Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 240416
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
915 PM PDT WED APR 23 2014

.SYNOPSIS...A FRONTAL SYSTEM WILL MOVE ACROSS THE REGION TONIGHT  AND
MOVE EAST OF THE AREA THURSDAY MORNING FOR CONTINUED PERSISTENT RAIN
AND HIGHER ELEVATION SNOW. THE PARENT UPPER LOW OR TROUGH WILL DIG
SOUTH TOWARD CALIFORNIA THURSDAY AFTERNOON AND THURSDAY NIGHT BEFORE
MOVING ONSHORE AND THROUGH THE AREA FRIDAY AND FRIDAY EVENING FOR
MORE SHOWERS. ANOTHER SIGNIFICANT FRONTAL SYSTEM IS EXPECTED LATE
SATURDAY AND SATURDAY NIGHT.
&&

.SHORT TERM...RAIN AND MOUNTAIN SNOW CONTINUES THIS EVENING AS A WARM
FRONT LIFTS NORTH ACROSS NW OREGON AND SW WASHINGTON AND A COLD FRONT
APPROACHES. IT IS DIFFICULT TO DETERMINE WHERE THE WARM FRONT IS ON
SATELLITE IMAGERY AS IT MAINLY SHOWS A BLOB OF UNORGANIZED
HIGH-LEVEL CLOUDS OVER THE FORECAST AREA. SURFACE OBSERVATIONS
SUGGEST THAT THE WARM FRONT IS DRAPING EAST TO WEST SOMEWHERE BETWEEN
SALEM OREGON AND KELSO WASHINGTON.

WATER VAPOR IMAGERY SHOWS A COMPLEX LOW OFFSHORE. SUBTLE FEATURES IN
WATER VAPOR AND INFRARED SATELLITES SHOW THAT THERE ACTUALLY MAY BE
TWO CLOSE-KNIT COLD FRONTS OFFSHORE. THE MAIN ONE ASSOCIATED WITH A
LOW NEAR 48N 128W. THERE APPEARS TO BE SIGNS OF ANOTHER WEAKER
SURFACE LOW AROUND 43N 129W. EXPECT BREEZY WINDS ESPECIALLY FOR THE
COAST TONIGHT AS THESE FRONTS APPROACH.

THE NORTH OREGON COAST RANGE HAS SEEN QUITE A BIT OF RAIN THIS
EVENING WITH MANY RAIN GAGES REPORTING AN INCH OF RAIN IN THE PAST 6
HOURS.THE WILLAMETTE VALLEY HAS MEASURED AROUND 0.3 INCH THE PAST 6
HOURS..AND THE SOUTH WASHINGTON CASCADES AROUND A HALF OF AN INCH.

SNOW LEVELS HAVE BEEN RISING AND ARE CURRENTLY AROUND 5500 FEET.
STILL THINK THE HIGHER ELEVATIONS WILL GET A GOOD DOSE OF SNOW
OVERNIGHT AND WILL LET HE WINTER WEATHER ADVISORY FOR THE CASCADES
RIDE OUT.

WE SHOULD SEE PLENTY OF SHOWERS THURSDAY BEHIND THE COLD FRONT.
MODEL LIFTED INDEX VALUES LOOK A LITTLE WEAK FOR THUNDER BUT WE
SHOULD AT LEAST SEE SOME SMALL HAIL...WITH MODEL SOUNDINGS SHOWING A
BIT OF A CAP AT 700 MB AS THE MAIN COLDER AIR ALOFT IS STILL
OFFSHORE. ON FRIDAY THE MAIN UPPER TROUGH WILL BE MOVING THROUGH
SOUTHWEST WASHINGTON AND NORTHWEST OREGON AND THUNDER CHANCES LOOK A
BIT BETTER AS TEMPS AT 500 MB FALL TO MINUS 28 DEG C.

WHILE THE UPPER TROUGH MOVES EAST OF THE AREA FRIDAY NIGHT...SOME
SHOWERS WILL CONTINUE FRIDAY NIGHT AND SATURDAY AS ONSHORE FLOW
CONTINUES AND THERE IS NOT MUCH UPPER RIDGING IN BETWEEN SYSTEMS.
THE NEXT STRONGER FRONT IS EXPECTED SATURDAY NIGHT. HARTLEY/TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...SATURDAY NIGHT
THROUGH WEDNESDAY...THE LATEST MEDIUM RANGE FCST MODELS CONTINUE TO
ADVERTISE A FRONTAL SYSTEM MOVING ONSHORE SAT NIGHT AND EARLY SUN.
KEPT CATEGORICAL POPS FOR THIS TIME PERIOD...WITH A TRANSITION TO
SHOWERS LATER IN THE DAY SUNDAY BEHIND THE TRAILING COLD FRONT. A
WEAK WARM FRONT MAY BRUSH THE FCST AREA WITH SOME LIGHT PRECIPITATION
ON MON...BUT THE TREND WILL BE TOWARD DRIER WEATHER AS UPPER LEVEL
RIDGING BUILDS OVER THE PAC NW. RIGHT NOW...CONFIDENCE IS PRETTY HIGH
THAT TUE WILL BE WARM AND DRY WITH THE RIDGE DIRECTLY OVERHEAD...AND
HIGH TEMPS WERE RAISED SIGNIFICANTLY WITH THE LATEST FCST PACKAGE.
MODEL UNCERTAINTY BEGINS
TO INCREASE WED...AS THE 12Z GFS AND SOME OF ITS ENSEMBLES INDICATE
THAT A TROF OVER THE NE PAC WILL SPLIT...WITH THE NORTHERN ENERGY
PUSHING INTO THE PAC NW WED AS AN OPEN TROF. THE 12Z ECMWF MAINTAINS
A NE PAC CLOSED LOW THAT HARDLY MOVES THROUGH THE END OF THE
WEEK...ALLOWING RIDGING TO REMAIN IN PLACE OVER THE PAC NW FOR
SEVERAL DAYS. HAVE KEPT SOME LOW CHANCE POPS ON WED DUE TO THIS
UNCERTAINTY. PYLE
&&

