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. --721FXUS66 KPQR 042204AFDPQRArea Forecast DiscussionNational Weather Service Portland OR304 PM PDT Tue Jun 4 2024.SYNOPSIS...
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Showers and gusty winds will diminish across thearea this evening as a frontal system dissipates and highpressure begins to build in from the south. This will bringincreasing temperatures through the end of the week, withtemperatures peaking around 90 degrees on Friday. Above normaltemperatures then persist into early next week.
-- End Changed Discussion --&&.SHORT TERM...
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Now through Thursday Night...Radar andobservations from around the area show numerous to scatteredshowers and gusty south-southwest winds ongoing as a frontpushes across northwest Oregon and southwest Washington thisafternoon, with deep onshore flow in place over the regionanchored by an unseasonably strong upper level jet focused onVancouver Island. Despite the blustery conditions by early Junestandards, a pattern change will soon commence and bring moresummerlike weather going forward as high pressure starts tobuild northward from California, causing the upper level jet tobuckle and shift farther north into Canada. Will see windsdiminish and showers begin to taper off across the area thisevening as the front dissipates, with a few showers lingering inthe Cascades through early Wednesday morning.Wednesday will bring much more pleasant conditions as the ridgebegins to take shape east of the Cascades, with increasingsubsidence ushering in plenty of sunshine and sending hightemperatures near or slightly above seasonal norms in the low70s in the interior valleys including the Portland metro.Temperatures will continue their upward trajectory on Thursdayas models show good agreement on 850 mb temps around 13-15 C,corresponding to highs in the low 80s. Light north-northeast lowlevel flow in response to a strengthening thermal trough mayeven allow some coastal communities to reach the low 70s byThursday. /CB.LONG TERM...Friday through Tuesday...Temperatures still look topeak on Friday as the ridge continues to strengthen east of theCascades, with the latest guidance holding steady with maximumtemps in the upper 80s to low 90s across the interior lowlands.This is reflected by NBM probabilistic guidance ranging fromaround a 60 percent chance to reach 90 degrees in thePortland/Vancouver metro to only around a 10 percent chance inEugene. The larger change is for Saturday as models havecontinues to push the ridge a little farther east and open thedoor to stronger onshore flow earlier than had previously beendepicted. As a result, high temperatures for Saturday havecontinued to trend towards the lower end of the guidanceenvelope, with the NBM now showing only a 15 percent chance toreach 90 in the Portland metro and less than 5 percent in mostother locations. That said, temperatures will still be solidlyabove seasonal norms on Saturday as highs climb into the 80sagain. The other forecast concern for Friday and Saturday aswill be the potential for a few thunderstorms along the OregonCascades as southwest flow aloft allows a few embeddeddisturbances and potential some enhanced mid level moisture toclip the area. The good news is that south-southwest steeringflow would tend to keep any activity that does develop confinedto the immediate crest or points east.Models diverge somewhat on how the ridge evolves beyondSaturday as a trough approaches from the Pacific, with somesolutions directing this energy north into Canada while otherstry to develop a split flow pattern and shunt some energy southtowards CA as a cutoff low. In terms of sensible weatherimpacts, expect mostly dry conditions to persist acrossnorthwest Oregon and southwest Washington with temperatures onSunday dropping a few degrees into the upper 70s or low 80s butgenerally remaining above seasonal norms. WPC ensemble clustersshow general agreement on maintaining high pressure over thePacific Northwest through early next week, while differing onprecise magnitude and placement. Temperatures are thereforeexpected to remain above normal through the period, but with awider range of outcomes. This is reflected by NBM probabilisticguidance which shows a 20-25 percent chance to reach 90 degreesand around a 10 percent chance to reach 95 degrees throughoutthe Willamette Valley next Tuesday. However, the 25th percentilesolution would result in temperatures inly in the mid 70s onTuesday. Generally speaking, the pattern favors a continuationof warm and dry weather through the extended, but with lessconfidence on where high temperatures will ultimately land. /CB
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A frontal system continues to push across the regiontoday with strong westerly flow aloft. Light rain will graduallydissipate through the day. Expect low MVFR to IFR conditions alongthe coast to gradually lift later this afternoon, becoming a mixof high end MVFR to VFR by 06Z Wednesday. Guidance continues tosuggest there is a 40-80% chance of MVFR through this afternoonwith predominately VFR becoming more likely after 00Z Wednesdayacross northern parts of the forecast area. Though, with theslowly moving front, MVFR CIGS are more likely to hang on longerthrough the southern and possibly central Willamette Valley,including KEUG where probs increase to 60-80% after 00Z and lingerthere through 15Z Wednesday. Southerly winds continue to gustthis afternoon to around 25-30 kt along the coast, but areexpected to quickly ease becoming southwest once the front movesonshore by 22-23Z this afternoon. Expect breezy south to southwestwinds with gusts to 20-25 kt continue through this afternoonacross the Willamette Valley.PDX AND APPROACHES...MVFR as of 20Z this afternoon. Chances forMVFR continue around 70-80% between through 22Z Tuesday.Predominately VFR becomes more likely again after 03Z Wednesday.Breezy southwest winds expected with gusts up to 20-25 kt throughthis afternoon. Then, once the front pushes through, winds areexpected to ease below 10 kt becoming more west to northwest./DH
-- End Changed Discussion --&&.MARINE...
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A frontal system will continue to slowly push onshoretoday, sliding south along the coast. Southwest winds around15-25 kt continue across much of the coastal waters thisafternoon, then are expected to gradually turn northwest andease further overnight. Will maintain the Small Craft Advisory asseas are expected to remain elevated through Wednesday night.Seas remain steep and choppy at around 10 to 12 feet throughtonight. An incoming northwesterly swell will likely cause seasto build to around 12 to 14 feet late tonight through Wednesday.High pressure builds midweek for more settled conditions. Expecta summertime pattern with high pressure offshore and a thermaltrough along the coast, bringing northerly winds gusting to 25 ktat times through the end of the week. Seas around 8 to 10 ft onThursday likely to subside to around 6 ft on Friday. /DH
-- End Changed Discussion --&&.PQR WATCHES/WARNINGS/ADVISORIES...
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OR...None.WA...None.PZ...Small Craft Advisory until 5 AM PDT Thursday for PZZ210- 251>253-271>273.
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