872
FXUS66 KPQR 201500 CCA
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
700 AM PST THU FEB 20 2025
SYNOPSIS
HIGH PRESSURE BEGINS TO MOVE OVER THE REGION, BRINGING
RELATIVELY DRY CONDITIONS THROUGH FRIDAY AFTERNOON. PATCHY FOG
IS POSSIBLE THIS MORNING AND FRIDAY MORNING WITH THE POTENTIAL
FOR CLEARER SKIES. A TAD BIT COOLER TONIGHT INTO TOMORROW
MORNING DUE TO EASTERLY WINDS. OTHERWISE, EXPECT A WARMING
TREND INTO EARLY NEXT WEEK, WITH A SERIES OF FRONT SYSTEMS
BRINGING WET CONDITIONS FRIDAY NIGHT AND THROUGH THE WEEKEND.
SHORT TERM...NOW THROUGH FRIDAY
BROKEN SKIES THIS MORNING
COULD RESULT IN PATCHY FOG WITHIN THE WILLAMETTE VALLEY,
ESPECIALLY WITH LIGHT WINDS AND TRANSIENT RIDGING OVERHEAD
AIDING IN CLEARER SKIES. TODAY, CONDITIONS WILL BE RELATIVELY
DRY AND WITH HIGH TEMPS IN THE LOW 50S. WILL SEE ONSHORE
SOUTHERLY WINDS FOR MOST OF TODAY, THEN SHIFTING EASTERLY IN THE
EVENING AND BRINGING COOLER TEMPERATURES OVERNIGHT INTO SW
WASHINGTON AND NW OREGON. TO COMPARE, THIS MORNINGS LOW TEMPS
WILL BE IN THE UPPER 30S AND LOW 40S, WHILE FRIDAY MORNING WILL
LIKELY HAVE LOW TEMPERATURES IN THE MID TO UPPER 30S (THE COAST
WILL HAVE SIMILAR TEMPS TO THIS MORNING, IN THE LOW 40S).
FRIDAY, THE RIDGE PERSISTS OVERHEAD, BRINGING A FEW DEGREES
WARMER TEMPERATURES TO THE REGION. SIMILAR TO THIS MORNING,
PATCHY FOG WILL BE POSSIBLE. FRIDAY NIGHT, EXPECT A CHANGE TO
THE WEATHER AS A TROUGH PUSHES EAST AND WEAKENS THE RIDGE
OVERHEAD. ALONG WITH IT, A SERIES OF FRONTAL SYSTEMS THAT WILL
BRING MORE WET WEATHER THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK. ~HALL
LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
THE FIRST COLD
FRONTAL SYSTEM OF THE SERIES WILL ARRIVE FRIDAY NIGHT. WHILE
MODELS HAVE SOME DISAGREEMENT IN TRACK AND IMPACTS OF THE RAIN,
THE RAIN WILL BE KEPT TO THE NORTH, MOSTLY IN SW WASHINGTON,
WITH NO IMPACTS EXPECTED.
SATURDAY AFTERNOON, THE SECOND FRONTAL SYSTEM, A TRAILING WARM
FRONT, WILL BRING WIDESPREAD RAIN AND BUILD ONTO THE POTENTIAL
FOR IMPACTS (FOR THE LONG RUN). THERE IS GOOD CLUSTER AGREEMENT
BUT SUBTLE DIFFERENCES WILL RESULT IN VARYING EXPECTED RAINFALL
AMOUNTS THROUGHOUT THE REGION. WITH SOUTHWESTERLY FLOW EXPECTED
DURING THIS SYSTEM, THE RAINSHADOW EFFECT WILL LIKELY LESSEN
RAINFALL AMOUNTS WITHIN THE WILLAMETTE VALLEY, AND KEEP THE
HIGH AMOUNTS OF RAINFALL IN THE ADJACENT HIGHER TERRAIN. CURRENT
GUIDANCE SUGGESTS A 20-40% CHANCE FOR 1 INCH OR MORE OF
RAINFALL FOR THE LOWLAND VALLEYS FROM 4 AM SATURDAY TO 4 AM
SUNDAY. ALONG THE COAST, A 20-40% CHANCE FOR 1.5 INCH OR MORE
OF RAINFALL. THE COAST RANGE HAS SIMILAR CHANCES FOR 2.5 INCHES
OR MORE OF RAINFALL. THE COAST WILL HAVE WIND GUSTS UP TO 35-40
MPH FROM THE AFTERNOON TO THE LATE EVENING.
SUNDAY, ANOTHER ROUND OF PRECIPITATION WILL PROVIDE A MORE
LIKELY CHANCE FOR IMPACTS GIVEN THE RECENT SYSTEMS THAT HAVE
PASSED, ALONG WITH SNOWMELT WITHIN THE FOOTHILLS. IN A WEEKEND
OVERVIEW FOR EXPECTED RAINFALL (48 HOUR TIMEFRAME), CURRENT
GUIDANCE SUGGESTS A 25-50% CHANCE FOR 1.5 INCH OR MORE OF
RAINFALL WITHIN THE VALLEY LOWLANDS FROM 4 AM SATURDAY TO 4 AM
MONDAY. WORST CASE SCENARIO, THERE IS A 5-20% CHANCE TO RECEIVE
2 INCHES OR MORE OF RAINFALL (LOWEST CHANCES IN THE PORTLAND AND
VANCOUVER METRO). THE COAST HAS A 40-70% CHANCE FOR 2 INCHES OR
MORE OF RAINFALL, WITH A WORST CASE SCENARIO SUGGESTING A 5-15%
CHANCE TO RECEIVE 3 INCHES OR MORE OF RAINFALL. HOW WILL RIVERS
RESPOND? WELL, HEFS GUIDANCE CURRENTLY SUGGESTS A LESS THAN 10%
CHANCE FOR MOST RIVERS TO REACH MINOR FLOOD STAGE. THE ONE
EXCEPTION IS THE WILSON RIVER NEAR TILLAMOOK, WHICH HAS A
25-30% CHANCE TO REACH MINOR FLOOD STAGE AND A 10-15% CHANCE TO
REACH MODERATE FLOOD STAGE. LASTLY, WITH SNOW LEVELS RISING TO
ABOVE 5000 FT THIS WEEKEND, LITTLE TO NO SNOWFALL IS EXPECTED
FOR ANY OF THE AFOREMENTIONED SYSTEMS.
