Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 280342
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
840 PM PDT MON APR 27 2015

.SYNOPSIS...A COLD FRONT WILL SWEEP ACROSS REGION TUE...WITH A RETURN
OF COOLER CONDITIONS AND AREAS OF RAIN. A SHOWERY PATTERN WILL BE
OVER THE AREA WED AND THU. DRIER CONDITIONS DEVELOP LATE IN THE WEEK
WITH DAYTIME TEMPERATURES SLIGHTLY ABOVE NORMAL.
&&

.SHORT TERM...TONIGHT THROUGH WEDNESDAY..
VERY PLEASANT DAY TODAY...EVEN ALONG THE COASTLINE. KAST HAD A HIGH
OF 81...JUST MISSING THE DAILY RECORD BY ONE DEGREE. OFFSHORE
LOW-LEVEL FLOW PICKED UP LATE THIS AFTERNOON AT THE WEST END OF THE
GORGE. KTTD-KDLS GRADIENT -4.2MB AS OF 03Z...YIELDING GUSTS OF 35-45
MPH AT CROWN POINT AND CORBETT. SOME OF THIS HAS FINALLY BROKEN
THROUGH TO KPDX AS THE KPDX-KTTD GRADIENT DROPPED TO 0.2 MB...WHICH
IS JUST BELOW THE 0.4 MB THRESHOLD FOR EAST WIND. THE GRADIENT
WEAKENS OVERNIGHT ACCORDING TO THE NAM AS THERMALLY-INDUCED LOW PRES
BECOMES MORE ESTABLISHED IN THE COLUMBIA BASIN...WITH LOWER PRES ALSO
ALONG THE COAST.

THE LEADING EDGE OF THE FRONT LOOKS TO BE NEAR 130W AT 03Z. WATER
VAPOR IMAGERY SUGGESTS THE UPPER TROUGH IS CONTINUING TO DEEPEN AND
THE FRONT IS BECOMING MORE PARALLEL TO THE MID AND UPPER FLOW. A
LITTLE CONCERNED TIMING MAY BE SLOWED A BIT. LATEST NAM SHOWS PRECIP
TO THE COAST AROUND 12Z TUE...WITH SOME PRE-FRONTAL INSTABILITY
SHOWERS OVER THE CASCADES. DYNAMICS ARE NOT ALL THAT IMPRESSIVE...
BUT SHOULD BE ENOUGH TO BRING A BAND OF RAIN TO THE COAST BY DAYBREAK
TUE...THEN PUSH INLAND. NOT A LOT OF RAINFALL...BUT LIKELY 0.10 TO
0.20 INCH OF RAIN...THOUGH MAY SEE LOCALLY HEAVIER AMOUNTS FOR AREAS
ON FAR N OREGON COAST/COAST RANGE AND NORTHWARD. COLD FRONT WILL PUSH
INLAND DURING THE DAY...WITH CHANGE OVER TO SHOWERY PRECIPITATION
DURING THE AFTERNOON. 850 MB TEMPS DROP FROM 12-14C 06Z TUE TO 2-7C
BY 00Z WED. PLENTY OF COLD ADVECTION DURING THE DAY SO CASCADE TEMPS
TO PEAK EARLY THEN STEADILY FALL THROUGH THE AFTERNOON.

MODELS CONTINUE TO BACK OFF ON THREAT OF SHOWERS FOR REGION LATER TUE
NIGHT AND WED. BUT WITH DECENT LATE APRIL SUNSHINE AND ANOTHER UPPER
LEVEL DISTURBANCE SCOOTING ACROSS REGION... SEEMS REASONABLE TO KEEP
LIKELY POPS FOR WED. STILL COOL WITH SEASONABLE TEMPS FOR LATE APRIL.
 WEISHAAR

