401
FXUS66 KPQR 252154
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
254 PM PDT THU APR 25 2024
SYNOPSIS
SHOWERY AND UNSETTLED CONDITIONS CONTINUE THROUGH
THE WEEKEND INTO NEXT WEEK AS THE PACIFIC NORTHWEST REMAINS
UNDER THE INFLUENCE OF A RATHER PROGRESSIVE SPRING-TIME WEATHER
PATTERN. BEYOND THE MORE PERSISTENT CHANCES FOR RAINFALL GOING
FORWARD SNOW LEVELS ARE EXPECTED TO DROP NEAR PASS LEVEL(4500FT)
TONIGHT INTO FRIDAY ALTHOUGH OUTSIDE OF SLUSHY PAVEMENT ACCUMULATION
MOST APPRECIABLE IMPACTS STAY ABOVE 5,500FT. THE WEATHER TRENDS
EVEN A TOUCH COOLER EARLY NEXT WEEK.
SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT
THIS AFTERNOON
SATELLITE AND RADAR INDICATE THE BULK OF THE STEADIER
PRECIPITATION HAS BEGUN TO DECREASE AND BREAK TO SHOWERS AS THE
FRONTAL BOUNDARY MOVES INLAND AD WE QUICKLY TRANSITION TO POST-
FRONTAL SHOWER ACTIVITY. WITH COOLER AIR NOW FILTERING IN ALOFT,
SNOW LEVELS WILL GRADUALLY DECREASE TONIGHT BOTTOMING OUT NEAR
4,300-4,500FT COME SUNRISE FRIDAY MORNING. AS A RESULT WET SNOW
LIKELY RETURNS TO THE HIGHER PASS AREAS LIKE SANTIAM AND
WILLAMETTE, THOUGH THAT’S NOT TO SAY SNOW OR A RAIN/SNOW MIX
CAN’T MIX DOWN TO THE HIGHEST REACHES OF US-26 DUE TO THE MORE
CONVECTIVE NATURE OF THE PRECIPITATION. STILL, EVEN AT SANTIAM
AND WILLAMETTE PASS THE WARM ANTECEDENT CONDITIONS WILL HELP TO
LIMIT PAVEMENT ACCUMULATION WITH THE BULK OF THE IMPACTS
OCCURRING ABOVE 5,300-5,500FT. DUE TO THE LATE SEASON NATURE OF
THE SNOWFALL WILL MAINTAIN THE CURRENT WINTER WEATHER ADVISORY
FOR THE CASCADES THROUGH FRIDAY EVENING. IT’S WORTH MENTIONING
AS FAR AS GENERAL PRECIPITATION CHANCES ARE CONCERNED THROUGH
FRIDAY, MODELS MAINTAIN THE MOST FREQUENT SHOWERS OVER THE COAST
RANGE, WILLAPA HILLS, AND CASCADES/CASCADE FOOTHILLS ALTHOUGH
THE PASSAGE OF THE BROADER TROUGH AXIS THROUGH WESTERN WA/OR
FRIDAY MIDDAY AND AFTERNOON LIKELY SERVERS TO INCREASE SHOWER
ACTIVITY REGION-WIDE; EVEN ACROSS THE WILLAMETTE VALLEY AND SW
WASHINGTON.
