432
FXUS66 KPQR 011223
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
423 AM PST SUN MAR 1 2026
SYNOPSIS
A LOW PRESSURE SYSTEM MOVING INTO NORTHERN
CALIFORNIA AND SOUTHERN OREGON WILL BRING PUSH RAIN SHOWERS
NORTHWARD INTO NORTHWEST OREGON TODAY. MOST OF THE RAIN IS
EXPECTED FROM LINCOLN/POLK/MARION COUNTY SOUTHWARD. EXPECT LOWER
CHANCES FOR RAIN NORTH OF THESE COUNTIES. BRIEF HIGH PRESSURE
RETURNS RELATIVELY DRIER CONDITIONS RETURN ON MONDAY. THE NEXT
SYSTEM ARRIVES TUESDAY-WEDNESDAY, BRINGING WIDESPREAD RAIN AND
PASS-LEVEL CASCADE SNOW. CHANCES FOR PRECIPITATION CONTINUE
THROUGH THE END OF THE WEEK.
DISCUSSION...TODAY THROUGH SATURDAY
RADAR AND SATELLITE
IMAGERY AS OF EARLY SUNDAY MORNING DEPICTS HIGH CLOUDS WITH SOME
PASSING VIRGA AS A CUT-OFF LOW PRESSURE SYSTEM APPROACHES THE
REGION FROM THE PACIFIC. THIS LOW WILL SWING THROUGH NORTHERN
CALIFORNIA AND SOUTHERN OREGON, BRINGING WRAP-AROUND SHOWERS
INTO THE SOUTHERN-MOST PORTIONS OF NORTHWEST OREGON TODAY. MOST
OF THE SHOWERS ARE EXPECTED FROM LINCOLN/POLK/MARION COUNTIES
SOUTHWARD. FOR LOCATIONS NORTH OF THESE COUNTIES, THERE IS ABOUT
A 15-30% CHANCE FOR RAIN AT ANY GIVEN HOUR THROUGH THIS
EVENING, WITH THE LOWEST CHANCES ACROSS SOUTHWEST WASHINGTON
SINCE THEY'LL BE MUCH FURTHER NORTH FROM THE SYSTEM.
THERE IS UNCERTAINTY WITH EXACT RAIN AMOUNTS GIVEN THE SHOWERY
NATURE OF THE PRECIPITATION, HOWEVER THERE IS HIGH CONFIDENCE
BASED ON HREF/REFS GUIDANCE THAT 24 HOUR RAIN AMOUNTS ENDING 4
AM MONDAY REMAIN UNDER 0.50 INCH FOR THE MAJORITY OF NORTHWEST
OREGON. AN EXCEPTION COULD BE THE LINN AND LANE COUNTIES, WHERE
CHANCES FOR EXCEEDING 0.50 INCH ARE AROUND 20-30% FOR THE
LOWLANDS AND 50-70% FOR THE ADJACENT FOOTHILLS AND HIGH
CASCADES DUE TO OROGRAPHIC ENHANCEMENT. LANE COUNTY IS EXPECTED
TO GET THE MOST PRECIPITATION, WITH THE WETTEST SCENARIO (10%
CHANCE) DEPICTED BY HREF/REFS BEING AROUND 0.70-1 INCH IN 24
HOURS. THIS WOULD BE MOST LIKELY TO COME TO FRUITION IF HEAVIER
SHOWERS PASS THROUGH. SNOW LEVELS WILL ALSO REMAIN ABOVE 6000 TO
7000 FEET THROUGH AT LEAST MONDAY, KEEPING SNOWFALL WELL-ABOVE
THE CASCADE PASSES.
TRANSIENT RIDGING RETURNS TO THE PACIFIC NORTHWEST ON MONDAY,
RETURNING A BRIEF PERIOD OF RELATIVELY DRIER CONDITIONS AND
WARMER TEMPERATURES IN THE UPPER 50S. COULD SEE SOME CLOUD
BREAKS, BUT THE HIGH PRESSURE WON'T BE STRONG ENOUGH OR LAST
LONG ENOUGH TO COMPLETELY RULE OUT SOME LIGHT PRECIPITATION.
15-30% CHANCES FOR PRECIPITATION CONTINUE ON MONDAY, HIGHEST
OVER THE COAST RANGE AND CASCADES.
THE NEXT WEATHER SYSTEM APPROACHES THE REGION ON TUESDAY WITH
THE MAJORITY OF ENSEMBLE MEMBERS (>80%) SUGGESTING WIDESPREAD
RAIN BEGINNING ALONG THE COAST BY TUESDAY MORNING AND SPREADING
INLAND BY THE AFTERNOON. MEANWHILE, 20-40% OF ENSEMBLE MEMBERS
HAVE RAIN STARTING EARLIER AROUND LATE MONDAY EVENING INTO EARLY
TUESDAY MORNING. IN EITHER SCENARIO, DRY WEATHER WILL COME TO AN
END BY TUESDAY EVENING. MORE SUBSTANTIAL RAIN ARRIVES
WEDNESDAY, WITH THE CHANCES FOR LIQUID PRECIPITATION EXCEEDING 1
INCH ENDING BETWEEN 4 AM TUESDAY TO 4 AM THURSDAY BEING AROUND
15-30% ALONG THE I-5 CORRIDOR FROM COWLITZ TO LANE COUNTY,
45-65% ALONG THE COAST, AND 70-90% FOR THE COAST RANGE AND
CASCADES. AT THIS POINT, NOT EXPECTING WIND IMPACTS WITH THIS
SYSTEM, THOUGH COULD SEE SOME GUSTS UP TO 25 MPH, LOCALLY UP TO
35-40 MPH OVER THE TERRAIN, AS THE FRONT PASSES ON WEDNESDAY.