MONDAY THROUGH WEDNESDAY, MIGHT SEE SOME WARMER WEATHER IN THE
UPPER 50S TO LOW 60S. DESPITE THE WARMER WEATHER, WET WEATHER
WILL LIKELY CONTINUE MONDAY THROUGH TUESDAY, WITH DRY WEATHER
AND CLEAR SKIES WEDNESDAY. ~HALL
AVIATION
HIGH PRESSURE OVER THE REGION WILL RESULT IN GENERALLY
VFR CONDITIONS FOR INLAND LOCATIONS AND PREDOMINATELY MVFR
CONDITIONS ALONG THE COAST. FLIGHT LEVELS INLAND ARE EXPECTED TO
BE IN-BETWEEN FL035 TO FL050. WEAK SOUTH/SOUTHWEST FLOW AT THE
SURFACE COMBINED WITH NORTH/NORTHWESTERLY FLOW ALOFT IS LOOKING TO
KEEP THE ATMOSPHERE WELL MIXED. THEREFORE, AM NOT EXPECTING ANY
IFR OR LIFR CONDITIONS TO DEVELOP THROUGH 12Z FRIDAY. HOWEVER,
SOME BREAKS IN CLOUD COVER COULD RESULT IN AROUND A 5-10%
PROBABILITY OF POCKETS OF IFR/LIFR CONDITIONS MANIFESTING WITHIN
THE WILLAMETTE VALLEY THROUGH 16Z THURSDAY. AFTER 17Z-19Z THURSDAY
EXPECT WIDESPREAD VFR WITH FLIGHT LEVELS ABOVE FL040 AND THESE
CONDITIONS ARE EXPECTED TO PERSIST THROUGH THE REMAINDER OF THE
TAF PERIOD.
PDX AND APPROACHES...HIGH PRESSURE IS RESULTING IN VFR CONDITIONS
WITH FLIGHT LEVELS GENERALLY BETWEEN FL040 TO FL050. BREAKS IN
CLOUD COVER COULD RESULT IN AROUND A 5% PROBABILITY OF POCKETS OF
IFR/LIFR CONDITIONS THROUGH 16Z THURSDAY. AFTER 17Z THURSDAY
EXPECT WIDESPREAD VFR WITH FLIGHT LEVELS ABOVE FL050. /42
MARINE
A BRIEF PERIOD OF BENIGN CONDITIONS ACROSS ALL WATERS IS
EXPECTED THROUGH TONIGHT AS HIGH PRESSURE LINGERS. HOWEVER, THIS
WILL BE SOMEWHAT SHORT LIVED AS A SERIES OF SYSTEMS WILL BRING
BACK ELEVATED WINDS AND SEAS FRIDAY AND SATURDAY. ON FRIDAY, A
FRONTAL SYSTEM WHICH IS ANCHORED TO A LOW PRESSURE SYSTEM MAKING
LANDFALL AROUND HAIDA GWAII, LOOKS TO BRING STRONG SMALL CRAFT OR
HAZARDOUS SEAS ACROSS ALL WATERS. EXPECT SOUTHERLY WINDS WITH
GUSTS UP TO 30 KT AND SEAS BUILDING TOWARDS 12 TO 15 FT AROUND 14
SECONDS. GIVEN THAT THERE IS SOME UNCERTAINTY AS IS SMALL CRAFT OR
HAZARDOUS SEA CONDITIONS WILL MANIFEST, HAVE ISSUED A HAZARDOUS
SEAS WATCH STARTING FRIDAY MORNING. THE SECOND, MUCH STRONGER
SYSTEM ON SATURDAY WILL LIKELY BRING SOUTHERLY GALE GUSTS UP TO 45
KT ACROSS ALL WATERS AS WELL AS MAINTAINING SEAS IN THE 12 TO 15
FT RANGE.
AS THE START OF THE UPCOMING WEEK APPROACHES, WINDS WILL SUBSIDE,
BUT SEAS WILL CONTINUE TO BE ELEVATED. HOWEVER, MODELS ARE SHOWING
A 980MB LOW MOVING TOWARDS VANCOUVER ISLAND HAS THE POTENTIAL TO
BRING AT A MINIMUM OF GALES INTO OUR WATERS WITH AROUND A 35%
PROBABILITY OF STORM FORCE CONDITIONS. SEAS ARE ALSO EXPECTED TO
BUILD TOWARDS 17 TO 19 FT WITH A 25% PROBABILITY FOR 20 FT SEAS.
WILL CONTINUE TO MONITOR THE SITUATION AS THE TRACK OF THE MONDAY
LOW WILL DICTATE WHERE THE STRONGEST CONDITIONS MANIFEST. /42
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 10 AM PST THIS MORNING FOR PZZ210-
251>253-271>273.
HAZARDOUS SEAS WATCH FROM FRIDAY MORNING THROUGH SATURDAY
MORNING FOR PZZ210-251>253-271>273.
WWW.WEATHER.GOV/PORTLAND
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