573
FXUS66 KPQR 131153
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
453 AM PDT THU MAR 13 2025
SYNOPSIS
CONFIDENCE REMAINS HIGH IN THE CONTINUATION OF AN
ACTIVE WINTER-LIKE WEATHER PATTERN TODAY THROUGH THE WEEKEND
INTO NEXT WEEK DEFINED BY PERIODS OF VALLEY RAIN, HEAVY CASCADE
SNOWFALL, LOCALLY BREEZY TO GUSTY WINDS, AND EVEN ISOLATED
THUNDERSTORMS (MAINLY TODAY). REGIONALLY WE’LL GET TO
EXPERIENCE A LITTLE BIT EVERYTHING! OUT THESE CONDITIONS MOUNTAIN
SNOWFALL, PARTICULARLY FRIDAY THROUGH SUNDAY, LOOKS TO BE THE
MOST IMPACTFUL WITH MULTIPLE FEET OF SNOW LIKELY AT PASS
ELEVATION. SO IF YOU ARE VENTURING ACROSS THE CASCADES OVER THE
NEXT 3-4 DAYS BE PREPARE FOR HAZARDOUS WINTER WEATHER
CONDITIONS. WINTER ISN'T DONE WITH US YET.
SHORT TERM...NOW THROUGH SATURDAY NIGHT
WIDESPREAD
PRECIPITATION EARLY THIS MORNING OBSERVED VIA RADAR IMAGERY IS
BEGINNING TO TRANSITION TO SHOWERS AS OUR LATEST WEATHER SYSTEM
AND ACCOMPANYING COLD-FRONTAL BOUNDARY IS TRANSITIONING EAST OF
THE CASCADES RESULTING IN A SWITCH TO POST-FRONTAL SHOWERS. A
FEW SURFACE OBSERVATIONS IN THE WILLAPA HILLS AND COAST RANGE
HAVE EXPERIENCE QUITE THE DROP IN TEMPERATURES RIGHT BEHIND
THIS FRONTAL BOUNDARY SUGGESTING SNOW LEVELS ARE BOTTOMING OUT
NEAR 1500-2000FT WHICH MAKES SENSE GIVEN THE -5C 850MB
TEMPERATURES EXPECTED TO MOVE IN ALOFT. FORTUNATELY, IT’LL BE
TOUGH SLEDDING TO GET SNOW TO STICK AT THIS LOWER ELEVATION
RANGE BESIDES THE POTENTIAL FOR BRIEF A SLUSH-UP IN THE GRASS
UNDER A HEAVIER SHOWER. MODERATE TO HIGH CONFIDENCE THE BULK OF
THE SNOW RELATED IMPACTS REMAIN ABOVE ~2500FT TODAY.
MODEL SOUNDINGS FROM THE GFS, NAM, ECMWF, GEM, ETC., IN
ADDITION TO THE HREF, ARE ALL STILL ON-BOARD WITH A DECENTLY
UNSTABLE ATMOSPHERE BY PNW STANDARDS THIS AFTERNOON WITH
100-500 J/KG OF MUCAPE AVAILABLE FOR ACTIVITY TO UTILIZE. WHILE
CAPE VALUES LIKE THESE WOULD BE SCOFFED AT ELSEWHERE, IT’LL BE
JUST ENOUGH TO PRODUCE BRIEF HEAVY RAIN, INFREQUENT LIGHTNING,
GUSTY OUTFLOW WINDS, AND SMALL HAIL/GRAUPEL. FOR THOSE WISHING
FOR “SPORTIER” ACTIVITY (LIKE WHAT OCCURRED BACK ON FEB 24TH)
THESE CAPE VALUES COMBINED WITH WEAK DIRECTIONAL/VERTICAL SHEAR
(~15-20 KNOTS OF EBWD) ARE NOT SUPPORTIVE OF STORM ORGANIZATION
SO THE PROBABILITY FOR A SEVERE THUNDERSTORM TODAY IS EXTREMELY
LOW (<1%). EXPECT THE POP-UP THUNDERSTORM THREAT TO SLOWLY
DIMINISH AFTER SUNSET WITH THE LOSS OF DAYTIME HEATING. IF YOU
HAPPEN TO BE OUTDOORS TODAY JUST REMEMBER WHEN THUNDER ROARS, GO
INDOORS.
