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[Printable]
851
FXUS66 KPQR 271752
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
950 AM PST THU NOV 27 2014

.SYNOPSIS...A WEAK COLD FRONT WILL PUSH SLOWLY INLAND TODAY. THE
FRONT WILL THEN STALL OVER SOUTH-CENTRAL OREGON TONIGHT AND FRI. THIS
FRONT WILL BEGIN TO LIFT NORTHWARD AGAIN EARLY FRI. ANOTHER STRONGER
COLD FRONT WILL MOVE S THROUGH THE REGION LATE FRI INTO SAT. THIS
FRONT WILL USHER IN MUCH COLDER WEATHER. SNOW LEVELS WILL FALL
RAPIDLY FRI NIGHT AND SAT...WITH A RAIN/SNOW MIX A POSSIBILITY FOR
THE INTERIOR LOWLANDS. HIGH PRES OVER THE INTERIOR NW WILL TURN THE
FLOW OFFSHORE BY SUN FOR DRY AND COLD WEATHER. ANOTHER SYSTEM COMING
UP FROM THE S SOMETIME EARLY NEXT WEEK WILL ATTEMPT TO SPREAD SOME
PRECIPITATION UP OVER THE COLD AIR MASS LEFT OVER FROM THE WEEKEND.

&&

.MORNING UPDATE...VERY FEW CHANGES WERE MADE TO THE EARLY MORNING
FORECAST PACKAGE...AS IT APPEARS TO BE TRACKING WELL.

THE 12Z SALEM SOUNDING WAS NOTABLE IN SHOWING A BIT OF ELEVATED
INSTABILITY...WITH ABOUT 150-200 J/KG OF SKINNY CAPE DUE THE MILD AND
MOIST AIR MASS BETWEEN 850-700 MB. SURE ENOUGH...THERE ARE SPORADIC
LIGHTNING STRIKES BEING DETECTED NEAR THE SOUTH OREGON COAST. IT
APPEARS THE BEST INSTABILITY SHOULD REMAIN THERE...THOUGH IT WOULD
NOT BE A COMPLETE SURPRISE TO SEE A STRAY LIGHTNING STRIKE OR TWO
SOUTH OF SALEM TODAY. 12Z NAM BUFR SOUNDINGS CONTINUE TO SHOW SKINNY
CAPE INTO FRIDAY...WHEN THERE MAY BE A SLIGHTLY BETTER CHANCE OF
THUNDER ALONG/AHEAD AS THE VIGOROUS COLD FRONT PROVIDES A BIT OF
EXTRA LIFT. THERE IS ALSO SOME FAIRLY DECENT SHEAR WITHIN THIS AREA
OF CONDITIONAL INSTABILITY. HAVE NOT ADDED THIS TO THE FORECAST
YET...BUT WE MAY ADD A SLIGHT CHANCE OF THUNDER FRIDAY WITH THE
AFTERNOON PACKAGE IF SUBSEQUENT MODEL RUNS CONTINUE TO SHOW THIS.

AS FAR AS THE POTENTIAL FOR LOW ELEVATION SNOW LATER FRI NIGHT
THROUGH SAT EVENING...PREVIOUS DISCUSSION BELOW CONTINUES TO REFLECT
CURRENT THINKING...SO NO CHANGES WERE MADE.  WEAGLE

/PREV DISC ISSUED 327 AM PST THU NOV 27 2014/

.SHORT TERM...TODAY THROUGH SATURDAY...BREEZY SOUTHERLY WINDS AHEAD
OF AN APPROACHING COLD FRONT ARE KEEPING EXCEPTIONALLY MILD
CONDITIONS IN PLACE ACROSS SOUTHWEST OREGON AND NORTHWEST OREGON
THIS MORNING. IN FACT...THE TEMPS IN THE UPPER 50S TO LOW 60S BEING
OBSERVED ACROSS MUCH OF THE REGION AT CURRENT ARE VERY CLOSE TO THE
RECORD DAILY HIGH TEMPS FOR THE LAST WEEK OF NOVEMBER. HOWEVER...THE
PERIOD OF MILD WEATHER THAT WE HAVE BEEN EXPERIENCING OVER THE PAST
FEW DAYS WILL BE COMING TO AN END VERY SHORTLY.

