759
FXUS66 KPQR 182304
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
304 PM PST WED DEC 18 2024
SYNOPSIS
RELATIVELY QUIETER WEATHER THROUGH FRIDAY. WEAK
FRONTS WILL BRING CHANCES FOR LIGHT PRECIPITATION, MAINLY ALONG
THE COAST AND COAST RANGE. WIDESPREAD RAIN RETURNS THIS WEEKEND
INTO EARLY NEXT WEEK AS SEVERAL FRONTAL SYSTEMS PUSH INLAND.
SHORT TERM...NOW THROUGH FRIDAY NIGHT
RELATIVELY QUIET
WEATHER CONDITIONS WILL PERSIST ACROSS NORTHWEST OREGON AND
SOUTHWEST WASHINGTON THROUGH FRIDAY AS BRIEF HIGH PRESSURE
BUILDS FOLLOWING THE PREVIOUS FRONTAL SYSTEM. THE LAST SYSTEM
HAS EXITED THE REGION AND PRECIPITATION AS ENDED FOR MOST PLACES
OTHER THAN A FEW LINGERING SHOWERS IN THE NORTH OREGON CASCADES
AND FOOTHILLS. THE GRAYS RIVER REMAINS IN MINOR FLOOD STAGE AS
OF 3 PM WEDNESDAY, BUT CONTINUES TO SUBSIDE. EXPECT THE GRAYS
RIVER TO FALL BELOW FLOOD STAGE SOME TIME LATE THIS AFTERNOON
OR EVENING.
A WEAK FRONTAL SYSTEM APPROACHES THE PACIFIC NORTHWEST LATE
TONIGHT INTO EARLY THURSDAY MORNING (MAINLY BEFORE 4-6 AM),
HOWEVER, PRECIPITATION AMOUNTS LOOK VERY LIGHT. MODELS SUGGEST
THE WARM FRONT WILL BRUSH THE AREA THURSDAY MORNING, WITH THE
HIGHEST CHANCES (40-60%) FOR PRECIPITATION ALONG THE COAST,
COAST RANGE, AND WILLAPA HILLS. 24 HOUR QPF AMOUNTS ENDING 4 PM
THURSDAY ARE FORECAST AROUND 0.10-0.25 INCH FOR THESE LOCATIONS,
WHILE AREAS EAST OF THE COAST RANGE ARE FORECAST TO RECEIVE LESS
THAN 0.05 INCH OF QPF, OR REMAIN COMPLETELY DRY. ONCE THE WARM
FRONT EXITS THE AREA, WILL SEE A BREAK FROM THE RAIN THROUGH THE
REST OF THE MORNING AND EARLY AFTERNOON. THE TRAILING COLD
FRONT WILL THEN ARRIVE LATE THURSDAY AFTERNOON/EVENING,
RETURNING PRECIPITATION CHANCES AND POTENTIALLY AN ADDITIONAL
TENTH OF AN INCH OF PRECIP ALONG THE NORTH OREGON AND SOUTH
WASHINGTON COAST AND COAST RANGE. NBM SUGGESTS A 30-50% CHANCE
THAT THESE LOCATIONS RECEIVE MORE THAN 0.50 INCH OF QPF, WHICH
WOULD MOST LIKELY OCCUR IF THESE FRONTS END UP MORE PERSISTENT
AND STRONGER THAN FORECAST.
A SIMILAR PATTERN OCCURS ON FRIDAY, WITH MOSTLY DRY CONDITIONS
FOR INLAND LOCATIONS WITH ANOTHER WEAK FRONT FORECAST TO BRING
LIGHT PRECIPITATION ALONG THE COAST AND COAST RANGE. BY FRIDAY
NIGHT, THE NEXT ROBUST FRONTAL SYSTEM WILL MOVE IN, RETURNING
WIDESPREAD RAIN TO THE REGION ALONG WITH STRONGER WINDS AS
MODELS ARE SUGGESTING TIGHTER PRESSURE GRADIENTS. -ALVIZ
LONG TERM...SATURDAY THROUGH TUESDAY
WPC CLUSTERS ARE IN
GOOD AGREEMENT THAT THE UPPER LEVEL RIDGE SHIFTS EAST BY THE
WEEKEND, ALLOWING FOR FRONTAL SYSTEMS TO PUSH INLAND. THERE IS
HIGH CONFIDENCE THAT WET WEATHER OVER THE WEEKEND CONTINUES INTO
NEXT WEEK. SNOW LEVELS APPEAR TO STAY RELATIVELY HIGH AROUND
4500-6000 FT THROUGH THE WEEKEND, BEFORE RISING AGAIN INTO
EARLY NEXT WEEK. MOST ENSEMBLE MEMBERS AREN'T SUGGESTING
SIGNALS FOR STRONG ATMOSPHERIC RIVERS, THOUGH THESE FRONTAL
SYSTEMS WILL LIKELY BRING DECENT ROUNDS OF RAIN THROUGH
CHRISTMAS EVE AND BEYOND. LESS THAN 5% OF ENSEMBLE MEMBERS
SUGGEST A STRONG TO EXTREME ATMOSPHERIC RIVER BETWEEN MONDAY-
WEDNESDAY NEXT WEEK. WILL ALSO CONTINUE TO MONITOR CHANCES FOR
POTENTIALLY STRONG WINDS INTO NEXT WEEK, ALTHOUGH AT THIS TIME
CONFIDENCE REMAINS LOW FOR ANY WIND STORMS DEVELOPING. WITH THE
WET PATTERN CONTINUING NEXT WEEK, WILL ALSO SEE RISES ON LOCAL
RIVERS, WITH HEFS SUGGESTING A 15-30% CHANCE THAT RIVERS ALONG
THE COAST/COAST RANGE REACH AT LEAST MINOR FLOOD STAGE.
