346
FXUS66 KPQR 200518 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
918 PM PST FRI DEC 19 2025
UPDATED AVIATION AND HYDRO DISCUSSIONS
SYNOPSIS
ALTHOUGH PRECIPITATION HAS ENDED ASIDE FROM SOME
SCATTERED RAIN SHOWERS IN THE LOWLANDS AND SNOW SHOWERS IN THE
CASCADES, WIDESPREAD RIVER FLOODING IS FORECAST TO CONTINUE OVER
THE NEXT 12-24 HOURS, EXCEPT INTO EARLY NEXT WEEK FOR SLOWER
RESPONDING RIVERS SUCH AS THE PUDDING RIVER AT AURORA. OTHERWISE
EXPECT A FAIRLY ACTIVE AND PROGRESSIVE WEATHER PATTERN TO
PERSIST THROUGH THE MIDDLE OF NEXT WEEK. ADDITIONAL WEATHER
IMPACTS FROM SUNDAY ONWARD APPEAR MUCH MORE IN-LINE WITH
CLIMATOLOGICAL NORMALS FOR MID TO LATE DECEMBER.
SHORT TERM...NOW THROUGH SUNDAY NIGHT
RADAR, SATELLITE, AND
SURFACE WEATHER OBSERVATIONS FROM EARLY FRIDAY AFTERNOON SHOWED
SCATTERED RAIN SHOWERS OCCURRING ACROSS SOUTHWEST WA AND
NORTHWEST OR, EXCEPT SNOW SHOWERS IN THE CASCADES FOR ELEVATIONS
ABOVE 2500-3000 FT. TRAVEL IMPACTS CONTINUE OVER THE CASCADE
PASSES WHERE AVAILABLE WEBCAM IMAGERY SHOWS SOME SNOW
ACCUMULATING ON ROADS. THEREFORE, A WINTER WEATHER ADVISORY
REMAINS IN EFFECT UNTIL 4 AM SATURDAY FOR THE LANE COUNTY
CASCADES, AND UNTIL 10 AM SATURDAY FOR THE SOUTH WA CASCADES AND
NORTH OR CASCADES TO THE NORTH OF LANE COUNTY. EXPECT AN
ADDITIONAL 1-3 INCHES OF SNOW AT PASS LEVEL THROUGH SATURDAY
MORNING, WITH HIGHER AMOUNTS ABOVE 5000-5500 FT. PREPARE FOR
WINTER-LIKE DRIVING CONDITIONS IF YOU PLAN TO TRAVERSE ACROSS
THE MOUNTAIN PASSES TONIGHT OR TOMORROW. ON A MORE POSITIVE
NOTE, SKIERS AND SNOWBOARDERS WILL FINALLY HAVE SOME FRESH
SNOWPACK FOR RECREATION.
FOR ELEVATIONS BELOW 2500 FT FROM THE CASCADE FOOTHILLS WESTWARD TO
THE COAST, RAIN SHOWERS HAVE BEEN RELATIVELY LIGHT AND NON-IMPACTFUL
THUS FAR TODAY. NO LIGHTNING HAS BEEN DETECTED OVER THE PAST 24 HOURS
WITHIN THE FORECAST AREA, LIKELY DUE TO LIMITED INSTABILITY. HOWEVER,
THERE HAVE BEEN SOME REPORTS OF SMALL HAIL OR GRAUPEL WITH STRONGER
SHOWERS NEAR THE NORTH OREGON COAST. HOURLY RAIN RATES WITH TODAY'S
SHOWERS HAVE GENERALLY STAYED BELOW 0.10-0.15 IN/HR, WHICH IS NOT
HEAVY ENOUGH TO RESULT IN URBAN AND SMALL STREAM FLOODING. THAT SAID,
WIDESPREAD RIVER FLOODING IS STILL CONTINUING AS ALL THE WATER FROM
YESTERDAY'S ATMOSPHERIC RIVER WORKS ITS WAY THROUGH THE RIVER
SYSTEMS. FOR DETAILS ON ONGOING RIVER FLOODING CONCERNS, PLEASE READ
THE HYDROLOGY DISCUSSION BELOW.
