293
FXUS66 KPQR 182353
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
353 PM PST MON NOV 18 2024
SYNOPSIS
SCATTERED SHOWERS CONTINUE ACROSS THE AREA TONIGHT,
WITH LINGERING WINTER WEATHER IMPACTS IN THE CASCADES. A
POWERFUL SYSTEM APPROACHES THE COASTAL WATERS ON TUESDAY,
BRINGING STRONG WINDS TO THE COAST AND BREEZY CONDITIONS TO THE
INTERIOR VALLEYS TUESDAY EVENING THROUGH EARLY WEDNESDAY
MORNING. THIS SYSTEM WILL ALSO BRING ANOTHER ROUND OF HEAVY SNOW
TO THE HIGH CASCADES. WET WEATHER CONTINUES THROUGH THE END OF
THE WEEK, BUT THE PROBABILITY FOR SIGNIFICANT HYDRO IMPACTS HAS
DIMINISHED WITH TIME AS A STRONG ATMOSPHERIC RIVER REMAINS SOUTH
OF THE AREA.
DISCUSSION
SCATTERED RAIN SHOWERS ARE ONGOING ACROSS THE
AREA THIS AFTERNOON IN MOIST ONSHORE FLOW BEHIND A DEPARTING
SHORTWAVE TROUGH, WITH LOCALLY HEAVY SNOW SHOWERS CONTINUING
ABOVE 2000 FEET. HAVE RECEIVED REPORTS TODAY OF SOME WET SNOW
MIXING IN WITH HEAVIER RAIN SHOWERS ALL THE WAY DOWN TO 700
FEET ELEVATION, WITH NO ACCUMULATION. SHOWERS WILL LINGER
ACROSS THE AREA THROUGH TONIGHT IN THE WAKE OF THE DEPARTING
TROUGH. THE WINTER WEATHER ADVISORY FOR THE HIGHER POINTS OF THE
COAST RANGE SHOULD BE ALLOWED TO EXPIRE AT 10 PM THIS EVENING,
BUT MAY NEED TO CONSIDER EXTENDING THE WINTER WEATHER HEADLINES
FOR THE CASCADES A BIT LONGER OVERNIGHT DEPENDING ON OBSERVED
TRENDS WITH RESPECT TO SHOWER COVERAGE AND INTENSITY. ALSO CAN'T
RULE OUT A FEW RUMBLES OF THUNDER AT LOWER ELEVATIONS THROUGH
THIS EVENING, BUT THUNDER CHANCES WILL GRADUALLY DIMINISH WITH
TIME AND MAINLY FAVOR THE COASTAL WATERS OVERNIGHT.
ATTENTION QUICKLY TURNS TO A POWERFUL SYSTEM DEVELOPING OVER THE
NE PACIFIC TONIGHT AND APPROACHING OUR REGION ON TUESDAY. WATER
VAPOR IMAGERY CURRENTLY DEPICTS A BROAD UPPER LEVEL TROUGH
CENTERED OVER THE GULF OF ALASKA, WITH A 150 KT JET STREAK
ROUNDING THE BASE OF THE TROUGH. A BAROCLINIC LEAF NOTED
CROSSING 150W SIGNALS IMMINENT DEVELOPMENT OF A SURFACE LOW
PRESSURE SYSTEM, AND THIS FEATURE WILL UNDERGO EXPLOSIVE
CYCLOGENESIS OVER THE NEXT 24 HOURS BENEATH THE LEFT EXIT REGION
OF THE UPPER LEVEL JET. MODELS ARE IN GOOD AGREEMENT IN
DEPICTING A SUB 950 MB LOW APPROXIMATELY 350-400 MILES OFF THE
WASHINGTON COAST BY LATE TOMORROW AFTERNOON, SENDING A STORM
FORCE FRONT THROUGH THE COASTAL WATERS DURING THE EVENING. WIND
IS OBVIOUSLY THE PRIMARY FORECAST CONCERN WITH THIS SYSTEM, AND
HAVE UPGRADED THE WATCHES TO HIGH WIND WARNINGS ALONG THE COAST
BEGINNING 4 PM TOMORROW AND CONTINUING THROUGH EARLY WEDNESDAY
MORNING. FORECAST DETAILS WILL BE TRICKY AS THE PRESSURE
GRADIENT RETAINS AN OFFSHORE COMPONENT UNTIL THE FRONT REACHES
THE COAST, WHICH WOULD TEND TO RESTRICT THE STRONGEST WINDS TO
THE IMMEDIATE COAST, HOWEVER VERY STRONG WINDS OF 80-90 KT
DEPICTED BY THE MODELS AT 925 MB LEAVE OPEN THE POSSIBILITY FOR
