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 190417
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
917 PM PDT FRI APR 18 2014

.SYNOPSIS...A PACIFIC FRONTAL SYSTEM WAS OFF THE COAST...AND WILL
APPROACH THE COAST LATE TONIGHT AND MOVE THROUGH SOUTHWEST WASHINGTON
AND NORTHWEST OREGON ON SATURDAY. THE FRONT WILL BE EAST OF THE
CASCADES BY LATE SATURDAY AFTERNOON OR EARLY SATURDAY EVENING.
SHOWERS WILL DECREASE SATURDAY NIGHT AS THE PARENT UPPER TROUGH
MOVES EAST AS WELL. WEAK HIGHER PRESSURE WILL MOVE IN SUNDAY FOR
GENERALLY DRY WEATHER ON EASTER...EXCEPT SOME MOISTURE MAY BRUSH THE
FAR NORTH COAST ZONES. THE NEXT FRONT WILL BECOME NORTH SOUTH
ORIENTED SUNDAY NIGHT AND STALL OFF THE COAST AS ENERGY DIGS TOWARD
CALIFORNIA FOR MORE MOSTLY DRY WEATHER...BUT THEN MOVE ONSHORE
MONDAY AND TUESDAY FOR MORE RAIN OR SHOWERS. THE REMAINDER OF NEXT
WEEK LOOKS UNSETTLED AS MORE PRECIPITATION MOVES IN AT TIMES.
&&

.SHORT TERM...TONIGHT THROUGH MONDAY...AFTER A DRY DAY TODAY...
ATTENTION TURNS TO THE NEXT FRONTAL SYSTEM THAT IS OFF THE COAST AND
WILL APPROACH THE COAST LATE TONIGHT. HIGHER CLOUDS WILL CONTINUE TO
INCREASE OVER THE AREA AND LOWER OVERNIGHT...AND THIS WILL LIKELY
PREVENT MUCH IF ANY FOG OR LOW CLOUDS FROM FORMING LATER TONIGHT.
PRECIPITATION WILL BE CLOSE TO THE COAST BY LATE TONIGHT.

THE FRONT AND THE PRECIPITATION WILL MOVE THROUGH SOUTHWEST
WASHINGTON AND NORTHWEST OREGON SATURDAY. EXPECT PRECIPITATION TO
BEGIN ACROSS THE INLAND AREAS FAIRLY EARLY IN THE MORNING...SO
OVERALL SATURDAY WILL BE PRETTY WET MOST AREAS. THE FRONT WILL BE
EAST OF THE CASCADES BY EVENING...AND POSSIBLY BY LATE AFTERNOON.
PRECIPITATION AMOUNTS SHOULD REMAIN ON THE MODEST SIDE...BUT ALL
AREAS SHOULD GET SOME MEASURABLE PRECIPITATION.

THE UPPER TROUGH MOVES THROUGH IN THE LATE AFTERNOON AND EARLY
EVENING AND MAY BRUSH THE NORTHERN AREAS...SAY NORTH OF ABOUT SALEM
AND TILLAMOOK OR PERHAPS A BIT NORTH OF THAT WITH A FEW MORE SHOWERS
THAN FARTHER SOUTH...THEN THE SHOWERS SHOULD DRAMATICALLY DECREASE
ALL AREAS THE REMAINDER OF SATURDAY NIGHT.

A FLAT UPPER RIDGE WILL BRING GENERALLY DRY WEATHER TO MOST OF THE
FORECAST AREA ON EASTERN SUNDAY. SOME MOISTURE MAY BRUSH THE SOUTH
WASHINGTON COAST WITH A FEW SHOWERS LATER SUNDAY...BUT THIS IS NOT
CERTAIN.

THE NEXT FRONT STALLS OFF THE COAST SUNDAY NIGHT...BECOMING MORE
NORTH TO SOUTH ORIENTED AS ENERGY FROM THE PARENT UPPER TROUGH DIGS
SOUTH TOWARD CALIFORNIA. THE SYSTEM THEN BEGINS TO PUSH ONSHORE
MONDAY AND ESPECIALLY MONDAY NIGHT WITH MORE SHOWERS. THE MODELS ARE
LOOKING CONVECTIVE IN THE INCREASING SOUTHERLY FLOW ALOFT...WHICH IN
APRIL BEGINS TO LOOK MORE LIKE A THUNDERSTORM PATTERN. MODEL LIFTED
INDICES FALL BELOW ZERO OVER THE CASCADES AND IN CENTRAL OREGON LATE
MONDAY AND MONDAY EVENING...SO WE MAY NEED TO CONSIDER ADDING
THUNDER TO OUR CASCADE ZONES FOR LATE MONDAY AND MONDAY EVENING AS
WE GET CLOSER TO THIS EVENT. TOLLESON

