312
FXUS66 KPQR 162344
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
344 PM PST MON DEC 16 2024
SYNOPSIS
A SERIES OF FRONTS WILL MAINTAIN ACTIVE WEATHER
THROUGH WEDNESDAY. HEAVIEST PRECIPITATION EXPECTED TONIGHT
THROUGH TUESDAY. SNOW FOR THE CASCADES ABOVE 4000 FT UNTIL SNOW
LEVELS RISE ABOVE 7000 FT BY TUESDAY AFTERNOON.EXPECT STRONG,
GUSTY WINDS ALONG THE COAST LATE TUESDAY INTO WEDNESDAY WITH THE
PASSAGE OF A STRONG FRONT. DRIER CONDITIONS LIKELY LATER
WEDNESDAY THROUGH FRIDAY, ALTHOUGH WEATHER REMAINS ACTIVE OVER
THE PACIFIC AND NEAR THE COAST. RAIN LIKELY RETURNS FOR THE
WEEKEND AS THE UPPER LEVEL RIDGE SHIFTS EAST ALLOWING FOR
FRONTAL SYSTEMS TO PUSH INLAND.
SHORT TERM...NOW THROUGH WEDNESDAY NIGHT
AN ACTIVE WEATHER
PATTERN WILL CONTINUE THROUGH WEDNESDAY AS SEVERAL DISTURBANCES
IMPACT THE AREA. A LARGE UPPER LEVEL TROUGH IS POSITIONED ACROSS
THE NORTHEAST PACIFIC WHICH WILL SEND SEVERAL SHORTWAVES TOWARD
THE PACNW. A LOW IS CURRENTLY LOCATED NEAR 45N AND 136W WITH AN
OCCLUDED FRONT EXTENDING SOUTHEAST TOWARD CENTRAL OR,
TRANSITIONING TO A COLD FRONT NEAR SOUTHERN OR COAST. THE
WEATHER SYSTEM ASSOCIATED WITH THIS FRONT WEAKENS AND MOVES
NORTHEAST AS UPPER LEVEL RIDGING BUILDS OVER THE WEST COAST INTO
BRITISH COLUMBIA. BENEATH THE RIDGE, A WARM FRONT QUICKLY
PUSHES INLAND, BRINGING ENHANCED PRECIPITATION LATER TONIGHT
THROUGH TUESDAY. CONDITIONS ARE EXPECTED TO DRY AGAIN LATER
TUESDAY AS THE FRONT LIFTS FROM SOUTH TO NORTH. A SHORTWAVE
TROUGH THEN PUSHES A COLD FRONT ACROSS THE AREA WEDNESDAY
MORNING, BRINGING ANOTHER QUICK SHOT OF RAIN.
THE FRONTAL SYSTEM TUESDAY INTO WEDNESDAY IS EXPECTED TO BRING HEAVY
RAINFALL AND STRONG GUSTY WINDS TO THE COAST AND COAST RANGE. THERE
IS SIGNAL FOR A MODERATE TO STRONG ATMOSPHERIC RIVER ASSOCIATED WITH
THIS FRONTAL BOUNDARY, LASTING FOR AROUND 24 TO 30 HOURS, MAINLY
BETWEEN 12Z TUESDAY TO 12Z WEDNESDAY. RAINFALL TOTALS WILL BE
HEAVIEST ACROSS THE NORTHERN OR AND SOUTHERN WA COAST RANGE.