A HIGHER END WIND EVENT IF ANY OF THOSE WINDS ARE ABLE TO MIX
DOWN TO THE SURFACE AS THE FRONT MOVES ONSHORE. FOR NOW, STILL
EXPECTING MAXIMUM GUSTS AROUND 60 MPH AT THE COAST, BUT HI-RES
GUIDANCE DOES SHOW AROUND A 25% PROBABILITY FOR GUSTS AS HIGH AS
70 MPH AND A 10% CHANCE FOR GUSTS AS HIGH AS 80 MPH ON THE
CENTRAL OREGON COAST, WITH THIS MOST LIKELY TO OCCUR ROUGHLY
4-10 PM TUESDAY EVENING. ALSO OPTED TO ISSUE A WIND ADVISORY FOR
THE WILLAMETTE VALLEY AND THE INTERIOR VALLEYS OF SOUTHWEST
WASHINGTON. WHILE WINDS WILL NOT BE AS STRONG AS THOSE SEEN AT
THE COAST, HI-RES MODELS DO INDICATE AROUND A 50% CHANCE FOR
WINDS TO GUST AS HIGH AS 45 MPH IN THE VALLEYS AS THE FRONT
MOVES THROUGH TUESDAY EVENING INTO EARLY WEDNESDAY MORNING.
THE FRONT WILL ALSO BRING ANOTHER BURST OF LOCALLY HEAVY RAIN
AND MOUNTAIN SNOW TUESDAY NIGHT INTO WEDNESDAY, WITH THE LATEST
FORECAST CALLING FOR AROUND 0.75-1.25" OF RAIN AT THE COAST AND
AROUND ANOTHER HALF INCH INLAND THROUGH EARLY WEDNESDAY. ISSUED
ANOTHER WINTER WEATHER ADVISORY FOR THE HIGH CASCADES TUESDAY
AFTERNOON THROUGH WEDNESDAY MORNING. SNOW LEVELS WILL INITIALLY
BE AROUND 2500-3000 FEET AT ONSET OF PRECIPITATION ON TUESDAY
BUT WILL QUICKLY RISE ABOVE 4000 FEET TUESDAY EVENING. THEREFORE
EXPECT THE HIGHEST ADDITIONAL SNOWFALL AMOUNTS OF 8-14 INCHES
TO BE MAINLY CONFINED TO THE PASSES AND ABOVE FOR THIS EVENT.
STRONG WINDS ASSOCIATED WITH THE FRONT WILL ALSO LEAD TO SOME
BLOWING SNOW CONCERNS, BUT RELATIVELY HEAVY, WET SNOW WITH
TEMPERATURES IN THE LOW 30S WILL NOT BE CONDUCIVE TO TRUE
BLIZZARD CONDITIONS. NONETHELESS, TRAVEL WILL BE VERY DIFFICULT
WITH HEAVY SNOW AND SEVERELY REDUCED VISIBILITIES AT TIMES.
AS FOR THE PREVIOUSLY ADVERTISED ATMOSPHERIC RIVER EVENT,
MODELS HAVE CONTINUED TO DEPICT THAT FEATURE SHIFTING SOUTH OF
THE AREA, WITH THE HEAVIEST RAIN FOCUSED OVER SOUTHWEST OREGON
AND NORTHERN CALIFORNIA THROUGH THE MIDDLE OF THE WEEK. AS SUCH,
MODEL QPF HAS CONTINUED TO TREND DOWNWARD WITH THE LATEST RUNS.
THE CURRENT MIDDLE GROUND SOLUTION WOULD GIVE THE COAST AROUND
4 INCHES OF RAIN FOR THE 72 HOUR PERIOD ENDING FRIDAY MORNING
WITH AROUND 1.50-2.00" IN THE WILLAMETTE VALLEY, WHILE A
REASONABLE WORST CASE AS DEPICTED BY NBM 90TH PERCENTILE
GUIDANCE WOULD BRING 5-6 INCHES TO THE COAST AND 2-3" IN THE
VALLEY. FLOOD GUIDANCE HAS CONTINUED TO TREND DOWNWARD AS A
RESULT, WITH NO AREA RIVERS CURRENTLY FORECAST TO REACH FLOOD
STAGE AND HEFS GUIDANCE GIVING AROUND A 10-20 PERCENT CHANCE OF
REACHING MINOR FLOOD STAGE ON THE MORE RESPONSIVE RIVERS
DRAINING THE COAST RANGE. WHILE SOME LOCAL PONDING OF WATER AND
DRAINAGE ISSUES CAN BE EXPECTED, THE BOTTOM LINE IS THE THE
PROBABILITY FOR SIGNIFICANT HYDRO IMPACTS THIS WEEK CONTINUE TO
TREND DOWNWARD AS QPF AMOUNTS TREND DOWN WITH RECENT MODEL RUNS.
