000
FXUS66 KPQR 170315
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
813 PM PDT THU MAY 16 2013

.SYNOPSIS...WEAK LOW PRESSURE OFFSHORE CONTINUES TO SPREAD SHOWERS
ACROSS WESTERN OREGON THIS EVENING. THIS SYSTEM WILL WEAKEN FOR
DECREASING SHOWERS FRIDAY. TRANSITORY HIGH PRESSURE MAY BRING A
BRIEF BREAK IN THE SHOWERS FRIDAY NIGHT BEFORE THE NEXT SYSTEM BRINGS
ANOTHER DECENT CHANCE FOR RAIN SATURDAY AND LINGERING SHOWERS 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 SUNDAY...SHOWERS CONTINUE TO SPREAD
NORTH THROUGH THE VALLEY AND ALONG THE CASCADES...WITH SOME DRIZZLE
ALONG THE COAST AS WELL. THESE HAVE GENERALLY BECOME LIGHTER THAN
THOSE SEEN EARLIER IN THE DAY...AND LIGHTNING HAS BEEN CONFINED JUST
EAST OF THE CASCADE CREST IN SW WASHINGTON...MAINLY NEAR GOLDENDALE.
THAT SAID WITH RELATIVELY HIGH MOISTURE CONTENT...STRONGER SHOWERS
WILL OCCASIONALLY PRODUCE HEAVIER DOWNPOURS...ESPECIALLY THIS
EVENING.  WV/IR IMAGERY SHOWS THE DEFORMATION BAND ASSOCIATED WITH
THE UPPER TROUGH PIVOTING OVER THE AREA WHILE THE BASE OF THE UPPER
TROUGH HEADS INTO SW OR/NW CA. SCATTERED SHOWERS WILL CONTINUE
TONIGHT...AND HAVE TRIED TO ACCENTUATE THE POP FORECAST THE N OR/S
WA CASCADES AND THE NORTH VALLEY AND BACK NW INTO COWLITZ COUNTY AND
THE WILLAPA HILLS AS THE DEFORMATION AXIS BECOMES SE-NW ORIENTED.
EXPECT ENOUGH MOISTURE AND INSTABILITY ON FRIDAY DUE TO UPPER TROUGH
LINGERING ACROSS THE PAC NW AND NOTHING TO SCOUR OUT THE LOWER LEVEL
MOISTURE. KMD

REST OF THE SHORT TERM DISCUSSION UNCHANGED...NAM BUFR SOUNDINGS SHOW
EVEN SHALLOWER INSTABILITY FRIDAY AS THE CAPPING INVERSION LOWERS TO
600-700 MB. THIS WILL LIMIT SHOWERS FRIDAY DESPITE A LITTLE MORE
SUNSHINE...BUT THERE WILL STILL BE ENOUGH INSTABILITY FOR SCATTERED
SHOWERS THROUGHOUT THE DAY. THESE WILL DISSIPATE FRI EVENING AS HIGH
PRESSURE MAY BRING A BRIEF BREAK IN THE PRECIPITATION. HOWEVER THE
NEXT SYSTEM NOW NEAR 150W WILL LIKELY SPREAD RAIN BACK ACROSS THE
DISTRICT SATURDAY. AS ADVERTISED IN THE MORNING DISCUSSION WE RAISED
POPS QUITE A BIT FOR SATURDAY AS A RESULT. QPF SHOULD BE MODEST WITH
AROUND 0.25 INCH IN THE VALLEYS AND UP TO 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 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.WEAGLE

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...AFTER A BRIEF BREAK OF
POTENTIALLY SUNNY AND SEASONABLE WEATHER MONDAY...IT APPEARS AN
EXTENDED COOL AND UNSETTLED PERIOD IS BECOMING INCREASINGLY LIKELY
FOR MIDWEEK. MODELS ARE SHOWING RELATIVELY GOOD AGREEMENT THAT A COLD
AND CLOSED UPPER LOW WILL DIG DOWN FROM ALASKA...SETTLING SOMEWHERE
NEAR THE PAC NW TUE AND LINGERING THROUGH THURSDAY. COLD AIR ALOFT
WILL KEEP THE AIR MASS UNSTABLE...WITH COOL SHOWERY WEATHER AND
POSSIBLY EVEN A THUNDERSTORM OR TWO DEPENDING ON HOW THINGS EVOLVE.

FAIRLY HIGH DEGREE OF CONFIDENCE OF BELOW NORMAL TEMPS DURING THIS
PERIOD ALONG WITH HIT AND MISS SHOWERS. SNOW LEVELS MAY VERY WELL GET
BELOW THE PASSES...BUT WE WILL PLAY IT CONSERVATIVE FOR NOW WITH SNOW
LEVELS BOTTOMING OUT AROUND 4000-4500 FT MIDWEEK. IF MODELS CONTINUE
TO BRING THE CENTER OF THE COLD POOL OVER THE PAC NW...THESE SNOW
LEVELS WILL NEED TO COME DOWN A BIT AND POSSIBLY AS LOW AS 2000-3000
FEET.  WEAGLE

&&

.AVIATION...SHOWERY AIR MASS OVER REGION THIS EVENING...WITH
GENERALLY VFR CONDITIONS. FEW ISOLATED TSTORMS OVER UNTIL 06Z.
SHOWERS WILL DECREASE OVERNIGHT...BUT EXPECT LOWER CLOUDS TO
FORM. SEEMS LIKELY THAT WILL HAVE MIX OF MVFR AND LOW VFR CIGS
INTO FRI...BUT WITH MOIST MILD AIR MASS SEEMS GOOD BET THAT MVFR
WILL BECOME MORE WIDESPREAD BETWEEN 09Z AND 11Z...AND PERSIST WELL
INTO FRI AM.

KPDX AND APPROACHES...VFR CONDITIONS WITH SCATTERED SHOWERS
THROUGH 07Z. AFTERWARDS...MIX OF LOW VFR AND MVFR CIGS...MOSTLY
AT 2000 TO 2500 FT LATER TONIGHT INTO FRI AM. SHOULD RETURN TO VFR
CIGS BY 20Z FRI AS AIR MASS DESTABILIZES A BIT.      ROCKEY.
&&

.MARINE...WEAK LOW PRES OVER THE COASTAL WATERS TONIGHT AND FRI.
THIS KEEPS WINDS 10 TO 15 KT RANGE...WITH SEAS NEAR 5 FT.

ANOTHER FRONT ARRIVES SAT...WITH WINDS PICKING UP A BIT AGAIN BUT
LOOKS AS IF WINDS REMAIN 20 KT OR LESS...BUT PERHAPS MAY REACH 20
TO 25 KT OVER THE N COASTAL WATERS SAT NIGHT. SEAS EXPECTED TO
STAY IN THE 4 TO 7 FT RANGE THIS WEEKEND.
&&

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

$$

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.