Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 290351 RRA
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND
846 PM PDT THU MAY 28 2015

.SYNOPSIS...HIGH PRESSURE ALOFT WILL BE OVER THE FORECAST AREA
THROUGH SATURDAY. MEANWHILE A CLOSED UPPER LEVEL LOW WILL MOVE INTO
BRITISH COLUMBIA. WARMER THAN AVERAGE WEATHER WILL LAST THROUGH AT
LEAST SATURDAY...WITH HIGH TEMPERATURES MOST LIKELY PEAKING ON
FRIDAY. THE UPPER RIDGE STARTS TO FLATTEN FRI AND SAT. THE HIGHER
CASCADES WILL CONTINUE TO HAVE A SLIM THREAT OF LATE-DAY
THUNDERSTORMS THE NEXT COUPLE OF DAYS. THE NEXT UPPER LOW SWINGS
TOWARD THE OREGON COAST SUNDAY...RESULTING IN A LITTLE MORE COOLING
BUT A BETTER CHANCE OF CASCADE THUNDERSTORMS. A MUCH DEEPER MARINE
LAYER IS EXPECTED OVER THE AREA EARLY NEXT WEEK.

&&

.UPDATE...A FEW THUNDERSTORMS DEVELOPED ALONG THE CASCADE CREST THIS
AFTERNOON BETWEEN SANTIAM PASS AND TIMOTHY LAKE.  SOME LIKELY
CONTAINED SMALL HAIL BUT WITH LITTLE MOVEMENT TO THE STORM CELLS
THERE WAS LIKELY A GOOD DRENCHING UNDER THEM. OTHERWISE FAIR
CONDITIONS ACROSS THE AREA EXCEPT FOR THE COAST WHERE SHALLOW MARINE
STRATUS CONTINUES.  AGAIN SOME OF THE STATUS WILL WORK INTO GAPS IN
THE COASTAL TERRAIN AND UP THE LOWER COLUMBIA RIVER TO THE PORTLAND
AREA.  MODELS SUGGEST ANOTHER ROUND OF CONVECTION OVER THE CASCADES
FRI AFTERNOON BUT LOOKS TO BE MORE FOCUSED OVER THE LANE COUNTY
CASCADES.    TEMPERATURES INLAND WILL BE AROUND 10 DEGREES ABOVE
NORMAL NEXT COUPLE OF DAYS. HOWEVER COASTAL AREAS WILL REMAIN UNDER
STRONG MARINE INFLUENCE SO TEMPS WILL BE AT OR BELOW NORMAL.

PREVIOUS DISCUSSION FOLLOWS...
SHORT TERM...TONIGHT THROUGH SUNDAY...AN UPPER LEVEL RIDGE IS
BUILDING OVER THE PAC NW TODAY. THIS RIDGE WILL BRING WARM AND DRY
WEATHER TO THE PAC NW THROUGH SAT. A CLOSED LOW WILL MOVE INTO B.C.
OVER THE NEXT COUPLE OF DAYS...WHICH WILL ACT TO FLATTEN THE RIDGE A
BIT...BUT OTHERWISE HAVE LITTLE IMPACT ON OUR SENSIBLE WEATHER.

WARM AND DRY WEATHER IS IN CONTROL TODAY WITH PLENTY OF SUNSHINE
ACROSS MOST OF THE REGION. THE EXCEPTION IS AT THE COAST...WHERE
MARINE CLOUDS AND A COOLING NW BREEZE ARE KEEPING TEMPS IN THE 50S
AND 60S. TEMPERATURES ARE STEADILY CLIMBING OVER THE INTERIOR...WITH
CURRENT OBSERVED TEMPS IN THE UPPER 70S AND LOW 80S FOR MOST OF THE
LOWLANDS. EXPECT HIGHS TO TOP OUT IN THE LOW TO MID 80S LATER THIS
AFTERNOON. VISIBLE SATELLITE IMAGERY HAS SHOWN CUMULUS BUILDING ALONG
THE CASCADE CREST SINCE AROUND MIDDAY. THERE IS A SLIGHT CHANCE THAT
A FEW OF THE CUMULUS BUILDUPS MAY DEVELOP INTO THUNDERSHOWERS DURING
THE LATE AFTERNOON AND EARLY EVENING.

FRI LOOKS TO BE VERY SIMILAR TO TODAY. EXPECT A WEAK MARINE PUSH
OVERNIGHT...WITH CLOUDS ONLY ABLE TO PUSH INTO THE COAST RANGE GAPS
AND A LITTLE WAY UP THE COLUMBIA RIVER...LEAVING MOST OF THE INTERIOR
CLOUD FREE. FRI LOOKS TO BE THE WARMEST DAY OF THE STRETCH WITH
AFTERNOON HIGHS A DEGREE OR TWO WARMER THAN TODAY. A SLIGHT THREAT OF
LATE AFTERNOON/EARLY EVENING THUNDERSTORMS ALONG THE CASCADE CREST
WILL CONTINUE AS WELL.

