Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 300943
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
243 AM PDT TUE JUN 30 2015

.SYNOPSIS...HIGH PRESSURE WILL DOMINATE THE WEATHER THE NEXT SEVERAL
DAYS. MARINE STRATUS WILL KEEP THE COASTAL TEMPERATURES IN THE 60S TO
LOW 70S...BUT HOT WEATHER WILL CONTINUE INLAND WITH AFTERNOON
TEMPERATURES MOSTLY IN THE 90S. AM UPPER LOW NORTH OF THE AREA THIS
WEEKEND WILL FLATTEN THE UPPER RIDGE AND PREVENT TEMPERATURES FROM
WARMING ABOVE THE 90S.

&&

.SHORT TERM...TODAY THROUGH FRIDAY...WATER VAPOR IMAGERY SHOWS A FLAT
UPPER RIDGE OVER NW OREGON AND SW WASHINGTON AS A COUPLE OF
SHORTWAVES RIDE OVER IT NORTH OF WASHINGTON STATE. ONE SHORT WAVE
APPROACHING THE BRITISH COLUMBIA COAST EARLY THIS MORNING HAS HELPED
KEEP THE MARINE LAYER DEEP ENOUGH FOR SOME OF THE MARINE CLOUDS ALONG
THE IMMEDIATE COAST TO PUSH INLAND.

THE LOW LEVEL FLOW IS WEST TO NORTHWEST ALLOWING MORE OF A MARINE
PUSH THROUGH THE NORTHERN GAPS THAN THE SOUTHERN. LOW CLOUDS HAS
MOVED UP THE LOWER COLUMBIA RIVER TO KELSO AND SCAPOOSE BY 2 AM...AS
WELL AS THROUGH MOST OF THE COASTAL GAPS OF THE COAST RANGE. EXPECT
THESE CLOUDS TO MOVE A LITTLE FURTHER INLAND THROUGH THE
MORNING...AND LIKELY REACHING PARTS OF THE PORTLAND METRO AREA BY
SUNRISE.

OTHERWISE THE SKIES ARE CLEAR...WITH MANY INLAND TEMPERATURES IN THE
60S. WOULD NOT BE SURPRISED IF SOME OF THE INLAND TEMPERATURES DROP
JUST BELOW 60. DESPITE THE COOLER START TO THE DAY...SOLAR HEATING
WILL QUICKLY WARM THE TEMPERATURES TODAY...AND HELP CLEAR THE INLAND
STRATUS. HEIGHTS WILL BUILD A TAD TODAY AND EXPECT MAXIMUM
TEMPERATURES THIS AFTERNOON TO BE SIMILAR OR SLIGHTLY WARMER THAN
WHAT WAS OBSERVED FOR MONDAY.

WATER VAPOR IMAGERY SHOWS ANOTHER UPPER LEVEL SHORTWAVE CURRENTLY
NEAR 40N 141W. THE FORECAST MODELS DO NOT FORECAST THIS
FEATURE...EXCEPT THE GFS HAS A WEAK VORT MAX NEAR ITS LOCATION. SINCE
THIS WAVE IS STRONGER THAN THE MODELS...SUSPECT THAT THEY ARE UNDER
FORECASTING THE POTENTIAL FOR MARINE CLOUDS TONIGHT INTO WED MORNING.
THIS WAVE LOOKS WEAKER THAN THE FIRST ONE...AND SHOULD ALSO TAKE A
NORTHERN TRACK AS THE UPPER RIDGE BUILDS. EXPECT THAT IT WILL
MAINTAIN WEAK W-NW LOW LEVEL WINDS AND PREVENT THE RIDGE FROM TOTALLY
SQUASHING THE MARINE LAYER. THEREFORE...I HAVE ADDED A RETURN OF LOW
CLOUDS TO THE IMMEDIATE COAST TONIGHT...PUSHING INTO THE COLUMBIA
RIVER VALLEY WED MORNING...BUT NOT TO THE PORTLAND METRO AREA.

THE MODELS HAVE BACKED OFF ON THE RIDGE AMPLIFYING WEDNESDAY AND
THURSDAY...POSSIBLY DUE TO THE SHORT WAVES RIDING OVER THE RIDGE. THE
UPPER HEIGHTS WILL RAISE ENOUGH THOUGH FOR THE AFTERNOON TEMPERATURES
TO CONTINUE TO WARM INLAND EACH DAY...PUSHING INTO THE MID TO UPPER
90S. ALSO THINK THAT THE MARINE CLOUDS WILL BECOME LESS OF AN
INFLUENCE WED NIGHT.

AN UPPER LOW WILL MOVE INTO WESTERN CANADA THURSDAY NIGHT AND FRIDAY
RESULTING IN THE RIDGE FLATTENING AGAIN OVER THE PACIFIC NW AND
BUILDING WEST OVER THE NE PACIFIC. THESE SUBTLE DIFFERENCES OF THE
UPPER HEIGHTS WILL BE BARELY NOTICEABLE...BUT THERE MAY BE A VERY
SLIGHT INCREASE OF A MARINE PUSH THURSDAY NIGHT AND VERY SLIGHT
COOLING FRIDAY.

