Area Forecast Discussion
Issued by NWS Portland, OR

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000 FXUS66 KPQR 110408 AAA AFDPQR Area Forecast Discussion National Weather Service Portland OR 907 PM PDT Wed Aug 10 2022 Updated aviation and short-term sections. .SYNOPSIS...Seasonable temperatures will continue through the weekend with an upper low off the coast slowly passing to our north and west. High pressure will slowly build during at least the first half of next work week, bringing the potential for another extended- duration heat wave. && .SHORT TERM...
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Through Saturday...At 9 PM, water vapor satellite reveals the upper low that brought thunderstorms to the area Tuesday evening situated around (47N, 128W). On the southeast side of this low, 500mb flow has become south-southwesterly to shut off the stream of monsoon moisture which was getting pulled into our area yesterday. The low is forecast to become quasistationary over the next couple days, leaving the PacNW in the south-southwest upper level flow regime that will foster more seasonable conditions through Friday. Deterministic guidance is suggesting the cut-off low will get gradually swept up by the upper level jet Friday into Saturday, and in response a weak cold/occluded front will swing into our area on Friday. This will bring a strong marine push, along with a chance for drizzle both Friday and Saturday mornings along the coast, in the Coast Range, and in the Cascade Foothills. With stratus forecast to blanket the area, high temperatures both days are likely to be a bit cooler compared with Thursday. Unsurprisingly, the NBM suggests highs will be somewhere in the upper 70s to lower 80s in the interior lowlands on both Friday and Saturday. -Bumgardner .LONG TERM...Sunday through Tuesday...As evident from WPC`s cluster analysis, the extended period is characterized by remarkable ensemble agreement for a change. All signs point to a warming trend beginning Sunday, with 500hPa heights continuing to rise through Wednesday or perhaps Thursday (beyond the scope of our forecast at this time). Even the mean of the CMCE, the coolest of the extended ensemble packages, is bringing 500hPa heights to 589 dam at PDX by Wednesday evening. The NBM gives a 81% chance for temperatures to surpass 90F, and an interquartile probable maximum temperature range spanning 94F to 105F for Wednesday in Portland. This has the potential to be another extended duration event as well; NBM is yielding a more than 50% chance for highs of 95F or higher for Salem from Tuesday through Friday. While this is very far out in time, confidence is building in the potential for another heave wave by the middle of the next work week. -Bumgardner
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&& .AVIATION...
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06Z TAFs: It took an entire day`s worth of solar heating to erode the stratocumulus deck, but alas by 03z Thursday the clouds have virtually completely vanished, with area-wide VFR conditions predominant in their wake. The pressure gradients are weaker across the region this evening, so the resulting onshore marine push will be less overnight compared with last night. Guidance is giving around a 30-50% chance for MVFR ceilings along the coast between roughly 12z and 16z, with much lower probabilities - mostly concentrated along the I-5 corridor - inland. With a shallower marine layer tonight, the stratus should break up quickly after dawn with (mostly) clear sky VFR taking hold through the end of the TAF period inland, and through around 02-04z along the coast. For detailed Pac NW aviation weather information, go online to: https://weather.gov/zse KPDX AND APPROACHES...VFR conditions are forecast to continue through the end of the TAF period, though guidance continues to suggest around a 30% probability for MVFR ceilings to develop near the terminal during the 12-16z Thursday timeframe. -Bumgardner
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&& .MARINE...
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A low pressure system well offshore from the WA/OR coast will remain nearly stationary Wednesday night through Friday before eventually lifting northeastward towards Vancouver Island Friday night. Until then, a prolonged period of southerly winds is expected to occur over the coastal waters. During that time, wind gusts should generally stay at or below 15-20 kt with significant wave heights around 4 to 5 ft. Confidence is high that both winds and seas will remain below small craft advisory thresholds through at least Friday. On Saturday, winds are expected to gradually veer from the south to a more northerly direction as a surface thermal trough becomes reestablished along the northern CA/southern OR coast. The thermal trough then looks to remain in place through the weekend and into early next week, setting the stage for a more typical summertime northerly flow regime with winds becoming breezy during the afternoon and evening hours. At this time, the next chance for small craft advisory level wind gusts will be Monday afternoon/evening, mainly over the central waters where the surface pressure gradient will be strongest. -TK For information about upcoming marine zone changes, go online to: https://www.weather.gov/pqr/marinezone
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&& .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland

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