THE UPPER RIDGE AXIS REMAINS OVER US FOR ONE LAST DAY ON SAT. EXPECT
IT WILL STILL BE WARM...BUT IT APPEARS THAT HIGH CLOUDS WILL BE
ARRIVING DURING THE DAY AHEAD OF THE NEXT APPROACHING UPPER LEVEL
LOW. ALTHOUGH 850 MB TEMPS ARE SIMILAR TO TODAY AND FRI...EXPECT
THESE CLOUDS MAY KNOCK SURFACE TEMPS DOWN A FEW DEGREES. THE FLOW
ALOFT WILL BEGIN TO TURN SOUTHWESTERLY. THERE MAY AGAIN BE A FEW
SHOWERS AND THUNDERSTORMS DURING THE AFTERNOON...WITH THE MAIN THREAT
REMAINING ALONG THE LANE COUNTY CASCADE CREST.

UPPER LEVEL LOW PRES WILL APPROACH THE COAST FROM THE SW ON SUN. THIS
WILL BRING A FURTHER INCREASE IN CLOUD COVER AND COOL TEMPS A LITTLE
MORE. THE FCST MODELS ALSO INDICATE A BETTER CHANCE OF AFTERNOON
THUNDERSTORMS IN THE CASCADES AS THE UPPER LEVEL FLOW TURNS
SOUTHERLY. PYLE

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...THE FIRST AND STRONGEST
UPPER LEVEL TROUGH WILL SLIDE N-NE INTO THE REGION LATE SUNDAY AND
CONTINUE TO ENHANCE SHOWER CHANCES THROUGH THE EARLY PART OF NEXT
WEEK. THE ASSOCIATED FRONT WILL CROSS THE REGION OVERNIGHT PROVIDING
FOR MUCH COOLER HIGH TEMPS ON MONDAY GIVEN THE ABUNDANT CLOUD COVER
AND MODELS SUGGESTING H8 TEMPS DECREASING AROUND 10 DEG C BY MONDAY
MORNING. WHILE MODELS SUGGEST SOME INSTABILITY...PARTICULARLY
TUESDAY AS THE COLD CORE ALOFT MOVES ACROSS THE AREA...THINK MUCH
COOLER SURFACE TEMPERATURES WILL LARGELY LIMIT THUNDER CHANCES.
HOWEVER...THE TIMING OF SHORTWAVE IMPULSES MAY ENHANCE THIS
POTENTIAL AT TIMES BUT CONFIDENCE IN THIS SCENARIO REMAINS LOW
ENOUGH TO EXCLUDE ANY THUNDERSTORMS IN THE EXTENDED PERIOD FOR NOW
WITH THE EXCEPTION OF MAINTAINING A CHANCE FOR MONDAY LATE
AFTERNOON/EVENING IN THE CASCADES SOUTH OF AROUND MT HOOD.
TEMPERATURES LIKELY REBOUND A LITTLE...CLOSER TO SEASONAL
NORMS...FOR THE SECOND HALF OF THE WEEK AS SHOWERS END AND WEAK
SHORTWAVE RIDGING PROVIDING FOR SOME AFTERNOON SUN AFTER MORNING
CLOUDS.  CULLEN
&&

.AVIATION...VFR CONDITIONS CONTINUE INLAND UNDER DRY
NORTHWESTERLY FLOW ALOFT. MVFR STRATUS POSSIBLE BETWEEN AFTER 12Z.
MARINE STRATUS ALONG THE COAST CONTINUES WITH IFR CIGS. PATCHY IFR
VSBY POSSIBLE AFTER 09Z. INLAND CONDITIONS IMPROVE TO VFR BY 18Z
FRIDAY BUT COASTAL SITES WILL LIKELY REMAIN IFR OR POSSIBLY RISE
TO MVFR.

KPDX AND APPROACHES...MVFR STRATUS POSSIBLE BETWEEN 12-18Z.
OTHERWISE VFR. BOWEN/64

&&

.MARINE...BENIGN CONDITIONS CONTINUE THROUGH THE FORECAST PERIOD.
WINDS WILL REMAIN BELOW 20 KT. MIXED SEAS AROUND 4 TO 6 FT WILL
CONTINUE THROUGH MUCH OF NEXT WEEK...WITH SWELL TRAINS OUT OF THE
W AND SW. BOWEN/64

&&

.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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