.LONG TERM...THURSDAY NIGHT THROUGH MONDAY. FEW CHANGES TO THE
EXTENDED PERIOD WITH THE MODELS REMAINING IN GOOD AGREEMENT THAT
NEARLY ZONAL FLOW ALOFT WILL REMAIN IN PLACE FOR THE END OF THE WEEK
AND INTO EARLY NEXT WEEK. A FEW WEAK UPPER LEVEL DISTURBANCES MAY
PASS SOMEWHAT CLOSE TO THE REGION BUT SHOULD GENERALLY STAY WELL TO
THE NORTH IN NORTHERN WASHINGTON OR SOUTHERN CANADA. WITH A
CONTINUED TREND OF MORE ENSEMBLE MEMBERS INDICATING DRY WEATHER...
IN ADDITION TO SUPPORT FROM THE OPERATIONAL 12Z RUNS...REDUCED POPS
TO ELIMINATE SLIGHT CHANCE MENTION FOR FRIDAY THROUGH MONDAY ACROSS
THE FORECAST AREA. OVERALL...EXPECT TEMPERATURES REMAINING  CLOSE TO
NORMAL THROUGH EARLY NEXT WEEK WITH DRY WEATHER AND GENERALLY PARTLY
CLOUDY SKIES. THE NEXT ORGANIZED FRONTAL SYSTEM WILL MOVE TOWARDS
THE AREA EARLY NEXT WEEK.   CULLEN
&&

.AVIATION...VFR PREVAILING WITH MID AND HIGH CLOUDS STREAMING
ACROSS THE FORECAST AREA AHEAD OF AN APPROACHING FRONT. MARINE
STRATUS AHEAD OF THE FRONT SLOWLY ADVANCING TO THE COAST LIKELY TO
BRING LOW MFR TO IFR CIGS TO THE COAST LATE THIS EVENING. A DEEPER
MARINE LAYER DEVELOPS AND PUSHES INLAND WITH MVFR CIGS SPREADING
INLAND DURING THE MORNING. THE FRONT APPEARS TO BE SLOWING DOWN A
LITTLE AS IT BECOMES MORE PARALLEL TO THE WIND FLOW SO WILL MAKE
SOME ADJUSTMENTS TO THE TIMING IN THE 06Z TAF PACKAGE. FLIGHT
CONDITIONS SHOULD TREND TOWARD VFR LATER TUE AFTERNOON BUT
PROBABLY RETURN TO MUCH OF THE AREA LATE TUE NIGHT.

KPDX AND APPROACHES...VFR PREVAILING THROUGH ABOUT 12Z TUE THEN
INCREASING CHANCES OF MVFR CIGS FROM 12Z-20Z. VFR CONDITIONS ARE
MORE LIKELY AFTER 00Z WED.

&&

.MARINE...THE NEXT FRONT APPROACHES THE REGION TONIGHT BRINGING
WITH IT INCREASING SOUTHERLY WINDS WITH GUSTS TO 25 KT THROUGH
TOMORROW MORNING. THE FRONT APPEARS TO BE TAKING A SLOWER PACE SO
WILL ADJUST THE TIMING OF THE SMALL CRAFT ADVISORY BY A FEW HOURS.
WINDS WEAKEN AND TURN WESTERLY BEHIND THE FRONT TOMORROW
AFTERNOON. A WEAK SURFACE TROUGH LOOKS TO BRUSH BY THE WATERS ON
WED. HIGH PRESSURE RETURNS FOR THE LATTER PART OF THE WEEK...WITH
A SURFACE THERMAL LOW LIKELY BUILDING OVER THE S OREGON/N
CALIFORNIA COAST. THIS WILL LIKELY BRING ADVISORY WINDS TO THE
WATERS THIS WEEKEND.

SEAS CURRENTLY RUNNING AROUND 6 TO 7 FT. HOWEVER...A BUILDING
WESTERLY SWELL BEHIND THE FRONT WILL LIKELY PUSH SEAS ABOVE 10 FT
LATE TUE AND WED. SEAS SUBSIDE BACK TO AROUND 6 TO 7 FT LATE WED
AND LOOK TO REMAIN BELOW 10 FT THROUGH THE WEEKEND.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 11 AM PDT TUESDAY FOR
     WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR FROM 10
     TO 60 NM-WATERS FROM CASCADE HEAD TO FLORENCE OR FROM 10 TO
     60 NM.

     SMALL CRAFT ADVISORY FOR WINDS FROM 3 AM TO 11 AM PDT TUESDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD
     OR OUT 10 NM-COASTAL WATERS FROM CASCADE HEAD TO FLORENCE
     OR OUT 10 NM.

&&

$$

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.


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