879  
FXUS66 KPQR 170958  
AFDPQR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PORTLAND OR  
258 AM PDT FRI OCT 17 2025  
   
SYNOPSIS  
TRANSIENT SHORTWAVE RIDGING FRIDAY NIGHT WILL BRING  
CHILLY OVERNIGHT TEMPERATURES AND AREAS OF FROST FOR SOME INLAND  
VALLEYS. A ROBUST FRONTAL SYSTEM ARRIVES LATE SATURDAY INTO SUNDAY,  
BRINGING WIDESPREAD SOAKING RAIN TO THE AREA WITH GUSTY SOUTHERLY  
WINDS. TRENDING DRIER SUNDAY NIGHT INTO EARLY NEXT WEEK, HOWEVER SOME  
UNCERTAINTY REMAINS WITH A 20-45% CHANCE OF RAIN RETURNING BY  
WEDNESDAY.  
 
 
   
SHORT TERM...NOW THROUGH SUNDAY NIGHT  
SATELLITE, RADAR AND SURFACE  
WEATHER OBSERVATIONS FROM EARLY FRIDAY MORNING DEPICTED A DECAYING  
COOL FRONT DRAPED OVER FAR NORTHWEST WASHINGTON, EXTENDING  
SOUTHWESTWARD INTO THE COASTAL WATERS. THIS FRONT SHOULD CONTINUE  
WEAKENING AS IT SLOWLY SAGS SOUTHWARD INTO SOUTHWEST WASHINGTON AND  
NORTHWEST OREGON, RESULTING IN VERY LITTLE TO NO MEASURABLE RAINFALL  
FOR MOST LOCATIONS. THE MAIN EXCEPTION WILL BE IN THE SOUTH  
WASHINGTON CASCADES/FOOTHILLS AND ALONG THE SOUTH WASHINGTON/NORTH  
OREGON COAST. THESE AREAS HAVE AN 80-90% CHANCE FOR AT LEAST 0.05" OF  
RAIN.  
 
TRANSIENT RIDGING BUILDS INTO THE AREA THIS AFTERNOON INTO EARLY  
SATURDAY, SETTING THE STAGE FOR CLEAR SKIES AND CALM WINDS. THIS WILL  
LEAD TO CHILLY TEMPERATURES ONCE AGAIN FOR INLAND VALLEYS  
FRIDAY NIGHT INTO SATURDAY MORNING. THE COLDEST AREAS WILL LIKELY BE  
THE UPPER HOOD RIVER VALLEY, SOUTH WA CASCADE FOOTHILLS, BATTLE  
GROUND AND RIDGEFIELD AREAS. CONFIDENCE IS GENERALLY OVER 70-80%  
THESE ZONES WILL SEE LOW TEMPERATURES DIP TO 33-36 DEGREES, WHICH HAS  
PROMPTED THE ISSUANCE OF FROST ADVISORIES FRIDAY NIGHT INTO SATURDAY  
MORNING. MEANWHILE, A FREEZE WARNING IS IN EFFECT FOR THE UPPER HOOD  
RIVER VALLEY FOR LOW TEMPERATURES AS COLD AS 29-30 DEGREES. WHILE  
FROST IS ALSO POSSIBLE IN PORTIONS OF THE SOUTHERN WILLAMETTE VALLEY,  
ESPECIALLY EAST OF I-5, CONFIDENCE IS CURRENTLY NOT HIGH ENOUGH TO  
INCLUDE THESE ZONES IN THE FROST ADVISORY. THIS IS DUE TO POTENTIAL  
LOW CLOUDS OR FOG THAT MAY DEVELOP INSTEAD OF FROST; THE HREF  
CURRENTLY SHOWS A 50-75% CHANCE FOR LOW CLOUD DEVELOPMENT MID TO LATE  
FRIDAY NIGHT, WHICH WOULD FAVOR TEMPS BOTTOMING OUT IN THE UPPER 30S  
WITH MINIMAL FROST CONCERNS. THE OVERALL WEATHER PATTERN BEYOND  
FRIDAY MORNING DOES NOT FAVOR WIDESPREAD FROST OR FREEZE CONCERNS, SO  
THIS ROUND OF FROST/FREEZE HEADLINES MAY WIND UP BEING THE LAST OF  
THIS GROWING SEASON.  
 
