Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 040505
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
858 PM PST TUE MAR  3 2015

.SYNOPSIS...HIGH PRESSURE WILL DOMINATE THIS WEEK AND MAINTAIN A DRY
WEATHER PATTERN. IT WILL BE COLD AGAIN TONIGHT...ESPECIALLY IN THE
INTERIOR VALLEYS. DAYTIME TEMPERATURES WILL GRADUALLY WARM EACH DAY
THIS WEEK WITH VALLEY HIGH TEMPERATURES CLIMBING WELL INTO THE 60S
OVER THE WEEKEND.

&&

.UPDATE...IN THE SHORT TERM...ADDED PATCHY FOG WORDING TO THE COASTAL
VALLEYS AND REMOVED FOG FROM THE NORTHERN WILLAMETTE VALLEY BASED ON
CURRENT DEWPOINT DEPRESSIONS AND DEWPOINT VALUES. TEMPERATURES THIS
EVENING ARE GENERALLY RUNNING A COUPLE OF DEGREES COLDER THAN THIS
TIME YESTERDAY SO THE CURRENT LOW TEMPERATURE FORECAST FOR
TONIGHT LOOKS ON TRACK. OVERALL...INHERITED FORECAST ONCE AGAIN
APPEARS ON TRACK IN THE LONGER TERM...AS LATEST MODEL GUIDANCE SHOWS
LITTLE CHANGE WITH TEMPERATURES WARMING WELL INTO THE 60S BY THIS
WEEKEND.

SEE OUR SOCIAL MEDIA OUTLETS FOR SOME OF THE CLIMATE FACTS OF LATE.
WE HAVE BEEN IN MASSIVE OUTLIER MODE FOR MUCH OF THE LAST 8
MONTHS...SOMETHING THAT IS NOT EASY TO DO WHEN CROSSING BETWEEN THE
SUMMER AND WINTER MONTHS. /NEUMAN

PREVIOUS DISCUSSION BELOW...

.SHORT TERM...TONIGHT THROUGH FRIDAY...HIGH PRESSURE AND DRY
CONDITIONS WILL PREVAIL THROUGH THE SHORT TERM AND BEYOND.
LARGE-SCALE FEATURES ON WATER VAPOR LOOP INCLUDE A HIGH AMPLITUDE
RIDGE CENTERED JUST INSIDE 140W...AN UPPER LOW NEAR BAJA AND AN UPPER
LEVEL TROUGH AXIS EXTENDING FROM THE DAKOTAS TO SRN NEVADA. VISIBLE
IMAGERY SHOWING SOME SMALL CUMULUS DEVELOPING OVER THE CASCADE
FOOTHILLS AND OREGON COAST RANGE EARLY THIS AFTERNOON.

EARLY-AFTERNOON TEMPERATURES RUNNING NEAR OR SLIGHTLY HIGHER THAN 24
HOURS AGO. THUS...FORECAST MAX TEMPS FOR TODAY LOOK TO BE ON TRACK.
MODEL 850 MB TEMPS FOR TODAY FORECAST TO BE JUST A TOUCH HIGHER THAN
YESTERDAY. THE 12Z MON NAM RUN APPEARED TO BE A LITTLE TOO STRONG
WITH THE FORECAST OFFSHORE GRADIENT THROUGH THE COLUMBIA GORGE. THE
KTTD-KDLS PEAKED AT -1.9 MB AT 16Z...ABOUT ONE MB LOWER THAN THE 12Z
MON GUIDANCE. THE GRADIENT IS WEAKENING THIS AFTERNOON...AS EXPECTED.
TODAYS 12Z RUN SHOWS THE GRADIENT PICKING UP JUST A BIT TONIGHT...
CLOSE TO WHAT IT WAS THIS MORNING. EXPECTING JUST PATCHY FOG TONIGHT
IN THE USUAL LOCATIONS. THERE MAY ABE ENOUGH OFFSHORE DRIFT ALONG THE
IMMEDIATE COAST TO PREVENT FOG...BUT WOULD NOT BE SURPRISED TO SEE
SOME FORM NEAR BAYS...SUCH AS KTMK AND KAST. ANOTHER COLD NIGHT IN
THE INTERIOR VALLEYS WITH MIN TEMPS SIMILAR TO THIS MORNING...
ALTHOUGH SLOPES AND RIDGES WILL WARM JUST A BIT AS SHALLOW
INVERSIONS DEVELOP.

NAM SHOWS ANOTHER VERLY WEAK UPPER-LEVEL DISTURBANCE MOVING ACORSS
THE AREA LATE TONIGHT AND WED MORNING FOR SOME HIGH CLOUDS. NAM
CROSS-SECTION FROM KAST THROUGH THE GORGE NOT AS SUPPORTIVE WITH HIGH
CLOUDS TONIGHT COMPARED TO THE PAST COUPLE OF RUNS. OTHER THAN
THAT...850 MB TEMPS SLOWLY WARM THROUGH THE SHORT TERM. THE UPPER
RIDGE WILL FLATTEN THURSDAY AS AN UPPER TROUGH MOVES INLAND NORTH OF
WASHINGTON. THERE MAY BE SOME CIRRUS WITH THIS FEATURE...BUT WILL
OTHERWISE HAVE LITTLE IMPACT TO THE WEATHER. NAM SUGGESTS THAT THERE
WILL BE A WIND REVERSAL ALONG THE COAST THURSDAY NIGHT. RESULTANT
ONSHORE LOW-LEVEL FLOW WILL LIKELY COOL THE COASTAL STRIP A COUPLE
DEGREES FRI. MAX TEMPS FRI FORECAST TO GET INTO THE LOWER 60S AT MANY
INLAND LOWLAND LOCATIONS. WEISHAAR

