549
FXUS66 KPQR 211807 CCA
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
946 AM PST SAT DEC 21 2024
AMMENDED TO RE-ADD BEACH HAZARDS SECTION.
UPDATED AVIATION SECTION.
UPDATE
THE SURFACE FRONT IMPACTING THE PACNW THIS MORNING HAS
MOVED MUCH FASTER THAN ORIGINALLY DESCRIBED. AS OF 9:30 AM,
OBSERVATIONS INDICATE THE SURFACE FRONT HAS ALREADY PUSHED
INLAND IN LINE FROM AROUND ABERDEEN, WA ALONG THE SOUTHERN COAST
TO THE EASTERN LANE COUNTY OR FOOTHILLS. THE FRONT IS EXPECTED
TO CONTINUE PUSHING EAST, PASSING OVER THE CASCADES OVER THE
NEXT FEW HOURS. BEHIND THE FRONT, SCATTERED SHOWERS CONTINUE
WITH A 10-20% CHANCE OF ISOLATED THUNDERSTORMS THROUGH THIS
EVENING, MAINLY ALONG THE COAST AND OVER THE WATERS.
SYNOPSIS
RAIN WILL SPREAD ACROSS THE REGION THIS MORNING AS
A FRONT MOVES INLAND. SHOWERS THIS AFTERNOON, DECREASING
OVERNIGHT. NEXT FRONT BRINGS RAIN FOR SUNDAY, AND SHOWERS SUNDAY
NIGHT INTO MONDAY. MOST OF THE DAY ON MONDAY LOOKS TO BE DRY,
BUT RAIN/SHOWERS AGAIN LATER MONDAY NIGHT INTO TUESDAY. THEN, A
RATHER WET AND BREEZY CHRISTMAS DAY, WITH RAIN AND BREEZY
WEATHER CONTINUING THROUGH FRI.
SHORT TERM...(TODAY THROUGH MONDAY)
AT 2 AM, NOAA
SATELLITE IMAGERY SHOWED A LOW PRESSURE CENTERED NEAR 45N 130W,
OR ROUGHLY ABOUT 400 MILES WEST OF ASTORIA. COLD FRONT EXTENDS
FROM THIS LOW TO THE SOUTH-SOUTHEAST TO 40N 127W. THE LOW WILL
CONTINUE MOVING NORTHWARD, WITH THE FRONT LIFTING NORTHEAST
TODAY, AND INLAND LATER THIS MORNING. TIMING WOULD PUT RAIN ON
THE COAST BETWEEN 4 AND 6 AM, WITH RAIN SPREADING INLAND
AFTERWARDS. WILL MAINTAIN BREEZY EAST WINDS IN/AROUND THE
WESTERN COLUMBIA RIVER GORGE WHERE IS GUSTING 45 TO 65 MPH. BIT
LESS ACROSS THE EAST PORTLAND/VANCOUVER METRO, BUT STILL BREEZY
WITH GUSTS 35 TO 50 MPH IN THOSE AREAS. THESE EAST WINDS WILL
EASE AS THE FRONT ARRIVES.
FRONT WILL PUSH ONSHORE ABOUT 10 AM ALONG THE COAST, MOVING TO THE
CASCADES BY 1 PM. NOT A BIG RAIN MAKER, BUT WILL PRODUCE ABOUT 0.25
TO 0.50 INCH ACROSS MUCH OF THE REGION. ONCE THE FRONT PASSES, WILL
TRANSITION TO SHOWERS FOR REST OF THE AFTERNOON, WITH SHOWERS
DECREASING LATER THIS EVENING. CAN NOT RULE OUT A STRAY THUNDERSTORM
ALONG THE COAST/COAST RANGE FROM LATE MORNING THROUGH THIS AFTERNOON,
AND PERHAPS INTO THE WILLAMETTE VALLEY LATER TODAY.
NEXT SYSTEM ARRIVES SUN MORNING, WITH RAIN INCREASING. OVERALL,
SHOULD BE RATHER WET AND GRAY DAY, ESPECIALLY FOR LATE MORNING AND
THE AFTERNOON. RAINFALL WILL BE BIT MORE HEFTY THAT THAT OF TODAY,
WITH 0.50 TO 0.75 INCH FOR MOST AREAS, AND 0.75 TO 1.25 INCH FOR THE
COAST RANGE, WILLAPA HILLS, AND CASCADES. ONCE THE FRONT MOVES
ONSHORE AND INLAND (LATE AFTERNOON/EARLY EVENING), WILL TRANSITION TO
SHOWERS AGAIN. SHOWERS WILL GRADUALLY DECREASE LATE SUN NIGHT INTO
EARLY MON MORNING. AT THIS TIME, DOES APPEAR THAT GOOD PART MON WILL
BE DRY. BUT, THAT ENDS LATER IN THE DAY, AS NEXT APPROACHING FRONT
BRINGS CLOUDS IN THE AFTERNOON, WITH RAIN BY EVENING.
