Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 170957
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
257 AM PDT WED SEP 17 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM REMAINS CENTERED OFF THE SOUTHERN
OREGON AND NORTHERN CALIFORNIA COAST THIS MORNING...AND WILL
CONTINUE TO SEND A FEW SURGES OF LIGHT MOISTURE INTO NORTHWEST
OREGON AND SOUTHWEST WASHINGTON TODAY. THE LOW WILL APPROACH THE
COAST THIS AFTERNOON...AND MOVE ONSHORE TONIGHT AND THURSDAY AS A
MORE ORGANIZED AREA OF MOISTURE MOVES ONSHORE TONIGHT. DAYTIME
HEATING WILL AID THE FORMATION OF MORE SHOWERS THURSDAY AFTERNOON AS
THE MAIN PART OF THE LOW MOVES SOUTH INTO CALIFORNIA. SHOWERS WILL
DECREASE THURSDAY NIGHT AND FRIDAY AS AN UPPER RIDGE BUILDS IN
BEHIND THE LOW. THE UPPER RIDGE WILL BE AT ITS STRONGEST THIS
WEEKEND AS A THERMAL TROUGH BUILDS UP THE COAST AGAIN...FOR A RETURN
OF DRY AND MUCH WARMER WEATHER. ONSHORE FLOW AND COOLER WEATHER ARE
EXPECTED TO RETURN NEXT WEEK...WITH POSSIBLY A FEW SHOWERS BY MID
WEEK. ONSHORE FLOW WILL KEEP MOST OF THE SMOKE FROM THE 36 PIT AND
DECEPTION COMPLEX FIRES OVER THE CASCADES AND TO THE EAST.
HOWEVER...HIGH PRESSURE AND OFFSHORE FLOW LOOK INCREASINGLY LIKELY
TO BUILD OVER THE REGION THIS WEEKEND SO EXPECT SMOKEY CONDITIONS TO
RETURN WITH INLAND TEMPERATURES POSSIBLY APPROACHING 90 DEGREES
AGAIN.
&&

.SHORT TERM...A LOW PRESSURE SYSTEM IS CENTERED OFF THE SOUTHERN
OREGON AND NORTHERN CALIFORNIA COAST THIS MORNING. IT HAS SPREAD SOME
LIGHT MOISTURE AND A FEW SHOWERS ACROSS PARTS OF NORTHWEST OREGON AND
SOUTHWEST WASHINGTON OVERNIGHT. THE MODELS INDICATE SOME MORE LIGHT
MOISTURE AND A FEW SHOWERS WILL CONTINUE TO SPREAD IN FROM THE
SOUTHWEST ACROSS OUR FORECAST AREA TODAY...THOUGH AMOUNTS WILL BE
LIGHT. THE EXPECTED CLOUD COVER WILL TEND TO KEEP TEMPS IN THE 75 TO
80 RANGE AGAIN TODAY ACROSS THE INTERIOR.

THE LOW WILL APPROACH THE COAST THIS AFTERNOON...AND A STRONGER AREA
OF VORTICITY AND MOISTURE WILL LIKELY SPREAD IN MAINLY THIS EVENING
AND OVERNIGHT TONIGHT AS THE LOW BEGINS TO MOVE ONSHORE. WILL HAVE
THE HIGHEST POPS DURING THAT TIME WITH CHANCE IN MANY AREAS AND SOME
SMALL AREAS OF LIKELY POPS ESPECIALLY THE SOUTHERN MOUNTAIN AREAS.

THE MAIN LOW CENTER THEN TENDS TO MOVE SOUTH INTO CALIFORNIA AS IT
MOVES INLAND ON THURSDAY. HOWEVER THERE IS ENOUGH MOISTURE IN
COMBINATION WITH DAYTIME HEATING FOR AN INCREASE IN SHOWERS IN THE
AFTERNOON FROM THE COAST RANGE EASTWARD. HAVE DECIDED TO GO
SCATTERED ON THE SHOWER COVERAGE THURSDAY AFTERNOON EXCEPT LIKELY IN
THE OREGON CASCADES.

THE MODELS SHOW SOME INSTABILITY BOTH THIS AFTERNOON AND THURSDAY
AFTERNOON IN THE OREGON CASCADES...SO HAVE A SLIGHT CHANCE OF THUNDER
IN THAT AREA BOTH DAYS.