PROBABILITY FOR 3 INCHES OVER 48 HOURS ENDING WEDNESDAY MORNING IS
GREATER THAN 70% AND BUMPING IT TO 4 INCHES GIVES PROBABILITIES
BETWEEN 40-70%. HEFS GUIDANCE SUGGESTS ONLY A 20% CHANCE OF COASTAL
RIVERS REACHING MINOR FLOOD STAGE WITH THE EXCEPTION OF THE GRAYS
RIVER NEAR ROSBURG, WA. THE RIVER HERE HAS A ROUGHLY 50% CHANCE OF
REACHING MINOR FLOOD STAGE LATE TUESDAY INTO WEDNESDAY. SOUTHERLY
WINDS ARE ALSO EXPECTED TO INCREASE ALONG THE COAST BY TUESDAY
AFTERNOON WITH GUSTS INCREASING TO AROUND 40-60 MPH, LIKELY
PERSISTING THROUGH TUESDAY NIGHT. HIGHEST WIND GUSTS ARE EXPECTED
FOR THE BEACHES AND HEADLANDS WITH A 40-60% CHANCE FOR WIND GUSTS
GREATER THAN OR EQUAL TO 58 MPH. WIND GUSTS WILL PEAK AS THE FRONT
MOVES THROUGH TUESDAY EVENING INTO THE OVERNIGHT, WARRANTING A HIGH
WIND WATCH FROM 21Z TUE TO 12Z WED. RAINFALL INLAND WILL BE LOWER
DURING THE SAME TIME FRAME, GENERALLY 1.25-1.75 INCHES.
PROBABILITIES FOR GREATER THAN 1.75 INCHES IS ROUGHLY 10-30%.
SNOWFALL ACROSS THE CASCADES WILL CONTINUE THROUGH TUESDAY MORNING,
WITH AN ADDITIONAL 8 TO 15 INCHES POSSIBLE ABOVE 4000 FEET. SLR
VALUES WILL BE 8:1 TO 12:1 THROUGH TUESDAY MORNING, PRODUCING WET,
HEAVY SNOW AROUND THE PASSES. SNOW LEVELS ARE EXPECTED TO QUICKLY
RISE OVER 7000 FT ON TUESDAY AS THE WARM FRONT LIFTS NORTHWARD. WILL
MAINTAIN THE WINTER STORM WARNING FOR THE HIGH CASCADES THROUGH 10
AM TUESDAY AS TRAVEL WILL LIKELY BE HAZARDOUS OVER THE PASSES
TONIGHT. -BATZ
LONG TERM...THURSDAY THROUGH SUNDAY
WHILE THERE STILL
REMAINS SOME UNCERTAINTY FOR LATER THIS WEEK, THERE IS GOOD
AGREEMENT AMONG THE MODELS AND THEIR ENSEMBLES IN THE OVERALL
SYNOPTIC PATTERN. CLUSTER ANALYSIS OF 500 MB HEIGHTS HAVE BEEN
CONSISTENT IN SHOWING AN AMPLIFIED PATTERN WITH UPPER LEVEL
RIDGING OVER MUCH OF THE WESTERN US FOR THURSDAY AND FRIDAY.
WITH UPPER LEVEL TROUGHING OVER THE PACIFIC, THE WEATHER WILL
REMAIN ACTIVE OFFSHORE. FRONTAL SYSTEMS MAY BRUSH BY NORTHWEST
OREGON AND SOUTHWEST WASHINGTON AT TIMES, BUT AT MOST LIGHT RAIN
AT THE COAST, WITH INLAND LOCATIONS TRENDING MOSTLY DRY WITH
OFFSHORE LOW LEVEL FLOW. GENERALLY LESS THAN A 30% CHANCE OF
MEASURABLE RAIN EAST OF THE COAST RANGE UNTIL SATURDAY. CLUSTERS
ARE ALSO IN GOOD AGREEMENT THAT THE UPPER LEVEL RIDGE SHIFTS
EAST BY THE WEEKEND, ALLOWING FOR FRONTAL SYSTEMS TO PUSH BACK
INLAND. SNOW LEVELS APPEAR TO STAY RELATIVELY ELEVATED ABOVE
5000-6000 FT THROUGH SUNDAY. /DH
AVIATION
GENERALLY VFR/MVFR CONDITIONS WITH LINGERING SHOWERS
ACROSS THE AIRSPACE. EXPECT A VERY SLOW TREND TOWARDS
PREDOMINATELY VFR WITH POCKETS OF MVFR ACROSS THE AIRSPACE.