THE COLD FRONT APPROACHING THE COAST THIS MORNING IS NOT TERRIBLY
IMPRESSIVE. LOOKING AT THE LATEST IR SATELLITE IMAGERY...IT IS
APPARENT THAT THE UPPER LEVEL FRONT AND ASSOCIATED MOISTURE HAS MOVED
OUT AHEAD OF THE SURFACE FRONTAL BOUNDARY. THE SURFACE FRONT CAN BE
MADE OUT ON SATELLITE JUST OFFSHORE AROUND BUOY 29. WITH ONLY SHALLOW
MOISTURE REMAINING AND LITTLE IN THE WAY OF FORCING ALOFT...THE
ASSOCIATED PRECIPITATION THAT IS MOVING ONSHORE IS DEFINITELY ON THE
PATCHIER SIDE. THE RAIN HAS BECOME A BIT STEADIER OVER THE PAST FEW
HOURS ALONG THE N COAST AND COAST RANGE...BUT MOST SITES ARE ONLY
PICKING UP A FEW HUNDREDTHS OF AN INCH OF RAIN PER HOUR. STILL...
EXPECT MOST LOCATIONS WILL SEE A DECENT STEADY RAIN AS THE FRONT
PUSHES ONSHORE THIS MORNING AND THEN MOVES INLAND THROUGH THE DAY.
THE FRONT WILL EVENTUALLY STALL OVER SOUTHERN AND CENTRAL OREGON
LATER THIS AFTERNOON AND THIS EVENING.

THE OTHER FEATURE OF INTEREST THAT WE ARE WATCHING THIS MORNING IS A
PERSISTENT STATIONARY BAROCLINIC ZONE THAT IS CURRENTLY DRAPED OVER
BRITISH COLUMBIA AND FAR NORTHERN WASHINGTON. AN UPPER LEVEL TROUGH
WILL DRIVE THIS BOUNDARY SOUTHWARD FRI AND FRI NIGHT AS A SHARP COLD
FRONT. AT THE SAME TIME...THE STALLED FRONT OVER CENTRAL OREGON IS
FCST TO PUSH NORTHWARD AGAIN FRI MORNING. BETWEEN THESE TWO FRONTAL
BOUNDARIES...EXPECT RAINFALL TO STEADILY INCREASE AS THE DAY
PROGRESSES FRI. AS THE SHARP COLD FRONT FROM THE NORTH DIVES
THROUGH THE REGION LATER FRI AND FRI NIGHT...A MUCH COLDER AIR MASS
ALOFT WILL MOVE INTO THE REGION.

THE PARENT UPPER LEVEL TROUGH WILL SWING INTO THE REGION FROM THE
NORTH ON SAT TO PROVIDE SOME UPPER LEVEL SUPPORT FOR POST FRONTAL
SHOWER ACTIVITY...WHILE LOW LEVEL ONSHORE FLOW SHOULD PROVIDE
ADDITIONAL MOISTURE TO KEEP SHOWERS GOING THROUGH MUCH OF THE DAY.
BASED ON MODEL 850MB TEMPS AND 1000-500 MB THICKNESS VALUES...IT
APPEARS THAT THERE IS THE POTENTIAL FOR A RAIN/SNOW MIX TO AFFECT THE
INTERIOR LOWLANDS AT TIMES ON SAT. THE TEMP AND THICKNESS INDICATORS
ARE ONLY MARGINAL AND THERE IS SOME UNCERTAINTY AMONGST THE MODELS
JUST HOW COLD THE AIR MASS WILL BE...SO CONFIDENCE IS NOT ALL THAT
HIGH THAT THE INTERIOR LOWLANDS WILL SEE ANY SIGNIFICANT FLAKES. AT
ANY RATE...WITH THE MILD TEMPS WE HAVE SEEN OVER THE PAST FEW DAYS IT
IS UNLIKELY THAT ROAD SURFACES WILL BE ABLE TO COOL FAST ENOUGH FOR
THERE TO BE MAJOR TRAVEL CONCERNS. PYLE


LONG TERM...SATURDAY NIGHT THROUGH WEDNESDAY...MOST GUIDANCE
SUGGESTS THE UPPER TROUGH AXIS RESPONSIBLE FOR SATURDAYS SHOWERS WILL
BE MOVING ACROSS THE CASCADES SAT NIGHT...  WITH ANY LINGERING SHOWERS
COMING TO END OVERNIGHT. EXPECT SOME CLEARING SAT NIGHT AS COLD HIGH
PRESSURE BUILDS DOWN FROM BRITISH COLUMBIA...WITH LOW TEMPS LIKELY
GETTING WELL INTO THE 20S FOR MOST SPOTS. WITH HIGH PRESSURE
STRENGTHENING EAST OF THE CASCADES...EXPECT STRONG EAST WINDS TO RAMP
UP THROUGH THE GORGE SUNDAY MORNING AND PERSIST FOR MUCH OF THE
PERIOD THROUGH WEDNESDAY...WITH BREEZY CONDITIONS SPILLING INTO THE
PORTLAND/VANCOUVER METRO. MONDAY MAY BE A BRIEF BREAK FROM THE WINDS
AS A SYSTEM PASSES BY TO OUR NORTH.

