936
FXUS66 KPQR 011745
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1045 AM PDT TUE SEP 1 2026
UPDATED AVIATION DISCUSSION.
SYNOPSIS
AN UNUSUALLY STRONG SERIES OF SYSTEMS, BY EARLY
SEPTEMBER STANDARDS, TAKES AIM AT THE PACIFIC NORTHWEST FOR THE
MIDDLE OF THE WEEK. THESE SYSTEMS LOOK TO BRING WIDESPREAD
RAINFALL, LOCALLY BREEZY/GUSTY WINDS, AND A 15-30% CHANCE FOR
POP-UP THUNDERSTORMS, WITH HIGHER CHANCES ON THURSDAY. CONDITIONS
TREND SLIGHTLY DRIER BY LATE THURSDAY/FRIDAY AND CONTINUE INTO
THE WEEKEND. HOWEVER, COOLER THAN NORMAL TEMPERATURES AND SHOWER
CHANCES PERSIST.
SHORT TERM...TODAY THROUGH THURSDAY NIGHT
WELL, THE DAYS
THAT WE HAVE BEEN TALKING ABOUT HAVE ARRIVED. A SERIES OF LOWS,
DROPPING OUT OF THE GULF OF ALASKA WILL BRING WIDESPREAD RAIN,
COOLER TEMPERATURES AND BREEZY/GUSTY SOUTHERLY WINDS ACROSS THE
CWA. TODAY, THE RELATIVELY WEAKER OF THE TWO LOWS WILL DIVE
SOUTHWARD TOWARDS THE OR/CA BORDER. THIS WILL BRING THE FIRST
TASTE OF FALL TO THE CWA AS CLOUD COVER WILL INCREASE, COOLER
TEMPERATURES WILL BE EXPERIENCED ALONG WITH A 20-30% CHANCE FOR
LIGHT SHOWERS. DAYTIME HIGHS WILL BE IN THE LOW TO MID 70S FOR
INLAND VALLEYS, UPPER 50S TO MID 60S FOR THE COAST, AND MID 50S
TO MID 60S FOR THE CASCADES. WINDS ALSO BEGIN TO TURN MORE
SOUTHERLY, GENERALLY REMAINING RELATIVELY LIGHT WITH GUSTS BELOW
20 MPH. AN EXCEPTION WILL BE THE COLUMBIA RIVER GORGE AND HOOD
RIVER VALLEY, WHERE WESTERLY GAP WINDS TUESDAY AFTERNOON APPEAR
PROMINENT WITH GUSTS APPROACHING 35 MPH.
WEDNESDAY, IS SHAPING UP TO BE FAR MORE IMPACTFUL FOR THE
REGION. AS MENTIONED ABOVE, A SECOND, MORE ROBUST LOW WILL
CLOSELY FOLLOW THE TRACK OF THE TUESDAY SYSTEM. HOWEVER, THIS
SYSTEM WILL BRING COOLER TEMPERATURES AND A SIGNIFICANT AMOUNT
OF MOISTURE. SO, LET'S GET TO THE MEAT OF THE FORECAST AND
ANSWER THE MOST PRESSING QUESTION: HOW MUCH RAIN TO EXPECT FROM
THIS SYSTEM? TAKING A LOOK AT NBM 48 HOUR TOTAL PROBABILITIES
(5AM WED-5AM FRI), THERE IS AN 85% OR BETTER PROBABILITY THAT
TOTAL RAINFALL AMOUNTS WILL BE AT LEAST 1 INCH FROM THE COAST TO
THE CRESTS OF THE CASCADES. CHANCES FOR 1.50 INCHES OR MORE IS
50-80% FOR THE COAST AND OUR HIGHER TERRAIN FEATURES AND 10-30%
ALONG THE I-5 CORRIDOR. AS FOR 2 INCHES OR MORE THERE IS AROUND
A 40-60% FOR THE COAST AND OUR HIGHER TERRAIN FEATURES AND 5-15%
CHANCE ALONG THE I-5 CORRIDOR. DAYTIME HIGHS ON WEDNESDAY ARE
ALSO LOOKING TO BE IN THE MID TO UPPER 60S FOR INLAND VALLEYS,
MID 50S TO MID 60S FOR THE COAST, AND LOW 50S TO LOW 60S FOR
THE CASCADES. FOLLOWING THE FRONTAL PASSAGE, THERE'LL ALSO BE
A 15-30% CHANCE FOR THUNDERSTORMS. SOUTHERLY WINDS ARE ALSO
EXPECTED TO INCREASE ON WEDNESDAY. EXPECT GUSTS APPROACHING 30
MPH FOR INLAND LOCATIONS, GUSTS APPROACHING 40 MPH FOR THE
COLUMBIA RIVER GORGE AND HOOD RIVER VALLEY AND LASTLY, GUSTS
ALONG THE BEACHES/HEADLANDS OF THE COAST PEAKING AROUND 55-60
MPH.
