Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
304 AM PDT MON AUG 31 2015

.SYNOPSIS...A WARM FRONT WILL BRING LIGHT RAIN TO AREAS NORTH OF A
TILLAMOOK TO MT HOOD LINE TODAY. ANOTHER FRONT WILL ARRIVE ON TUE...
THEN A SHOWERY AIR MASS FOR WED THROUGH FRI. DRIER AND WARMER WEATHER
RETURNS NEXT WEEKEND. 
&&

.SHORT TERM...TODAY THROUGH WEDNESDAY...
WESTERLY FLOW ALOFT WILL PUSH OCCASIONAL FRONTS INTO THE PAC NW OVER
NEXT SEVERAL DAYS. BUT MAIN THRUST OF PRECIPITATION WILL BE ACROSS
BRITISH COLUMBIA AND WESTERN WASHINGTON. NEXT FRONT NOW APPROACHING
FROM THE NW...AND IS PUSHING ACROSS VANCOUVER ISLAND. THIS FRONT WILL
PUSH OCCASIONAL RAIN INTO SW WASHINGTON AND THE N OREGON COAST LATER
THIS AM...WITH THE RAIN SPREADING INLAND THIS AFTERNOON. THREAT OF
RAIN BE HARD PRESSED TO MOVE SOUTH OF A NEWPORT TO SALEM LINE...SO
WILL KEEP ONLY MINOR THREAT OF RAIN...IF ANY...IN THOSE AREAS. THIS
FRONT WILL STALL OVER THE REGION TONIGHT...THEN LIFT BACK INTO
WASHINGTON STATE. AS SUCH...RAIN THREAT WILL ALSO LIFT NORTHWARD. BUT
WILL KEEP QUITE A BIT OF CLOUDS OVER REGION TONIGHT. 

THE NEXT FRONT WILL MOVE INTO THE REGION LATER TUE. ONCE AGAIN...
WILL CLOUDS INCREASE TUE AM...WITH RAIN THREAT INCREASING OVER REGION
FROM NW TO SE DURING THE DAY. THIS FRONT WILL BRING BETTER THREAT OF
RAIN...BUT AGAIN MAIN AREA OF RAIN WILL BE ON THE COAST AND INLAND
AREAS TO NORTH OF SALEM. ONCE THAT FRONT PASSES LATE TUE
AFTERNOON...AIR MASS WILL COOL...WITH SHOWERY WEATHER ON TAP FOR TUE
NIGHT AND WED. SNOW LEVELS ALSO DROP DOWN TO NEAR 6000 FT...BUT ONLY
EXPECTING MINOR ACCUMULATIONS. 

MODELS ALL AGREE ON COOL SHOWERY WEATHER CONTINUE ON WED. MANY AREAS
WILL LIKELY REMAIN IN THE 60S FOR HIGH TEMPERATURES ON WED...EVEN
INLAND. TO EARLY TO TELL YET...BUT WITH COOL AIR MASS OVER THE REGION
AND DECENT INSTABILITY...COULD SEE A FEW THUNDERSTORMS OVER THE
REGION. WILL LET LATER SHIFTS LOOK AT THE POTENTIAL. SEEMS FIRST FEW
DAYS OF SEPTEMBER WILL FEEL LIKELY EARLY OCTOBER.   /QUINTON 
 
.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY. THE UPPER LEVEL TROUGH 
AXIS WILL REMAIN NEAR THE COAST LATE WEDNESDAY INTO THURSDAY AND 
TRIES TO SLIDE EASTWARD...THOUGH MODELS SUGGEST THIS WILL BE SLOW TO 
OCCUR AS A FEW SHORTWAVES ON THE BACK SIDE OF THE TROUGH MAY SLOW 
THE PROGRESS AS THE TROUGH SLIDES A BIT SOUTH. THIS WILL BRING 
CONTINUED COOL...AND AT TIMES SHOWERY...CONDITIONS TO THE REGION FOR 
THURSDAY AND FRIDAY...WITH THE BASE OF THE TROUGH OVERHEAD FRIDAY 
BEFORE SHIFTING EAST OF THE CASCADES. HEIGHTS LOOK TO RISE A BIT FOR 
THE WEEKEND FOR DRY AND WARMER WEATHER...PERHAPS BACK TO NEAR 
SEASONAL NORMALS FOR SUNDAY.   CULLEN
&&


