Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 231033
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
330 AM PDT WED JUL 23 2014

.SYNOPSIS...A LOW PRESSURE SYSTEM WILL BRING AN INCREASING THREAT OF
RAIN SHOWERS AND THUNDERSTORMS TO THE AREA TODAY. DRIER WEATHER WITH
MORE SEASONAL TEMPERATURES ARE EXPECTED TO ARRIVE LATE THURSDAY AND
FRIDAY...BEFORE TEMPERATURES PUSH 90F LATE IN THE WEEKEND.

&&

.SHORT TERM...TODAY THROUGH FRIDAY...AFTER A QUIET PERIOD OVERNIGHT
SHOWER ACTIVITY IS ON THE INCREASE.  WATER VAPOR IMAGERY SHOWS VORT
CENTER OFF THE NRN CA COAST INTERACTING WITH AN UPPER LOW SAGGING
OVER THE WASHINGTON AND OREGON OFFSHORE WATERS.  REGIONAL RADAR
NETWORK INDICATING TWO SEPARATE BANDS OF PCPN AFFECTING THE AREA. ONE
OVER THE COAST AND COAST RANGE...AND THE OTHER MOVING INTO THE
SOUTHERN AREA OF THE CWA.  MODELS INDICATE A BROAD AREA OF LIFT
MOVING INTO THE AREA TODAY. SO HAVE INCREASED POPS TO CATEGORICAL AND
INCREASED QPF FOR TODAY AND THIS EVENING.

CONVECTION POTENTIAL FOR TODAY WILL INCREASE THROUGH THE AFTERNOON.
HAVE KEPT A MENTION OF SLIGHT CHANCE OF THUNDERSTORMS OVER THE AREA
EARLY THIS MORNING. THOUGH LOOKING AT MODEL SOUNDINGS IT APPEARS
THUNDERSTORM THREAT LOW.  HOWEVER FOR THE AFTERNOON TO EARLY EVENING
AS THE UPPER LOW NEARS THE AIR MASS DESTABILIZES...MORE TO THE NORTH
PART OF THE CWA THAN THE SOUTH...CONVECTION BECOMES MORE LIKELY.
MODEL SOUNDINGS HAVE -3 LIFTED INDEX OVER THE NORTH WILLAMETTE VALLEY
AND 0 TO 2 LI OVER THE SOUTH VALLEY. CAPE VALUES AROUND 400-600 J/KG
NORTH AND UNDER 100 J/KG SOUTH.  EQUILIBRIUM LEVELS PEAK AT AROUND
THE -30C LEVEL IN THE NORTH SO THERE IS POTENTIAL FOR FAIRLY DEEP
CONVECTION FOR HAIL DEVELOPMENT. ALSO OF NOTE IS VERTICAL WIND SHEAR
AHEAD OF THE TROUGH. CONVECTION DEVELOPMENT IN THIS ENVIRONMENT WILL
BE LESS PULSE TYPE THUNDERSTORM AND BE LONGER LIVED.  ALSO WITH A
SURFACE LOW PRESSURE LINGERING JUST OFF THE SOUTHWEST WASHINGTON
COAST THERE MAY BE A TENDENCY FOR SURFACE WINDS IN THE WILLAMETTE
VALLEY AND ALONG THE LOWER COLUMBIA RIVER TO HAVE A BIT MORE OF A S
TO SSE COMPONENT THAN OTHERWISE EXPECTED. COMBINED WITH WSW WINDS OF
25 KT AT 900MB AND 40KT AT 500MB...A RAPIDLY STRENGTHENING UPDRAFT
COULD ROTATE BRIEFLY. HOWEVER...CONFIDENCE IS VERY LOW IN THIS
ACTUALLY OCCURRING SOMEWHERE WITHIN THE CWA...BUT IT WILL STILL BE
WORTH MONITORING. THE MORE EXPECTED HAZARDS...GUSTY WINDS AND SMALL
HAIL WERE ADDED TO THE THUNDER.