AS THURSDAY APPROACHES, WINDS WILL EASE, BUT COOLER DAYTIME
HIGHS AND SHOWERS REMAIN IN THE FORECAST AS THE UPPER LEVEL LOW
MEANDERS OVER WESTERN OREGON. THUNDERSTORM CHANCES WILL ALSO
CONTINUE THROUGH THURSDAY AND LOOK TO BE SLIGHTLY MORE FAVORED
WHEN LOOKING AT MODELS SOUNDINGS. WHILE THE SHEAR ENVIRONMENT
DOESN'T LOOK SUPPORTIVE OF LONG LIVED CELLS, POP-CORN THUNDERSTORMS
ARE VERY POSSIBLE. IN ADDITION, COLD AIR ALOFT WILL ALSO PUT
INTO PLAY THE POTENTIAL DEVELOPMENT OF COLD CORE FUNNEL CLOUDS.
ANY PASSING THUNDERSTORMS MAY PRODUCE LIGHTNING, HEAVY RAIN,
ERRATIC WINDS, AND SMALL HAIL. -42/99
LONG TERM...FRIDAY THROUGH MONDAY
CHANCES FOR SHOWERS LIKELY
LINGER THROUGH THE START OF NEXT WEEK AS THE UPPER-LEVEL LOW
WEAKENS AND STALLS ALONG THE COASTLINE. DAYTIME HIGHS LOOK TO BE
IN THE 60S TO 70S WITH AMPLE CLOUD COVER. LATE MONDAY,
SHORTWAVE RIDING LOOKS TO BRING A RETURN OF RATHER BENIGN
CONDITIONS AS ENSEMBLE MODEL TRENDS ARE POINTING TOWARDS A
SLIGHT WARMING AND DRYING TREND TO THE PAC NW. -42
AVIATION...THROUGH 18Z WEDNESDAY
LATEST TERMINAL OBSERVATIONS
SHOW LARGELY MVFR CIGS INLAND WITH LOW-END VFR CIGS ALONG THE
COAST. CIGS LIFTING TO 4-6 KFT IS EXPECTED AT ALL TERMINALS AS
DIURNAL MIXING FAVORS MORE WIDESPREAD VFR INTO THIS AFTERNOON.
CHANCES FOR FURTHER MVFR CIGS INCREASE TO 50% OR GREATER AFTER
00-03Z WED AT COASTAL TERMINALS, WHILE LOWERING CIGS SHOULD
REMAIN AT LOW-END VFR LEVELS INLAND, WITH 10-20% CHANCES OF MVFR
AFTER 06Z WED. THE CHANCES FOR SCATTERED RAIN SHOWERS ALSO TEND
TO INCREASE AFTER 00Z WED, THOUGH CONFIDENCE IN THE OCCURRENCE
AND PLACEMENT OF THESE SHOWERS IS TOO LOW TO INCLUDE IN TAFS AT
THIS POINT; ANY SHOWERS THAT DO AFFECT A TERMINAL WILL BE LIGHT
WITH VERY BRIEF OR LIMITED IMPACTS. SOUTH-SOUTHWEST WINDS WILL
RISE TO 8-12 KT INLAND AND 10-15 KT WITH GUSTS OF 20-25 KT ALONG
THE COAST THROUGH THIS AFTERNOON.