MEANWHILE...A DISTURBANCE FROM THE ALEUTIANS IS EXPECTED TO CUT OFF
FROM THE MAIN PACIFIC JET AND SETTLE OFF THE CALIFORNIA COAST BY
SUNDAY...WHERE IT WILL LIKELY LINGER FOR A COUPLE DAYS. THERE IS A
CHANCE THIS SYSTEM COULD COME CLOSE ENOUGH TO SPREAD SOME PRECIP
NORTHWARD INTO OUR FORECAST AREA EARLY NEXT WEEK. IF THIS
OCCURS...THERE MAY BE SOME LIGHT FREEZING RAIN IN PORTIONS OF THE
WILLAMETTE VALLEY WITH SOME SNOW OR LIGHT FREEZING RAIN IN THE
GORGE. CUTOFF LOWS SUCH AS THIS ONE ARE NOTORIOUSLY DIFFICULT TO
FORECAST...AS MODELS STRUGGLE WITH THEM IN THE EXTENDED FORECAST
PERIOD. WHERE THIS UPPER LOW GOES WILL DICTATE THE WEATHER THROUGH
MIDWEEK...BUT TEMPS ARE EXPECTED TO SLOWLY MODERATE TUESDAY AND
WEDNESDAY.  WEAGLE

&&

.AVIATION...GENERALLY A MIX OF IFR TO VFR CONDITIONS ALONG THE
COAST...AND VFR OVER THE INTERIOR LOWLANDS. FRONTAL BOUNDARY
EXPECTED TO WEAKEN AND STALL OVER THE INTERIOR TODAY...WITH PLENTY
OF LOW-LEVEL MOISTURE. THUS...EXPECT MAINLY MVFR OR LOWER
CONDITIONS ACROSS THE AREA THROUGH TONIGHT. HIGHER TERRAIN...SUCH
AS THE OREGON COAST RANGE...SW WA WILLAPA HILLS AND THE CASCADES
WILL REMAIN OBSCURED THROUGHOUT THE PERIOD. EXPECT PRECIP
INTENSITY TO INCREASE OVERNIGHT INTO FRI MORNING.

KPDX AND APPROACHES...VFR CONDITIONS AS OF 16Z...BUT STILL EXPECT
MVFR TO BE THE PREDOMINANT CATEGORY AFTER 18Z. LITTLE CHANGE IN
OVERALL FLIGHT CATEGORY THIS AFTERNOON THROUGH TONIGHT. 12Z SALEM
UPPER AIR SOUNDING AND MODEL SOUNDINGS FOR KPDX INDICATED SE-S
WIND OF AROUND 10 KT AT THE SURFACE...BUT SW WIND 35-40 KT AT
FL020. THIS HAS PRODUCED LLWS NEAR THE AIR FIELD SO HAVE INCLUDED
IT IN THE TAF FOR THIS MORNING. WEISHAAR

&&

.MARINE...GALE FORCE WIND HAS DIMINISHED TO SMALL CRAFT ADVISORY
SPEEDS. MODELS SUGGEST GUSTS TO 25 KT AT TIMES MOST OF THE DAY.
THERE MAY BE SHORT PERIOD OF SUB-ADVISORY WIND SPEEDS THROUGH
TONIGHT...BUT WILL KEEP THE CURRENT SMALL CRAFT ADVISORY AS IS. A
MORE ROBUST COLD FRONT...WHICH HAS MUCH COLDER AIR BEHIND IT...WILL
MOVE SOUTH THROUGH THE COASTAL WATERS LATE FRI AND EARLY FRI EVENING
FOR CONTINUED SMALL CRAFT ADVISORY WINDS. THE WIND WILL SWITCH TO
THE NORTHWEST BEHIND THIS FRONT. THE NORTHWEST WINDS WILL EASE ON
SATURDAY...THEN OFFSHORE GAP ENHANCED EAST WINDS WILL DEVELOP
SATURDAY NIGHT AND SUNDAY...PROBABLY OF THE SMALL CRAFT ADVISORY
VARIETY. THESE OFFSHORE WINDS WILL CONTINUE INTO NEXT WEEK.

SEAS ARE UP TO 10 TO 13 FT THIS MORNING AND WILL REMAIN IN THAT
RANGE THROUGH TONIGHT. SEAS CONTINUE TO HOVER AROUND 10 FT INTO
SATURDAY...THEN FALL BELOW 10 FT BY SUNDAY. SEAS TODAY WILL BE
CHOPPY WITH AROUND 8 SECOND PERIODS FROM THE SOUTHWEST. PERIODS
WILL LENGTHEN TO AROUND 14 SECONDS LATER TODAY AND TONIGHT...THEN
SHIFT AND BE FROM THE NORTHWEST WITH PERIODS AND 10 OR 11 SECONDS
FRIDAY NIGHT INTO SATURDAY. WEISHAAR

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 8 AM PST SATURDAY FOR
     COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT
     60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 8 AM PST SATURDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR
     OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 10 PM PST FRIDAY
     FOR COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60
     NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR UNTIL 6 AM
     PST 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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