BY LATE SATURDAY, MODELS AND THEIR ENSEMBLES CONTINUE TO SHOW
WESTERLY FLOW ALOFT BECOMING WEST-SOUTHWEST SATURDAY NIGHT INTO
SUNDAY MORNING, BEFORE BECOMING SOUTHWESTERLY SUNDAY AFTERNOON. THIS
WILL BE IN RESPONSE TO A LONGWAVE TROUGH OVER THE PACIFIC NEARING THE
WASHINGTON/OREGON COAST, WHICH IS SET TO PUSH INLAND SUNDAY
EVENING/NIGHT. WHILE SCATTERED SHOWERS WILL PERSIST ACROSS THE AREA
ON SATURDAY AND SUNDAY AHEAD OF THIS TROUGH, THE BULK OF THE HEAVIEST
PRECIPITATION THIS WEEKEND WILL OCCUR SUNDAY EVENING/NIGHT WITH THE
TROUGH PASSAGE. NOT EXPECTING MUCH IN THE WAY OF IMPACTS WITH THIS
SYSTEM, ASIDE FROM TRAVEL IMPACTS OVER THE CASCADE PASSES. FROM 4AM
SUNDAY THROUGH 4AM MONDAY, THE NBM SUGGESTS THERE IS A 50% CHANCE FOR
6 INCHES OF SNOW OR MORE AT WILLAMETTE PASS, A 70% CHANCE AT SANTIAM
PASS, AND A 45% CHANCE ON HIGHWAY 26 NEAR GOVERNMENT CAMP. IF THESE
PROBABILITIES INCREASE, A WINTER WEATHER ADVISORY WILL LIKELY BE
NEEDED. PROBABILITIES FOR 12 INCHES OF SNOW OR MORE ARE MUCH LOWER AT
10-20%. -23
LONG TERM...MONDAY THROUGH THURSDAY NIGHT
WPC'S CLUSTER ANALYSIS
FROM MONDAY THROUGH THURSDAY DEPICTS GOOD AGREEMENT BETWEEN THE
GEFS/GEPS/ENS ENSEMBLES REGARDING THE SYNOPTIC SCALE PATTERN, SHOWING
BROAD UPPER LEVEL TROUGHING AT 500 MB OVER THE NORTHEASTERN PACIFIC
WITH VERY LITTLE MOVEMENT. HOWEVER, A SERIES OF SHORTWAVE TROUGHS
ROTATING AROUND THE BROAD LONGWAVE TROUGH ARE SET TO MOVE UP THE U.S.
WEST COAST FROM THE SOUTH/SOUTHWEST, BRINGING CONTINUED CHANCES FOR
SHOWERS OVER NORTHWEST OR AND SOUTHWEST WA EACH DAY NEXT WEEK. THERE
IS MODERATE CONFIDENCE ONE OF THESE SHORTWAVES ARRIVES THE SECOND
HALF OF MONDAY INTO MONDAY NIGHT. IN ADDITION TO INCREASING SHOWERS,
BREEZY SOUTH WINDS WILL ACCOMPANY THIS SYSTEM. 6 HOUR MAX WIND GUST
GUIDANCE FROM THE GEFS AND EPS SUGGESTS WIND GUSTS WILL LIKELY PEAK
BETWEEN 20-30 MPH INLAND AND BETWEEN 30-40 MPH AT THE COAST. CHANCES
FOR STRONGER WIND GUSTS OF 45 MPH OR STRONGER ARE NEAR 0%, EXCEPT
10-20% AT THE COAST. THIS SUGGESTS WIND IMPACTS SHOULD BE MINIMAL.
BY THE MIDDLE OF THE WEEK THE AFOREMENTIONED UPPER LEVEL TROUGH IS
EXPECTED TO TRANSITION INTO A CLOSED LOW WHILE RETROGRADING AND
DROPPING SOUTHWARD LEAVING US IN BOARD SOUTHERLY FLOW. FROM THIS
POINT ONWARD FORECAST UNCERTAINTY SIGNIFICANTLY INCREASES AS MODEL
GUIDANCE STRUGGLES TO RESOLVE THE PLACEMENT OF A POTENTIAL CLOSED
SURFACE LOW THAT WILL LIKELY MOVE INTO NORTHERN CALIFORNIA AND/OR
SOUTHWEST OREGON. THE VAST MAJORITY OF ENSEMBLE GUIDANCE CONTINUES TO
SHOW AN AREA OF HEAVY RAINFALL AND STRONG WINDS WELL TO OUR SOUTH IN
CALIFORNIA. THIS SUGGESTS NORTHWEST OREGON AND SOUTHWEST WASHINGTON
WILL BE SPARED FROM THIS STORM, BUT THE FORECAST WILL BE WORTH PAYING
ATTENTION TO THIS WEEK IN CASE THE STORM TRACK SHIFTS FURTHER TO THE
NORTH. -23/99
AVIATION
WIDESPREAD VFR WITH SHOWERS EXPECTED ACROSS THE
AIRSPACE THROUGH AROUND 06Z SATURDAY. AROUND 06Z-09Z SATURDAY,
FLIGHT CONDITIONS WILL LIKELY SETTLE IN THE POST FRONTAL
ENVIRONMENT AND LEAD TOWARDS A HIGH-END MVFR/LOW-END VFR FLIGHT
CONDITIONS THROUGH THE REMAINDER OF THE TAF PERIOD. WESTERLY WINDS
WILL BECOME MORE SOUTHERLY THROUGH THE OVERNIGHT HOURS ACROSS THE
AIR SPACE UP TO 12 KT SUSTAINED. EXPECT GUSTS ALONG THE COAST UP
TO 25 KT STARTING AROUND 17Z SATURDAY AND GUSTS UP TO 20 KT FOR
KUAO AND KTTD STARTING AROUND 10Z SATURDAY.