MONSOONAL MOISTURE SHOULD REMAIN SOUTH OF THE AREA THROUGH THE SHORT
TERM. SOME CUMULUS MAY DEVELOP OVER THE CASCADES IN THE AFTERNOONS
BUT EXPECT SUBSIDENCE FROM THE HIGH TO PREVENT THE CUMULUS FROM
GROWING TALL ENOUGH TO GENERATE SHOWERS OR THUNDERSTORMS. TJ

.LONG TERM...FRIDAY NIGHT THROUGH MONDAY...THE UPPER LOW OVER WESTERN
CANADA WILL DEEPEN AS IT SHIFTS EASTWARD NEXT WEEKEND RESULTING IN
UPPER HEIGHTS DECREASING SOME OVER THE PACIFIC NW. THIS WILL HELP
MODERATE THE TEMPERATURES SOME...BUT STILL EXPECT DAYTIME HIGHS TO BE
WELL ABOVE NORMAL...AND LIKELY IN THE 90S INLAND. COASTAL CLOUDS
SHOULD CONTINUE TO KEEP THE COASTAL TEMPERATURES CLOSER TO THE
SEASONAL NORMALS. THE UPPER TROUGH WILL DESTABILIZE THE ATMOSPHERE IN
THE CENTRAL OREGON CASCADES FOR POSSIBLY ISOLATED THUNDERSTORMS IN
THE AFTERNOONS AND EVENINGS...MAINLY NEAR THE CREST OF THE CASCADES
IN LANE COUNTY. THE MODELS VARY CONSIDERABLY FOR MONDAY WITH THE
ECMWF REBUILDING THE RIDGE OVER US...AND THE GFS DROPPING AN UPPER
LOW SOUTHWARD ALONG THE WESTERN CANADA COAST. LEFT THE MONDAY
FORECAST UNCHANGED DUE TO THESE DIFFERENCES. TJ
&&

.AVIATION...SATELLITE FOG PRODUCT AS OF 09Z SHOWED IFR TO LIFR
CIGS ALONG THE COAST AND PUSHING INTO THE MAJOR COASTAL RIVER
DRAINAGES. IFR TO LOW-END MVFR STRATUS ALSO PUSHING UP THE
COLUMBIA TO KKLS. EXPECT THE COAST TO REMAIN IFR OR LIFR THROUGH
THE MORNING THEN IFR TO LOW-END MVFR IN THE AFTERNOON. THERE MAY
BE A SHORT-LIVED PERIOD OF VFR BUT EXPECT MVFR STRATUS TO RETURN
TUE EVENING. INLAND AREAS TO REMAIN VFR THROUGH TUE EVENING...
EXCEPT FOR MVFR CIGS UP THE COLUMBIA TO NEAR KPDX THROUGH 17Z.

KPDX AND APPROACHES...VFR CONDITIONS TO PREVAIL THROUGH TUE
EVENING. HOWEVER...IT IS LOOKING MORE LIKELY THAT MVFR STRATUS
WILL MAKE IT TO THE TERMINAL AND VICINITY AROUND SUNRISE. ANY
STRATUS THAT DOES MOVE IN IS EXPECTED TO DISSIPATE BY 17Z.
WEISHAAR
&&

.MARINE...WIND SPEEDS UNDER 10 KT EARLY THIS MORNING...BUT WILL
INCREASE LATER THIS MORNING AND INTO THE AFTERNOON. EXPECT SMALL
CRAFT ADVISORY WIND SPEEDS ACROSS THE MAJORITY OF THE WATERS BY
19Z TUE. HAVE ADJUSTED THE TIMING OF THE SMALL CRAFT ADVISORY TO
START IT A BIT LATER AND EXTEND IT THROUGH WED AFTERNOON.
STRONGEST WIND SPEEDS WILL BE OVER THE SRN WATERS...GENERALLY S OF
HECETA HEAD WHERE AFTERNOON AND EARLY-EVENING GUSTS TO 30 KT CAN
BE EXPECTED. MODELS SHOW WIND SPEEDS GRADUALLY DECREASING LATE IN
THE WEEK AND OVER THE WEEKEND.

GENERALLY WIND-WAVE DRIVEN SEAS FOR THE NEXT FEW DAYS. SPECTRAL
ANALYSIS MAINTAINS A RESIDUAL BACKGROUND LONG-PERIOD SW SWELL FOR
THE NEXT COUPLE OF DAYS AND HAVE INDICATED THIS IN THE GRIDS.
OTHERWISE...STEEP AND CHOPPY CONDITIONS WILL PREVAIL DUE TO THE
LARGE WIND-WAVE COMPONENT. A BUILDING NW SWELL LOOKS TO ARRIVE
OVER THE WEEKEND AND COULD REACH 10 FT. WEISHAAR
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 10 AM THIS MORNING TO 5 PM
     PDT WEDNESDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

&&

$$

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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