FXUS66 KPQR 012240
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
238 PM PST TUE DEC  1 2009

.SYNOPSIS...AN EASTERN PACIFIC UPPER RIDGE TO SHARPEN ALONG THE WEST
COAST. A SURFACE HIGH WILL DROP SOUTH INTO THE AREA EAST OF THE
CASCADES TODAY AND INTENSIFY TONIGHT...WITH INCREASING EAST WINDS
THROUGH THE COLUMBIA RIVER GORGE. THE OFFSHORE FLOW WILL THEN
CONTINUE THROUGH AT LEAST THURSDAY. GENERAL TREND FOR LATE IN THE
WEEK AND THROUGH THE WEEKEND IS FOR A COOLER AIR MASS TO PUSH INTO
THE REGION FOR NORTHWESTERN CANADA. SOME PRECIPITATION IS POSSIBLE
AROUND FRIDAY.

&&

.SHORT TERM...STRATUS CLEARED OUT OF THE NORTHERN ZONES. THE CLEARING
HAS MADE SOUTH OF SALEM AT 2 PM. CLEARING MAY REACH THE EUGENE AREA
LATER IN THE AFTERNOON...BUT MAY NOT BE ENOUGH TIME TO DRY OUT TO
INHIBIT FOG TO REFORM TONIGHT.	UPPER RIDGE ALONG THE WEST COAST
SHARPENS THROUGH WED TO BRING A MORE NORTHERLY FLOW ALOFT TO OUR
AREA. IN RESPONSE A SURFACE HIGH DRAGS SOUTHWARD INTO THE REGION EAST
OF THE CASCADES INCREASING OFFSHORE FLOW. EAST WINDS HAVE INCREASED
THROUGH THE COLUMBIA RIVER GORGE AND SHOULD INCREASE A LITTLE MORE
TONIGHT WITH 6 TO 7 MB VALUE THROUGH ABOUT THURSDAY. THIS SHOULD GIVE
GUSTS TO 40 OR 45 MPH AT THE WEST END OF THE GORGE BEGINNING 
TONIGHT. THIS SHOULD ALSO DECREASE THE AMOUNT OF FOG IN THE PORTLAND 
AREA...BUT THINK SOME MAY STILL FORM DOWN NEAR EUGENE IN THE LATE 
NIGHTS AND MORNINGS. THE GRADIENT REMAINS MOSTLY EASTERLY...SO 
MIXING OF DRY AIR UP THE WILLAMETTE VALLEY WILL TAKE SOME TIME AND 
MAY NOT ENTIRELY PREVENT FOG TO THE SOUTH THROUGH THURSDAY. PLACES 
THAT CLEAR AND DO NOT REFORM MUCH FOG BUT ALSO WHERE THE WINDS EASE 
AT NIGHT MAY SEE SOME TEMPS DOWN BELOW FREEZING THE NEXT COUPLE OF 
MORNINGS. LATER IN THE SHORT TERM...MODELS CONTINUE WITH SHARP UPPER 
RIDGE OFFSHORE REACHING INTO ALASKA. THE DIFFERENCES BETWEEN THE GFS 
AND ECMWF IS HOW IT HANDLES SHORTWAVE ENERGY MOVING AROUND THE RIDGE 
THAT ARRIVES ON FRIDAY. BOTH RESULT IN A COOLER AIR MASS BUT ECMWF 
IS MORE DEVELOPED CLOSING OFF AN UPPER LOW OVER WESTERN WA AND 
OREGON BY FRI NIGHT. HAVE TRENDED POPS HIGHER TO ACCOUNT FOR THIS. 

.LONG TERM...GFS AND ECMWF RESUMES FAIRLY STRONG OFFSHORE FLOW INTO
THE WEEKEND WITH INCOMING SYSTEMS OFF THE PACIFIC HEAD TO THE SOUTH
OF THE FORECAST AREA. WHILE UNCERTAINTY IN MODELS GREATLY INCREASE
EARLY NEXT WEEK GENERAL PATTERN IS FOR MORE SYSTEMS TO APPROACH THE
WEST COAST. THIS COULD BE AN INTERESTING PATTERN DEVELOPMENT WITH
OFFSHORE FLOW THROUGH THE GORGE IF ENOUGH COLD AIR REMAINS IN PLACE
INLAND. CURRENT FORECASTS TAKE A CONSERVATIVE APPROACH AND WILL
CONTINUE THAT FOR NOW...BUT WILL NEED TO MONITOR HOW THIS DEVELOPS. 
&&

.AVIATION...IFR CONDITIONS CONTINUING THIS AFTERNOON IN THE S 
WILLAMETTE VALLEY AT KEUG...BUT SHOULD BREAK OUT THIS EVENING AS DRY 
OFFSHORE FLOW SCOURS MOST OF THE LOW LEVEL MOISTURE FROM THE S 
VALLEY. ELSEWHERE VFR CONDITIONS ACROSS THE AREA. OVERNIGHT COOLING 
MAY ALLOW PATCHY FOG TO REFORM WITH THE MAIN THREAT S WILLAMETTE 
VALLEY AND LOCALLY AT THE COAST. 

KPDX AND APPROACHES...VFR CONDITIONS THROUGH WED. GUSTY E WINDS WILL 
DECREASE AROUND 04Z-06Z THIS EVENING AND MAY ACTUALLY TURN LIGHT NW 
OVERNIGHT WITH LOW LEVEL WIND SHEAR CONDITIONS POSSIBLE...WHILE E 
WINDS CONTINUE AT KTTD. E WINDS RESUME AT KPDX BY 18Z WED.

&&

.MARINE...SEAS REMAINING AROUND 8 TO 9 FT THROUGH TONIGHT. WILL 
ALLOW THE SCA FOR ROUGH BAR TO EXPIRE AS WINDS REMAIN OFFSHORE AND 
ARE EXPECTED TO STRENGTHEN TONIGHT. WINDS SHOULD STAY BELOW 
ADVISORY LEVELS BUT WILL SEE GUSTS TO 20 KT AS THE WINDS VEER FROM 
NORTH TO NORTHEAST TOMORROW AFTERNOON...ESPECIALLY NEAR COASTAL 
GAPS. MODELS DELAYED THE ARRIVAL OF THE NEXT WEAK FRONT. PREVIOUSLY 
THOUGHT TO ARRIVE THU....RATHER IT WILL ENTER THE WATERS ON FRI FOR 
SEAS NEAR 10 FT...FOLLOWED BY NEAR SMALL CRAFT NORTHERLIES AFTER 
FRONTAL PASSAGE FOR THE REMAINDER OF THE WEEKEND. RAMIREZ

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 
      TO 6 PM THIS EVENING.

&&

$$

MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND

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.