THERE IS A 15-25% CHANCE FOR ALONG THE COAST THROUGH THE TAF
PERIOD. ANY THUNDERSTORMS COULD PRODUCE LOCALLY GUSTY WINDS AND
SMALL HAIL.
KPDX AND APPROACHES...GENERALLY VFR CONDITIONS THROUGH AROUND 10Z
SATURDAY. AFTERWARDS, CIGS EXPECTED TO FALL TOWARDS FL040 OR LESS
AND FLUCTUATE BETWEEN HIGH-END MVFR/LOW-END VFR THROUGH THE
REMAINDER OF THE TAF PERIOD. /42
MARINE
GUSTY WEST WINDS AND A ROBUST NORTHWESTERLY WELL WILL
MAINTAIN SEAS AROUND 9 TO 11 FT WITH WESTERLY GUSTS UP TO 30 KT
THROUGH THIS EVENING. CONDITIONS WILL SLOWLY SUBSIDE THROUGH
TONIGHT AND INTO TOMORROW, WHICH WILL CAUSE SUSTAINED WINDS TO
SUBSIDE TOWARDS 8 TO 10 FT WITH GUSTS UP TO 25 KT THROUGH
SATURDAY. THEREFORE, WILL MAINTAIN A SMALL CRAFT ADVISORY ACROSS
ALL WATERS AND THE COLUMBIA RIVER BAR. THERE IS ALSO A 15-30%
PROBABILITY FOR THUNDERSTORMS ACROSS THE COLUMBIA RIVER BAR AND
INNER WATERS THROUGH TONIGHT. ANY THUNDERSTORMS COULD RESULT IN
BRIEF ERRATIC WINDS, HEAVY RAIN, AND LIGHTNING.
WINDS TURN SOUTHWEST TONIGHT AS A FRONTAL SYSTEM APPROACHES THE
WATERS. SOUTH WINDS WILL PERSIST INTO NEXT WEEK AS A SERIES OF
FRONTS MOVE ACROSS THE WATERS. A FRESH WEST SWELL WILL RESULT IN
SEAS BUILDING ABOVE 10 FEET AGAIN BY SUNDAY EVENING. SEAS ARE
LIKELY TO CONTINUE TO BUILD THROUGH THE START OF NEXT WEEK TOWARDS
THE LOW TO MID TEENS. /42
HYDROLOGY
ALTHOUGH HEAVY RAIN HAS ENDED OVER THE AREA,
WIDESPREAD MINOR TO ISOLATED MODERATE RIVER FLOODING CONTINUES
OVER THE AREA. AS OF 10 PM FRIDAY, THE CLACKAMAS RIVER NEAR
OREGON CITY AND THE LUCKIAMUTE RIVER NEAR SUVER REMAIN IN
MODERATE FLOOD STAGE. MEANWHILE, THE FOLLOWING RIVERS REMAIN IN
MINOR FLOOD STAGE: THE TUALATIN RIVER NEAR DILLEY, THE NEHALEM
RIVER NEAR FOSS, THE SANTIAM RIVER AT JEFFERSON, THE COWLITZ
RIVER AT KELSO, AND THE MARYS RIVER NEAR PHILOMATH. THE PUDDING
RIVER AT AURORA WAS AT ACTION STAGE, BUT IS FORECAST TO REACH
MODERATE FLOOD STAGE BY 9-10AM SATURDAY AS THIS IS A SLOWER
RESPONDING RIVER. MOST RIVERS ARE FORECAST TO FALL BELOW FLOOD
STAGE BY LATE FRIDAY NIGHT/EARLY SATURDAY MORNING, ASIDE FROM
THE LUCKIAMUTE RIVER WHICH IS FORECAST TO FALL BELOW FLOOD STAGE
AROUND 3PM SUNDAY, AND THE PUDDING RIVER WHICH IS FORECAST TO
FALL BELOW FLOOD STAGE AROUND 3PM TUESDAY. THE LATEST RIVER
FORECASTS ACROSS THE REGION CAN BE FOUND AT WWW.WATER.NOAA.GOV/WFO/PQR.
BE SURE TO NEVER DRIVE THROUGH A FLOODED ROAD AND HEED ANY
LINGERING ROAD CLOSURES.
PQR WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY UNTIL 10 AM PST SATURDAY FOR ORZ126-127.
WINTER WEATHER ADVISORY UNTIL 4 AM PST SATURDAY FOR ORZ128.
WA...WINTER WEATHER ADVISORY UNTIL 10 AM PST SATURDAY FOR WAZ211.
PZ...SMALL CRAFT ADVISORY UNTIL 10 PM PST SATURDAY FOR PZZ210-251>253-
271>273.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
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