174
FXUS66 KPQR 080545 AAA
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
945 PM PST SAT MAR 7 2026
UPDATED AVIATION DISCUSSION
SYNOPSIS
A WEAK COLD-FRONTAL SYSTEM IS SLATED TO ARRIVE ON
SUNDAY BRINGING A BURST OF LIGHT PRECIPITATION TO THE REGION.
HOWEVER, THE FOCUS REMAINS ON MONDAY AND TUESDAY WHEN COOLER AIR
FILTERING INTO THE REGION LIKELY FACILITATES A PERIOD OF LOWER
SNOW LEVELS. WHILE A CONDITIONAL RAIN/SNOW MIX CAN'T BE RULED
OUT ALL THE WAY TO THE SURFACE DURING THE SUNRISE HOURS TUESDAY
MORNING, YOU'LL ALMOST CERTAINLY NEED SOME ELEVATION
(1000-1500FT+) TO EXPERIENCE ANY NOTEWORTHY IMPACTS.
TEMPERATURES AND SNOW LEVELS MODERATE WITH THE ARRIVAL OF A
WARM-FRONTAL SYSTEM MIDWEEK FOLLOWED BY THE CONTINUATION OF AN
ACTIVE AND PROGRESSIVE WEATHER PATTERN INTO NEXT WEEKEND.
SHORT TERM...NOW THROUGH TUESDAY
GENERALLY DRY CONDITIONS
PREVAIL ACROSS THE REGION THIS AFTERNOON HEADED INTO THE
EVENING HOURS ALL THANKS TO A WEAK UPPER-LEVEL RIDGE WHICH WILL
SOON BEGIN TO DEPART EASTWARD. ON SUNDAY THE FORECAST BEGINS TO
SHIFT AS A COLD FRONTAL SYSTEM ARRIVES FROM THE WNW ACCOMPANIED
A SURFACE LOW MOVING INTO VANCOUVER ISLAND AND BROAD ZONAL FLOW
ALOFT. THIS SYSTEM LIKELY BRINGS ANOTHER ROUND OF PRECIPITATION
ALTHOUGH BOTH RAINFALL AND MOUNTAIN SNOWFALL ACCUMULATION IS
FAIRLY UNIMPRESSIVE AND POSSESS LITTLE TO NO IMPACT. HOWEVER,
IT LIKELY SETS THE STAGE FOR INCREASING SNOWFALL IMPACTS EARLY
NEXT WEEK, ESPECIALLY ACROSS THE SOUTH WASHINGTON CASCADES AND
POTENTIALLY PORTIONS OF THE NORTH OREGON CASCADES AND HIGHER
REACHES OF THE COAST RANGE AS WELL.
SUNDAY NIGHT INTO MONDAY WE WILL BEGIN TO SEE A COLDER AIRMASS,
ALBEIT MODIFIED, FILTER OVERHEAD OFF THE PACIFIC OCEAN. THIS
COLD AIR IS WRAPPING AROUND A LOW PRESSURE SYSTEM IN THE GULF OF
ALASKA WHICH IS SLOWLY DROPPING SOUTHWARD INTO BRITISH
COLUMBIA. THERE IS HIGH CONFIDENCE 850 MB TEMPERATURES DROP TO
AROUND -6 TO -7 DEGREES C, WHICH UNDER THE RIGHT CONDITIONS CAN
RESULT IN LOWER SNOW LEVELS. FOR NOW, MODELS INDICATE THEY
LIKELY FLUCTUATE BETWEEN 1000-2000 FT EARLY NEXT WEEK. THAT
SAID, THERE IS A 10-25% CHANCE THAT WE SEE SNOW LEVELS NEAR
SURFACE ACROSS THE SOUTHWEST WASHINGTON LOWLANDS AS EARLY AS THE
SUNRISE HOURS ON MONDAY BUT THIS ASSUMES THE PASSAGE OF A
MODERATE TO HEAVY SHOWER TEMPORARILY PUSHING SNOW LEVEL LOWER.
