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 112144
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
241 PM PDT FRI JUL 11 2014

.SYNOPSIS...MOIST AND UNSTABLE SOUTH FLOW ALOFT WILL CONTINUE TO
SPREAD INTO THE AREA TONIGHT. THIS WILL RESULT IN THE THREAT OF
THUNDERSTORMS TO THE CASCADES AND POSSIBLY AS FAR WEST AS THE COAST
RANGE BY LATE THIS EVENING. AN UPPER LOW OFF THE NORTH CALIFORNIA
COAST SATURDAY IS EXPECTED TO MOVE NORTH TO NORTHEAST AND INLAND INTO
EXTREME SW OREGON SUNDAY FOR ANOTHER THREAT OF THUNDERSTORMS...
EXTENDING FROM THE COAST RANGE...THE VALLEYS AND TO THE CASCADES.
WELL-ABOVE NORMAL DAYTIME TEMPERATURES CAN BE EXPECTED THROUGH THE
MIDDLE OF NEXT WEEK.

&&

.SHORT TERM...TONIGHT THROUGH MONDAY...PRIMARY FORECAST CHALLENGES
REMAIN THE THUNDERSTORM POTENTIAL THROUGH TONIGHT AND AGAIN SUNDAY.
VISIBLE AND INFRA-RED SATELLITE IMAGERY SHOW MID AND HIGH-LEVEL
MOISTURE CONTINUNING TO STREAM N INTO THE AREA FROM SWRN OREGON. IR
LOOP INDICATED THE COLDEST TOPPPED CLOUDS IN DOUGLAS COUNTY AND
EXTREME SERN LANE COUNTY. LOCAL LIGHTNING DETECTION PRODUCT AS OF 20Z
NOT SHOWING ANYMORE LIGHTNING. WATER VAPOR IMAGERY SHOWS THE PRIMARY
CIRCULATION CENTER NEAR 40N 129W GRADUALLY DRIFTING NW. THERE MAY BE
A SECONDARY SUBTLE SHORT-WAVE NEAR KBOK. STILL... DEFORMATION AXIS
OVER SRN AND CENTRAL OREGON AS SEEN IN WATER VAPOR CONTINUES TO
MIGRATE NWD THIS AFTERNOON. NAM AND GFS MODEL SOUNDINGS FOR VARIOUS
LOCATIONS IN THE WILLAMETTE VALLEY NOT AT ALL IMPRESSIVE REGARDING
CONVECTION. MAIN INHIBITING FACTOR SEEMS TO BE CONVECTIVE INHIBITION
OR CIN AND THE HIGH CONVECTIVE TRIGGER TEMPS. 12Z NAM VALID 03Z SAT
SHOWED THE HIGHEST 700 MB THETA-E AIR GENEALLY S OF A FLORENCE TO
EUGENE LINE. ALSO...700 MB EAST FLOW WILL TEND TO PUSH THE BEST
DYNAMICS FURTHER AWAY FROM THE AREA. THE 18Z HRRR ALSO NOT VERY
SUPPORTIVE OF CONVECTION IN THE CWA. AT 23Z IT DEPICTS AN AREA OF
35-45 DBZ ECHOES IN CENTRAL AND WRN DOUGLAS COUNTY...BUT BY 02Z SAT
REFLECTIVITY COVERAGE QUICKLY DIMINISHES WITH JUST WEAK RETURNS OFF
THE CENTRAL COAST AND ANOTHER AREA IN ERN LANE COUNTY. WILL LEAVE
CURRENT THUNDERSTORM FORECAST FOR TONIGHT ALONE BUT WOULD NOT BE
SURPRISED IF VERY LITTLE LIGHTNING OCCURRED.

SATURDAY LOOKS TO BE AN IN-BETWEEN DAY AS A TRANSITORY 500 MB RIDGE
MOVES OVER THE AREA IN THE WAKE OF TONIGHTS SHORT-WAVE. MODEL
SOUNDINGS FOR SAT AFTERNOON...PARTICULARLY THE GFS...ARE SOMEWHAT
DRY...POSSIBLY INDICATING DECENT SUBSIDENCE BEHIND THE DEPARTING
SYSTEM...BUT MORE LIKELY THAT THE AIR MASS WILL BE SO WARM AND CAN
HOLD MUCH MORE MOISTURE THAN AN AIR MASS UNDER SEASONAL CONDITIONS.
MAIN ISSUE SATURDAY WILL BE THE RISING 850 MB TEMPS...CLIMBING TO
AROUND 22C OVER KPDX. THIS WILL BE THE START OF A MULTI-DAY HOT
SPELL. WILL ISSUE A HEAT ADVISORY FOR THIS EPISODE. HAVE KEPT ANY
THUNDERSTORM MENTION SAT TO THE CASCADES WHERE MID-LEVEL LAPSE RATES
CLOSE TO 8C/KM ARE FORECAST BY THE GFS MODEL SOUNDING.

