVE ACROSS THE REGION...BUT WILL NOT CONTRIBUTE MUCH...IF AT
ALL...TO THE LOCAL SNOW PACK. TJ

PREVIOUS SHORT TERM...TODAY THROUGH MONDAY...PERSISTENCE LOOKS LIKE
THE WAY TO GO TODAY. SATELLITE FOG IMAGERY AS OF 0930Z SHOWED
CONSIDERABLE FOG IN THE SOUTH WILLAMETTE VALLEY AND LOWER COLUMBIA
AROUND KKLS...WITH LESSER AMOUNTS IN THE CENTRAL AND NORTH WILLAMETTE
VALLEY. THIS PATTERN APPEARS TO BE SIMILAR TO 24 HRS AGO. KTTD-KDLS
GRADIENT WAS A MEAGER -2.3 MB AT 10Z...PRETTY CLOSE TO THE 3-HR FCST
OFF THE 06Z NAM. THE NAM DOES INCREASE THE GRADIENT THIS AFTERNOON TO
-5 TO -6 MB BY 21Z. MODEL 850 MB TEMPS DO NOT SHOW ANY APPRECIABLE
CHANGE TODAY COMPARED TO FRI SO WENT CLOSE TO PERSISTENCE TEMPS FOR
MOST AREAS. NAM MAINTAINS SOLID STRATUS IN THE GORGE TO AROUND KCZK.
NAM CROSS-SECTION FROM KAST THROUGH THE COLUMBIA GORGE SHOWS
INCREASING HIGH-LEVEL MOISTURE AFTER 03Z SUN. THIS MAY HAVE AN IMPACT
ON FOG FORMATION...BUT SUSPECT THE CENTRAL AND SOUTH WILLAMETTE
VALLEY WILL SEE THE FOG RETURN.

MODELS CONTINUE TO ADVERTISE A CHANGE IN THE OVERALL PATTERN
BEGINNING SUNDAY. A FRONTAL SYSTEM REACHES THE COAST LATE SAT NIGHT
THEN INLAND SUN. MODELS SEEM TO FASTER WITH THIS SYSTEM COMPARED TO
EARLIER RUNS. MODEL QPF WITH THIS ONE NOT ALL THAT IMPRESSIVE.
MOUNTAINS NOT GOING TO GET MUCH IN THE WAY OF NEEDED SNOWFALL AS SNOW
LEVELS EXPECTED TO BE ABOVE 5K FEET. A MORE IMPRESSIVE SYSTEM IMPACTS
THE FORECAST AREA LATE SUN NIGHT AND MON. GFS IS QUITE BULLISH ON THE
QPF...WITH A CORE OF OVER AN INCH IN 6 HRS ON THE CENTRAL OREGON
COAST MON MORNING. WENT MORE WITH THE ECMWF QPF AMOUNTS...WITH MAYBE
UP TO ONE-HALF INCH IN 6 HRS FOR THE COAST MON MORNING. FAIRLY DECENT
850 MB OROGRAPHIC FLOW INTO THE COAST RANGE AND CASCADES 18Z MON
THROUGH 00Z TUE. UNFORTUNATELY...AS HAS BEEN THE CASE MOST OF THIS
WINTER...SNOW LEVELS WILL STAY ABOVE THE CASCADE PASSES. SLIGHTLY
LOWER SNOW LEVELS FOR THE S WA CASCADES MON WITH 1000-500 MB
THICKNESS VALUES NEAR 540 DM...BUT SNOW LEVELS LIKELY TO BE A BIT
LOWER DUE TO SOME DEGREE OF EAST LOW-LEVEL FLOW. WEISHAAR