IN CASES LIKE THESE YOU MAY SEE SNOW IN THE AIR OR BRIEFLY STICK
TO THE GRASS WITH MORE NOTICEABLE IMPACTS AS YOU GAIN ELEVATION
(800-1500FT+) AND/OR HAVE ADDITIONAL SHOWER ACTIVITY TRAIN
OVERHEAD.
SHOWERY PRECIPITATION CHANCES CONTINUE INTO TUESDAY AS MOISTURE
CONTINUES STREAMING OVER THE EASTERN PACIFIC RIDGE, AND A WEAK
SHORTWAVE ALONG THE FLOW PULLS THAT MOISTURE INTO THE REGION.
DAYTIME TEMPERATURES INTO THE MID TO UPPER 40S ACROSS THE
LOWLANDS, SO THE MAIN TIME PERIOD FOR ANY WET SNOW OR A
RAIN/SNOW MIX MAKING IT DOWN TO THE LOWEST ELEVATIONS WOULD BE
DURING THE LATE OVERNIGHT TO MORNING HOURS WHEN TEMPERATURES
ARE THE COLDEST. IN A SIMILAR MINDSET TO THE NIGHT PRIOR TO
MONDAY NIGHT INTO TUESDAY MORNING, A RAIN/SNOW MIX OR WET SNOW
DOWN TO THE LOWEST ELEVATIONS WILL BE CONDITIONAL, CONTINGENT ON
A HEAVIER AND PERSISTENT ENOUGH SHOWER ACTIVITY TO DRIVE
DYNAMIC COOLING. WITHOUT A BIT OF ELEVATION IMPACTS APPEAR
EXTREMELY MINIMAL GIVEN THE SET-UP. EXPLORING NBM PROBABILITIES,
SNOWFALL ACCUMULATION CHANCES FOR 1 INCH OR MORE FROM 11PM MON
TO 11PM TUESDAY ARE LESS THAN 5-10% ACROSS MUCH OF THE INTERIOR
LOWLANDS WITH A 10-20% IN COWLITZ COUNTY WHERE SHOWERS APPEAR
MORE FREQUENT.
ONCE YOU GAIN SOME ELEVATION, THE LIKELIHOOD FOR SNOWFALL
IMPACTS DO INCREASE. THE COAST RANGE, ESPECIALLY IN NORTHERN
OREGON AND THE WILLAPA HILLS HAVE GREATER THAN AN 60-80% CHANCE
OF 2 INCHES OR MORE OF SNOW GENERALLY ABOVE 800-1000FT DURING
THIS SAME 11PM MONDAY TO 11PM TUESDAY TIME PERIOD LIKELY DUE IN
PART TO THE HIGH FREQUENCY OF SHOWERS. BUT GIVEN THE TIME OF
YEAR (BETTER SUN ANGLE), ANY SNOWFALL IMPACTS ACROSS THE COAST
RANGE/WILLAPA HILLS AT PASS ELEVATION WILL LARGELY DIMINISH DURING
THE DAYTIME HOURS. DETERMINISTIC AND ENSEMBLE GUIDANCE ARE IN
EXCELLENT AGREEMENT FOR DECENT SNOWFALL (AND WITH MORE
LONGEVITY) ACROSS PORTIONS OF THE CASCADES DURING THE
MONDAY/TUESDAY TIME PERIOD, ESPECIALLY ACROSS SOUTHERN
WASHINGTON ABOVE 2000-2500FT. CONFIDENCE HAS INCREASED ENOUGH
TO ISSUE A WINTER WEATHER ADVISORY FOR THE AFOREMENTIONED
REGION. SHOULD MODELS INCREASE QPF/SNOWFALL ACROSS THE NORTH
OREGON CASCADES, THEY MAY ALSO NEED A HEADLINE AS WELL. WHETHER
YOU'RE DRIVING OVER THE COAST RANGE OR CASCADE PASSES EARLY
NEXT WEEK, BE MINDFUL OF TRAVEL CONDITIONS DUE TO WINTRY WEATHER
AND ADJUST ACCORDINGLY. -99
LONG TERM...TUESDAY NIGHT THROUGH FRIDAY
HEADED INTO THE
MIDDLE OF NEXT WEEK THE COLD AIR EXITS AS QUICKLY AS IT MOVED
IN. A HIGH PRESSURE SYSTEM OFF OF THE CALIFORNIA COAST INTERACTS