ON THE FIRE FRONT...MOST LOCATIONS ACROSS THE FORECAST AREA SHOULD
SEE WETTING RAINS OF A QUARTER TO HALF INCH WITH A FEW LOCATIONS
LIKELY PUSHING AN INCH OF RAIN...PARTICULARLY ACROSS SOUTHWEST
WASHINGTON. IT SHOULD BE NOTED WETTING RAINS ARE LESS LIKELY TOWARDS
LANE COUNTY...BUT CERTAINLY APPEAR POSSIBLE WEDNESDAY.

THE UPPER LOW SHIFTS EAST OF THE CASCADES TONIGHT AND THU WITH WEAK
RIDGING DEVELOPING SO EXPECT A DRYING AND WARMING TREND HEADING INTO
THE WEEKEND.

.LONG TERM...HIGH PRESSURE WILL BUILD WESTWARD ACROSS THE CONUS
AMPLIFYING AN UPPER-LEVEL RIDGE THAT WILL SET UP OVER THE
NORTHWESTERN U.S. THIS WILL INCREASE TEMPERATURES BACK TO ABOVE
NORMAL OVER THE WEEKEND.  THERE IS A POSSIBLE DISTURBANCE THAT COULD
MOVE THROUGH AS EARLY AS SUNDAY NIGHT...BUT MUCH UNCERTAINTY EXISTS
IN THE TIMING OF THIS SYSTEM AND LOCATION.  -MCCOY

&&

.AVIATION...WIDESPREAD CHANCE FOR THUNDERSTORMS ACROSS THE REGION
GENERALLY AFTER 12Z AND EXTENDING INTO THE EVENING HOURS. COULD
SEE A LIGHTNING STRIKE OR TWO BEFORE 12Z WITH THE CURRENT BAND OF
SHOWERS AFFECTING COASTAL SITES BUT NOT LIKELY. RAIN AND MVFR
CIGS MOVE INTO THE VALLEY STARTING AROUND 12Z AT EUG AND
SPREAD NORTH THROUGH THE MORNING. COULD BE SOME IFR VSBY AT ANY
TERMINALS WHICH DO EXPERIENCE A STORM BUT CHANCES ARE LOW ENOUGH
THAT HAVE NOT INCLUDED THAT POSSIBILITY IN THE FORECAST.

KPDX AND APPROACHES...EXPECT VFR TO CONTINUE THROUGH EARLY MORNING
WITH CIGS ABOVE 4000 FT. RAIN CHANCES INCREASE AFTER 12Z WITH
CIGS LOWERING TO MVFR. 20 PERCENT CHANCE OF THUNDERSTORMS
IMPACTING KPDX AND APPROACHES AFTER 12Z AND CONTINUING THROUGH
ABOUT 03Z.


&&

.MARINE...RELATIVELY QUIET CONDITIONS OVER THE WATERS CONTINUE
TONIGHT AS THE SURFACE GRADIENT REMAINS WEAK IN BETWEEN
SYSTEMS...KEEPING WINDS 15 KT OR LESS. SEAS REMAIN 3-4 FT TONIGHT
WITH A CONTINUED SMALL W-NW SWELL.

A LOW PRESSURE SYSTEM WILL PASS THROUGH THE WATERS. MODELS
CONTINUE TO INDICATE AN AREA OF WIND GUSTS TO 25 KT LATE THIS
AFTERNOON THROUGH TONIGHT IN THE NORTHERN OREGON OFFSHORE
WATERS...BUT WITH SUCH MARGINAL NUMBERS WILL HOLD OFF FOR NOW ON
ISSUING AN SCA. LATER THIS WEEK...HIGH PRES REDEVELOPS OVER NE PAC
AS THERMAL LOW PRES BUILDS OVER N CALIFORNIA. THIS WILL BRING A
RETURN TO GUSTY N WINDS AND STEEP WIND DRIVEN SEAS...PARTICULARLY
IN THE LATE AFTERNOON AND EVENING HOURS FRI THROUGH THE WEEKEND.

&&

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

&&

$$


MORE WEATHER INFORMATION ONLINE AT...HTTP://WEATHER.GOV/PORTLAND


INTERACT WITH US VIA SOCIAL MEDIA
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
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.
COMMONLY REFERRED TO AS THE FORECAST AREA.



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