228
FXUS66 KPQR 211527
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
827 AM PDT TUE MAY 21 2013
SYNOPSIS
A COLD UPPER LOW WILL MOVE OVER NW OREGON THIS
AFTERNOON...RESULTING IN LOWERING SNOW LEVELS...CONVECTIVE SHOWERS
CONTAINING SMALL HAIL...AND POSSIBLY A FEW THUNDERSTORMS THROUGH
THIS EVENING. COOL AND UNSETTLED WEATHER WILL CONTINUE THROUGH THE
WORK WEEK AS THE LOW REMAINS OVER THE PACIFIC NW. THE LOW WILL
WEAKEN AND SHIFT FURTHER INLAND FRIDAY...AND THE SHOWERS WILL
DECREASE OVER THE WEEKEND. HOWEVER...ANOTHER APPROACHING LOW WILL
MAINTAIN AT LEAST A SLIGHT CHANCE FOR SHOWERS SATURDAY THROUGH
MONDAY.
SHORT TERM
COLD FRONT PUSHED THROUGH THE AREA EARLIER THIS
MORNING...WITH COLDER AIR EXPECTED TO CONTINUE TO FILTER IN TODAY.
RADAR AND SATELLITE IMAGES SHOW A LARGE AREA OF RAIN AHEAD OF THE
MAIN UPPER TROUGH OFFSHORE. UPPER TROUGH AXIS IS EXPECTED TO ROTATE
INLAND TODAY AS THE UPPER LOW HEADS TOWARDS NW OREGON...
DESTABILIZING ATMOSPHERE WITH COLDER AIR ALOFT. AS SNOW LEVELS LOWER
AND AIR MASS BECOMES MORE UNSTABLE...EXPECT TO SEE SMALL HAIL
DEVELOP WITH THE SHOWERS LATER TODAY AND CONTINUING INTO WED.
REMAINDER OF SHORT TERM DISCUSSION FOLLOWS...
SNOW LEVELS WILL LOWER TODAY AND TONIGHT AND ARE EXPECTED TO FALL
BELOW THE CASCADE PASSES AROUND SUNSET TONIGHT AND DOWN TO AROUND
3000 FEET BY WEDNESDAY MORNING. SNOW WILL BE SLOW TO ACCUMULATE ON
ROADS DUE TO PRECEDING WARM ROAD TEMPERATURES BUT MELTING SNOW MAY
STILL RESULT IN SLICK DRIVING CONDITIONS AND THOSE TRAVELING OVER THE
CASCADES SHOULD PREPARE FOR WINTER CONDITIONS THROUGH THURSDAY
MORNING. THE LATE SEASON SNOW WILL ALSO BE A THREAT FOR
HIKERS...CLIMBERS...AND CAMPERS. TH
LONG TERM...THURSDAY EVENING THROUGH MONDAY
SEVERAL SHORTWAVE
SYSTEMS WILL ROTATE AROUND A PROMINENT CLOSED LOW THAT WILL
STUBBORNLY LINGER ACROSS THE REGION LATE THIS WEEK. THIS MEANS THERE
WILL BE PERIODS OF SHOWERS MIXED WITH SPORADIC SUN BREAKS THROUGH
THIS WEEKEND...WITH THE BULK OF THE MOISTURE PUSHING THROUGH THE
AREA FRIDAY AND SATURDAY. BEHIND THE MAIN FRONTAL SYSTEM...SNOW
LEVELS RISE ABOVE CASCADE PASS LEVEL AND TEMPERATURES WARM UP CLOSER
TO NORMAL. WET AND UNSETTLED WEATHER APPEARS TO CONTINUE THROUGH
EARLY NEXT WEEK. /27
AVIATION
EXPECT CONDITIONS TO TREND TOWARD VFR THIS MORNING AS
THE ATMOSPHERE BECOMES INCREASINGLY UNSTABLE. THERE IS A CHANCE OF
SMALL HAIL IN ANY HEAVIER SHOWERS ALONG WITH A SLIGHT CHANCE OF A FEW
CLAPS OF THUNDER...PRIMARILY TOWARDS THIS EVENING. CONDITIONS SHOULD
GENERALLY REMAIN VFR OVERNIGHT...BUT BRIEF MVFR CIGS WILL BE
POSSIBLE JUST ABOUT ANYWHERE UNDERNEATH A PASSING SHOWER.
KPDX AND APPROACHES...EXPECT MVFR CONDITIONS THIS MORNING TO TREND
TOWARDS VFR BY THIS AFTERNOON. ANY SHOWER WILL HAVE A CHANCE OF
PRODUCING A BRIEF MVFR CIG THROUGH WEDNESDAY. /NEUMAN
MARINE
AN APPROACHING LOW PRESSURE SYSTEM WILL TIGHTEN THE
PRESSURE GRADIENT OVER THE WATERS THIS MORNING...BRINGING INCREASING
NW WINDS IN THE 15 TO 25 KT RANGE WITH GUSTS UP TO 30 KT. GUSTY WINDS
WILL LIKELY CONTINUE THROUGH WEDNESDAY.
THE TREND WILL BE TOWARD MORE BENIGN WEATHER LATE THIS WEEK INTO
NEXT WEEKEND AS THE UPPER LOW HIGH PRESSURE WEAKENS AND HIGHER
SURFACE PRESSURE BUILDS INTO THE WATERS.
EXPECT SEAS TO RISE ABOVE 10 FT THIS AFTERNOON...WHERE THEY WILL
LIKELY HOVER AROUND THROUGH WEDNESDAY. SEAS SHOULD THEN SLOWLY
SUBSIDE TOWARDS THE WEEKEND. /NEUMAN
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR WINDS UNTIL 5 PM PDT WEDNESDAY FOR
COASTAL WATERS FROM CAPE SHOALWATER WA TO FLORENCE OR OUT 60 NM.
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 PM PDT
WEDNESDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA TO
FLORENCE OR OUT 60 NM.
SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR FROM 5 PM
THIS AFTERNOON TO 5 PM PDT WEDNESDAY.
MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND
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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