WITH THE LOW PRESSURE IN GULF OF ALASKA AND THE COMPRESSION OF
THE FLOW ALOFT IN-BETWEEN THESE TWO FEATURES SHOOTS A STRONGER
WARM-FRONTAL SYSTEM OVER THE REGION. THE AXIS OF THE HEAVIEST
PRECIPITATION AGAIN APPEARS TO BE WITHIN WASHINGTON AND BRITISH
COLUMBIA BUT AS THE THE ACCOMPANYING SHORTWAVE PUSHING THROUGH,
THAT PRECIPITATION ALONG A SECONDARY FRONTAL BOUNDARY WILL
SPREAD FURTHER SOUTH. WHILE THIS SYSTEM HAS SOME OF THE DYNAMICS
OF AN ATMOSPHERIC RIVER (DECENTLY ROBUST SWATH OF ADVECTED
MOISTURE), IT WILL GENERALLY BEHAVE MUCH LIKE A TYPICAL MARCH
RAINY SYSTEM AND WILL HAVE MINIMAL IF ANY IMPACTS. ONE CHALLENGE
WILL BE THE TIMING OF THE PRECIPITATION OF THIS SYSTEM TO ANY
LINGERING COLD AIR. IF THERE REMAINS COOLER AIR TRAPPED IN THE
SOME OF THE COAST RANGE/CASCADE VALLEYS DURING THE ONSET OF THIS
PROLONGED SYSTEM, WE CANNOT RULE OUT ANOTHER LOW-CONFIDENCE
SNOW TYPE SCENARIO FOR A FEW LOCALIZED AREAS. HOWEVER WITH THE
WARMER AIR TRAILING QUICKLY ON WEDNESDAY, ANY SNOW THAT WOULD
FALL AT THE LOWER ELEVATIONS WOULD END QUICKLY. ADDITIONAL
MODERATE TO HEAVY SNOW IS POSSIBLE IN THE SW WASHINGTON CASCADES
THURSDAY INTO FRIDAY, BUT NOT MUCH ELSE SOUTH OF THIS NEAR PASS
ELEVATION.
IN TERMS OF OTHER IMPACTS, RAIN AMOUNTS WILL BE STEADY THROUGH
THE REMAINDER OF THE WEEK BUT THERE ARE NO CONCERNS FOR FLOODING
OR RAPID SNOW MELT. THIS IS A DYNAMICALLY CHANGING FORECAST WITH
MANY COMPONENTS TO CONSIDER SO EVEN A SLIGHT SHIFT WILL
COMPLETELY CHANGE THE OUTCOME. -99/27
AVIATION
WESTERLY FLOW ALOFT INCREASES WHILE A WEAK COLD FRONT
DROPS SOUTH ACROSS THE REGION ON SUNDAY. THIS WILL LIKELY BRING
STEADILY DETERIORATING CONDITIONS ACROSS THE AREA TONIGHT INTO
SUNDAY. AS OF 05Z, PREDOMINATELY IFR TO LOW MVFR CONDITIONS ARE
OCCURRING ALONG THE COAST, WHILE INCREASING LOW STRATUS OVER
NORTHERN PORTIONS OF THE AREA ARE PRODUCING MVFR TO LOW VFR CIGS
NORTH OF KUAO. VFR CONDITIONS UNDER MOSTLY CLEAR SKIES CURRENTLY
PERSISTS ACROSS THE SOUTHERN AND CENTRAL WILLAMETTE VALLEY, BUT
CLOUDS ARE EXPECTED TO BEGIN FILLING IN BY 12Z AS PROBS FOR MVFR
SIGNIFICANTLY RISE TO AROUND 70-80%. THERE IS ALSO A 10-30% CHANCE
FOR IFR CONDITIONS TO MANIFEST BETWEEN 12-18Z SUNDAY WITHIN THE
SOUTHERN AND CENTRAL PARTS OF THE WILLAMETTE VALLEY. AS ONSHORE
FLOW CONTINUES, EXPECT CONDITIONS ALONG THE COAST TO TREND TOWARD
LIFR AS PROBS INCREASE TO AROUND 40% BY 10Z SUNDAY. LIGHT RAIN IS
EXPECTED WITH THE FRONTAL PASSAGE BEGINNING AT THE NORTH COAST BY
12Z SUNDAY MORNING, AND SLOWLY SPREADING INLAND AND DROPPING SOUTH
THROUGH SUNDAY AFTERNOON.
