Area Forecast Discussion
Issued by NWS Portland, OR

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000
FXUS66 KPQR 310415
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
915 PM PDT THU OCT 30 2014

.SYNOPSIS..STEADY RAIN ASSOCIATED WITH A MOIST FRONTAL BOUNDARY HAS
PUSHED INLAND THIS EVENING. THE STALLED FRONT WILL CONTINUE TO
PRODUCE RAIN OVERNIGHT INTO FRI MORNING...WITH THE HEAVIEST RAIN
BECOMING FOCUSED OVER THE CASCADES. THE DISSIPATING FRONT WILL PUSH
EAST OF THE CASCADES BY LATE MORNING...WITH SHOWERS REMAINING FRI
AFTERNOON BEHIND THE FRONT. EXPECT SHOWERS TO CONTAIN BRIEF HEAVY
RAIN...SMALL HAIL AND POSSIBLY SOME THUNDER. SHOWERS SHOULD BEGIN TO
TAPER OFF DURING THE EVENING HOURS FOR THOSE TRICK OR TREATING. SOME
SHOWERS MAY LINGER INTO SATURDAY...BEFORE LIGHT RAIN SPREADS BACK
ACROSS OUR NORTHERN ZONES SUNDAY AHEAD OF ANOTHER WET SYSTEM ON TAP
FOR LATE MONDAY AND TUESDAY OF NEXT WEEK.
&&

.SHORT TERM...TONIGHT THROUGH MONDAY...WATER VAPOR SATELLITE IMAGERY
SHOWS A MOIST FRONTAL SYSTEM SPREADING ABUNDANT MOISTURE INTO THE PAC
NW. A SHORTWAVE ROTATING AROUND THE PARENT UPPER LEVEL TROUGH ON THE
SE SIDE OF THE LOW IS SLOWING THE BAROCLINIC ZONE AND PIVOTING IT
FROM A NE-SW ORIENTATION TO A N-S ORIENTATION. A BAND OF MODERATE TO
HEAVY PRECIPITATION AHEAD OF THE COLD FRONT SPREAD ONTO THE COAST
THIS AFTERNOON AND HAS PUSHED SLOWLY INLAND THIS EVENING. THERE IS
STILL SUBTROPICAL MOISTURE FEEDING INTO THIS SYSTEM...WITH AMSU
DERIVED SATELLITE SHOWING 1 TO 1.2 INCHES OF PRECIPITATION OVER
WESTERN OREGON...WHICH IS SIGNIFICANTLY ABOVE NORMAL. THE SURFACE
COLD FRONT MOVED ONSHORE OVER THE PAST SEVERAL HOURS...BUT APPEARS
TO HAVE WEAKENED AND LOST SOME DEFINITION AS IT PASSED OVER THE
COAST RANGE. THE STEADIER FRONTAL RAIN HAS SHIFTED EAST AND IS NOW
FOCUSED OVER THE WILLAMETTE VALLEY AND CASCADES...WHILE THERE IS A
BACK EDGE TO THE PRECIPITATION BAND SHOWING UP BEHIND THE FRONT
ALONG THE COAST AND NORTHERN COAST RANGE. ANOTHER INTERESTING
DEVELOPMENT THIS EVENING WAS A LINE OF THUNDERSTORMS THAT DEVELOPED
OVER THE SOUTHERN AND CENTRAL OREGON CASCADES...EXTENDING INTO LANE
COUNTY. THE LATEST RUNS OF THE SHORT TERM RAP MODEL SHOWED A STRONG
BAND OF LOW LEVEL FRONTOGENESIS IN THIS REGION...WHICH WOULD SEEM TO
EXPLAIN THE THUNDER. TRACKING THE RAP OVER THE NEXT FEW HOURS...IT
APPEARS THAT THE FORCING WEAKENS AND MOVES EAST OF THE CASCADES
AFTER MIDNIGHT. ADDED THUNDER TO THE FCST EARLIER THIS EVENING FOR
THE CASCADES SOUTH OF MT HOOD...WITH THE THREAT ENDING AFTER 06Z.

THE FOCUS OF THE HEAVIEST PRECIPITATION WILL SHIFT MAINLY TO THE
CASCADES AND FOOTHILLS OVERNIGHT...WITH PLENTY OF SHOWERS CONTINUING
BEHIND THE FRONT. THE FRONT SHOULD DISSIPATE AND MOVE EAST OF THE
CASCADES BY MID TO LATE MORNING TOMORROW. BEHIND THE FRONT...A
SIGNIFICANTLY COLDER AND SOMEWHAT UNSTABLE AIR MASS WILL
SPREAD INTO THE AREA. EXPECT PLENTY OF SHOWERS TO DEVELOP IN THIS
POST FRONTAL AIR MASS WITH THE BRIEF HEAVY RAIN AND SMALL HAIL
POSSIBLE AS THE COLD UPPER TROUGH MOVES THROUGH THE AREA. BASED ON
THE INSTABILITY APPARENT ON SATELLITE UNDERNEATH THE UPPER
LOW...CANNOT RULE OUT A FEW RUMBLES OF THUNDER NEAR THE COAST...OR
OVER THE INTERIOR DURING THE LATE AFTERNOON. SHOWER ACTIVITY SHOULD
DECREASE SIGNIFICANTLY MOVING INTO FRIDAY EVENING.  AS THE COLDER AIR
MASS SETS IN BEHIND THE FRONT...SNOW LEVELS WILL DROP INTO THE 4500
TO 5000 FT RANGE LATE FRIDAY INTO SATURDAY. ACCUMULATIONS SHOULD
REMAIN FAIRLY LIGHT AND BELOW ADVISORY CRITERIA...THOUGH MOTORISTS
TRAVELING OVER THE HIGHER CASCADE PASSES INCLUDING SANTIAM AND
WILLAMETTE SHOULD BE AWARE OF THE POTENTIAL FOR AT LEAST ENOUGH SNOW
TO IMPACT TRAVEL LATE FRIDAY EVENING INTO EARLY SATURDAY.