LONG TERM...MONDAY NIGHT THROUGH FRIDAY...IN THE WAKE OF THE SYSTEM
THAT MOVES THROUGH MONDAY...THE MODELS DEVELOP A WARM FRONT AND
ATTEMPT TO EVENTUALLY LIFT IT NORTH THROUGH THE PACIFIC NORTHWEST IN
THE MID WEEK PERIOD. UNFORTUNATELY...THE MODELS ARE HAVING A TOUGH
TIME SETTLING ON WHEN AND WHERE IT WILL FORM AND HOW WET IT WILL BE.
IT WILL LIKELY FORM SOMEWHERE OVER SOUTHWEST OREGON OR EXTREME
NORTHERN CALIFORNIA...THEN LIFT NORTH AROUND WEDNESDAY. FOR NOW HAVE
BROAD BRUSHED THE POPS A BIT DUE TO THE TIMING AND INTENSITY
PROBLEMS. THE NEXT RATHER MATURE AND DECENTLY STRONG OCCLUDED FRONT
COMES IN AROUND THURSDAY...FOLLOWED BY A SERIES OF RATHER WET FRONTS
LATE NEXT WEEK INTO THE WEEKEND. THE GENERAL TREND NEXT WEEK IS
TOWARD A WETTER MORE ACTIVE PATTERN. AT THIS POINT...OTHER THAN A
COUPLE OF BRIEF DIPS...SNOW LEVELS REMAIN RATHER HIGH AND THESE
SYSTEMS WILL NOT LIKELY ADD MUCH IF ANYTHING TO THE DEFICIENT SNOW
PACK IN THE CASCADES. WEISHAAR
&&

.AVIATION...LIFR VALLEY FOG WILL PERSIST THROUGH AT LEAST 21Z
TODAY FOR MOST LOCATIONS...WITH A FEW SPOTS REPORTING FZFG AS
TEMPS HOVER JUST BELOW OR RIGHT AROUND 32 DEG. INCREASING HIGH
CLOUDS ASSOCIATED WITH AN APPROACHING FRONT WILL SPREAD OVER THE
AREA THIS AFTERNOON...WITH INCREASING MID CLOUDS TONIGHT. COASTAL
SITES SHOULD REMAIN VFR TODAY...WITH SOME PATCHY SHALLOW IFR FOG
THROUGH 18Z THIS MORNING. LIGHT RAIN SHOULD IMPACT THE SW WA/FAR
NW OR COASTS EARLY SUN MORNING.

KPDX AND APPROACHES...LIFR FOG WITH CIGS AROUND 200 FT WILL LINGER
THROUGH 19Z-21Z THIS MORNING BEFORE CLEARING TO VFR THIS
AFTERNOON. INCREASING EAST WINDS WILL IMPACT KTTD AND KPDX AFTER
21Z. MID AND HIGH CLOUDS INCREASE OVERNIGHT WITH CIGS BETWEEN
5K-10K FT. /27
&&

.MARINE...A CHANGE IN THE WEATHER PATTERN IS ON THE MENU FOR THIS
WEEKEND...WITH THE FIRST IN A SERIES OF PROGRESSIVELY STRONGER
FRONTAL SYSTEMS MOVING THROUGH SUNDAY MORNING. THIS FIRST FRONT ON
SUNDAY BRINGS THE POSSIBILITY OF SOME SMALL CRAFT ADVISORY GUSTS
ABOVE 20 KTS WHILE BRINGING SEAS UP TO AROUND 8 FT. THE SECOND
FRONTAL SYSTEM MOVES THROUGH ON MONDAY...BRINGING SOLID SMALL
CRAFT ADVISORY WINDS WITH GUSTS 30 TO 35 KTS LIKELY. STRONG WINDS
WILL RAMP UP EARLY MONDAY MORNING AND PERSIST THROUGH THE DAY
UNTIL WINDS EASE BEHIND THE FRONT LATE MONDAY NIGHT OR EARLY
TUESDAY. THIS SYSTEM WILL ALSO BRING SEAS UP TO AROUND 12 TO 13
FT ON MONDAY. CONFIDENCE IS INCREASING FOR AN EVEN STRONGER SYSTEM
THURSDAY OR FRIDAY WHICH COULD GENERATE SOUTHERLY GALES AND BRING
SEAS UP TO NEAR 20 FT. -MCCOY
&&

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

$$

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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