000
FXUS66 KPQR 200422
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
830 PM PST WED NOV 19 2008
.SYNOPSIS...GUSTY EASTERLY GORGE WINDS WILL CONTINUE TONIGHT AS HIGH
PRESSURE BUILDS EAST OF THE CASCADES. A GULF OF ALASKA LOW PRESSURE
SYSTEM AND ASSOCIATED STRONG COLD FRONT WILL SPREAD RAIN AND MOUNTAIN
SNOW ACROSS THE DISTRICT THURSDAY...WITH A SECOND FRONTAL SYSTEM
LIKELY BRINGING RAIN AT LEAST TO THE NORTHERN HALF OF THE DISTRICT
LATE FRIDAY AND FRIDAY NIGHT. DRIER WEATHER LIKELY RETURNS BY
SATURDAY NIGHT AND SUNDAY AS AN UPPER LEVEL RIDGE BUILDS BACK ACROSS
THE PACIFIC NORTHWEST.
&&
.SHORT TERM...SATELLITE IMAGERY SHOWS A VERY WEAK FRONT MOVING NE AND
DISSIPATING OVER THE EAST SIDE OF THE FORECAST AREA THIS EVENING...
WHILE FAIRLY STRONG HIGH PRES CONTINUES TO BUILD SE FROM BRITISH
COLUMBIA. OFFSHORE PRES GRADIENTS THROUGH THE GORGE HAVE RISEN A BIT
MORE...TO OVER 7 MB THIS EVENING...AND SHOULD REMAIN THERE OR RISE
SLIGHTLY MORE OVERNIGHT AS INDICATED BY MODELS. THIS GIVES GUSTS TO
AROUND 35 MPH AT KTTD...AND POSSIBLY 50 MPH GUSTS IN THE GORGE FROM
CASCADE LOCKS WESTWARD.
FURTHER OFFSHORE...INFRARED AND WATER VAPOR SATELLITE IMAGERY SHOW A
TIGHTLY WRAPPED COLD LOW MOVING E NEAR 40N/135W...WITH A COLD FRONT
AHEAD OF IT NEARING 130W. THIS FRONT WILL MOVE ONSHORE INTO OR/WA THU
MORNING...SPREADING RAIN AND COOLER TEMPERATURES ACROSS THE DISTRICT.
ONSHORE FLOW AND INSTABILITY WILL FOLLOW BY THU AFTERNOON GIVING A
GOOD SHOT OF COOL OROGRAPHIC FLOW INTO THE CASCADES. SNOW LEVELS WILL
FALL TO BELOW PASS LEVELS THU AFTERNOON AND EVENING. GUIDANCE
SUGGESTS SNOW AMOUNTS WILL BE NEAR ADVISORY AMOUNTS WITH A BRIEF
BURST OF MODERATE SNOW SHOWERS. WILL ISSUE A SNOW ADVISORY FOR THE
CASCADES...WITH THE GREATEST ACCUMULATIONS AT THE SKI RESORTS. GIVEN
SATELLITE IMAGERY WILL ALSO ADD A SLIGHT CHANCE OF THUNDERSTORMS TO
MUCH OF THE AREA THU AFTERNOON.
MODELS LOOKING A BIT SLOWER WITH THE NEXT FRONT APPROACHING ON FRI...
MAINLY WITH 12Z AND 18Z GFS/ECMWF SPREADING ANOTHER ROUND OF RAIN
INTO THE NORTHERN HALF OF THE DISTRICT FRI EVENING. IF FUTURE MODEL
RUNS CONTINUE THE DRIER FRI FORECAST THEN A FURTHER REDUCE IN POPS
WILL BE NECESSARY. SHOWERS DECREASE ON SAT AS GUIDANCE SHOWS ANOTHER
SHORT WAVE RIDGE PUSHING INTO THE PAC NW.
.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
UPPER RIDGE BUILDS IN ON SATURDAY NIGHT AND SUNDAY...ALLOWING SURFACE
HIGH PRESSURE TO STRENGTHEN EAST OF THE CASCADES AS COOL AIR FLOWS
INTO THE COLUMBIA BASIN. WILL PROBABLY SEE SOME FOG IN THE VALLEY SAT
NIGHT AND SUN MORNING...BUT STRENGTHENING OFFSHORE FLOW SHOULD CLEAR
THINGS OUT NICELY ON SUNDAY. STAYED MORE IN LINE WITH THE CANADIAN
AND EURO FOR MONDAY...BOTH OF WHICH BRING IN A FRONT ON MONDAY
AFTERNOON. MODEL SOLUTIONS DIVERGE BEYOND MONDAY SO WENT MORE WITH
CLIMATOLOGY FOR THE REST OF THE EXTENDED. DALTON
&&
.AVIATION...MOSTLY GOOD FLYING WEATHER TONIGHT...WITH OFFSHORE WINDS
KEEPING MOST LOCATIONS IN VFR CONDITIONS. HOWEVER...FROM SALEM
SOUTHWARD...WHICH IS MORE SHELTERED FROM THE WINDS...LOW STRATUS AND
FOG REMAINS. NOT EXPECTING MUCH CHANGE IN CONDITIONS OVERNIGHT.
FRONT OFFSHORE WILL SPREAD MORE SOLID LOW VFR AND HIGH END MVFR
AFTER 12Z...WITH RAIN SPREADING INLAND AFTER 14Z.
KPDX AND APPROACHES...NO SIGNIFICANT WEATHER IMPACTS EXPECTED THRU
18Z AS DRY EAST WINDS KEEP AREA UNDER VFR CONDITIONS. BUT...WILL SEE
CEILINGS LOWER TO MVFR BETWEEN 18Z AND 20Z AS FRONT APPROACHES. CCDR.
&&
.MARINE...NO CHANGES AT MOMENT. SOLID SMALL CRAFT ADVISORY WINDS
TONIGHT ON THE COASTAL WATERS. STILL EXPECT WINDS TO GUST INTO GALE
FORCE RANGE LATE TONIGHT INTO THU MORNING. SEAS ARE DOWN...BUT WILL
BUILD AS WINDS KICK UP QUITE A BIT OF SHORT FETCH SEAS. WINDS WILL
LAY DOWN LATER IN AFTERNOON ONCE THE FRONT MOVES FURTHER INLAND.
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR/WA...SMALL CRAFT ADVISORY FOR WIND CAPE SHOALWATER TO FLORENCE
THIS EVENING THROUGH EARLY THU MORNING.
GALE WARNING CAPE SHOALWATER TO FLORENCE 2 AM TO 10 AM THU.
WINTER WEATHER ADVISORY FOR SNOW FOR THE CASCADES THU AND THU
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.