LATE FRIDAY INTO SATURDAY THE UPPER-LEVEL TROUGH DEEPENS AND
QUICKLY PROGRESS SOUTHEASTWARD INTO THE FOUR CORNERS REGION OF
THE GREAT BASIN. WE’LL BRIEFLY SEE UPPER-LEVEL HEIGHTS RISE OVER
THE REGION DUE TO THE PASSAGE OF A WEAK TRANSIENT SHORTWAVE
RIDGE AND BOTH DETERMINISTIC/ENSEMBLE GUIDANCE SEEM CONFIDENT IN
A LULL OR AT LEAST NOTICEABLE DECREASE IN LINGERING SHOWERS OVER
THE LOWER ELEVATIONS, ESPECIALLY THE CENTRAL AND SOUTHERN
WILLAMETTE VALLEY. HOWEVER, THE ARRIVAL OF FAST MOVING UPPER-
LEVEL SHORTWAVE AND FRONTAL BOUNDARY EXTENDING SOUTHWARD OFF A
PARENT LOW PARKED OVER THE GULF OF ALASKA INCREASES CHANCES FOR
PRECIPITATION SATURDAY AFTERNOON INTO THE EVENING. AT LEAST
PRECIPITATION AMOUNTS DON’T LOOK PARTICULARLY NOTEWORTHY DUE TO
THE QUICK PROGRESSION OF THE AFOREMENTIONED FEATURE ON SATURDAY
WITH AN ADDITIONAL ~0.1” FOR THE INLAND VALLEYS AND 0.3-0.5” FOR
THE COAST RANGE/CASCADES. ONCE THE FRONT PASSES SHOWERS CHANCES
GENERALLY REVERT BACK TO THE ELEVATED TERRAIN FEATURES AROUND
WESTERN WA/OR THE SECOND HALF OF THE NIGHT. SNOW LEVELS FRIDAY
NIGHT THROUGH SATURDAY NIGHT CONTINUE TO FLUCTUATE BETWEEN
4500-5500FT. -SCHULDT
LONG TERM...SUNDAY THROUGH WEDNESDAY NIGHT
FOR THE EARLY TO
MIDDLE PORTION OF NEXT WEEK CONFIDENCE IS HIGH THE PATTERN STAYS
RATHER PROGRESSIVE, WITH FRONTS MOVING OFF THE NORTHEAST PACIFIC
INTO THE PACIFIC NW. DURING THE LATE SUNDAY INTO MONDAY TIME PERIOD
YET ANOTHER FRONT WILL PUSH ACROSS THE REGION WITH POST-FRONTAL
SHOWERS ON TAP BY AT LEAST THE SECOND HALF OF MONDAY - MODEL
UNCERTAINTY IS HIGHER REGARDING THE EXACT TIMING OF THIS
DISTURBANCE. STILL A BIT COOLER THAN THAT EXPECTED FOR LATE
APRIL, WITH OVERALL TEMPERATURES IN THE LOWLANDS IN THE 50S TO
LOWER 60S. SNOW LEVELS WILL RUN 3000 TO 4000 FT, WHICH WILL
MAINTAIN SOME SNOW AT TIMES FOR THE HIGHER TERRAIN OF THE
FOOTHILLS, AS WELL AS MOST OF THE CASCADES.
FEW SHOWERS LINGER AROUND REGION ON TUESDAY, BUT THINK MOST OF
THE DAY WILL END UP BEING MOSTLY DRY FOR THE INLAND VALLEYS, AS
A WEAK TRANSIENT RIDGE GLIDES OVER THE REGION. BUT, MODELS SHOW
ANOTHER POTENT FRONT OFFSHORE LATER TUE NIGHT/EARLY WED, WITH
THAT FRONT PUSHING INLAND LATE WED INTO WED NIGHT. WITH THIS,
DOES LOOK TO BE MORE RAINY THAT SHOWERY BY THURSDAY. AFTER
THAT, MODELS STILL IN QUITE A BIT OF FLUX WITH LOW FORECAST
CONFIDENCE DUE TO LARGE DISCREPANCIES IN THE LONGWAVE PATTERN
OVER THE EASTERN PACIFIC AND CONUS. -SCHULDT/ROCKEY
AVIATION
POSTFRONTAL SHOWERY CONDITIONS DOMINATE, WITH SOME
FOLLOWUP WAVES OF MOISTURE, WITH A MORE MAJOR ONE AROUND 15Z THU.
