National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS66 KPQR 180305
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
800 PM PDT FRI MAY 17 2013

.SYNOPSIS...SCATTERED SHOWERS WILL SHIFT INTO THE CASCADES THIS
EVENING AS WEAK SURFACE HIGH PRESSURE BUILDS INTO OREGON AND SW
WASHINGTON. THE NEXT PACIFIC SYSTEM WILL MOVE IN FOR SATURDAY...
BRINGING A PERIOD OF STEADY LIGHT RAIN SATURDAY FOLLOWED BY
DECREASING SHOWERS SATURDAY NIGHT AND SUNDAY. DRIER WEATHER IS
EXPECTED SUN NIGHT/MON... BUT IT IS LOOKING MORE LIKELY THAT A COOL
AND UNSETTLED PATTERN WILL SET UP OVER THE PACIFIC NORTHWEST FOR THE
MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH MONDAY...THE BACK EDGE OF SLOW MOVING
SHOWER ACTIVITY HAS SHIFTED INTO THE FOOTHILLS AND CASCADES AS HIGH
PRESSURE NOSES INTO NW OREGON AND SW WASHINGTON. HIGH PRESSURE WILL
REMAIN IN PLACE FOR THE REMAINDER OF THE EVENING AND INTO THE EARLY
OVERNIGHT HOURS...THUS EXPECT MOST AREAS OUTSIDE OF THE CASCADES AND
EVENTUALLY THE COAST TO REMAIN DRY UNTIL LATE TONIGHT.

A GRADUAL END TO SHOWER ACTIVITY HAS OCCURRED BUT MANY AREAS WILL
REMAIN MOSTLY CLOUDY DUE TO THE MOIST LOW LEVEL AIR MASS. THE
EXCEPTION WILL BE IN LEE OF THE COAST RANGE FOR THE REMAINDER OF THE
EVENING.  NAM CROSS SECTIONS THROUGH THE WILLAMETTE VALLEY SEEM TO
SUPPORT THIS THINKING. EITHER WAY...IT WILL NOT BE LONG BEFORE HIGHER
CLOUDS BEGIN TO MOVE IN AHEAD OF OUR NEXT SYSTEM NOW SHOWN INSIDE
130W ON IR/WV SATELLITE IMAGERY. KMD

REST OF THE SHORT TERM FORECAST DISCUSSION UNCHANGED...STILL LOOKS
LIKE A DECENT CHANCE FOR RAIN THROUGHOUT THE DISTRICT SATURDAY AS
THAT MODEST FRONTAL SYSTEM MOVES ONSHORE. THERE WILL BE SOME WEAK
ISENTROPIC LIFT AHEAD OF THIS SYSTEM...SO JUST ABOUT EVERYONE SHOULD
GET SOME LIGHT RAIN. ONLY MODEST OROGRAPHIC ENHANCEMENT WITH 15-25
KT SW 850 MB WINDS...SO EXPECT RAIN TOTALS TO RANGE FROM 0.10-0.25
INCH IN THE VALLEYS AND 0.50 TO LOCALLY 1 INCH IN THE HIGHER
TERRAIN. RAIN WILL TAPER TO SHOWERS SATURDAY NIGHT WITH A FEW
LINGERING INTO SUNDAY...MAINLY OVER THE HIGHER TERRAIN.

TEMPERATURES WILL HOVER NEAR OR A LITTLE BELOW NORMAL THROUGH THE
WEEKEND. SNOW LEVELS SHOULD REMAIN ABOVE THE PASSES THROUGHOUT THE
WEEKEND...BUT MAY GET AS LOW AS 4500-5000 FT AT TIMES. MONDAY APPEARS
TO BE A DRIER DAY WITH MILD TEMPS AS A SHORTWAVE RIDGE MOVES ACROSS
THE PACIFIC NORTHWEST...BUT THIS WILL BE BRIEF AS THE NEXT SYSTEM
LOOMS FOR TUESDAY AND MIDWEEK. WEAGLE

.LONG TERM...MONDAY EVENING THROUGH FRIDAY...COLD CLOSED LOW
PRESSURE SYSTEM WILL PUSH ONSHORE MONDAY NIGHT...BRINGING RAIN AND
MUCH COOLER TEMPERATURES TO THE AREA. THIS LOW WILL LINGER OVER THE
PAC NW TUESDAY AND MUCH OF THE DAY WEDNESDAY...WITH RECORD LOW
MAXIMUM TEMPERATURES POSSIBLE ON WEDNESDAY. BY THURSDAY MODELS
DISAGREE ON WHERE THE LOW WILL PROPAGATE...BUT THE OVERALL TREND IS
FOR SHOWERY AND COOL CONDITIONS TO PERSIST THROUGH THE END OF THE
WEEK. BURGESS

&&

.AVIATION...AIR MASS STABILIZING THIS EVENING...AS MORE STABLE AIR
MASS SPREADS INTO THE REGION. SKIES REMAIN VFR THIS EVENING...WITH
WORST CONDITIONS AGAINST THE CASCADES. AS FRONT APPROACHES...CIGS
GRADUALLY LOWER LATE TONIGHT...WITH MVFR AND OCCASIONAL RAIN
INCREASING BETWEEN 10Z AND 14Z SAT. FRONT IS FAST MOVING...SO
RETURN TO VFR LIKELY BETWEEN 19Z AND 22Z...FIRST ON COAST AND
LATER INLAND AS THE FRONT SWEEPS EAST OF THE CASCADES BY MID
AFTERNOON.

KPDX AND APPROACHES...VFR TONIGHT. AREAS OF MVFR CIGS DOWN NEAR
2500 FT INCREASE BETWEEN 12Z AND 15Z. MVFR WITH RAIN DOMINATES
SAT AM. FRONT WILL PUSH ACROSS KPDX OPS AREA BETWEEN 20Z AND
22Z...WITH RETURN TO VFR WITH SCATTERED SHOWERS.ROCKEY.
&&

.MARINE...WINDS WILL GRADUALLY TURN MORE SOUTHERLY TONIGHT AS
ANOTHER FRONT APPROACHES. THIS FRONT WILL PUSH ACROSS THE COASTAL
WATERS SAT AM...THEN INLAND IN THE AFTERNOON. WINDS NOT ALL THAT
IMPRESSIVE BUT SEEMS THAT BE ENOUGH GRADIENT TO POP GUSTS 20 TO 25
KT SAT AM. SO WILL PUT UP SMALL CRAFT ADVISORY FOR THAT TIME
FRAME. OTHERWISE...WINDS TURN W TO NW BEHIND THE FRONT IN THE
AFTERNOON AND BEGIN TO EASE.

HIGH PRES WILL BUILD OVER THE NE PAC FOR SUN INTO EARLY NEXT WEEK.
THIS WILL KEEP NW WINDS 10 TO 15 KT THROUGH MUCH OF THE COMING
WEEK...THOUGH MAY BRIEFLY GET 20 TO 25 KT GUSTS MON AFTERNOON INTO
THE EVENING.

SEAS REMAIN AT 5 TO 6 FT FOR INTO EARLY NEXT WEEK. MAY SEE SEAS
BUILD UP AND BECOME CHOPPY AT TIMES WITH THE BRISK NW WINDS ON THE
CENTRAL OREGON COASTAL WATERS NEXT WEEK.       ROCKEY.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS SAT AM ON ALL COASTAL WATERS.

&&


$$

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.