DESPITE THE CHILLY TEMPERATURES IN PLACE SATURDAY MORNING,  
TEMPERATURES WILL REBOUND NICELY IN THE AFTERNOON WITH HIGHS IN THE  
60S, EXCEPT NEAR 70 DEGREES IN EUGENE-SPRINGFIELD, CRESWELL, BLUE  
RIVER, LOWELL AND OAKRIDGE. THESE AREAS WILL SEE SUNNY SKIES  
THROUGHOUT THE DAY, HOWEVER NORTHERN AREAS WILL SEE CLOUDS BEGIN TO  
INCREASE AHEAD OF THE NEXT FRONTAL SYSTEM. MODELS ARE IN GOOD  
AGREEMENT ON THE TIMING OF THIS FRONT, BRINGING STRATIFORM RAIN TO  
SOUTHWEST WASHINGTON AND THE NORTH OREGON COAST SATURDAY EVENING AND  
THEN THE REST OF NORTHWEST OREGON FROM LANE COUNTY NORTHWARD SATURDAY  
NIGHT INTO SUNDAY MORNING. PERSISTENT STRATIFORM RAIN WILL TRANSITION  
TO POST-FRONTAL SHOWERS BY LATE SUNDAY MORNING OR EARLY SUNDAY  
AFTERNOON. THIS IS WHEN FORECAST SOUNDINGS SHOW 850 MB TEMPERATURES  
COOLING TO +1 TO +2 DEGREES CELSIUS, WITH SBCAPE VALUES INCREASING  
TO 100-200 J/KG AND EQUILIBRIUM LEVELS GENERALLY BELOW -10 DEGREES  
CELSIUS. HOWEVER, 0-3 KM AGL BULK SHEAR VALUES ARE FAIRLY HIGH AT  
30-35 KT (HAVE OPTED TO USE 0-3 KM AGL BULK SHEAR VALUES INSTEAD OF  
0-6 KM AS CLOUD TOPS GENERALLY LOOK TO STAY NEAR OR BELOW 3 KM). BOTH  
SPEED SHEAR AND DIRECTIONAL SHEAR ARE IN PLACE, AS THE WIND DIRECTION  
WILL VEER WITH HEIGHT FOR A FEW HOURS OR SO AS THE UPPER LEVEL TROUGH  
AXIS MOVES OVERHEAD. THE LIMITED INSTABILITY AND SHALLOW NATURE OF  
SUNDAY'S CONVECTION SUGGESTS OVERALL LIGHTNING ACTIVITY WILL MOST  
LIKELY BE LIMITED (WHICH HELPS EXPLAIN WHY NBM THUNDER PROBABILITIES  
ONLY PEAK AROUND 10-15%). HOWEVER, WHETHER LIGHTNING OCCURS OR NOT,  
STRONGER SHOWERS WILL HAVE THE POTENTIAL TO PRODUCE A FUNNEL CLOUD,  
LANDSPOUT, OR GUSTY OUTFLOW WINDS UP TO 45 MPH GIVEN THE  
ENVIRONMENTAL WIND PROFILE IN PLACE, MEANING HIGHLY LOCALIZED WIND  
DAMAGE IS POSSIBLE. NOTE SOUTHERLY WINDS WILL BE BREEZY IN GENERAL  
SATURDAY NIGHT AND SUNDAY, EVEN AWAY FROM SHOWERS AND THUNDERSTORMS.  
CURRENTLY EXPECTING SOUTHERLY WIND GUSTS UP TO 20-30 MPH FOR INLAND  
AREAS AND UP TO 30-40 MPH FOR THE SOUTH WA/NORTH OR COAST. GUSTS UP  
TO 40-50 MPH APPEAR LIKELY IN THE HIGH CASCADES. WINDS WILL WEAKEN  
SUNDAY NIGHT WHILE ANY LINGERING SHOWERS BEGIN TO DISSIPATE. -23  
 
   
LONG TERM...MONDAY THROUGH NEXT FRIDAY  
MOST MODEL GUIDANCE  
SUGGESTS DRY WEATHER WITH SEASONABLE TEMPERATURES, RELATIVELY LIGHT  
WINDS AND A MIX OF CLOUDS AND SUN MONDAY AND TUESDAY. THAT SAID,  
THERE REMAINS A HANDFUL OF GEFS/ENS ENSEMBLE MEMBERS WITH LIGHT QPF  
AMOUNTS MONDAY MORNING/AFTERNOON AND TUESDAY MORNING/AFTERNOON AS A  
PAIR OF WEAK UPPER LEVEL IMPULSES MOVE OVERHEAD. AS SUCH, THERE IS A  
10-30% CHANCE OF LIGHT RAIN SHOWERS ON MONDAY AND 15-35% CHANCE ON  
TUESDAY. PROBABILITIES ARE HIGHEST ALONG THE SOUTH WA/NORTH OR COAST.  
 