AN UPPER RIDGE BUILDS IN THURSDAY NIGHT AND FRIDAY FOR DRYING AND
SLOWLY WARMING WEATHER. THERE IS ENOUGH ONSHORE FLOW AND LEFT OVER
MOISTURE FOR A FAIR AMOUNT OF MORNING LOW CLOUDS FRIDAY MORNING...
THAT MAY HANG AROUND THROUGH MUCH OF THE DAY IN THE MOUNTAINS FROM
ABOUT PORTLAND NORTH...FINALLY CLEARING IN THE EVENING. TEMPS WILL
START TO RISE A BIT FRIDAY...BUT THE MORE SUBSTANTIAL WARMING WILL
HOLD OFF UNTIL THE WEEKEND.

SMOKE FROM THE 36 PIT AND DECEPTION COMPLEX FIRES WILL TEND TO SPREAD
OUT TO THE NORTH AND NORTHEAST TODAY...THEN MORE TO THE EAST THURSDAY
AND FRIDAY. EAST WINDS MAY RETURN THIS WEEKEND WHICH WOULD BRING THE
SMOKE BACK INTO THE WILLAMETTE VALLEY AGAIN. TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...FRIDAY NIGHT
THROUGH TUESDAY...THE GFS...DGEX...AND ECMWF MODELS ALL SHOW A
RETURN TO EASTERLY FLOW ON SATURDAY WHICH WILL WARM TEMPERATURES
ACROSS THE AREA. THIS WARM UP WILL ONLY LAST THROUGH SUNDAY...AS
WINDS SHIFT BACK TO THE WEST FROM AN UPPER-LEVEL TROUGH AND
ASSOCIATED CYCLONE DEEPENING OVER THE GULF OF ALASKA. THIS WILL COOL
TEMPERATURES AND BRING THE MARINE LAYER BACK IN AT NIGHT MONDAY AND
TUESDAY. -MCCOY
&&

.AVIATION...TRANQUIL CONDITIONS CONTINUE THIS MORNING WITH LIGHT
WINDS AND VARIABLE MID AND HIGH CLOUDS PROVIDING FOR VFR CONDITIONS
AREA WIDE. NOT EXPECTING ANY FOG OR LOW CLOUDS EARLY THIS MORNING
WITH QUITE WEAK ONSHORE GRADIENT...THOUGH CAN NOT COMPLETELY
ELIMINATE A FEW PATCHES OF FOG IN BAYS AND COAST RANGE VALLEYS EARLY
THIS MORNING. WILL SEE INCREASING MID LEVEL CLOUDS TODAY ALONG WITH
THE POTENTIAL FOR A FEW SHOWERS.

SMOKE FROM THE 36-PIT FIRE CONTINUES TO DRIFT TO THE E AND NE. WILL
SEE SMOKE CONTINUE IN EAST COLUMBIA GORGE...UPPER HOOD RIVER VALLEY
AND AROUND MT HOOD...WITH SOME SMOKE TRAPPED SETTLING IN VALLEYS TO E
AND N OF THE FIRE. WITH S WINDS ALOFT OVER NEXT FEW DAYS...SMOKE FROM
FIRES OVER SW OREGON AND NW CALIFORNIA WILL DRIFT N TO NE...AFFECTING
SLANTWISE VISIBILITY FROM CASCADES EASTWARD.

KPDX AND APPROACHES...VFR CONTINUES WITH VARIABLE HIGH CLOUDS THIS
MORNING. INCREASING MID LEVEL CLOUDS TODAY...WITH CIGS LIKELY FORMING
IN THE 4000-5000 FT RANGE THIS AFTERNOON/EVENING WITH INCREASING
CHANCES FOR A SHOWER OR TWO. CULLEN
&&

.MARINE...FAIRLY BENIGN CONDITIONS CONTINUE OVER THE WATERS FOR THE
NEXT FEW DAYS AS WEAK LOW PRES WILL MAINTAIN S TO SE WIND LESS THAN
15 KT. THERE WILL BE A MIX OF WAVE TRAINS WITH VARYING PERIODS...
FROM THE NW...W AND SW. EXPECT NW SWELL TO DOMINATE TODAY AT AROUND
15 SECONDS. OVERALL SEAS RUNNING 6 TO 8 FT...WITH HIGHEST FURTHER
OFFSHORE.

HIGH PRES WILL REBUILD OVER THE WATERS FRI AND SAT...WITH THERMAL LOW
PRES OVER THE COAST AND COASTAL WATERS. THIS WILL BRING ANOTHER ROUND
OF E TO NE WINDS TO THE WATERS THIS WEEKEND WITH WINDS POSSIBLY
GUSTING TO 25 KT ON SAT AND SAT NIGHT. CULLEN
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...NONE.
&&

$$

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 AS THE FORECAST AREA.


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