THE UPPER TROUGH FINALLY SLIDES INTO THE GREAT BASIN ON SUNDAY AND
SHOWERS END AS SOME WEAK RIDGING DEVELOPS OVER THE PACIFIC NW AHEAD
OF THE NEXT SYSTEM. SOME LIGHT RAIN MAY DEVELOP OVER THE NORTHERN
ZONES AS A WEAK WARM FRONT MAY CLIP THE REGION. MORE STEADY RAIN
INCREASE LATE SUNDAY OR EARLY MONDAY AS THE NEXT FRONTAL SYSTEM
APPROACHES.  PYLE/CULLEN
&&


.LONG TERM...MONDAY THROUGH THURSDAY...A STRONGER FRONTAL SYSTEM
APPROACHES THE REGION BY MONDAY BRINGING MORE WIDESPREAD RAINFALL.
MODELS ARE IN REASONABLE AGREEMENT WITH A SYSTEM APPROACHING...BUT
SIGNIFICANT DIFFERENCES DO REMAIN IN TERMS OF THE LOCATION AND
AMOUNTS OF PRECIPITATION. SOME INDICATION THAT SOME SUBTROPICAL
MOISTURE BE ASSOCIATED WITH THIS SYSTEM...THOUGH THE PATTERN DOES
APPEAR TO STAY A BIT PROGRESSIVE IN NATURE. THEREFORE...INCREASED
POPS
THROUGH MIDWEEK AS ANOTHER WET WEEK APPEARS IN STORE. CULLEN
&&

.AVIATION...A COLD FRONT APPEARS TO HAVE SOMEWHAT STALLED AND IS
PETERING OUT OVER THE WILLAMETTE VALLEY THIS EVENING. RAIN IS
BEGINNING TO TRANSITION TO A MORE SHOWERY NATURE WITH MVFR TO VFR
CIGS. WITH NEAR CALM WINDS AT THE COAST...COULD SEE SOME MVFR VIS
DEVELOP THROUGH AT LEAST FRIDAY MORNING. MORE UNCERTAINTY INLAND
DUE TO SEEMINGLY FIZZLING FRONT. AT THIS POINT IT DOESN`T LOOK
LIKE A SIGNIFICANT WIND SHIFT WILL PROBABLY OCCUR AND IF MOISTURE
LINGERS...COULD SEE ANOTHER MORNING WITH IFR OR EVEN LIFR CIGS
AROUND SLE AND EUG. SHOWERS WILL CONTINUE THROUGH FRIDAY WITH A
SMALL CHANCE OF THUNDER MAINLY DURING THE AFTERNOON HOURS BUT
CONFIDENCE IS TOO LOW TO MENTION AT THIS POINT.


KPDX AND APPROACHES...WITH FRONT NOT MAKING A CLEAN SWEEP THROUGH
THE AREA...MVFR CIGS MAY LINGER THROUGH THE OVERNIGHT HOURS.
SLIGHT CHANCE OF THUNDER FRIDAY AFTERNOON. VFR CONDITIONS DOMINANT
BY ABOUT 18Z FRIDAY OUTSIDE OF ANY STORMS. BOWEN

&&

.MARINE...WINDS HAVE DROPPED TO 10 KT OR LESS BEHIND THE FRONT
THIS EVENING. WITH SWELL CONTINUING TO DECREASE...CONDITIONS WILL
REMAIN BENIGN OUTSIDE OF THE COLUMBIA BAR TONIGHT AND FRIDAY
MORNING BEFORE WNW SWELL INCREASES SEAS TO AT LEAST NEAR SCA
CRITERIA FRIDAY EVENING AND OVERNIGHT. RAISED SEAS TO AROUND 10 FT
BASED ON LATEST MODEL GUIDANCE...BUT SEAS FORECAST IS SOMEWHAT
UNCERTAIN AND BORDERLINE FOR SCA SO WILL LET MIDNIGHT SHIFT
REASSESS AND ISSUE IF NECESSARY. COULD SEE A COUPLE OF STORMS
FRIDAY AFTERNOON WITH ASSOCIATED LOCALIZED GUSTY WINDS. WINDS
OVERALL WILL SHIFT SOUTHERLY ON FRIDAY AND INCREASE A BIT WITH
GUSTS LESS THAN 20 KT. BOWEN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 1 AM
    PDT FRIDAY.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 10 AM TO
    2 PM 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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