AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
856 AM PDT WED JUN 19 2013
.SYNOPSIS...PERSISTENT UPPER LEVEL LOW PRESSURE CONTINUES TO BRING
CLOUDS AND OCCASIONAL RAIN TO SOUTHWEST WASHINGTON AND NORTHWEST
OREGON. TEMPERATURES TODAY AND THURSDAY WILL BE WELL BELOW NORMAL.
SHOWERS WILL LINGER BUT PROBABLY BE LESS NUMEROUS THURSDAY AND FRIDAY
AS THE UPPER LOW MEANDERS TOWARD THE IDAHO PANHANDLE AND NORTHERN
ROCKIES. TEMPERATURES WILL CLIMB BACK CLOSER TO NORMAL FRIDAY AND
SATURDAY WITH SOME RELATIVELY DRIER WEATHER...BUT IT APPEARS AN
ACTIVE PACIFIC JET STREAM WILL BRING MORE WET WEATHER SUNDAY INTO
EARLY NEXT WEEK.
&&
.SHORT TERM...DEEP MARINE AIR HAS PUSHED ONSHORE WITH A RATHER SOLID
STRATOCUMULUS DECK BANKING UP AGAINST THE CASCADES. BASED ON AIRCRAFT
SOUNDINGS IT APPEARS THERE IS A BIT OF A CAP ABOVE THIS MOIST LAYER
AROUND 750 MB OR 9000 FT. SHOWERS ARE BEGINNING TO FILL IN WITHIN THE
STRATOCUMULUS DECK...WITH PRECIPITATION BECOMING MORE STRATIFORM IN
NATURE. WITH BROAD LOW-LEVEL LIFT STILL EXPECTED BY THE 12Z NAM CROSS
SECTIONS TODAY...IT APPEARS WE WILL BE CLOUDY AND UNSEASONABLY COOL
WITH OCCASIONAL RAIN. HIGH TEMPS SHOULD STRUGGLE TO GET OUT OF THE
LOWER 60S IN THE LOWLANDS...WITH 40S AND 50S IN THE HIGHER TERRAIN.
WITH DEEP MOIST WESTERLY FLOW IT DOES NOT APPEAR THERE WILL BE ENOUGH
SFC-BASED INSTABILITY TO SUPPORT THUNDER SO WE TOOK IT OUT OF THE
FORECAST FOR OUR CASCADE ZONES.
BY THURSDAY THE MAIN PORTION OF THE UPPER LOW WILL PUSH INTO EASTERN
WASHINGTON AND OREGON...BUT THERE SHOULD STILL BE A WEAKER SECONDARY
LOW OVER WESTERN WA/OR. THIS WILL KEEP THINGS UNSETTLED WITH A CHANCE
FOR SHOWERS ESPECIALLY FOR OUR NORTHERN ZONES. NAM BUFR SOUNDINGS
SHOW A STRONG CAP AROUND 700 MB SO ANY SHOWERS WILL BE SHALLOW. WITH
A LITTLE MORE SUNSHINE TEMPS MAY BE SLIGHTLY WARMER THU BUT STILL
BELOW NORMAL.
THE UPPER LOW MEANDERS TOWARD THE IDAHO PANHANDLE FRIDAY...BUT STILL
REMAINS CLOSE AND BROAD ENOUGH TO ALLOW WRAPAROUND MOISTURE TO KEEP
THE SHOWER THREAT GOING FOR OUR NORTHERN ZONES. TEMPS WILL CONTINUE
THEIR SLOW RECOVERY AS THE AIR MASS SLOWLY WARMS UP...WITH THE DRYING
AND WARMING TREND BACK TOWARD NORMAL CONTINUING INTO SATURDAY AS THE
UPPER LOW FINALLY TRIES TO MOVE ACROSS THE NORTHERN ROCKIES. WEAGLE
.LONG TERM...FRIDAY NIGHT THROUGH MONDAY...GIVEN THE LAST COUPLE OF
MODEL RUNS WE ARE STARTING TO LOSE CONFIDENCE IN OUR WEEKEND RIDGING
AND WARMUP. THE UPPER LOW FESTERING OVER THE MID-COLUMBIA BASIN NOW
APPEARS TO LINGER INTO FRIDAY...NOT REALLY ALLOWING THE UPPER RIDGE
TO BUILD IN FULL FORCE BEFORE THE NEXT PACIFIC FRONTAL SYSTEM
APPROACHES FOR THE WEEKEND. THERE ARE A COUPLE FACTORS TO CONSIDER
HERE. THERE IS A HISTORICALLY STRONG UPPER LEVEL RIDGE OVER ALASKA...
WITH OUR UPPER LOW STUCK BELOW IT IN A REX BLOCK PATTERN. THE
TENDENCY WILL BE FOR THE PACIFIC JET TO TRY TO UNDERCUT THE ALASKAN
RIDGE THIS WEEKEND AND THIS IS WHAT THE MODELS ARE BEGINNING TO SHOW.
ADDITIONALLY THE MADDEN-JULIAN OSCILLATION SEEMS TO BE ENTERING ITS
MOST ACTIVE PHASE SINCE FEBRUARY...WHICH IS IMPRESSIVE FOR JUNE. ALL
THIS POINTS TO A WET WEEK NEXT WEEK...SO WE SIGNIFICANTLY TRENDED
POPS UPWARD AND COOLED OFF TEMPERATURES BEGINNING SUNDAY. WEAGLE
&&
.AVIATION...A SHOWERY UNSTABLE AIRMASS WILL LEAD TO MAINLY VFR
CONDITIONS AROUND THE AREA TODAY WITH ONLY OCCASIONAL MVFR CIGS
EXPECTED IN AND AROUND SHOWERS. THE LOWER ATMOSPHERE WILL REMAIN
MODESTLY UNSTABLE TONIGHT SO EXPECT A MIX OF MVFR AND VFR
CONDITIONS AREAWIDE. CONFIDENCE IN THE DETAILS REMAINS LOW THOUGH.
KPDX AND APPROACHES...EXPECT SCATTERED SHOWERS TODAY UNDER MAINLY
VFR CONDITIONS TODAY AS THE LOWER ATMOSPHERE REMAINS RELATIVELY
UNSTABLE. A MIX OF MVFR AND VFR CIGS LOOK PROBABLE OVERNIGHT...BUT
CONFIDENCE IN DETAILS IS LOW. /NEUMAN
&&
.MARINE...EXPECT TRANQUIL WINDS AND SEAS THROUGH SATURDAY AS HIGH
PRESSURE MOVES OVER THE NORTHEAST PACIFIC. A COUPLE WEAK STORM
SYSTEMS
COULD CAUSE WINDS AND SEAS TO INCREASE A BIT LATE IN THE WEEKEND
AND EARLY NEXT WEEK. HOWEVER...SEAS SHOULD REMAIN BELOW 10 FT AND
LITTLE MORE THAN SMALL CRAFT ADVISORIES FOR WINDS APPEAR POSSIBLE.
/NEUMAN
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...NONE.
&&
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.
