Area Forecast Discussion
Issued by NWS Portland, OR

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KPQR 252146
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
246 PM PDT MON MAY 25 2015

.SYNOPSIS...A CLOSED UPPER LEVEL LOW IS MOVING INTO NORTHERN
WASHINGTON TODAY. MODERATE LOW LEVEL ONSHORE FLOW WILL CONTINUE
THROUGH TUE ON THE BACKSIDE OF THE LOW...WITH NIGHT AND MORNING
CLOUDS AND POSSIBLE COASTAL DRIZZLE GIVING WAY TO PARTIAL AFTERNOON
CLEARING ESPECIALLY FURTHER SOUTH. THERE IS A THREAT FOR A FEW
SHOWERS OR THUNDERSTORMS TO FORM ALONG CREST OF THE S WASHINGTON
CASCADES TODAY AND TUE DURING THE AFTERNOON AND EVENING HOURS. THE
UPPER LOW WILL DRIFT INTO IDAHO LATE TUE INTO WED...ALLOWING HIGH
PRES TO APPROACH THE PAC NW. THE ONSHORE FLOW WILL WEAKEN AND WINDS
WILL TURN MORE NORTHERLY BEGINNING WED. THIS WILL RESULT IN FEWER
CLOUDS AND WARMER TEMPERATURES FOR THE SECOND HALF OF THE WEEK AND
INTO THE WEEKEND. HOWEVER...THE THREAT FOR A FEW SHOWERS AND
THUNDERSTORMS WILL CONTINUE FOR THE CASCADE CREST EACH AFTERNOON AND
EVENING. SOUTHWEST FLOW ALOFT NEXT WEEKEND MAY BRING A RETURN TO THE
MARINE LAYER AND POSSIBLY A FEW THUNDERSTORMS OVER THE CASCADES.

&&

.SHORT TERM...A CLOSED UPPER LEVEL LOW IS SLOWLY SAGGING SOUTH INTO
NORTHERN WA TODAY. ONSHORE FLOW ON THE BACKSIDE OF THE LOW BROUGHT
EXTENSIVE MARINE CLOUD COVER ONSHORE THIS MORNING. THE CLOUDS ARE
GRADUALLY DISSIPATING THIS AFTERNOON...WITH THE BEST CLEARING
OCCURRING OVER THE SOUTHER HALF OF THE FCST AREA. EXPECT THE CLOUDS
TO CONTINUE TO THIN THROUGH THE REST OF THE AFTERNOON...WITH
SUN BREAKS DEVELOPING FOR MOST LOCATIONS WITH THE EXCEPTION OF THE FAR
NW PORTIONS OF THE FCST AREA. THERE HAS BEEN QUITE A BIT OF SUN OVER
THE CASCADES TODAY...AND A FEW ECHOES ARE NOW SHOWING UP ON THE EAST
SLOPES OF THE WA CASCADES OVER THE PAST HOUR OR TWO...SO WILL KEEP A
SLIGHT CHANCE OF SHOWERS OR THUNDERSTORMS ALONG THE S WA CASCADE
CREST INTO THIS EVENING.

EXPECT TUE WILL BE A NEAR REPEAT OF TODAY AS THE UPPER LOW DRIFTS
INTO EASTERN WA AND THE ONSHORE FLOW CONTINUES. BASED ON THE LATEST
VISIBLE SATELLITE IMAGERY...THERE ARE STILL PLENTY OF MARINE
STRATOCUMULUS CLOUDS JUST OFFSHORE THAT SHOULD PUSH INLAND TONIGHT
INTO TUE MORNING. LIKE TODAY...EXPECT THE CLOUDS AND PATCHY COAST AND
COAST RANGE DRIZZLE TO BE AROUND FOR THE MORNING...THEN GRADUALLY
BURN OFF FROM SOUTH TO NORTH DURING THE AFTERNOON. THE MARINE LAYER
MAY BE A BIT MORE SHALLOW...SO THE CLOUDS MAY BURN OFF JUST AN HOUR
OR TWO FASTER THAN TODAY WITH TEMPS A COUPLE OF DEGREES WARMER. THE
MODELS ARE STILL SHOWING SOME INSTABILITY FOCUSED ALONG THE S WA
CASCADES...SO WILL KEEP A THUNDER THREAT IN THE FCST NEAR THE CREST
DURING THE AFTERNOON AND EVENING HOURS.

BY WED...THE UPPER LOW WILL BE FURTHER EAST INTO IDAHO. THIS WILL
ALLOW A RIDGE OF HIGH PRES TO PUSH TOWARD THE PAC NW...RESULTING IN
WINDS TURNING MORE NORTHERLY AND AN EVEN SHALLOWER MARINE LAYER.
EXPECT THERE WILL STILL BE A MORNING MARINE STRATUS PUSH WED
MORNING...BUT THE THICKNESS OF THE CLOUDS SHOULD BE LESS. AS A
RESULT...EXPECT MORE SUNSHINE AND WARMER TEMPS. FCST HIGHS OVER THE
INTERIOR LOWLANDS ARE INTO THE MID 70S. THE MODELS CONTINUE TO
INDICATE SOME INSTABILITY ALONG THE CASCADE CREST WED...AND WITH THE
700 MB WINDS TURNING MORE NORTHERLY ANY STORMS THAT DO FORM COULD TRY
TO RIDE ALONG THE CREST INSTEAD OF DRIFTING EASTWARD.