FRIDAY TO SATURDAY NIGHT, OUR NEXT TWO IMPULSES OF PRECIPITATION
IN FORM OF A NEGATIVELY TILTED SHORTWAVE TROUGH QUICKLY
FOLLOWED BY ANOTHER SHORTWAVE BOTH SWING INTO THE PACIFIC
NORTHWEST USHERING IN ADDITIONAL RAIN, BREEZY WINDS, AND CASCADE
SNOW. AS AN INITIAL WEAK WARM FRONT WITH THE FIRST DISTURBANCE
GRADUALLY LIFTS OVER THE AREA FRIDAY, SNOW LEVELS WILL
EVENTUALLY RISE TO 2500-3500 FEET, HOWEVER, FOR MUCH OF THE DAY
THE LOW-LEVEL FLOW MAINTAINS A DECENT EASTERLY COMPONENT WHICH
MAY HELP HOLD SNOW-LEVELS CLOSER TO ~1500FT THROUGH THE MIDDAY
HOURS AND LOCALLY CLOSER TO 800-1000FT FOR SPOTS LIKE THE UPPER-
HOOD RIVER VALLEY. GIVEN THIS DUBIOUS SET-UP, FORECAST
CONFIDENCE FOR SNOW-LEVELS ON FRIDAY ARE ONLY MODERATE. IF IT
WAS DECEMBER/JANUARY AND/OR WE HAD AN ARCTIC AIR IN PLACE THIS
LOW-LEVEL FLOW PATTERN WOULD BE MUCH MORE CONCERNING, BUT ALAS
IT’S MID-MARCH AND THE ADDED DAYTIME HEATING WILL SUBSTANTIALLY
TEMPER ANY IMPACTS IN THE FOOTHILLS/COAST RANGE/HIGH CASCADE
VALLEYS ON FRIDAY SHOULD SNOW LEVEL DIP A TOUCH LOWER THAN
EXPECTED. THAT SAID, THIS LESSENING OF IMPACTS WON’T BE THE
CASE FOR CASCADE PASSES WHERE HEAVY SNOW IS LIKELY AND A WINTER
STORM WATCH REMAINS IN EFFECT FROM EARLY FRIDAY MORNING TO LATE
SATURDAY AFTERNOON. PROJECTED SNOWFALL TOTALS ACROSS THE
CASCADES DURING THIS TIMEFRAME HAVE STAYED AROUND 1 TO 2 FEET,
SO EXPECT HAZARDOUS TRAVEL CONDITIONS THROUGH THE PASSES.
-SCHULDT
LONG TERM...SATURDAY NIGHT TO WEDNESDAY
THE AFOREMENTIONED
FRIDAY TO SATURDAY SYSTEMS ARE IMMEDIATELY FOLLOWED BY THIRD
DEEPER UPPER-LEVEL TROUGH ON SUNDAY/MONDAY GIVING ALMOST NO
REPRIEVE TO THE ONSLAUGHT OF PRECIPITATION. IT STILL APPEARS
THERE IS ADDED COMPLEXITY OF A WARM-FRONTAL BOUNDARY INITIALLY
PUSHING INTO WESTERN OREGON SATURDAY NIGHT AND SUNDAY MORNING
WHICH WOULD BRIEFLY PUSH SNOW-LEVELS UP TO 4000-5000 FEET IN THE
OREGON CASCADES (3000-4000 FEET SW WA CASCADES) BEFORE FALLING
AGAIN BY SUNDAY NIGHT. IT’S ALSO WORTH HIGHLIGHTING
DETERMINISTIC AND ENSEMBLE GUIDANCE HAVE TRENDED TOWARDS HIGHER
QPF OVER WESTERN OREGON ON SUNDAY DUE IN-PART TO AN AREA OF
SUBSTANTIAL LOW TO MID LEVEL ISENTROPIC LIFT AND MOISTURE
TRANSPORT SETTING UP OVERHEAD WHICH HAD PREVIOUSLY BEEN POINTED
FURTHER SOUTH. THERE IT STILL SOME UNCERTAINTY AS TO HOW FAR
NORTH THE AXIS OF THE HEAVIEST PRECIPITATION COULD PROGRESSES
BUT IN ANY CASE THE CASCADES COULD EASILY SEE ANOTHER ONE TO TWO
FEET OF ADDITIONAL SNOWFALL AT PASS-LEVEL AND ABOVE. ENSEMBLE
GUIDANCE AND THE NBM POINT TO A HIGH PROBABILITY (80-90%) FOR AT
LEAST 12 INCHES OF SNOWFALL FOR SPOTS LIKE SANTIAM AND
WILLAMETTE PASS (CLOSER TO 60-70% US-26 NEAR GOV CAMP) SATURDAY
NIGHT THROUGH MONDAY. JUST REMEMBER TO WINTERIZE YOUR VEHICLE
AND HAVE A WINTER EMERGENCY DRIVING KIT READILY AVAILABLE IF YOU
DO PLAN ON HITTING THE SLOPES OR TRAVELING OVER THE CASCADES
THIS WEEKEND INTO EARLY NEXT WEEK.