/CB
THE WET WEATHER LOOKS TO CONTINUE INTO THE WEEKEND WITH
ENSEMBLES SHOWING THE POTENTIAL FOR A WEAKER WEATHER SYSTEM
SATURDAY. DETAILS STILL REMAIN UNCERTAIN AT THIS TIME AFTER
WEDNESDAY. WILL NEED TO KEEP AN EYE ON HOW MODELS RESOLVE THE
COMPLICATED FEATURES OF THE FORECAST. -HEC
AVIATION
A MIX OF VFR/MVFR CONDITIONS CONTINUES THIS AFTERNOON
WITH SCATTERED SHOWERS CONTINUING ACROSS THE REGION. A
STABILIZING AIRMASS OVERNIGHT WILL LEAD TO INCREASING
PROBABILITIES FOR MVFR AND IFR CONDITIONS TO BECOME THE DOMINANT
FLIGHT CONDITION AT ALL TAF SITES. STATISTICAL GUIDANCE SUGGESTS
GREATER THAN A 80% CHANCE OF MVFR CONDITIONS AT ANY GIVEN HOUR AT
NEARLY EVERY INLAND TAF SITE BEGINNING BETWEEN 06-09Z TUESDAY AND
CONTINUE THROUGH 18Z TUESDAY. THE PROBABILITY FOR IFR CONDITIONS
CLIMB ABRUPTLY INTO THE 20-50% STARTING AROUND 06-09Z BUT ONLY
LASTS UNTIL 15Z OR SO. IT SHOULD BE NOTED THAT THERE IS A 20-30%
CHANCE FOR A BRIEF THUNDERSTORM, PRIMARILY FOR THE COAST TAF SITES
THROUGH AT LEAST THIS EVENING. SHOWERS WILL CONTINUE TONIGHT
BEFORE A STRONG FRONT APPROACHES AND BRINGS A STEADIER RAIN
THROUGH TUESDAY.
SOUTHWEST WINDS ALONG THE COAST CONTINUE AT AROUND 10 KTS WHILE
WINDS INLAND CONTINUE FROM THE SOUTH AT 10-15 KTS AND A FEW GUSTS
UP TO 20 KTS. WINDS WILL INCREASE LATE TONIGHT INTO TUESDAY
MORNING AS A STRONG FRONT APPROACHES. EXPECT WINDS ALONG THE COAST
TO TURN SOUTHERLY AT 20-25 KTS AND GUSTS TO 35 KTS WHILE INLAND
WINDS INCREASE TO 15-20 KTS WITH GUSTS 25-30 KTS FROM THE
SOUTHEAST.
PDX APPROACHES...SCATTERED SHOWERS CONTINUE THROUGH TONIGHT. A
STABILIZING AIRMASS OVERNIGHT WILL LEAD TO INCREASING
PROBABILITIES FOR MVFR AND IFR CONDITIONS TO BECOME THE DOMINANT
FLIGHT CONDITION BETWEEN 06-09Z TUESDAY AND CONTINUE THROUGH 18Z
TUESDAY. SOUTH TO SOUTHWESTERLY WINDS TODAY WILL MOST LIKELY BACK
TO EASTERLY BETWEEN 06-12Z TUESDAY. WINDS EXPECTED TO INCREASE TO
10-15 KTS WITH GUSTS TO 20 KTS TUESDAY AS THE FRONT APPROACHES.
-BATZ
MARINE
WESTERLY WINDS WILL GRADUALLY SHIFT SOUTHERLY TONIGHT
AHEAD OF AN APPROACHING COLD FRONT. SEAS REMAIN STEEP WITH
HEIGHTS IN THE LOW TO MID TEENS AT 13-14 SECONDS, WARRANTING A HAZ
SEAS WARNING. SEAS WILL DIP A FEW FEET FOR THE NORTHERN ZONES AND
THE INNER WATER ZONES, DROPPING INTO SMALL CRAFT ADVISORY
CRITERIA THIS EVENING THROUGH 10 AM TUESDAY.