.LONG TERM...FRIDAY NIGHT THROUGH TUESDAY...THE UPPER RIDGE WILL
GRADUALLY SHIFT FROM BEING CENTERED NEAR 130W LATE THIS WEEK TO THEN
EXPAND EASTWARD ACROSS THE WESTERN CONUS THROUGH EARLY NEXT WEEK.
MAIN CHANGE WAS TO BUMP TEMPERATURES UP ANOTHER COUPLE DEGREES FOR
THE WEEKEND BRINGING MOST VALLEY LOCATIONS INTO THE MID 60S AND THE
COASTAL AREAS TO THE UPPER 50S TO LOWER 60S. NOT MUCH SURFACE
PRESSURE GRADIENT TO SPEAK OF OR ELSE WE COULD HAVE EASILY HIT THE
MAGICAL 70 DEGREE MARK IF WE HAD OFFSHORE FLOW. AS THE UPPER RIDGE
EXPANDS EASTWARD MONDAY...MODELS ARE SHOWING A SOMEWHAT AGGRESSIVE
TROUGH SWING SOUTH FROM ALASKA AND DRAG A CUTOFF LOW OUT TOWARD 150W
TOWARD THE PACNW COAST. HAVE DELAYED ANY MENTION OF RAIN UNTIL
TUESDAY AS MEDIUM RANGE MODELS ARE IN MODEST AGREEMENT IN BRINGING
THE FILLING UPPER LOW CLOSE ENOUGH TO THE COAST TO SPREAD RAIN WELL
INLAND TUESDAY NIGHT. AM SOMEWHAT SKEPTICAL THIS WILL FULLY COME TO
FRUITION AS THE MODELS INDICATE AS WE HAVE SEEN THIS TIME AND AGAIN
THIS WINTER AT THAT TIME RANGE. THIS ONE IS A LITTLE DIFFERENT,
HOWEVER, AS THE EASTERN HALF OF THE CONUS APPEARS TO BE LOSING ITS
SEMI-PERSISTENT TROUGH WHICH COULD OPEN THE DOOR AS ADVERTISED.
ANOTHER FACTOR IS THE TIMING OF THE ALASKA TROUGH. IF IT`S MUCH
FASTER OR SLOWER AT SWINGING ACROSS THE NORTH THEN THE TIMING WILL
BE OFF AND IT MAY NOT GATHER THE CUTOFF LOW AND LEAVE IT WELL
OFFSHORE. /JBONK

&&

.AVIATION...MAINLY VFR CONDITIONS EXPECTED THROUGH 06Z THU UNDER
DRY AND STABLE NORTHERLY FLOW ALOFT. WINDS WILL CONTINUE TO DROP
OFF OVER THE NEXT COUPLE OF HOURS...AND WILL BE LIGHT TONIGHT
WITH WEAK SURFACE PRESSURE GRADIENT. WITH LITTLE WIND AND CLEAR
SKIES...EXPECT EFFICIENT RADIATIONAL COOLING AGAIN TONIGHT. THIS
MAY ALLOW SHALLOW PATCHY FOG TO FORM ALONG THE COAST AND IN THE
SOUTHERN WILLAMETTE VALLEY INCLUDING KEUG. ANY FOG THAT DOES
MANAGE TO FORM SHOULD DISSIPATE QUICKLY BY MID MORNING

KPDX AND APPROACHES...VFR CONTINUES THROUGH THE PERIOD UNDER N-NW
FLOW ALOFT. PYLE

&&

.MARINE...HIGH PRESSURE FIRMLY IN CONTROL OVER THE REGION TONIGHT AND
WILL REMAIN THROUGH MUCH OF THE WEEK. SURFACE PRESSURE GRADIENT
REMAINS FAIRLY WEAK WHICH WILL KEEP LIGHT NORTHERLY WINDS AT OR
BELOW 15 KT FOR THE NEXT SEVERAL DAYS. THE ONE EXCEPTION WOULD BE
A FEW STRONGER GUSTS UP AROUND 20 KT OVER THE CENTRAL OREGON
WATERS MAINLY SOUTH OF NEWPORT AS A WEAK THERMAL TROUGH BUILDS UP
THE COAST INTO SOUTHERN OR CENTRAL OREGON. SOME MODELS SUGGEST A
SOUTHERLY WIND REVERSAL MAY REACH THE CENTRAL OREGON WATERS BY
LATE IN THE WEEK. SEAS REMAIN 3 TO 5 FT AND FAIRLY SHORT PERIOD.
SEAS WILL HOLD AROUND 5 FT THROUGH THE WEEKEND...WITH THE SWELL
INCREASINGLY COMPRISED OF NUMEROUS SMALL SWELLS AT VARYING
DIRECTION AND PERIOD. PYLE/CULLEN

&&

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

&&

$$

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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