IN REGARDS TO RISES ON RIVERS AND GUSTY WIND POTENTIAL REALLY
NOT MUCH HAS CHANGED THE LAST FEW FORECAST CYCLES WITH LIMITED
IMPACTS EXPECTED OVERALL. WHILE LOCAL RIVERS WILL SEE RISES
GOING FORWARD, THE LATEST 10 DAY HEFS (HYDROLOGIC ENSEMBLE
FORECAST SYSTEM) GUIDANCE KEEPS PROBABILITIES FOR RIVERS TO
REACH MINOR FLOOD STAGE ARE GENERALLY LESS THAN 10-15%, EVEN FOR
THE “FLASHIEST” LOCAL RIVERS. BUT IF QPF TOTALS KEEP TRENDING
HIGHER ON SUNDAY THESE PROBABILITIES MAY INCREASE SOMEWHAT. IN
TERMS OF WINDS, THERE IS STILL UNCERTAINTY IN JUST HOW
BREEZY/GUSTY IT’LL GET THIS WEEKEND BUT IT GENERALLY ISN'T
LOOKING TO BE IMPACTFUL ACROSS THE WILLAMETTE VALLEY AND
PORTLAND/VANCOUVER METRO WITH GUSTS OF 20-35 MPH THE MOST LIKELY
OUTCOME. WIND SPEEDS SATURDAY TO SUNDAY WILL ULTIMATELY BE
DECIDED BY THE EXACT STRENGTH AND TRACK OF THE SURFACE LOW
PRESSURE SYSTEMS SWINGING INTO THE REGION. IF THESE LOWS END UP
TRACKING CLOSE TO OR RIGHT ALONG THE COASTLINE, IT WOULD INDUCE
STRONGER WINDS THAN CURRENTLY FORECASTED WITH MAXIMUM GUSTS
POTENTIALLY EXCEEDING 55 MPH AT THE COAST AND 45 MPH INLAND. IN
THIS CASE, WINDS OF THIS MAGNITUDE COULD LEAD TO ISOLATED POWER
OUTAGES AND/OR DOWNED TREES. CURRENTLY, THERE IS A 20-40% CHANCE
FOR WIND GUSTS EXCEEDING 55 MPH ALONG THE COAST AND A 10-30%
CHANCE FOR WIND GUSTS EXCEEDING 45 MPH INLAND OVER THE WEEKEND.
AT LEAST THERE IS EXCELLENT AGREEMENT BETWEEN MODEL GUIDANCE IN
A RETURN TO SLIGHTLY CALMER CONDITIONS AROUND TUESDAY OF NEXT
WEEK DUE TO A TRANSIENT RIDGE OF HIGH PRESSURE SHIFTING INTO THE
REGION. WE MAY NOT SEE CHANGES FOR PRECIPITATION COMPLETELY END
DURING THIS PERIOD ALTHOUGH ANY LINGERING SHOWER ACTIVITY WOULD
BE LIGHTER AND MORE CONFINED TO TERRAIN FEATURES LIKE THE COAST
RANGE AND CASCADES. COME THE MIDDLE TO END OF NEXT WEEK ANY
BREAK COMES TO AN END WITH SURPRISINGLY GOOD DETERMINISTIC AND
ENSEMBLE MODEL AGREEMENT SUGGESTING ANOTHER UPPER-LEVEL TROUGH
OF LOW PRESSURE MARCHES INTO THE PACIFIC NORTHWEST - THIS
PROGRESSIVE WINTER-LIKE PATTERN HAS NO INTENTION OF GOING QUIETLY.
-SCHULDT/ALVIS
AVIATION
UPPER LEVEL TROUGH WILL BRING UNSTABLE CONDITIONS
ACROSS THE REGION TODAY. CURRENTLY SEEING A MIX OF MVFR AND VFR
CIGS ACROSS THE AREA WITH RAIN SHOWERS. EXPECT CONDITIONS TO TREND
TOWARD PREDOMINATELY VFR BY 18Z. THERE IS ALSO A 15-30% CHANCE OF
THUNDERSTORMS LATER THIS MORNING THROUGH 03Z THIS EVENING. ANY
THUNDERSTORM OR HEAVY SHOWER COULD PRODUCE GUSTY AND ERRATIC WINDS
ALONG WITH LOWERING VIS AND CIGS. GENERALLY EXPECT SOUTHWESTERLY
WINDS INCREASING THIS AFTERNOON TO AROUND 8-12 KT.
PDX AND APPROACHES...MVFR CIGS THIS MORNING WITH ONGOING RAIN
SHOWERS. EXPECT CIGS TO LIFT AS CONDITIONS TREND TOWARD
PREDOMINATELY VFR AFTER 15Z THIS MORNING. THERE IS AROUND A 15-25%
CHANCE OF THUNDERSTORMS THIS AFTERNOON. SOUTHWEST WINDS AROUND 5-7
KT EXPECTED TO INCREASE TO AROUND 10 KT AFTER 18Z. /DH
MARINE
BREEZY ONSHORE WINDS ARE EXPECTED TODAY WITH GUSTS UP
TO 20-25 KT, WHILE A CHANCE OF THUNDERSTORMS PERSISTS THROUGH
THIS EVENING. THUNDERSTORMS COULD PRODUCE ERRATIC AND GUSTY WINDS.