HOWEVER, ANOTHER APPROACHING FRONT WILL ARRIVE AROUND 23Z
MONDAY-04Z TUESDAY FOR THE COAST AND 00Z-06Z TUESDAY FOR INLAND
LOCATIONS. THIS WILL BRING ANOTHER ROUND OF INCREASED
PRECIPITATION AND PREDOMINATELY MVFR CONDITIONS FOR THE AIRSPACE.
WINDS WILL REMAIN AROUND 10-15 KT WITH GUSTS UP TO 25 KT AT SOME
INLAND LOCATIONS. EXPECT HIGHER GUSTS ALONG THE COAST THROUGH TAF
PERIOD WITH THE HIGHEST GUSTS (UP TO 30 KT) LIKELY AROUND KONP.
PDX AND APPROACHES...MIXTURE OF VFR AND MVFR CONDITIONS PERSIST.
AN INCOMING FRONTAL SYSTEM WILL BRING ANOTHER ROUND OF
PRECIPITATION AND PREDOMINATELY MVFR CONDITIONS AROUND 02Z
TUESDAY. SOUTH/SOUTHEASTERLY WINDS AROUND 8-10 KTS. COULD SEE SOME
GUSTY WINDS EAST OF THE TERMINAL AS GUSTY, EASTERLY WINDS FROM
THE MOUTH OF THE COLUMBIA RIVER GORGE. /42
MARINE
ACTIVE WEATHER WILL CONTINUE THROUGH THE MAJORITY OF
THE WEEK AS A SERIES OF SYSTEMS MOVE THROUGH THE REGION. EACH
SYSTEM WILL BRING BUILDING WINDS AND SEAS ACROSS ALL WATERS. THE
FIRST SYSTEM WILL BRING HAZARDOUS SEAS AND GALE FORCE GUSTS UP TO
50 KT THROUGH AT LEAST WEDNESDAY MORNING. THE NEXT TRIO OF SYSTEMS
WILL BRING THREE SOMEWHAT QUICK PUNCHES TO OUR WATERS ON
THURSDAY, WITH ROUND TWO ON FRIDAY AND THE FINAL, STRONGEST (AT
THIS TIME) BLOW ON SATURDAY. GUSTS UP TO 30 KT ON THURSDAY AND
FRIDAY (50%-70% PROBABILITY), WITH GUSTS UP TO 45 KT (50%-70%
PROBABILITY) ON SATURDAY.
GIVEN THE MINIMAL DOWNTIME BETWEEN SYSTEMS THIS WEEK, EXPECT SEAS
TO REMAIN ELEVATED. FOR TUESDAY INTO WEDNESDAY AFTERNOON 13-16 FT
SEAS. WEDNESDAY TO FRIDAY, SEAS 10-13 FT. FRIDAY AND SATURDAY,
SEAS 13-16 FT BUILDING TOWARDS 18-20 FT BY SATURDAY WITH A 30-50%
PROBABILITY OF SEAS GREATER THAN 20 FT. /42
PQR WATCHES/WARNINGS/ADVISORIES
OR...HIGH WIND WATCH FROM TUESDAY AFTERNOON THROUGH LATE TUESDAY
NIGHT FOR ORZ101>103.
WINTER STORM WARNING UNTIL 10 AM PST TUESDAY FOR ORZ126>128.
WA...HIGH WIND WATCH FROM TUESDAY AFTERNOON THROUGH LATE TUESDAY
NIGHT FOR WAZ201.
WINTER WEATHER ADVISORY UNTIL 10 AM PST TUESDAY FOR WAZ211.
PZ...SMALL CRAFT ADVISORY UNTIL 1 AM PST TUESDAY FOR PZZ210-251>253.
HAZARDOUS SEAS WARNING FROM 1 AM TO 10 AM PST TUESDAY FOR PZZ210-
251>253.
GALE WARNING FROM 10 AM TUESDAY TO 7 AM PST WEDNESDAY FOR PZZ210-
251>253-271>273.
SMALL CRAFT ADVISORY UNTIL 10 PM PST THIS EVENING FOR PZZ271>273.
HAZARDOUS SEAS WARNING FROM 10 PM THIS EVENING TO 10 AM PST
TUESDAY FOR PZZ271>273.
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