.AVIATION...DISORGANIZED YET POTENT FRONTAL SYSTEM CONTINUES TO
SPREAD RAIN AND GENERAL MVFR AND LOCAL IFR CONDITIONS ACROSS THE
FORECAST AREA THIS EVENING. THIS SYSTEM WILL ALSO CONTINUE TO
PRODUCE GUSTY SOUTH WINDS...ESPECIALLY ALONG THE COAST WHERE WINDS
MAY GUST TO 40 KNOTS. COLD FRONT WILL PUSH ONSHORE 08Z-10Z...THEN
PUSH INLAND TO THE CASCADES BY 13Z-15Z.

BEHIND THIS FRONT THE AIR MASS WILL BECOME MORE CONVECTIVE IN
NATURE...WITH BETTER MIXING AND CIGS PUSHING BACK UP INTO THE
2000-3000 FT RANGE. STEADY RAIN WILL SWITCH TO SHOWERS BEHIND THE
FRONT WITH IMPROVED VSBYS OUTSIDE OF SHOWERS. SHOWERS WILL PERSIST
THROUGH THE DAY THURSDAY...ALONG WITH A FEW BREAKS IN THE CLOUDS.
HEAVIER SHOWERS MAY PRODUCE SMALL HAIL IN THE AFTERNOON.

KPDX AND APPROACHES...CIGS LIKELY TO HOLD AROUND 1500 FT IN
OCCASIONAL RAIN THROUGH 12Z. S WINDS WILL BECOME GUSTY AT TIMES...
UP TO 25 KT WITH THE PASSAGE OF A COLD FRONT 12Z-14Z. AFTER THAT
WINDS TURN W-SW WITH IMPROVING CIGS/VSBYS BUT CONTINUED SHOWERS.
EXPECT GENERAL MVFR WITH SHOWERS THURSDAY...THOUGH PERIODS OF VFR
ARE LIKELY BETWEEN SHOWERS.  WEAGLE
&&

.MARINE...COMPLEX LOW PRESSURE OFF THE PAC NW COAST ALREADY
BROUGHT ONE SURGE OF S WINDS TO THE COASTAL WATERS THIS EVENING...
AND IS EXPECTED TO BRING ANOTHER VERY EARLY THU MORNING. GUSTS TO
GALE FORCE WILL BE COMMON...ESPECIALLY IN THE COASTAL JET...PRIOR
TO 12Z. DECIDED TO END THE GALE WARNING FOR OUR SOUTHERN WATERS
JUST AFTER THE COLD FRONT MOVES THROUGH EARLY THU MORNING...BUT
WILL KEEP IT THROUGH MIDDAY FOR THE NORTHERN WATERS AS A FEW GALE
GUSTS COULD LINGER AS THE PARENT LOW PUSHES INTO VANCOUVER ISLAND.

OTHERWISE AFTER SUNRISE...BLUSTERY AND SQUALLY W-SW FLOW WILL
DOMINATE THURSDAY...THOUGH WINDS WILL BE GRADUALLY EASING
THROUGHOUT THE DAY. VERY CHOPPY COMBINED SEAS 12-16 FT LIKELY
THROUGH THU MORNING...BUT THIS SHOULD SLOWLY SUBSIDE LATER THU/THU
NIGHT. LIGHTER CONDITIONS EXPECTED FRI/EARLY SAT AS THE LOW
PRESSURE SYSTEM FILLS OVER BRITISH COLUMBIA AND PRESSURE
GRADIENTS SLACKEN OVER THE AREA.  WEAGLE
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...GALE WARNING UNTIL 11 AM PDT THURSDAY FOR COASTAL WATERS FROM
     CAPE SHOALWATER WA TO CASCADE HEAD OR OUT 60 NM.

     GALE WARNING UNTIL 8 AM PDT THURSDAY FOR COASTAL WATERS FROM
     CASCADE HEAD OR TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 PM
     PDT THURSDAY.
&&

$$

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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