A WEST-NORTHWESTERLY SWELL WILL MAINTAIN SEAS AROUND 9 TO 11 FT
WITH A PERIOD OF AROUND 14 SECONDS ACROSS ALL COASTAL WATERS
THROUGH TONIGHT. THEREFORE, A SMALL CRAFT ADVISORY REMAINS IN
PLACE THROUGH THURSDAY NIGHT.
A DYNAMIC AND ACTIVE PATTERN RETURNS EARLY FRIDAY AND CONTINUES
THROUGH THE WEEKEND. AN OCCLUDED FRONT WILL APPROACH THE WATERS
LATE TONIGHT INTO FRIDAY. MODEL GUIDANCE SUGGESTS SURFACE LOW
PRESSURE DEVELOPS ALONG THE FRONT AS IT LIFTS ACROSS THE COASTAL
WATERS. TIMING AND STRENGTH OF THE LOW STILL REMAINS SOMEWHAT
UNCERTAIN, THEREFORE HAVE CONTINUED WITH THE GALE WATCH. BUT, HAVE
ALSO EXTENDED IT THROUGH FRIDAY NIGHT AS THE WESTERLY WINDS ON THE
BACKSIDE OF THE LOW MAINTAIN AROUND A 70% CHANCE OF GALE FORCE
WIND GUSTS. CURRENTLY, STRONGEST WINDS ARE MOST LIKELY SOUTH OF
THE CAPE FALCON/TILLAMOOK HEAD AREA. SEAS WILL HOVER AROUND 8 TO
11 FT THROUGH FRIDAY AFTERNOON, BUT ARE EXPECTED TO QUICKLY BUILD
FRIDAY NIGHT, PEAKING AROUND 14 TO 18 FT AS A MID-PERIOD WESTERLY
SWELL MOVES IN.
ANOTHER LOW PRESSURE SYSTEM IS CURRENTLY FORECAST TO APPROACH THE
OREGON COAST LATER SATURDAY. UNCERTAINTY REMAINS REGARDING THE
PATH OF THE SYSTEM, BUT THE POTENTIAL FOR AT LEAST GALE FORCE
WINDS REMAINS HIGH FOR THE CENTRAL OR COASTAL WATERS. YET ANOTHER
SYSTEM WILL BE POSSIBLE ON SUNDAY. THE CHANCE FOR STORM FORCE WIND
GUSTS REMAINS LOW, AROUND 10-30% THROUGH THE WEEKEND. SEAS ARE
ALSO LIKELY TO REMAIN ELEVATED THROUGH THE WEEKEND, WITH AROUND A
10% CHANCE OF SEAS EXCEEDING 20 FT ON SUNDAY. /DH
BEACH HAZARDS
THERE IS A THREAT OF SNEAKER WAVES THROUGH
TONIGHT AS A WESTERLY SWELL OF 9 TO 11 FT AT 14-15 SECONDS IS
EXPECTED. WAVES CAN RUN UP SIGNIFICANTLY FARTHER ON A BEACH THAN
NORMAL, INCLUDING OVER ROCKS AND JETTIES. SNEAKER WAVES CAN
SUDDENLY KNOCK PEOPLE OFF OF THEIR FEET AND QUICKLY PULL THEM INTO
THE FRIGID OCEAN, WHICH MAY LEAD TO SERIOUS INJURY OR DROWNING.
BEACH GOERS BEWARE, INCLUDING RAZOR CLAMMERS. NEVER TURN YOUR BACK
TO THE OCEAN.
PQR WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY UNTIL 11 PM PDT THIS EVENING FOR
ORZ126.
WINTER STORM WATCH FROM LATE TONIGHT THROUGH SATURDAY
AFTERNOON FOR ORZ126>128.
WINTER STORM WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ127-
128.
WA...WINTER WEATHER ADVISORY UNTIL 11 PM PDT THIS EVENING FOR
WAZ211.
WINTER STORM WATCH FROM LATE TONIGHT THROUGH SATURDAY
AFTERNOON FOR WAZ211.
PZ...SMALL CRAFT ADVISORY UNTIL 5 PM PDT FRIDAY FOR PZZ210-251-271.
SMALL CRAFT ADVISORY UNTIL 5 AM PDT FRIDAY FOR PZZ252-253-272-
273.
GALE WATCH FROM LATE TONIGHT THROUGH LATE FRIDAY NIGHT FOR
PZZ252-253-272-273.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
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X.COM/NWSPORTLAND
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