CHANCES FOR RAIN GRADUALLY INCREASE LATE WEDNESDAY THROUGH THURSDAY  
NIGHT, PEAKING NEAR 75-85% BY EARLY FRIDAY MORNING. THIS SYSTEM HAS  
THE POTENTIAL TO BRING MORE IMPACTFUL RAIN AMOUNTS AND GUSTY SOUTH  
WINDS, HOWEVER UNCERTAINTY IS HIGH IN REGARDS TO EXACT RAIN AMOUNTS  
AND EXACT WIND SPEEDS, AS THE OUTCOME WILL BE HIGHLY DEPENDENT ON THE  
EXACT TRACK AND STRENGTH OF A NEGATIVELY TILTED TROUGH AND ASSOCIATED  
DEEPENING SURFACE LOW THAT WILL BE MOVING SOMEWHERE OVER THE COASTAL  
WATERS DURING THAT TIME. ENSEMBLE LOW LOCATIONS VARY SIGNIFICANTLY  
BOTH SPATIALLY AND TEMPORALLY, WITH SOME ENSEMBLE GUIDANCE SUGGESTING  
A FAIRLY WEAK LOW WITH MINIMAL IMPACTS, WHILE OTHER MEMBERS SUGGEST A  
VERY STRONG LOW CAPABLE OF WIND DAMAGE SOMEWHERE ALONG THE  
WASHINGTON, OREGON, OR NORTHERN CALIFORNIA COAST. THERE IS CURRENTLY  
A 15-25% CHANCE FOR MAX WIND GUSTS OF 45 MPH OR STRONGER ACROSS ALL  
OF NORTHWEST OREGON AND SOUTHWEST WASHINGTON, EXCEPT FOR A 35-50%  
CHANCE AT THE COAST AND ON EXPOSED RIDGES IN THE COAST RANGE AND  
CASCADES. THIS SYSTEM WILL ALSO BRING A 40-80% CHANCE OF 1" OF RAIN  
OR MORE, WITH THE LOWEST PROBABILITIES IN THE PORTLAND METRO AND  
WILLAMETTE VALLEY WEST OF THE I-5 CORRIDOR AND THE HIGHEST  
PROBABILITIES IN THE MOUNTAINS AND AT THE COAST. -23  
 
 
   
AVIATION  
A WEAK COOL FRONT WILL CONTINUE SAGGING SOUTHWARD OVER  
SOUTHWEST WA AND FAR NORTHWEST OR THIS MORNING, BRINGING MVFR CIGS  
TO THE COAST. MVFR CIGS HAVE ALREADY DEVELOPED AT KAST, AND SHOULD  
SPREAD SOUTHWARD DOWN TO KONP AROUND 12-14Z FRIDAY AS THE FRONT  
PROGRESSES. IT APPEARS INLAND AREAS WILL REMAIN VFR THROUGH 12-15Z  
FRIDAY BEFORE A BRIEF PERIOD OF MVFR CIGS BETWEEN 15-18Z FRIDAY  
AS THE FRONT DECAYS OVERHEAD. THERE IS A 60-80% CHANCE FOR CIGS  
BELOW 3000 FT AT ALL INLAND TERMINALS, EXCEPT 30-40% AT KEUG).  
WINDS WILL REMAIN LIGHT AND VARIABLE AROUND 5 KT OR LESS AT ALL  
TAF SITES THROUGH 12Z SATURDAY.  
 
KPDX AND APPROACHES...VFR CIGS THROUGH THE TAF PERIOD, WITH CIGS  
LIKELY LOWERING TO AROUND 2800-3000 FT AFTER 12-15Z FRI WITH A  
WEAK FRONTAL PASSAGE (75% CHANCE FOR CIGS AT OR BELOW 3000 FT).  
LIGHT AND VARIABLE WINDS UNDER 5 KT CONTINUE. -23  
 
 
   
