Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 250411
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
810 PM PST SAT JAN 24 2015

.SYNOPSIS...HIGH PRESSURE ALOFT WILL STRENGTHEN TONIGHT AND SUNDAY
RESULTING IN UNSEASONABLY WARM TEMPERATURES FOR THE COAST AND HIGHER
TERRAIN. SOME LOCATIONS COULD SEE RECORD HIGH TEMPERATURES SUNDAY.
VALLEY INVERSIONS WILL ALSO STRENGTHEN OVER THE NEXT COUPLE OF DAYS.
A VERY WEAK FRONTAL SYSTEM NEARS THE COAST TUESDAY FOR A THREAT OF
SOME LIGHT RAIN OR DRIZZLE. HOWEVER...HIGH PRESSURE AND DRY WEATHER
ARE EXPECTED TO RETURN AROUND MID-WEEK AND LAST INTO NEXT WEEKEND.

&&
.UPDATE...WATER VAPOR IMAGERY SHOWS A REX BLOCK OVER THE WESTERN U.S.
COAST WITH HIGH PRESSURE ALOFT OVER THE PACIFIC NW AND A CLOSED UPPER
LOW OFFSHORE OF MEXICO. THIS BLOCKING PATTERN MEANS THAT THERE WILL
BE LITTLE CHANGE IN THE PRESSURE PATTERN FOR THE NEXT SEVERAL
DAYS..AND HIGH PRESSURE WILL DOMINATE THE LOCAL WEATHER.

SOME HIGH AND THIN CLOUDS WILL STREAM OVER THE AREA TONIGHT AS A
FRONT WELL OFFSHORE MOVES NORTH OVER THE RIDGE. THESE CLOUDS MAY SLOW
THE RADIATION COOLING A LITTLE...BUT ARE NOT THICK ENOUGH TO INHIBIT
VALLEY FOG OVERNIGHT AS A STRONG SUBSIDENCE INVERSION DEVELOPS.
SURFACE OBSERVATIONS SHOW THAT FOG IS STARTING TO FORM ALONG THE
IMMEDIATE COAST THIS EVENING AND THE PDX AIRPORT IS BEGINNING TO SHOW
SIGNS OF SHALLOW FOG. HAVE ADDED PATCHY FOG FOR THE COAST WITH THE
EVENING UPDATE...BUT OTHERWISE LEFT THE FORECAST UNCHANGED. TJ

PREVIOUS SHORT TERM...TONIGHT THROUGH TUESDAY...TODAY DEFINITELY DOES
NOT SEEM LIKE LATE JANUARY...MORE LIKE MID-APRIL. WATER VAPOR IMAGERY
WITH MODEL 500 MB HEIGHT OVERLAYS SHOW A 590 DM HIGH PRES CENTER NEAR
35N 130W. THE MODEL 582 DM CONTOUR WAS AS FAR N AS KTMK. SOME
LOCATIONS ALREADY THREATENING RECORD HIGH TEMPS FOR THE DAY DUE TO
MINIMAL MORNING INVERSIONS. KPDX WAS 60 DEG AT 21Z...JUST ONE OFF THE
RECORD FOR THE DATE. KTTD WAS 62 DEG AT 21Z...ALREADY TOPPING THE
RECORD OF 61 SET ON THIS DATE IN 1984.

THE 12Z NAM AND GFS INDICATE ANY REMAINING ISENTROPIC LIFT THIS
AFTERNOON TO BE CONFINED TO THE SW WA ZONES. NO SIGNIFICANT CHANGES
TO THE FORECAST PATTERN FOR THE REST OF THE SHORT TERM. THE UPPER
RIDGE WILL STRENGTHEN CONSIDERABLY TONIGHT AND SUN. VALLEY INVERSIONS
WILL STRENGTHEN TONIGHT WITH BETTER RADIATIVE CONDITIONS FOR FOG AND
LOW CLOUD DEVELOPMENT. STRONGER INVERSIONS CAN BE EXPECTED SUN
THROUGH SUN NIGHT. INLAND VALLEY MAX TEMP FORECASTS WILL BECOME MORE
CHALLENGING OVER THE NEXT COUPLE OF DAYS. THE LATEST NAM HINTS AT A
LITTLE LIGHT OFFSHORE GRADIENT THROUGH THE COLUMBIA GORGE TONIGHT...
BUT LIKELY NOT ENOUGH TO STIR THE BOUNDARY LAYER ALL THAT MUCH.

