Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 230332
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
831 PM PDT TUE APR 22 2014

.SYNOPSIS...MORE WET WEATHER AHEAD FOR THIS WEEK.  SHOWERS WILL
CHANGE TO RAIN TONIGHT AS A WARM FRONT APPROACHES THE COAST...KEEPING
A THREAT FOR RAIN GOING INTO WED. THERE WILL BE SNOW
DOWN TO THE CASCADE PASS LEVELS TONIGHT AND WEDNESDAY.A MORE
ROBUST SYSTEM WILL BRING MORE RAIN AND WINDY CONDITIONS TO THE COAST
LATER WED INTO THU. ANOTHER COOL SHOWERY TROUGH IS EXPECTED FOR THE
LATTER HALF OF THE WEEK.

&&

.UPDATE...SHOWERS CONTINUE THIS EVENING AS AN UPPER LEVEL TROUGH
APPROACHES THE WASHINGTON COAST. THE TROUGH AXIS WILL MOVE ONSHORE
AROUND MIDNIGHT TONIGHT AND MOVE EAST OF THE CASCADES EARLY WEDNESDAY
MORNING. SATELLITE IMAGERY SHOWS THE NEXT PACIFIC STORM APPROACHING
WITH THE ASSOCIATED LOW JUST ABOUT TO CROSS 140W. THIS SYSTEM WILL
PRODUCE MORE RAIN...MOUNTAIN SNOW AND BREEZY COASTAL WINDS WEDNESDAY
AND WEDNESDAY NIGHT. MADE NO CHANGES TO THE EVENING FORECAST AND
PREVIOUS DISCUSSION FOLLOWS.

PREVIOUS DISCUSSION...A COOL UPPER TROUGH OVER THE REGION WILL SLOWLY
MOVE EAST TONIGHT. MEANWHILE DAYTIME HEATING AND A SOMEWHAT UNSTABLE
AIR MASS INCREASED SHOWER ACTIVITY AND INTENSITY.  THERE WERE A FEW
REPORTS OF PEA SIZED HAIL ON THE COAST AND NORTHERN INTERIOR ZONES.
CONVECTIVE PARAMETERS ARE MARGINAL FOR THUNDERSTORMS...BUT CURRENT
RADAR SHOWING SOME SMALL CELLS WITH 50DBZ ECHOES...SO WILL ADD A
SLIGHT CHANCE OF THUNDERSTORMS WEST OF THE CASCADES FOR A FEW HOURS
THIS EVENING.

DEEPER MOISTURE MOVES IN LATER TONIGHT AND WED MORNING AS A LOW
LEVEL WARM AIR ADVECTION PATTERN SETS UP WITH THE APPROACHING RIDGE
ALOFT. BEST MOIST ISENTROPIC LIFT IS FOUND BETWEEN 285K AND 290K
ISENTROPIC SURFACES FROM LATE TONIGHT UNTIL WED EVENING. THIS
COUPLED WITH RATHER GENEROUS QPF FORECASTS IN ALL THE MODELS GIVES
HIGH CONFIDENCE FOR AN EXTENDED PERIOD OF RAIN WED. DEEP MOISTURE
REMAINS IN PLACE UNTIL THU MORNING...AS LIFTING MECHANISM SWITCHES
TO DYNAMICS GENERATED BY A COLD FRONT AND ACCOMPANYING SHORTWAVE THU
MORNING. THIS WILL KEEP POPS CATEGORICAL THROUGH THU. MODELS SHOW A
FAIRLY DEEP LOW APPROACHING VANCOUVER ISLAND THU MORNING. MODELS
VARY SOME ON THE POSITION BUT NOT BY MUCH. THE LOWEST CENTRAL
PRESSURE RANGES FROM 989MB TO 995MB. EITHER WAY THE FRONT ASSOCIATED
WITH THE LOW WILL BRING FAIRLY WINDY CONDITIONS TO THE COAST...AND
IT COULD BE BREEZY INLAND AS WELL ON THU.  SHOWERS LIKELY BEHIND THE
FRONT THU AFTERNOON AS THE NEXT COLD UPPER TROUGH DIGS IN TOWARDS
THE COAST.

SNOW LEVELS WILL REMAIN BELOW CASCADE PASSES INTO WED...POSSIBLY INTO
WED EVENING...BEFORE WARMER AIR PUSHES IN WED NIGHT AND EARLY THU.
OROGRAPHICS ARE NOT GREAT LIKE A WINTER TIME STORM...BUT MODEL QPF
COMBINED WITH MODERATE OROGRAPHICS SHOULD BE ENOUGH TO ACCUMULATE
ABOUT 6 INCHES OF NEW SNOW ABOVE 3500 FEET FOR TONIGHT AND WED.
MODELS GENERALLY FOCUS OF THE HIGHER QPF AMOUNTS NORTH OF MOUNT
JEFFERSON INTO THE SOUTH WASHINGTON CASCADES WHERE A SNOW ADVISORY
WILL BE IN EFFECT FOR TONIGHT AND WED.

