Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 300358
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
854 PM PDT SUN MAR 29 2015

.SYNOPSIS...MILD AND MOSTLY DRY WEATHER WILL CONTINUE THROUGH MON AS
A FLAT UPPER LEVEL RIDGE REMAINS OVER THE PAC NW. A COLD FRONT WILL
PUSH ACROSS THE REGION MONDAY EVENING USHERING IN A MUCH COOLER AND
MORE SEASONABLE AIR MASS ALONG WITH SHOWERS AND LOWER SNOW LEVELS
THAT WILL LAST THROUGH THE END OF THE WEEK.

&&

.SHORT TERM...OCCASIONAL LIGHT RAIN OR SPRINKLES CONTINUE ALONG THE
WASHINGTON COAST THIS EVENING...BUT THIS WILL LIFT N A BIT MORE
OVERNIGHT. BUT MODELS DIFFER ON HOW FAR N. SO WILL MAINTAIN LOW POPS
FOR THAT AREA INTO MON MORNING. ELSEWHERE EXPECT DRY WEATHER
TO CONTINUE THROUGH MON AS THE FLAT UPPER RIDGE HOLDS. GOOD
RADIATIONAL CONDITIONS TONIGHT OVER MUCH OF THE SE PART OF THE ARE
WILL ALLOW TEMPS TO DIP DOWN CLOSE TO NORMAL...WITH ABOVE NORMAL
AFTERNOON TEMPS RETURNING MON.

MODELS REMAIN SIMILAR WITH THE NEXT SYSTEM ARRIVING MON NIGHT...
PUSHING A COLD FRONT INLAND DURING THE EVENING. TIME HEIGHT CROSS
SECTIONS SHOW STRONG LIFT AND MOISTURE BELOW 500 MB TO JUSTIFY
CATEGORICAL POPS FOR MON NIGHT. THIS USHERS IN A COOLER UNSTABLE AIR
MASS FOR TUE AND CONTINUING INTO WED AS A COLD UPPER TROUGH MOVES
ACROSS. WITH H8 TEMPS EXPECTED TO DROP A FEW DEGREES BELOW ZERO C
SURFACE HIGH TUE AND WED ARE LIKELY TO COME BACK DOWN CLOSER TO
NORMAL. MODEL SOUNDINGS INDICATING GOOD INSTABILITY TUE...AT LEAST
BY PACNW STANDARDS...WITH GFS AND NAM CAPE VALUES MAXING OUT IN
TRIPLE DIGITS. WITH THE TOP OF THE UNSTABLE LAYER APPROACHING 20K FT
IN ADDITION TO SHOWERS LIKELY WILL NEED TO INCLUDE A CHANCE FOR
THUNDER IN THE AFTERNOON AND EVENING AS THE COLD TROUGH ALOFT MOVES
ACROSS. ANOTHER SHORTWAVE WITH A COLD POOL ALOFT...H5 TEMPS AGAIN
DOWN NEAR -32 DEG...WILL KEEP SLIGHT CHANCE FOR THUNDER AGAIN WED.

.LONG TERM...THE COLD UPPER TROUGH OF MIDWEEK IS DEPICTED BY MODELS
EXITING THE REGION THU...WITH A WEAK RIDGE MOVING ACROSS LATE THU
AND FRI. GFS AND ECMWF BOTH INDICATE SOME LIGHT RESIDUAL
PRECIPITATION THU...BUT WITH UPPER DYNAMICS SHIFTED E AND MAINLY
JUST SOME SHALLOW LOW LEVEL MOISTURE LEFT WILL CUT BACK ON POPS A
BIT FOR THU. 12Z MODEL RUNS ALSO A BIT SLOWER IN DIGGING IN THE NEXT
TROUGH AND COLD FRONT LATE FRI SO WILL BACK OFF ON POPS ACROSS THE S
PART OF THE FORECAST AREA FRI. OVER THE WEEKEND MODELS NOW TENDING
TO DIG THE NEXT TROUGH DOWN OFF THE COAST...CLOSE ENOUGH TO PUSH A
FRONT THROUGH SAT AND KEEP THE REGION IN A COOL UNSTABLE AIR MASS
FOR SUN.
&&