THE STRONG H5 RIDGE BECOMES CENTERED OVER THE FORECAST AREA SUN.
MODELS CONTINUE TO ADVERTISE +15C TO +18C 850 TEMPS OVER MUCH OF THE
REGION SUN. THE LATEST NAEFS OUTPUT STILL INDICATES MAX 850 MB TEMP
PERCENTILES 06Z SUN THROUGH 00Z TUE. IF IT WERE LATE MAY OR JUNE
INLAND MAX TEMPS WOULD LIKELY BE PUSHING 90 DEG. OBVIOUSLY...SUN
ANGLE IS A MAJOR FACTOR. EXPECT AREAS N OF KUAO TO HAVE A HIGHER
CHANCE OF CLEARING SUN AND MON. AREAS S OF KUAO LIKELY TO HAVE MORE
PERSISTENT FOG AND LOW CLOUDS... ESPECIALLY MON IF A LIGHT NLY
SURFACE GRADIENT DEVELOPS. KAST AND KONP LIKELY TO BREAK RECORD HIGH
TEMPS SUN. THERE HAVE ONLY BEEN A FEW JANUARY DAYS WITH 850 MB TEMPS
AT OR ABOVE 17C SINCE THE 1950S WHEN UPPER AIR RECORDS ARE FIRST
AVAILABLE. SIMILARLY...LOW TEMPS SUN AND MON MORNING EXPECTED TO BE
MILD ABOVE THE INVERSION IN THE MOUNTAINS. THE UPPER RIDGE AXIS
SHIFTS WELL E OF THE REGION MON WITH H8 TEMPS COOLING TO 10 TO 12C.

GFS...NAM AND ECMWF TRY TO BRING SOME ENERGY NWD THROUGH NEVADA MON
NIGHT FROM A TROUGH SLIDING INTO CENTRAL AND SRN CALIFORNIA.
MEANWHILE...A WEAK PACIFIC FRONTAL SYSTEM WILL BE APPROACHING THE
COAST AT ABOUT THE SAME TIME. MODELS HOLD THE NEVADA MOISTURE OVER
EXTREME SRN OREGON TUE WHILE THE WEAKENING PAC FRONT FALLS APART AS
IT TRIES TO MOVE INLAND. EXPECT AREAS OF DRIZZLE OR VERY LIGHT RAIN
OVER SW WA AND COASTAL AREAS OF NW OREGON TUE. WEISHAAR

.LONG TERM...TUESDAY NIGHT THROUGH SATURDAY...A WEAK FRONTAL SYSTEM
WILL MOVE ACROSS THE REGION LATE TUESDAY BRINGING LIGHT
PRECIPITATION THROUGH LATE WEDNESDAY NIGHT AT LEAST...AS THE FRONT
DRAGS AND LINGERS. MODELS SHOW THE UPPER LEVEL RIDGE REBUILDING BY
THURSDAY...BRINGING THE RETURN OF VALLEY FOG AND LOW CLOUDS AND
BENIGN CONDITIONS. AFTERNOON TEMPERATURES THROUGH THE EXTENDED
FORECAST WILL CONTINUE TO BE UNSEASONABLY WARM AT MOST LOCATIONS.
/27
&&


.AVIATION...STABLE AND RATHER MILD AIR MASS REMAINS OVER REGION
THROUGH SUN...WITH VARIABLE HIGH CLOUDS ON SW FLOW ALOFT. AREAS OF
IFR FOG AND STRATUS ALREADY FORMING ACROSS REGION...AND WILL
CONTINUE TO INCREASE TONIGHT. WITH WARM AIR ALOFT...LIKELY TO SEE
TOPS OF FOG/CLOUDS RUNNING AT 1000 TO 1500 FT. COASTAL FOG/CLOUDS
WILL BURN OFF SUN AM...BUT INLAND FOG/CLOUDS WILL TAKE MUCH
LONGER. SUSPECT MANY INLAND AREAS...SUCH AS COWLITZ VALLEY AND
THE WILLAMETTE VALLEY TO S OF KSLE...MAY NOT BREAK OUT TO VFR TIL
CLOSE TO 23Z.

KPDX AND APPROACHES...NOT MUCH GRADIENT...SO LIKELY TO SEE FOG AND
LOW CLOUDS INCREASE ACROSS KPDX OPS AREA BETWEEN 04Z AND 08Z...
AND PERSIST WELL INTO SUN AM. LOCAL GUIDANCE SUGGEST WILL
GRADUALLY BREAK OUT TO VFR BETWEEN 19Z AND 21Z SUN.ROCKEY.
&&

.MARINE...NOT A LOT OF CHANGE...AS HIGH PRES WILL REMAIN OVER THE
REGION. WINDS WILL REMAIN 15 KT OR LESS THROUGH MON AM...BUT WILL
PICK UP A TAD LATER MON INTO MON NIGHT AS A WEAK FRONT PUSHES
ACROSS THE REGION.

SEAS STILL HOLDING AT 10 FT ACROSS THE N WATERS...OR N OF CASCADE
HEAD. SEAS NOW RUNNING 8 TO 9 FT TO THE S OF CASCADE HEAD. WILL
KEEP SMALL CRAFT ADVISORY FOR N WATERS TONIGHT. ANOTHER BAND OF
SWELL WILL ARRIVE ON SUN...BUT THIS SWELL WILL BE DECAYING AS IT
ARRIVES. NO ADVISORY YET...AS APPEARS THIS SWELL WILL REMAIN UNDER
10 FT. WILL LET NEXT SHIFT RE-EVALUATE. ROCKEY.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL LATE TONIGHT
     ON COASTAL WATERS BETWEEN CAPE SHOALWATER AND CASCADE HEAD.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA BAR CONDITION THIS
     EVENING...AND AGAIN SUN AM.

&&

$$

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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