.AVIATION...VFR ACROSS THE BOARD AT THIS TIME. COLD FRONT HAS
SOMEWHAT STALLED NORTH OF THE AREA WITH A FAIRLY STEADY MID LEVEL
DECK IN PLACE AROUND FL008 TO FL100. IT IS LOWERING A BIT OVER THE
NORTH COAST WITH KAST CIGS AT 050. NONE OF THE GUIDANCE APPEARS
TO HAVE A GOOD HANDLE ON THE CURRENT SITUATION WITH MODELS
INDICATING CLOUDS MUCH LOWER. A WARM FRONT WILL CROSS THE AREA
AROUND MID-DAY AND BRING LIGHT RAIN TO THE NORTHERN AREAS. MAY SEE
CIGS LOWER WITH THAT FRONTAL CROSSING BUT SEE MIXED MESSAGES AS
THE GFS KEEPS MVFR CIGS AT THE COAST AND VFR INLAND WHILE THE NAM
BRINGS IFR AT THE COAST AND MVFR INLAND. GIVEN THIS IS A WARM
FRONT AND THE NAM'S TENDENCY TO OVERREACT WITH WARM
PROCESSES...WILL FOLLOW THE GFS AS A FIRST GUESS.

KPDX AND APPROACHES...VFR THE NEXT 24 HOURS. PERIODS OF LIGHT RAIN
POSSIBLE LATE THIS AFTERNOON AND EARLY THIS EVENING. /JBONK
&&

.MARINE...A WARM FRONT MOVES ACROSS THE WATERS TODAY WITH A WEAK
COASTAL JET DEVELOPING. CONTINUE TO EXPECT WINDS GUSTING AROUND 25
KT ACROSS THE NORTHERN WATERS WITH THE PEAK COASTAL JET WINDS
OCCURRING THIS MORNING.

SEAS ARE REMAINING SOMEWHAT STEEP AS THE COLD FRONT TO THE NORTH
IS BRINGING A MODERATELY LONG FETCH AND ASSOCIATED WEST TO
NORTHWEST SWELL. THE COLD FRONT WILL SLOWLY DRIFT SOUTH TONIGHT
AND TUESDAY. WILL SEE SEAS HOVER JUST SHY OF THE 10 FT HAZARDOUS
SEAS ADVISORY CRITERIA UNTIL PERHAPS EARLY WEDNESDAY MORNING. 11
SECOND PERIOD SWELL WILL PERSIST THROUGH WEDNESDAY AS WELL.

THE PARENT UPPER LOW ALONG THE BRITISH COLUMBIA COAST WILL SHIFT
EAST WEDNESDAY AND ALLOW NORTHEAST PACIFIC HIGH PRESSURE TO BUILD
OVER THE REGION FOR THE LATTER HALF OF THE WEEK AND THE WEEKEND. A
THERMAL TROUGH BUILDS UP THE CALIFORNIA COAST BUT DOESN'T MAKE
MUCH PROGRESS NORTH UNTIL CLOSER TO SUNDAY. WILL SEE NORTHERLY
WINDS GRADUALLY RAMP UP THURSDAY THROUGH AT LEAST MONDAY PRODUCING
LATE AFTERNOON AND EVENING SMALL CRAFT ADVISORY GUSTS FOR THE
CENTRAL OREGON WATERS. /JBONK
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 6 PM TODAY FOR THE
 COASTAL WATERS FROM CAPE SHOALWATER TO CASCADE HEAD.
     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA BAR CONDITIONS 
 UNTIL 9 AM TODAY...AND AGAIN 5 PM TO 10 PM TODAY. 
&&


$$

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.

National Weather Service Glossary of Abbreviations