KPDX AND APPROACHES...LOW STRATUS CONTINUES TO FILL ACROSS THE
AREA WITH CIGS AROUND 2500-3500 FT, PRODUCING PREDOMINATELY MVFR
CONDITIONS. CONDITIONS WILL LIKELY FLUCTUATE BETWEEN MVFR AND VFR
THROUGH 12Z SUNDAY, AFTER WHICH TIME PROBS FOR MVFR INCREASE TO
AROUND 60-70% THROUGH 00Z MONDAY. CHANCES FOR LIGHT RAIN INCREASE
AFTER 16Z SUNDAY. LIGHT NORTHWEST WINDS ARE EXPECTED TO BECOME
SOUTH TO SOUTHWESTERLY EARLY SUNDAY MORNING. /DH
MARINE
A PERSISTENT NORTHWESTERLY SWELL WILL MAINTAIN SEAS AT
AROUND 6 TO 9 FT AT 10 TO 12 SECONDS THROUGH SUNDAY. A WEAK FRONT
WILL DROP ACROSS THE COASTAL WATERS ON SUNDAY, WITH NORTHWEST
WINDS BEHIND THE FRONT LIKELY PRODUCING GUSTS UP TO 20 KT, THOUGH
THERE IS A 20-40% CHANCE THAT WINDS REACH SMALL CRAFT ADVISORY
CRITERIA FOR AN EXTENDED PERIOD OF TIME. HOWEVER, THERE IS A
35-50% CHANCE OF ISOLATED GUSTS UP TO 25 KT, WITH THE HIGHEST
PROBABILITY ACROSS THE NORTHERN WATERS OF PZZ251 AND PZZ271. THE
NORTHWEST SWELL IS ALSO EXPECTED TO INCREASE SLIGHTLY, WHICH WILL
RESULT IN SEAS BUILDING TOWARDS 9 TO 11 FT BY MONDAY AND 10 TO 12
FT BY TUESDAY.
AS THE MIDDLE OF THE WEEK APPROACHES, A RELATIVELY STRONGER
SYSTEM LOOKS TO BRING STRONGER WINDS AND ELEVATED SEAS BY
WEDNESDAY AND THURSDAY. SOUTHERLY WINDS WILL INCREASE ON WEDNESDAY
WITH THE INCOMING SYSTEM, WITH CURRENT MODEL AND ENSEMBLE
GUIDANCE HAVE A 50-70% CHANCE OF SEEING GALE FORCE WIND SPEEDS
DURING THIS TIME, BUT THERE IS STILL SOME UNCERTAINTY AS TO WHERE
EXACTLY THE INCOMING SYSTEM GOES. IN ADDITION TO THE ELEVATED
WINDS, SEAS WILL ALSO BUILD WEDNESDAY INTO THURSDAY TOWARDS 13-15
FT. LOOKING BEYOND TOWARDS THE END OF NEXT WEEK, OVERALL
CONDITIONS LOOK TO SUBSIDE WITH SEAS FALLING BELOW 10 FT BY FRIDAY
AND WINDS GUSTS AROUND 20 KT. /42
PQR WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY FROM 5 AM MONDAY TO 5 PM PST TUESDAY FOR
ORZ126.
WA...WINTER WEATHER ADVISORY FROM 5 AM MONDAY TO 5 PM PST TUESDAY FOR
WAZ211.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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X.COM/NWSPORTLAND
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