National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Portland, OR

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-- Discussion containing changed information from previous version are highlighted. --942FXUS66 KPQR 072213AFDPQRArea Forecast DiscussionNational Weather Service Portland OR245 PM PDT Fri Jun 7 2024.SYNOPSIS...High pressure of varying intensity across the PacificNorthwest will maintain mostly above average temperatures through atleast the middle of next week. Precipitation chances remain lowduring this period, but peak across the Cascades late Saturday intoearly Sunday and then across coastal areas and southwest WashingtonMonday night into Tuesday.&&.SHORT TERM...
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Tonight through Sunday...Models and their ensembles arein good agreement shortwave ridging and 500mb heights across thePacific Northwest will gradually subside through the weekend, whichwill result in a gradual cooling trend while still maintaining aboveaverage temperatures across inland portions of northwest Oregon andsouthwest Washington.Water vapor satellite imagery reveals a shortwave ridge extendingfrom the Desert SW north-northwestward through the Pacific Northwest.However, an embedded shortwave trough is cutting through the ridgeacross Oregon, and will bring a slight chance for thunderstorms thisevening, but for areas mainly east of the Cascades late thisafternoon and evening.Water vapor satellite imagery also reveals an embedded shortwavetrough near 130W off the California coast. Models and their ensemblesare in good agreement this feature will lift northeastward and bringincreased mid and high cloud cover to the region on Saturday. Aslightly more southerly component to the flow aloft on Saturday willallow for shower and thunderstorm chances to increase across theCascades. At this point, nearly all of the HREF guidance suggestsstorms will still remain east of the Cascades so NBM`s low PoPs(20-30%) and low thunderstorm chances (<20%) seem reasonable. /Neuman
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Sunday Night through Friday...The global ensembles arein good agreement 500mb heights will remain above average early nextweek, which will maintain above average temperatures across most ofnorthwest Oregon and southwest Washington during this time.Nonetheless, there are approximately 10-15% of the members that draga weakening front into the region, which would drop temperatures downto or slightly below average while producing some light rain acrossthe northern portions of the CWA late Monday or Tuesday. As we moveinto the latter part of next week, the ensembles reveal uncertaintyin the overall pattern does grow substantially. For example, about20% of the global ensemble membership drops a shortwave trough intothe region that would result in a much cooler and wetter patternacross the entire CWA as early as late Thursday or Friday. About 35%of the ensemble memberships suggests there shortwave trough will dropclose enough to the region to bring rain chances to at least thenorthern portions of our CWA as early as Friday. Meanwhile, theremaining global ensemble membership suggests the area will remaindry and mild under a shortwave ridge. /Neuman
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Surface high pressure offshore and lower surface pressureover the Great Basin will lead to a typical summertime northwesterlywind regime across northwest Oregon and southwest Washington withpredominantly VFR conditions areawide through 00z Sunday. The mainexception to that statement will be along the immediate coast whereupwelling near the coast may allow for low end MVFR or IFR stratus todevelop overnight into Saturday morning. Current statistical guidancesuggests the probability of this happening is generally around 30-40%at KONP and KAST between 09-18z Saturday.PDX AND APPROACHES...Surface high pressure offshore and lowersurface pressure over the Great Basin will lead to a typicalsummertime northwesterly wind regime with VFR conditions through00z Sunday. /Neuman
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Surface high pressure remains anchored over thenortheast Pacific with thermally induced lower pressure residingover the Great Basin. This will result in periods of northerly windgusts exceeding 21 kt through early this evening from Cape Falconsouthward. The current Small Craft Advisory covers this hazard well.Northerly winds today and upwelling along the coast will bring a 20-40% chance of a low cloud deck forming along the immediate coastovernight that could bring locally dense fog to primarily the innerwaters Saturday morning. At this point, confidence is stillrelatively low this will come to fruition so will hold off on adense fog advisory for now.Gusty winds will subside a bit earlier overnight than is typicalin these summertime northerly wind patterns as a weak frontpushes into the northeast Pacific and weakens the surface highpressure. The main impact from this front will be for seas totemporarily climb back into the 7-9 ft range Saturday nightinto Sunday.Another weak front may brush the waters early next week, but theprobability for winds to rise into Small Craft Advisory thresholdsof 21 kt or more is less than 30%. There is good agreementnortherly winds will strengthen midweek with over an 80% chancethat Small Craft Advisory level wind gusts of 21 kt or more return.Seas look to respond accordingly and appear most likely to climbback into the 7-9 ft range during that time as well.There will be another very strong ebb current early Saturday morningso expect Rough Bar conditions along the Columbia River Bar forapproximately a 3-hour window centered around the strongest ebbcurrent. /Neuman
-- End Changed Discussion --&&.PQR WATCHES/WARNINGS/ADVISORIES...OR...None.WA...None.PZ...Small Craft Advisory until 11 PM PDT this evening forPZZ252-253-272-273.&&$$www.weather.gov/portlandInteract with us via social media:www.facebook.com/NWSPortlandwww.twitter.com/NWSPortland