SNOW WILL ALSO RETURN TO THE CASCADE PASSES AS SNOW LEVELS DROP
TO AROUND 3500-4500 FEET ON WEDNESDAY. CHANCES FOR 6+ INCHES OF
SNOW IN A 48 HOUR PERIOD FROM 4 PM TUESDAY THROUGH 4 PM THURSDAY
ARE AROUND 80-95% ALONG THE SANTIAM AND WILLAMETTE PASSES AND
50% FOR HIGHWAY 26 AT GOVERNMENT CAMP, WITH THE MOST SNOW
FALLING LATE TUESDAY INTO WEDNESDAY. THOSE PLANNING TO TRAVEL
THROUGH THE CASCADES MID-WEEK SHOULD CHECK ROAD CONDITIONS
BEFORE LEAVING AND CARRY AN EMERGENCY SUPPLY KIT.
THURSDAY TO SATURDAY, THERE IS STILL SOME UNCERTAINTY WITH THE
EXACT UPPER LEVEL PATTERN OVER OUR AREA, BUT THE MAJORITY OF
ENSEMBLE MEMBERS ARE SUGGESTING RIDGING FAR OFFSHORE OVER THE
NORTHEAST PACIFIC. THE OFFSHORE PLACEMENT OF THIS RIDGE WON'T
BE FAVORABLE FOR A RETURN TO DRY AND SUNNY WEATHER. MOST
ENSEMBLE GUIDANCE SUGGESTS THAT MOISTURE WILL RIDE THE
NORTHERN/NORTHEASTERN PERIPHERY OF THE RIDGE AND TRACK TOWARDS
THE PACIFIC NORTHWEST, MAINTAIN CHANCES FOR PRECIPITATION
THROUGH THE END OF THE WEEK. -10
AVIATION
SATELLITE IMAGERY AND TERMINAL OBSERVATIONS AS OF
EARLY SUNDAY MORNING DEPICTS VFR CONDITIONS WITH HIGH CLOUDS
ACROSS NORTHWEST OREGON AHEAD OF THE NEXT LOW PRESSURE SYSTEM.
THIS SYSTEM WILL MOVE INTO NORTHERN CALIFORNIA AND SOUTHERN
OREGON TODAY, SPREADING RAIN SHOWERS FROM SOUTH TO NORTH
BEGINNING 18-21Z SUN AND LASTING THROUGH 06-09Z MON. MOST OF
THE SHOWERS WILL BE FROM KSLE/KONP SOUTHWARD. CIGS WILL ALSO
GRADUALLY LOWER THROUGHOUT THE DAY, WITH CHANCES FOR MVFR CIGS
INCREASING TO 50-70% ACROSS THE WILLAMETTE VALLEY AND THE
CENTRAL OREGON COAST AT ANY GIVEN HOUR AFTER 00Z MON. THE
HIGHEST CHANCES WILL BE AT KONP/KEUG GIVEN THAT THESE TERMINALS
ARE FURTHER SOUTH AND CLOSER TO THE INCOMING SYSTEM. VARIABLE
WINDS UNDER 5 KT ACROSS THE REGION TODAY EXCEPT FOR LIGHT EAST
WINDS THROUGH THE COLUMBIA RIVER GORGE AND FAR EAST PORTLAND
METRO.
KPDX AND APPROACHES..PREDOMINATELY VFR CONDITIONS THROUGH THE
TAF PERIOD WITH A 20-40% CHANCE FOR MVFR CIGS AT ANY GIVEN
HOUR AFTER 06Z MON AS THE SYSTEM FROM THE SOUTH SPREADS LOWER
CIGS. 15-20% CHANCE FOR RAIN AFTER 00Z MON. VARIABLE WINDS
AROUND 5 KT OR LESS. -10
MARINE
BENIGN CONDITIONS EXPECTED THROUGH MONDAY NIGHT.
SURFACE HIGH PRESSURE OFFSHORE AND A WEAK THERMAL TROUGH ALONG
THE COAST WILL MAINTAIN NORTHEASTERLY WINDS 5-10 KT ACROSS THE
WATERS TODAY. SEAS FALL TO 3-4 FT AT 9-10 SEC TONIGHT INTO
MONDAY. WINDS TURN MORE SOUTHERLY ON MONDAY AHEAD OF THE NEXT
SYSTEM, BUT REMAIN LIGHT. THE NEXT FRONTAL SYSTEM ARRIVES ON
TUESDAY, LIKELY RETURNING SMALL CRAFT CONDITIONS. THERE IS A
60-70% CHANCE FOR FREQUENT AND WIDESPREAD SOUTHERLY WIND GUSTS
OF 22 KT OR GREATER ACROSS THE WATERS ON TUESDAY. SEAS WILL ALSO
GRADUALLY BUILD ON WEDNESDAY AND THURSDAY AS A WESTERLY SWELL
MOVES IN. CHANCES FOR SEAS EXCEEDING 10 FT ARE 30-50% DURING
THIS TIME, WITH THE HIGHEST CHANCES BEYOND 10-20 NM OFFSHORE.
-10
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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