-ALVIZ/DH
AVIATION
GENERALLY VFR WITH ISOLATED POCKETS OF MVFR
CONDITIONS ACROSS THE AIRSPACE. SOUTHERLY WINDS ALONG THE COAST
WITH LIGHT AND VARIABLE WIND FOR INLAND LOCATIONS THROUGH THE
MAJORITY OF THE TAF PERIOD.
ANOTHER FRONT WILL ARRIVE AROUND 05Z TO 09Z THURSDAY. THIS FRONT
WILL TRACK SOUTH TO NORTH AND BRING RAIN AND MID TO HIGH LEVEL
CLOUDS. STILL EXPECTING GENERALLY VFR CONDITIONS FOR INLAND
LOCATIONS AND A MIXTURE OF VFR/MVFR ALONG THE COAST FOR AREAS
OTHER THAN KONP. KONP, WILL LIKELY HOLD ONTO LOWER FLIGHT
CONDITIONS WITH A MIXTURE OF IFR AND LIFR.
THIS FRONT WILL KEEP CLOUDS OVER THE NORTHERN WILLAMETTE VALLEY
WITH SOME CLEARING EXPECTED FOR THE CENTRAL AND SOUTHERN
WILLAMETTE VALLEY. CLEARING AND MINIMAL WIND, WILL RESULT IN A
60%-70% PROBABILITY FOR IFR/LIFR CONDITIONS TO DEVELOP WITHIN THE
SOUTHERN WILLAMETTE VALLEY (KEUG) STARTING AROUND 16Z THURSDAY.
WHILE THE CENTRAL WILLAMETTE VALLEY (KSLE) ARE EXPECTED TO CLEAR
OUT, BUT UPPER LEVEL CLOUDS WILL LIKELY LINGER AND RESULT IN A 20%
PROBABILITY FOR IFR/LIFR DEVELOPMENT.
PDX AND APPROACHES...GENERALLY VFR THROUGH THE TAF PERIOD. FRONTAL
PASSAGE AROUND 08Z THURSDAY WILL BRING RAIN (75% PROBABILITY) AND
CIGS AROUND FL040 (25% PROBABILITY). /42
MARINE
AN ACTIVE WEATHER PATTERN CONTINUES THROUGH THE
MAJORITY OF THE WEEK AS A SERIES OF SYSTEMS MOVE THROUGH THE
REGION. EACH SYSTEM WILL BRING INCREASING WINDS AND SEAS ACROSS
ALL WATERS. THE NEXT SYSTEM WILL ARRIVE TONIGHT AND THROUGH
THURSDAY MORNING, BRINGING STRONG SMALL CRAFT ADVISORY CONDITIONS
TO ALL WATERS. THEREFORE, HAVE EXTENDED THE CURRENT SMALL CRAFT
ADVISORIES TO REFLECT THIS.
A BRIEF REPRIEVE IN THE ACTIVE WEATHER IS EXPECTED THURSDAY INTO
FRIDAY AFTERNOON, BUT SEAS WILL REMAIN AROUND 10 FT DURING THIS
TIME. BY FRIDAY AFTERNOON, THE NEXT MAJOR SYSTEM (OUT OF THREE)
IS EXPECTED TO BRING GALES ACROSS ALL WATERS (50-60% PROBABILITY)
WITH A STRONGER SYSTEM EXPECTED SATURDAY WITH A 40-50% PROBABILITY
FOR STRONG GALES AND AROUND A 20% PROBABILITY FOR STORM FORCE
CONDITIONS. THE THIRD SYSTEM LOOKS TO BE SLIGHTLY STRONGER THAN
THE SATURDAY SYSTEM WITH A 10-20% PROBABILITY OF STORM FORCE
CONDITIONS.
IN ADDITION TO THE INCREASING WINDS, SEAS ARE ALSO EXPECTED TO
BUILD TOWARDS THE MID-TEENS BY FRIDAY/SATURDAY. SATURDAY
AFTERNOON SEAS IN THE UPPER TEENS WITH THE OUTER WATERS LIKELY
BUILDING TOWARDS 20-22 FT (50-60% PROBABILITY) BY SATURDAY
EVENING/SUNDAY MORNING. SEAS WILL REMAIN IN THE UPPER TEENS TO LOW
20S THROUGH SUNDAY AND INTO MONDAY FOR ALL WATERS (15-25%
PROBABILITY). THERE REMAINS SOME UNCERTAINTY AS TO THE EXACT TRACK
AND STRENGTH OF THE AFOREMENTIONED SYSTEMS, BUT WE WILL BE PAYING
CLOSE ATTENTION AND ADJUSTING THE FORECAST AS NEEDED. /42
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 1 AM PST THURSDAY FOR PZZ210.
SMALL CRAFT ADVISORY UNTIL 7 PM PST THURSDAY FOR PZZ251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
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