A MORE POTENT FRONTAL BOUNDARY LOOKS TO APPROACH THE REGION LATE
IN THE PERIOD, BRINGING WIDESPREAD LIGHT TO MODERATE RAIN
BEGINNING BY 12-18Z WED. THERE IS HIGH CONFIDENCE IN FURTHER
MVFR CIGS AT COASTAL TERMINALS AS RAIN BEGINS, WHILE VFR CIGS
ARE MORE LIKELY TO PREVAIL THROUGH AT LEAST 18Z WED INLAND. MVFR
VIS IS ALSO MORE LIKELY ALONG THE COAST FOLLOWING PRECIPITATION
ONSET. WINDS WILL INCREASE ACROSS THE AIRSPACE AS THE BOUNDARY
NEARS, REACHING 15-20 KT WITH GUSTS OF 25-30 KT ALONG THE COAST
AND 10-15 KT AT INLAND TERMINALS.
KPDX AND APPROACHES...DIURNAL MIXING WILL FAVORING CURRENT MVFR
CIGS LIFTING TO VFR AT 4-5 KFT THIS AFTERNOON. VFR CONDITIONS
ARE THEN FAVORED TO PREVAIL THROUGH THE REMAINDER OF THE PERIOD,
ALTHOUGH CHANCES FOR MVFR CIGS INCREASE LATE IN THE PERIOD,
AFTER 15Z WED, AS STEADY RAIN ARRIVES FROM THE WEST. SOUTH-
SOUTHWEST WINDS CONTINUE THROUGH THE PERIOD, BUT INCREASING
TOWARD 10-12 KT AS THE FRONTAL BOUNDARY APPROACHES WEDNESDAY
MORNING. -36
MARINE
A SERIES OF LOWS WILL MOVE ACROSS ALL WATERS THROUGH
WEDNESDAY. THESE SYSTEMS WILL RESULT IN SOUTHERLY WINDS
CONTINUING TO DEVELOP THROUGH TODAY WITH WINDS DEVELOPING INTO
GALES STARTING LATE TONIGHT THROUGH AT LEAST WEDNESDAY EVENING.
WINDS WILL BUILD THROUGH WEDNESDAY AFTERNOON, WITH GUSTS NEARING
35 KT BY LATE TUESDAY NIGHT/EARLY WEDNESDAY MORNING. PEAK WINDS,
WITH GUSTS APPROACHING 45 KT ARE MOST LIKELY FROM 6 AM THROUGH
2 PM PDT WEDNESDAY ACROSS THE MAJORITY OF THE WATERS, AND FROM
11 AM THROUGH 5 PM PDT WEDNESDAY WITHIN 10 NM OF THE COAST.
THERE IS A 20- 40% CHANCE OF ISOLATED STORM-FORCE GUSTS WITHIN
20 NM OF THE COAST. SEAS ARE EXPECTED TO BUILD TOWARDS 10-14 FT
DURING THIS PERIOD, PEAKING WEDNESDAY MORNING WITH ONLY UP TO A
5-10% CHANCE THAT SIGNIFICANT WAVE HEIGHTS EXCEED 15 FT. BEHIND
THIS SYSTEM, THERE ARE 10-20% CHANCES FOR THUNDERSTORMS ACROSS
THE WATERS ON THURSDAY. WINDS EXPECTED TO FALL BELOW 15 KT BY
WEDNESDAY NIGHT, SEAS WILL BE SLOWER TO SUBSIDE LIKELY FALLING
BELOW 10 FT LATE THURSDAY/EARLY FRIDAY. -42/36
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...GALE WARNING FROM 11 PM THIS EVENING TO 5 PM PDT WEDNESDAY FOR
PZZ210-251>253-271>273.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page