SNOW LEVELS WILL BE ON A ROLLER COASTER RIDE FOR THE NEXT 2 TO 3
DAYS, RUNNING AT/ABOVE 6500 FT, THEN DROPPING TO NEAR 4500 FT IN THE
POST-FRONT AIR (LATE TODAY/TONIGHT AND AGAIN SUN NIGHT INTO MON).
COULD GET 2 TO 8 INCHES LATER TODAY INTO TONIGHT, MAINLY ABOVE 5000
FT. NO ADVISORIES AT THIS TIME, AS MOST OF THE MAIN PASSES WILL
REMAIN WET DURING THE DAY, WITH 1 TO 3 INCHES OF SNOW EXPECTED AT
NIGHT WITH THE SNOW SHOWERS. /ROCKEY
LONG TERM...(TUESDAY TO FRIDAY)
FORECAST IS CHARACTERIZED
BY A SERIES OF FRONTS MOVING INTO THE PACIFIC NORTHWEST, WITH A
POTENTIALLY VERY WET FRONTS LATER THIS WEEK AS POTENT
ATMOSPHERIC RIVER TAKES AIM AT THE REGION. HOWEVER, THE SHORT-
DURATION OF EACH ONE WITH BREAKS IN BETWEEN WILL HELP MINIMIZE
CONCERNS FOR WIDESPREAD, LARGE-SCALE IMPACTS.
NEXT SYSTEM ARRIVES MONDAY NIGHT INTO TUESDAY, WITH RAIN TURNING TO
SHOWERS ON TUESDAY. SHOWERS DECREASING TUESDAY NIGHT.
THEN THE MAIN SHOW ARRIVES. NO, NOT CHRISTMAS AND SANTA. RATHER A
STRONG FRONT WILL APPROACH, WITH RATHER RAINY AND BREEZY CONDITIONS
FOR LATE WED AFTERNOON OR EVENING, LASTING INTO THURSDAY. MODELS
STILL SHOWING MODERATE TO STRONG ATMOSPHERIC RIVER TIED TO THIS
FRONT, ENHANCING THE RAINFALL. OVERALL, TOTAL RAINFALL FOR WED INTO
THU COULD RUN AT 2 TO 4 INCHES ALONG THE COAST, WITH 3 TO 6 INCHES
ACROSS THE COAST RANGE AND WILLAPA HILLS. EVEN INLAND, RAINFALL OF 1
TO 3 INCHES LOOKS REASONABLE FOR THIS TIMEFRAME, WITH 2 TO 5 INCHES
ACROSS THE CASCADES. THIS INDEED WILL PUSH RIVERS UPWARD. HARD TO
SAY IF WILL HAVE FLOODING, BUT AT THIS TIME, APPEARS HAVE A 25-45%
CHANCE SOME RIVERS (SUCH AS WILSON AND THE NEHALEM, AS WELL AS THE
GRAYS AND NASELLE) COULD REACH FLOOD STAGE GIVEN THIS RAINFALL. SO,
WILL HAVE TO WATCH LATER NEXT WEEK CLOSELY, PARTICULARLY THE RAINFALL
FORECASTS AS THAT WILL HEAVILY AFFECT WHICH RIVERS SEE SIGNIFICANT
RISES, AND WHETHER OR NOT THEY REACH FLOOD STAGE TOWARDS THU OR FRI.
GIVEN SNOW LEVELS WILL BE ON THE RISE, WILL HAVE CONTINUED SNOWMELT,
GIVING MORE WATER TO FLOW INTO THE RIVERS.
YET ANOTHER STRONG FRONT WILL ARRIVE ON FRIDAY, BUT TOO EARLY TO TELL
HOW MUCH RAIN OR WIND IT WILL BRING. THIS MAINLY DUE TO MODEL
DIFFERENCES ON STRENGTH/LOCATION OF THE MAIN SURFACE LOW. HOWEVER,
GIVEN RATHER MOIST JET STREAM OVER THE REGION, ODDS AREA GOOD FOR
ANOTHER ROUND OF HEAVY RAIN. /ROCKEY
AVIATION
MIX OF MVFR AND VFR CONDITIONS AS RAIN CONTINUES TO
MOVE ACROSS THE AREA. RAIN BECOMES MORE SHOWERY BEFORE NOON BEFORE
DECREASING SIGNIFICANTLY 00-06Z SUNDAY. SOUTHEASTERLY WINDS WILL
ALSO PICK UP INTO THE MIDDAY HOURS, WITH GUSTS UP TO 20-30 KTS
POSSIBLE AT MOST TERMINALS. GENERALLY VFR CONDITIONS AFTERWARDS
ALTHOUGH WE'LL HAVE TO KEEP AN EYE OUT FOR FOG, PARTICULARLY IN
THE SOUTHERN WILLAMETTE VALLEY.