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...FRIDAY NIGHT
THROUGH TUESDAY...EXPECT COOL AND SHOWERY CONDITIONS FOR MOST OF THE
LONG TERM FCST PERIOD. POST FRONTAL SHOWERS LINGERING THU NIGHT AND
FRI AS THE UPPER LEVEL TROF AND ASSOCIATED INSTABILITY PASS OVER THE
REGION. THERE MAY BE A BIT OF A BREAK TO START THE WEEKEND...BUT
ANOTHER FRONT IS PUSH ONSHORE LATE SAT OR SUN WHICH SHOULD BRING
ANOTHER ROUND OF MORE ORGANIZED PRECIPITATION. THE LATEST MODEL TREND
IS NOW TOWARD BUILDING AN UPPER LEVEL RIDGE OVER THE PAC NW TO START
NEXT WEEK. IT IS STILL QUITE A WAY OUT...BUT RECENT TRENDS IN MODELS
GIVE HIGHER CONFIDENCE EARLY NEXT WEEK WILL BE WARMER AND DRIER.

&&

.AVIATION...MOSTLY VFR CONDITIONS TONIGHT AS A MORE ORGANIZED
BAND/FRONT MOVES ONSHORE. STILL MAY SEE SOME SMALL HAIL IN HEAVIER
SHOWERS AND AS STEADIER RAIN INCREASES TONIGHT...MVFR CONDITIONS
OR EVEN LOCALLY LOWER CONDITIONS ARE POSSIBLE. MOISTURE IS
EXPECTED TO CONTINUE SPREADING ONSHORE INTO WEDNESDAY AS
SUBSEQUENT WAVES OF MOISTURE MOVE THROUGH...AND OCCASIONAL SHOWERS
WILL CONTINUE...POSSIBLY PRODUCING MVFR CONDITIONS AT TIMES.

KPDX AND APPROACHES...MAINLY VFR CONDITIONS PREVAIL AS A MORE
ORGANIZED BAND OR A FRONT OF SHOWERS MOVE THROUGH THIS EVENING.
MVFR CONDITIONS ARE POSSIBLE WITH CIGS AROUND 2500-3500 FT. A
MIXTURE OF VFR AND MVFR CONTINUES WEDNESDAY. PT/27

&&

.MARINE...SOUTH WINDS WITH GUSTS NEAR 25 KT WILL CONTINUE THROUGH
EARLY WEDNESDAY AS A 1000 MB LOW OUT NEAR 48N 130W MOVES TOWARD
VANCOUVER ISLAND THEN SLOWLY WEAKENS AND STALLS NEAR THE COAST. A
TRAILING DISTURBANCE WILL BRING SOME LOW END GALE FORCE WINDS WITH
GUSTS TO 35 KT LATER WEDNESDAY MORNING INTO EARLY WEDNESDAY EVE.
THEN A STRONGER LOW WILL DEEPEN TO 993 MB AS IT HEADS TOWARD
VANCOUVER ISLAND WEDNESDAY NIGHT AND THURSDAY FOR MORE GALE FORCE
WINDS BEFORE THE LOW WEAKENS ALONG THE COAST AGAIN LATER THURSDAY
INTO FRIDAY. ANOTHER RATHER STRONG PACIFIC FRONT IS EXPECTED LATE
SATURDAY AND SATURDAY NIGHT AND WILL PRODUCE HIGH END SMALL CRAFT
ADVISORY OR POSSIBLY GALE FORCE WINDS AGAIN.

SEAS WILL HOVER AROUND 10 TO 12 FT STARTING TONIGHT WITH THE
FIRST LOW...AND CONTINUE THROUGH LATE THIS WEEK. SEAS MAY POSSIBLY
EVEN CLIMB ANOTHER FOOT OR TWO WITH THE SYSTEMS WEDNESDAY AND
THURSDAY. PT

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...WINTER WEATHER ADVISORY UNTIL 5 PM PDT WEDNESDAY FOR NORTHERN
     OREGON CASCADES.

WA...WINTER WEATHER ADVISORY UNTIL 5 PM PDT WEDNESDAY FOR SOUTH
     WASHINGTON CASCADES.

PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 10 AM PDT WEDNESDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER TO FLORENCE OUT 60 NM.

     GALE WARNING FROM 10 AM WEDNESDAY TO 11 AM PDT THURSDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER TO FLORENCE OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 AM PDT
     WEDNESDAY FOR COASTAL WATERS FROM CAPE SHOALWATER TO
     FLORENCE OUT 60 NM.

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

&&

$$

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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