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS...
MONDAY NIGHT THROUGH THURSDAY...FLOW CONTINUES TO AMPLIFY SUNDAY
NIGHT AND THIS WILL ORIENT THE COLD FRONT OFFSHORE MORE NORTH TO
SOUTH...THUS ANY PRECIPITATION WILL REMAIN WELL OFFSHORE SUNDAY
NIGHT. THE COLD FRONT FINALLY GETS A SHOVE AS THE UPPER JET NOSES
INTO THE AREA. PRECIPITATION IS MAINLY TIED TO THE FRONT...BUT WITH
THE MARGINALLY UNSTABLE SW FLOW...MODELS SHOW THAT THERE COULD BE
SOME SHOWERS IN THE AFTERNOON MAINLY FOR THE CASCADES...AS MID LEVEL
LAPSE RATES HOVER IN THE 6 TO 7 DEG/KM RANGE. INSTABILITY PARAMETERS
ARE NOT THAT IMPRESSIVE...SO THUNDER POTENTIAL LOOKS LOW AT THIS
TIME.

LOOKS LIKE TUE AND WED WILL BE CHARACTERIZED BY COOL AND DAMP
CONDITIONS AS THE DEEP UPPER LOW MIGRATES ACROSS THE PAC NW AND INTO
THE NRN ROCKIES. AFTER THE FIRST LARGE UPPER TROUGH CLEARS LATE
TUESDAY NIGHT AND MAYBE A BREAK IN SHOWERS WEDNESDAY...ANOTHER DEEP
UPPER LOW WILL SPREAD SEVERAL WAVES OF SHOWER ACTIVITY THROUGH THE
AREA FOR THE LATTER HALF OF THE WEEK.. /KMD
&&

.AVIATION...VFR PREVAILING THROUGH MOST OF TONIGHT. A COLD FRONT IS
FORECAST TO REACH THE COAST AROUND MID MORNING SAT...AND TO THE
INTERIOR VALLEYS AROUND MIDDAY. EXPECT MVFR CIGS AROUND 12Z-15Z SAT
AT THE COAST AND 18Z-20Z SAT AT INLAND TAF SITES. CONDITIONS TRENDING
TOWARD VFR LATER SAT AFTERNOON.

KPDX AND APPROACHES...VFR EXPECTED THROUGH EARLY SAT MORNING THEN
MVFR CIGS BECOMING LIKELY BY 18Z SAT AS A COLD FRONT APPROACHES THE
AREA.
&&

.MARINE...A RELATIVELY QUIET PERIOD THIS EVENING WITH WEAK HIGH OVER
THE WATERS. THE HIGH PRES GIVES WAY TO A FRONT LATER TONIGHT WHICH
SHOULD BRING SMALL CRAFT ADVISORY WINDS OVER ALL WATERS LATER TONIGHT
AND SAT. COULD SEE SOME GUSTS 30-35 KT AS THE FRONT MOVES
THROUGH...MOVING ASHORE AROUND SUNRISE SAT. WINDS THEN DIMINISH FROM
SOUTH TO NORTH SAT AFTERNOON AND NIGHT.

A LARGE SWELL TRAIN WILL FOLLOW THE FRONT SAT EVENING INTO SUN. SEAS
APPEAR ON TRACK TO RAPIDLY BUILD TO 17 TO 20 FT AT 16 SECONDS AROUND
11 PM SAT NIGHT...PEAKING BETWEEN MIDNIGHT AND 5 AM SUN. SEAS WILL
SLOWLY SUBSIDE SUN MORNING BUT REMAIN IN THE 13 TO 16 FT RANGE
THROUGH SUN NIGHT...AND TO 10 FT LATE MON. A SMALL CRAFT ADVISORY FOR
SEAS HAS BEEN ISSUED FOR THIS SWELL TRAIN.

A HIGH SURF ADVISORY CONTINUES FOR LATER SAT NIGHT THROUGH SUN
MORNING FOR THE SOUTH WASHINGTON AND NORTH OREGON COASTS. THE CENTRAL
COAST WILL PROBABLY REMAIN JUST UNDER ADVISORY CRITERIA.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HIGH SURF ADVISORY FROM 10 PM SATURDAY TO 10 AM PDT SUNDAY FOR
     NORTH OREGON COAST.

WA...HIGH SURF ADVISORY FROM 10 PM SATURDAY TO 10 AM PDT SUNDAY FOR
     SOUTH WASHINGTON COAST.

PZ...SMALL CRAFT ADVISORY FOR WINDS FROM 2 AM TO 9 PM PDT SATURDAY
     FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO CASCADE HEAD OR
     OUT 60 NM.

     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 4 PM SATURDAY TO 6
     AM PDT MONDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
     FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR WINDS FROM 2 AM TO 4 PM PDT SATURDAY
     FOR COASTAL WATERS FROM CASCADE HEAD OR TO FLORENCE OR OUT 60
     NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 5 AM TO
     10 AM PDT SATURDAY.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 4 PM TO
     11 PM PDT SATURDAY.

&&

$$

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..


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