PDX AND APPROACHES...A MIX OF MVFR AND VFR CONDITIONS EXPECTED
TODAY. SHOWERS MAY OCCASIONALLY BRING VISIBILITIES DOWN TO 4-5 SM
WITH CIGS TO AROUND 2500-3000 FEET. SHOWERS TAPER OFF AFTER 00Z
SUN. WINDS PICK UP AROUND THAT TIME AS WELL, WITH SOUTHEASTERLY
GUSTS UP TO 18-25 KT POSSIBLE. -BATZ/SCHULDT
MARINE
GOING THROUGH THE NEXT WEEK A VERY ACTIVE WEATHER
PATTERN IS ANTICIPATED AS A BROAD UPPER-LEVEL LOW REMAINS PARKED
OVER THE NE PACIFIC AIMING A PARADE OF WEATHER DISTURBANCE AT
THE PACIFIC NORTHWEST. OUR NEXT FRONTAL BOUNDARY IS BEGINNING TO
ENTER THE COASTAL WATERS EARLY THIS MORNING WITH WINDS QUICKLY
JUMPING TO GALE CRITERIA AFTER 4-6AM. THROUGH THE MIDDAY HOURS
EXPECT GUSTS BETWEEN 35-45 KNOTS WITH SEAS INCREASING INTO THE
LOW TEENS BY FOLLOWED BY SEAS PEAKING IN THE UPPER TEENS TO
AROUND 20 FEET THIS AFTERNOON. SEAS MAY DECREASE A FEW FEET INTO
THE MID TEENS TONIGHT BUT WILL JUMP BACK UP INTO THE UPPER
TEENS WITH THE NEXT FRONTAL SYSTEM ON SUNDAY. MOVING INTO MONDAY
WE'LL SEE THE ARRIVAL OF A LONG PERIOD SWELL (~20 SECONDS) WITH
SIGNIFICANT WAVE HEIGHTS LIKELY PEAKING IN THE LOW 20S. AFTER A
LULL TUESDAY INTO EARLY WEDNESDAY MORNING A STRONGER SYSTEM MID
TO LATE WEEK WILL INCREASE WINDS TO AT LEAST GALES AND USHER IN
SEAS NEAR 20 FEET YET AGAIN. THE NBM CURRENTLY PROJECTS A
30-40% CHANCE FOR STORM FORCE (>48 KNOT GUSTS) IN THE WEDNESDAY
AFTERNOON THROUGH THURSDAY TIME PERIOD TOO - SOMETHING TO WATCH.
MARINERS SHOULD BE PREPARED FOR CONTINUED HAZARDOUS CONDITIONS
THROUGH THE END OF NEXT WEEK. -SCHULDT
BEACH HAZARDS
A LARGE, ENERGETIC WESTERLY SWELL WILL BUILD
OVER THE COASTAL WATERS AND BEGIN IMPACTING THE COASTLINE SATURDAY
INTO EARLY NEXT WEEK. SEAS IN EXCESS OF 18 TO 20 FEET WITH A PERIOD
OF AROUND 19-21 SECONDS WILL LIKELY RESULT IN BREAKING WAVES
APPROACHING 25 TO 30 FEET IN THE SURF ZONE. THE HIGH SURF ADVISORY
WILL BE MAINTAINED FOR SATURDAY MORNING THROUGH MONDAY EVENING.
MONDAY IN PARTICULAR WILL SEE THE LARGEST WAVES, POTENTIALLY
APPROACHING HIGH SURF WARNING CRITERIA, ALTHOUGH THERE ISN'T ENOUGH
CONFIDENCE IN DEGREE OF WAVE ENERGY REQUIRED TO UPGRADE THE
HIGHLIGHT AS OF THIS FORECAST CYCLE. A SLIGHT INCREASE IN EITHER
SWELL HEIGHT/PERIOD WOULD PUSH ENERGY VALUES TO WARNING CRITERIA.
CONTINUE TO MONITOR FUTURE FORECASTS FOR CHANGING CONDITIONS.
BEACHGOERS SHOULD BE PREPARED FOR DANGEROUS SURF CONDITIONS AND
LARGE WAVES RUNNING FAR UP ONTO THE BEACH BEGINNING LATE SUNDAY AND
CONTINUING THROUGH EARLY NEXT WEEK. -SCHULDT/BATZ
PQR WATCHES/WARNINGS/ADVISORIES
OR...HIGH SURF ADVISORY UNTIL 10 PM PST MONDAY FOR ORZ101>103.
WA...HIGH SURF ADVISORY UNTIL 10 PM PST MONDAY FOR WAZ201.
PZ...GALE WARNING UNTIL 1 PM PST THIS AFTERNOON FOR PZZ210-251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
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