CONDITIONS BECOME TREACHEROUS AS A STRONG STORM APPROACHES THE
WATERS TUESDAY, EASILY BRINGING STORM FORCE WINDS FROM TUESDAY
AFTERNOON TO LATE TUESDAY NIGHT. A STORM WARNING GOES INTO EFFECT
AT 10 AM TUESDAY WITH GUSTS BETWEEN 50-60 KTS EXPECTED LATE
TUESDAY AFTERNOON. SPORADIC GUSTS ABOVE 60 KTS WILL ALSO BE
POSSIBLE. NBM GUIDANCE SUGGESTS AROUND A 10-40% CHANCE OF
HURRICANE FORCE WINDS (64 KTS OR HIGHER), FOR PORTIONS OF THE
OUTER WATERS WHILE HREF SUGGESTS HURRICANE FORCE WINDS COULD BE
MORE WIDESPREAD WITH PROBABILITIES 50-70%, WITH THE HIGHEST PROBS
ACROSS THE SOUTHERN ZONES. WITH STRONG WIND WAVES AND SWELL
REMAINING ELEVATED, SEAS WILL BE QUITE HIGH, WITH CURRENT
FORECASTED PEAK WAVES AT 20-26 FT AT 13-15 SECONDS TUESDAY
AFTERNOON INTO LATE TUESDAY NIGHT. SUSTAINED WINDS PEAK BETWEEN
40-50 KTS WITH GUSTS TO 60, A FEW HURRICANE FORCE GUSTS (>64 KTS)
POSSIBLE DURING THE 1 PM TO 7 PM TIMEFRAME. WINDS EXPECTED TO FALL
BACK INTO GALE CRITERIA THEREAFTER. -BATZ
BEACH HAZARDS
HIGH SNEAKER WAVE THREAT REMAINS IN PLACE
THROUGH TODAY DUE TO AN INCREASING WESTERLY SWELL WITH A DOMINANT
WAVE PERIOD AROUND 10-14 SECONDS. WITH THE PERIGEAN SPRING TIDES
UNDERWAY (COMMONLY REFERRED TO AS "KING TIDES"), IT IS A GOOD IDEA
TO TAKE EXTRA PRECAUTION ON BEACHES. 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. THE SNEAKER WAVE THREAT LOOKS TO REMAIN HIGH
THROUGH EARLY NEXT WEEK.
PQR WATCHES/WARNINGS/ADVISORIES
OR...HIGH WIND WARNING FROM 4 PM TUESDAY TO 4 AM PST WEDNESDAY FOR
ORZ101>103-106-107.
WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR
ORZ106-107.
WIND ADVISORY FROM 4 PM TUESDAY TO 4 AM PST WEDNESDAY FOR
ORZ108>118.
WINTER STORM WARNING UNTIL 10 PM PST THIS EVENING FOR
ORZ123>128.
WINTER WEATHER ADVISORY FROM 4 PM TUESDAY TO 10 AM PST
WEDNESDAY FOR ORZ126>128.
WA...HIGH WIND WARNING FROM 4 PM TUESDAY TO 4 AM PST WEDNESDAY FOR
WAZ201.
WIND ADVISORY FROM 4 PM TUESDAY TO 4 AM PST WEDNESDAY FOR
WAZ204>207.
WINTER STORM WARNING UNTIL 10 PM PST THIS EVENING FOR WAZ211.
WINTER WEATHER ADVISORY FROM 4 PM TUESDAY TO 10 AM PST
WEDNESDAY FOR WAZ211.
PZ...HAZARDOUS SEAS WARNING UNTIL 7 PM PST THIS EVENING FOR PZZ210-
251>253-271.
SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 10 AM PST
TUESDAY FOR PZZ210-251>253-271.
GALE WARNING FROM 10 AM TUESDAY TO 4 AM PST WEDNESDAY FOR
PZZ210.
STORM WARNING FROM 10 AM TUESDAY TO 4 AM PST WEDNESDAY FOR
PZZ251>253-271>273.
HAZARDOUS SEAS WARNING UNTIL 1 AM PST TUESDAY FOR PZZ272-273.
SMALL CRAFT ADVISORY FROM 1 AM TO 10 AM PST TUESDAY FOR PZZ272-
273.
WWW.WEATHER.GOV/PORTLAND
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