.AVIATION...VFR CONDITIONS EXPECTED TO CONTINUE THROUGH TONIGHT
WITH VARIABLE HIGH CLOUDS. NEAR KAST SCT-BKN CIGS NEAR 2500 FT
KAST WILL PROBABLY AFFECT THAT AREA THROUGH THE NIGHT BUT SHOULD
BE GONE MID MIDDAY MON. ANOTHER CONCERN IS IFR STRATUS ON THE
COAST WORKING ITS WAY UP TO KAST LATER TONIGHT. LAST GOOD
VISIBLE SAT IMAGE SHOWED STRATUS HAD DEVELOPED AS FAR NORTH AS
PACIFIC CITY. SO IT SEEMS PROBABLE SOME IFR CIGS WILL MAKE IT TO
KAST LATER TONIGHT GIVEN THE LIGHT ONSHORE FLOW. THE LOW STRATUS
SHOULD PULL OFFSHORE A LITTLE BY MIDDAY MON.

ELSEWHERE...VFR LIKELY PERSISTS WITH VARIABLE HIGH CLOUDS. MAY
AGAIN SEE SHALLOW FOG OR STRATUS DEVELOP LATE TONIGHT/EARLY MON
PARTICULARLY IN THE SOUTH VALLEY AND IN MORE FOG-PRONE LOCATIONS.

KPDX AND APPROACHES...VFR CONDITIONS CONTINUE TONIGHT AND MONDAY.
/26

&&

.MARINE...SOUTHERLY WINDS EXPECTED TO INCREASE ON MONDAY AHEAD OF
THE NEXT FRONTAL SYSTEM THAT WILL CROSS THE WATERS TOMORROW. SMALL
CRAFT ADVISORY FOR WINDS WILL BEGIN AT 5 AM IN THE NORTH WHERE
WINDS WILL INCREASE TO 20 KT. EXPECT WINDS TO PEAK AROUND 25 KT
WITH GUSTS TO 30 KT DURING THE LATE AFTERNOON AND EVENING HOURS.
MODELS ARE IN GOOD AGREEMENT THAT STRONGER WINDS WILL NOT ARRIVE
IN THE SOUTHERN WATERS UNTIL THE AFTERNOON SO THE ADVISORY BEGINS
AT 2 PM FOR THE CENTRAL OREGON WATERS. WINDS SHOULD EASE BY 11 PM
ACROSS ALL WATERS.

MEANWHILE SEAS REMAIN AROUND 10 TO 11 FT OVER NORTHERN WATER.
SPARSE OBSERVATIONS MAKE IT A BIT TOUGHER TO DISCERN IF SEAS HAVE
DROPPED OFF A BIT IN THE SOUTH...SO ELECTED TO MAINTAIN THE
ADVISORY FOR HAZARDOUS SEAS AS IS...THROUGH 5 AM. THIS WILL LIKELY
NEED TO BE EXTENDED IN THE NORTH...BUT SUSPECT ENOUGH OF A RESPITE
IN SEAS WILL OCCUR IN THE SOUTH TO LET IT EXPIRE. HOWEVER...SEAS
AGAIN WILL BUILD TO NEAR 12 FT ACROSS ALL WATERS BEHIND THE FRONT
AND INTO TUESDAY. CULLEN

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS TONIGHT ON ALL
  COASTAL WATERS.
     SMALL CRAFT ADVISORY FOR WINDS FOR 5 AM TO 11 PM MON ON
  COASTAL WATERS FROM CASCADE HEAD TO FLORENCE.
     SMALL CRAFT ADVISORY FOR WINDS FOR 2 PM TO 11 PM MON ON
  COASTAL WATERS FROM CASCADE HEAD TO FLORENCE.
     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR
  TONIGHT...AND AGAIN MON AFTERNOON.

&&

$$

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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