COASTAL PRECIPITATION IS HEAVIER THAN INLAND, WITH GENERALLY MVFR
CONDITIONS OCCASIONALLY BRIEFLY DETERIORATING TO IFR CONDITIONS AS
STRONGER BANDS OF MOISTURE PASS THROUGH. CHANCE OF LIFR
CONDITIONS AT THIS POINT IS <10%. INLAND, CEILINGS ARE BOUNCING
BETWEEN VFR AND MVFR, WITH AROUND A 60% CHANCE OF JUST MVFR
CEILINGS EXPECTED. SOUTHERLY GUSTS UP TO 25 KT CONTINUE POSSIBLE
THROUGHOUT THURSDAY, WITH WINDS DROPPING OFF AROUND 04Z FRI.
ANOTHER BAND OF MOISTURE ARRIVES BETWEEN 15-18Z FROM THE WEST,
LIKELY RETURNING ALL INLAND TERMINALS TO MVFR CEILINGS. COASTAL
TERMINALS CURRENTLY SEE AROUND A 80-90% CHANCE OF AT LEAST A BRIEF
PERIOD OF IFR CEILINGS AROUND THAT TIME.
NOTES: THE ASOS AT KTTD IS ONLY AVAILABLE VIA THE DIAL IN OPTION.
THE AWOS AT KMMV IS STILL OUT OF COMMISSION. THERE IS NO
ESTIMATED TIME OF REPAIR.
PDX AND APPROACHES...A BRIEF PERIOD OF PREDOMINANTLY VFR
CONDITIONS ARE EXPECTED UNTIL 00Z FRI. AROUND THAT TIME, THE NEXT
WAVE OF MOISTURE ARRIVES, DETERIORATING CONDITIONS BACK TO MVFR.
HIGH-END MVFR CONDITIONS CONTINUE UNTIL AROUND 17Z FRI, WHEN THE
NEXT MORE MAJOR BAND OF MOISTURE ARRIVES. CONDITIONS REMAIN MVFR,
BUT DETERIORATE SLIGHTLY TO LOW-END MVFR. 50-60% CHANCE OF
CEILINGS BELOW 2000 FEET AT THAT TIME. WINDS CONTINUE GUSTING TO
25 KT UNTIL 00-01Z FRI, AFTER WHICH GUSTS WILL FALL BELOW 10 KT.
-JLIU
MARINE
THE WARM FRONT HAS PASSED, THOUGH POST-FRONTAL
CONDITIONS ALLOW THE SMALL CRAFT ADVISORY TO CONTINUE, WITH GUSTS
UP TO 30 KT POSSIBLE, DECREASING AFTER MIDNIGHT TONIGHT. SEAS
ARE CHOPPY, CURRENTLY SITTING AROUND 7-10 FT AT 9 SECONDS.
WINDS TURN MORE WESTERLY/NORTHWESTERLY THURSDAY NIGHT INTO FRIDAY
AS THE LOW PRESSURE SYSTEM PUSHES INLAND. WINDS BEGIN TO EASE
SLIGHTLY WITH GUSTS TO 20-25 KT. HOWEVER, A WESTERLY SWELL WILL
ENTER THE WATERS AND BUILD SEAS TO AROUND 9-11 FT. THESE ELEVATED
SEAS ARE BRIEF, AS THE SWELL HEIGHT FALLS FRIDAY NIGHT TO
SATURDAY. THE NEXT FRONTAL SYSTEM ARRIVES ON SATURDAY, WILL RETURN
GUSTY SOUTHWESTERLY WINDS. THE LATEST NBM HAS DECREASED
CONFIDENCE IN GALES, ONLY AROUND 10% ON SATURDAY.
-ALVIZ/JLIU
PQR WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY UNTIL MIDNIGHT PDT FRIDAY NIGHT FOR
ORZ127-128.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 2 AM PDT SATURDAY FOR PZZ210-251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
WWW.TWITTER.COM/NWSPORTLAND
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