SUNDAY LOOKS TO BE QUITE INTERESTING. ANOTHER ROUND OF MOIST SOUTH
FLOW ALOFT BEGINS TO SPREAD INTO SWRN OREGON AS EARLY AS SAT EVENING.
GFS AND ECMWF SIMILAR WITH THE OVERALL DETAILS...BUT THE 12Z NAM
APPEARS TO BE AN OUTLIER. THE  12Z ECMWF AND 12Z GFS BRING THE NEXT
LOW CENTER TO NEAR 41N 129W BY 12Z SUN. THE NAM IS A LITTLE MORE SW
WITH THE FEATURE AND MUCH SLOWER MOVING IT THROUGH THE FORECAST AREA.
UNLIKE TODAYS SYSTEM...THIS NEXT ONE IS EXPECTED TO
HAVE JET SUPPORT. GFS AND ECMWF SHOW A 60-80 KT 300 MB JET SEGMENT
MOVING INTO SWRN OREGON SUN MORNING. FORECAST AREA WILL BE IN THE
FAVORED QUADRANT OF THE JET SEGMENT FOR ADDITIONAL CONVECTIVE
SUPPORT. GFS MODEL SOUNDINGS FOR KPDX AND FOR A POINT IN THE N OREGON
CASCADES VALID SUN AFTERNOON ARE QUITE IMPRESSIVE. THE KPDX SOUNDING
VALID 00Z MON HAS A SURFACE-BASED CAPE OF NEARLY 600 J/KG...LIFTED
INDEX OF -2...TOTAL TOTALS OF 51 AND PRECIPITABLE WATER OF 1.37
INCHES. THE CASCADE SOUNDING IS EVEN MORE IMPRESSIVE WITH A CAPE OF
OVER 900 J/KG...LI OF -4...TOTAL TOTALS OF 54...0-6KM BULK SHEAR OF
NEARLY 40 KT...PRECIPITABLE WATER 1.66 INCHES...AND A SWEAT INDEX OF
311 (WE USE 250 AS THE BENCHMARK FOR POSSIBLE SEVERE). THE SREF
CALIBRATED PROBABILITY OF THUNDERSTORMS VALID 00Z-03Z MON SHOWS A 50
PERCENT BULLS-EYE OVER THE CASCADES AND THE 30 PERCENT CONTOUR TO THE
COAST. ALL IN ALL...MODELS ARE SHOWING SEVERAL INGREDIENTS COMING
TOGETHER FOR A CLASSIC PAC NW THUNDERSTORM EVENT. THUNDERSTORM
ACTIVITY SHOULD CONTINUE THROUGH SUN NIGHT...ESPECIALLY IN THE NERN
ZONES. WILL ALSO TONE DOWN SUN MAX TEMPS AS THERE SHOULD BE EXTENSIVE
CLOUD COVER DESPITE 850 MB FORECAST TEMPS OF 21-23C.

WOULD EXPECT A FLOOD OF MARINE AIR SUN NIGHT AND MON MORNING BEHIND
THE DEPARTING SHORT-WAVE. THIS WILL QUICKLY STABILIZE THINGS SUCH
THAT BY MON AFTERNOON ANY CONVECTION SHOULD BE WELL EAST OF THE AREA.
850 TEMPS 00Z TUE TO REMAIN IN THE 21-23C RANGE AND A 1000-500 MB
THICKNESS RIDGE NEAR THE OREGON COAST RANGE. WEISHAAR

.LONG TERM...MONDAY NIGHT THROUGH FRIDAY...MAIN EMPHASIS WILL BE ON
THE UNSEASONABLY HOT CONDITIONS THROUGH MUCH OF THE PERIOD. 12Z ECMWF
MAINTAINS THE HOT PATTERN THROUGH AT LEAST WED. IT DOES HINT AT THE
POSSIBILITY OF A LITTLE MARINE AIR SEEPAGE BEGINNING WEDNESDAY...BUT
MORE SO ON THURSDAY. DO NOT AGREE WITH THE GFS SOLUTION OF HAVING A
DEEP UPPER LOW SWING THROUGH LATE IN THE WEEK. 12Z ECMWF KEEPS THE
AREA IN NWLY FLOW ALOFT AND ONSHORE LOW-LEVEL FLOW...KEEPING DAYTIME
TEMPERATURES SLIGHTLY ABOVE AVERAGE. A PRIMARY CONCERN WILL BE THE
HIGH DEW POINTS...RESULTING IN UNCOMFORTABLE NIGHTTIME PERIODS.
WEISHAAR