THE UPPER LEVEL RIDGE AXIS WILL BE NEAR THE COAST ON THU. EXPECT A
WEAKER MARINE PUSH THU MORNING...AND MOST OF THE FCST AREA
SHOULD SEE QUITE A BIT OF SUN DURING THE LATE MORNING AND AFTERNOON.
HIGHS WILL LIKELY APPROACH 80 FOR THE MANY INTERIOR LOWLAND
LOCATIONS...WITH IS A GOOD 10 DEGREES ABOVE SEASONAL NORMALS. PYLE

.LONG TERM...THURSDAY NIGHT THROUGH MONDAY...WEAK RIDGE OVER THE
REGION WITH CONTINUED ONSHORE FLOW WILL CONTINUE BRINING MARINE
CLOUDS INLAND OVERNIGHT...BUT STRATUS SHOULD FOR THE MOST PART CLEAR
OUT BY MIDDAY ALLOWING TEMPERATURES INLAND TO REACH INTO THE 70S OR
LOW 80S FRIDAY AND SATURDAY. THE CASCADES COULD SEE AFTERNOON
SHOWERS OR EVEN POSSIBLY THUNDERSTORMS FRIDAY AFTERNOON THROUGH THE
WEEKEND. BOTH THE GFS AND ECMWF AS WELL AS THE MAJORITY OF THE GEFS
ENSEMBLE MEMBERS SUGGEST A LONGWAVE TROUGH APPROACHING SUNDAY AND
MONDAY WHICH WILL DISRUPT THE PERSISTENT PATTERN. SUNDAY AND MONDAY
WILL LIKELY SEE A SHIFT TO SOUTHWESTERLY FLOW WITH A CHANCE OF
SHOWERS ACROSS THE AREA ON MONDAY AS THE TROUGH AND ASSOCIATED LOW
PRESSURE SYSTEM MOVES CLOSER. BECAUSE OF HOW FAR OUT IN THE FORECAST
PERIOD THIS SYSTEM IS...TIMING COULD VERY WELL CHANGE AS WE APPROACH
THIS WEEKEND. -MCCOY
&&

.AVIATION...MVFR CIGS STARTING TO SLOWLY LIFT TO VFR CIGS THIS
AFTERNOON. WE MAY SEE SOME THIN SPOTS OR EVEN SEE THE CLOUDS GO
BRIEFLY SCATTERED LATE THIS AFTERNOON AND EARLY EVENING. THE
ONSHORE FLOW WILL CONTINUE TONIGHT WITH A LOW INLAND OVER
WASHINGTON AND A LOT OF STRATOCUMULUS OFF THE COAST THAT WILL
ADVECT ONSHORE. EXPECT A RETURN TO MVFR CIGS MOST AREAS TONIGHT
AND TUESDAY MORNING. CIGS WILL LIKELY LIFT TO VFR TUESDAY
AFTERNOON AND WE MAY EVEN SEE MORE AREAS GO SCATTERED IN THE
AFTERNOON.

KPDX AND APPROACHES...CIGS ARE LIFTING TO VFR 030 TO 035 THIS
AFTERNOON. CLOUDS SHOULD BECOME BKN IN THE MID TO LATE AFTERNOON
AND POSSIBLY BECOME SCATTERED FOR A COUPLE OF HOURS EITHER SIDE OF
00Z. CIGS SOLIDIFY AROUND 035 IN THE EVENING NEAR 26/03Z THEN
GRADUALLY LOWER TO MVFR OVERNIGHT TONIGHT. EXPECT CIGS TO AGAIN
LIFT TO VFR TUESDAY AFTERNOON AND POSSIBLY GOING TO SCATTERED
CLOUDS. PT

&&

.MARINE...HIGH PRES CONTINUES TO REMAIN OVER THE NORTHEAST PACIFIC
WITH LOWER PRESSURE WELL INLAND OVER THE PACIFIC NORTHWEST FOR
THE NEXT SEVERAL DAYS. NORTHWEST WINDS WILL REMAIN BELOW SMALL
CRAFT ADVISORY THRESHOLDS THROUGH THE WEEK...THOUGH A FEW GUSTS TO
AROUND 20 KT ARE POSSIBLE ALONG THE CENTRAL COAST IN THE
AFTERNOONS AND EVENINGS AT TIMES. MIXED SEAS WILL CONTINUE
THROUGH MOST OF THIS WEEK...WITH CHOPPY CONDITIONS EXPECTED AT
TIMES DUE TO A FRESH NORTHWEST SWELL MIXED WITH A LONGER PERIOD
MORE WEST TO NORTHWEST SWELL. PT
&&

.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.


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.