MARINE  
WINDS RETURN TO A NORTHERLY DIRECTION BEHIND A WEAK  
FRONTAL PASSAGE FRIDAY MORNING AROUND 10-15 KT AS HIGH PRESSURE  
REBUILDS. SEAS HOLD AROUND 4-6 FT AT 14-15 SECONDS. CONDITIONS  
BECOME MORE ACTIVE ON FRIDAY EVENING AS A NORTHWESTERLY SWELL  
ENTERS THE WATERS DUE TO A LOW PRESSURE SYSTEM OVER THE GULF OF  
ALASKA. THIS SWELL WILL BUILD SEAS TO 11-13 FT AT 14-16 SECONDS,  
RESULTING IN HAZARDOUS CONDITIONS FOR SMALL CRAFT. SMALL CRAFT  
ADVISORIES GO INTO EFFECT ACROSS ALL WATERS INCLUDING THE COLUMBIA  
RIVER BAR 5 PM FRIDAY AND LAST THROUGH AT LEAST SATURDAY EVENING.  
WINDS WILL STAY RATHER TAME OUT OF THE NORTH WITH GUSTS UP TO  
10-15 KT INTO SATURDAY MORNING.  
 
THE WEATHER PATTERN REMAINS ACTIVE SATURDAY NIGHT INTO EARLY NEXT  
WEEK AS A STRONGER FRONTAL SYSTEM PROGRESSES THROUGH THE WATERS  
AND BRINGS BREEZY SOUTHERLY TO WESTERLY WINDS. MARINE CONDITIONS  
QUICKLY AMPLIFY AS A HIGHER NORTHWESTERLY SWELL ENTERS THE WATERS,  
BUILDING SEAS ABOVE 15 FT AT 15 SECONDS (>90% CHANCE) ON SUNDAY.  
CHANCES FOR SEAS ABOVE 20 FT HAVE DECREASED AND ARE NOW NEAR 0%,  
INDICATING INCREASING CONFIDENCE IS THE WAVE HEIGHT FORECAST. IN  
ADDITION TO INCREASING SEAS, WINDS WILL LIKELY GUST UP TO 25-30  
KT. BRIEF AND ISOLATED GALE FORCED WIND GUSTS UP TO 35 KT ARE  
POSSIBLE OVER THE NORTHERN INNER WATERS WITH THE FRONTAL PASSAGE  
SATURDAY NIGHT INTO EARLY SUNDAY MORNING, INCLUDING THE MAIN  
CHANNEL OF THE COLUMBIA RIVER BAR.  
 
SEAS WILL DECREASE LATER MONDAY INTO TUESDAY MORNING, BOTTOMING  
OUT AROUND 8-10 FT AT 13 SECONDS BEFORE ANOTHER POTENT  
NORTHWESTERLY SWELL ARRIVES TUESDAY AFTERNOON AND EVENING PUSHING  
SEAS INTO THE 10-15 FT RANGE AGAIN. -23/10/99  
 
 
   
BEACH HAZARDS  
A NORTHWEST SWELL OF 10-12 FT AT 15 TO 18 SECONDS  
SECONDS IS EXPECTED TO ENTER THE WATERS FRIDAY EVENING. THIS  
INCREASE IN WAVE ENERGY WILL SUPPORT A HIGH THREAT FOR SNEAKER  
WAVES THROUGH THIS WEEKEND. A BEACH HAZARDS STATEMENT REMAINS IN  
EFFECT ACROSS THE CENTRAL AND NORTHERN COAST OF OREGON AND THE  
SOUTH WASHINGTON COAST, WHICH IS NOW IN EFFECT THROUGH SUNDAY  
EVENING. SNEAKER WAVES CAN RUN UP SIGNIFICANTLY FARTHER ON A  
BEACH THAN NORMAL, INCLUDING OVER ROCKS, LOGS, AND JETTIES.  
SNEAKER WAVES CAN SUDDENLY KNOCK PEOPLE OFF OF THEIR FEET AND  
QUICKLY PULL THEM INTO THE OCEAN WHICH MAY LEAD TO SERIOUS INJURY  
OR DROWNING. CAUTION SHOULD BE USED WHEN IN OR NEAR THE WATER.  
ALWAYS KEEP AN EYE ON THE WAVES, AND BE ESPECIALLY WATCHFUL OF  
CHILDREN AND PETS. REMEMBER, NEVER TURN YOUR BACK ON THE OCEAN!  
-23/10/99  
 
 
   
PQR WATCHES/WARNINGS/ADVISORIES  
 
OR...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM PDT SATURDAY FOR  
ORZ104.  
 
FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM PDT SATURDAY FOR  
ORZ121.  
 
WA...FROST ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM PDT SATURDAY FOR  
WAZ205-208.  
 
PZ...SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 2 PM PDT  
SATURDAY FOR PZZ210.  
 
SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 8 PM PDT  
SATURDAY FOR PZZ251>253-271>273.  
 
 
 
 
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