&&

.AVIATION...MARINE STRATUS REMAINS ALONG THE COASTLINE WITH IFR
AND LOCAL LIFR CIGS AND VIS THIS AFTERNOON. SOME AREAS WILL CLEAR
TO THE COASTLINE BUT EXPECT STRATUS TO MOVE BACK IN TO THE COAST
RANGE EARLY THIS EVENING WITH EXTENSIVE IFR AND LIFR TONIGHT. NOT
MUCH CHANGE FOR TOMORROW ALONG THE COAST. INLAND AREAS WILL REMAIN
VFR WITH THE MAIN THREAT BEING THE MID LEVEL MOISTURE MOVING UP FROM
THE SOUTH ASSOCIATED WITH THE DISTURBANCE ALOFT OVER SOUTHERN
OREGON. CIGS WILL BE 8000 TO 12000 FEET TONIGHT WITH SOME ISOLATED
SHOWERS MOSTLY ALOFT DURING THE EVENING IN THE SOUTH SPREADING
NORTH. THERE IS A SLIGHT CHANCE OF ELEVATED THUNDERSTORMS FROM
KSXT TO KCVO 23Z-04Z...INCLUDING THE ADJACENT COAST RANGE AND
CASCADES. THERE REMAINS A POSSIBILITY OF SOME ELEVATED
THUNDERSTORMS SPREADING NORTH KCVO-KPDX DURING THE EVENING 03Z-
09Z. SCHNEIDER

KPDX AND APPROACHES...VFR TODAY AND TONIGHT. THERE WILL BE A 15
PERCENT CHANCE OF A THUNDERSTORM AFTER 03Z AND LIKELY A LOT OF MID
LEVEL CLOUDS WITH A FEW SHOWERS MOSTLY ALOFT FROM 03Z-09Z AS DEBRIS
FROM STORMS ELSEWHERE MOVES OVER THE AREA. STRATUS IS NOT EXPECTED
TO REACH THE TERMINAL SATURDAY MORNING. SCHNEIDER

&&

.MARINE...HIGH PRES WILL REMAIN OVER THE NE PAC THROUGH THE
WEEKEND...KEEPING WINDS FROM THE N TO NW. THE GRADIENTS WILL
CONTINUE TO BE WEAK FOR LIGHTER WINDS TONIGHT THROUGH SATURDAY
NIGHT. THE OFFSHORE HIGH AND THE INLAND THERMAL LOW WILL
STRENGTHEN SUNDAY FOR INCREASING NORTHWEST WINDS BY AFTERNOON AND
LIKELY REACH SMALL CRAFT ADVISORY LEVELS...THEN REMAIN BRISK INTO
THE MIDDLE OF NEXT WEEK.

SEAS CONTINUE TO FALL TONIGHT AND SATURDAY. BY SATURDAY AFTERNOON
THE NORTHWEST FRESH SWELL ABATES UNDER LIGHT WINDS AND THE ENP
MODEL INDICATES WE WILL START TO SEE A LONG PERIOD WEST SWELL OF 2
TO 3 FT. THIS WOULD NORMALLY BE MASKED BY THE NORTHWEST WIND
SEAS. ALL IN ALL THE SEAS WILL REMAIN BELOW 5 FT UNTIL THE
NORTHWESTERLY INCREASE SUNDAY AFTERNOON. THE COLUMBIA BAR WILL
SEE A VERY STRONG EBB EARLY SATURDAY MORNING BUT WITH RELATIVELY
LIGHT INCOMING SWELL WAVES WILL REMAIN BELOW SMALL CRAFT
LEVELS...STILL MARINERS SHOULD BE CAUTIOUS CROSS THE BARS DURING
THIS VERY STRONG EBB. SCHNEIDER

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...HEAT ADVISORY FROM 5 AM SATURDAY TO 2 PM PDT TUESDAY FOR
     CASCADE FOOTHILLS IN LANE COUNTY-CASCADES IN LANE
     COUNTY-CENTRAL COAST RANGE OF WESTERN OREGON-CENTRAL COLUMBIA
     RIVER GORGE-CENTRAL WILLAMETTE VALLEY-COAST RANGE OF NORTHWEST
     OREGON-GREATER PORTLAND METRO AREA-LOWER COLUMBIA-NORTHERN
     OREGON CASCADE FOOTHILLS-NORTHERN OREGON CASCADES-SOUTH
     WILLAMETTE VALLEY-UPPER HOOD RIVER VALLEY-WESTERN COLUMBIA
     RIVER GORGE.

WA...HEAT ADVISORY FROM 5 AM SATURDAY TO 2 PM PDT TUESDAY FOR
     CENTRAL COLUMBIA RIVER GORGE-GREATER VANCOUVER AREA-I-5
     CORRIDOR IN COWLITZ COUNTY-SOUTH WASHINGTON CASCADE
     FOOTHILLS-SOUTH WASHINGTON CASCADES-WESTERN COLUMBIA RIVER
     GORGE-WILLAPA HILLS.

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.



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