Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
511 FXUS66 KPQR 061801 AFDPQR Area Forecast Discussion National Weather Service Portland OR 1101 AM PDT Thu Jun 6 2024 && .SYNOPSIS... High pressure will maintain mostly clear skies and warm conditions through the weekend. The warmest day will be tomorrow (Friday), with afternoon highs well above-normal. Recent rain may make things feel a bit more humid. Expect increasing cloud cover Saturday-Sunday with a weak trough, but no precipitation expected. Above-normal temperatures continue into the long term forecast, but uncertainty remains with how strong high pressure will be. && .SHORT TERM...Now through Sunday... Today through Saturday...High pressure will persist over the Pacific Northwest through the end of the week, maintaining dry and warm conditions. Expect sunny skies today, with afternoon highs in the low 80s for interior valleys and 60s to 70s for higher terrain. We`ll maintain onshore (northwest) flow, so afternoon sea breezes will support temperatures in the 60s along the coast. The upper level ridge will reach it`s maximum amplitude tomorrow (Friday), likely bringing the warmest temperatures of the week. Friday afternoon highs for inland locations are expected to be 15-20 degrees above normal, with temps forecast in the upper 80s. The latest NBM guidance suggests that there is a 30-50% chance of afternoon temperatures exceeding 90 degrees from Salem to the Portland Metro Area, the Columbia River Gorge, and Upper Hood River Valley. These locations will have a moderate heat risk - this level of heat affects most individuals sensitive to heat, especially those without effective cooling and/or adequate hydration. Also considering the recent rain, we could feel a bit more humidity in the warm air. Friday night, the upper level ridge begins to move eastward as a weak shortwave trough approaches the Pacific Northwest. This will bring more southwesterly flow aloft as well as increasing mid to high level cloud cover late Friday night into Saturday. Since our air mass will be so dry when this shortwave moves in, it`s unlikely that we`ll see any precipitation or thunderstorm activity. As a result, did reduce NBM PoPs to below 25% in the Cascades Saturday afternoon and Saturday night. If any showers or thunderstorms did form, the westerly component to the flow aloft would likely carry it east of the Cascade crest. Otherwise, we could see virga at best. High temps on Saturday will likely begin to cool with increasing cloud cover, but still remain above normal inland. 500 mb heights remain above-normal, representing the warm air mass in place. In addition, ensemble guidance still show 850 mb temps around 14 deg C, which would support high temps reaching the low 80s for interior valleys. NBM guidance suggests a 50-70% chance that locations in the Willamette Valley exceeds 80 degrees on Saturday. -Alviz .LONG TERM...Sunday Night through Thursday... Saturday night through Wednesday...The upper level shortwave trough will push through the region and weaken Saturday night to Sunday. Still expect mostly dry conditions as our air mass will be too dry to support precipitation. Sunday morning could start off with some cloud cover, but clouds would dissipate by the afternoon as high pressure re-builds behind the shortwave. Most WPC clusters are in general agreement of maintaining high pressure with above-normal 500 mb heights over the Pacific Northwest through mid next week. However, the clusters still differ on the precise magnitude and placement of the ridging. The most uncertainty comes Tuesday-Wednesday, when ensemble guidance shows an upper trough near the Gulf of Alaska pushing into British Columbia. Depending on how far south this trough ends up, this would influence the strength of high pressure over us and thus how warm we end up getting. Temperatures are expected to remain above normal through the long term period, but with a wider range of outcomes. NBM probabilistic guidance which shows a 10-15% chance of reaching 90 degrees and less than a 5 percent chance to reach 95 degrees throughout the Willamette Valley next Tuesday. However, the 25th percentile solution would result in temperatures in the mid to upper 70s on Tuesday and Wednesday. Generally speaking, the pattern favors a continuation of warm and dry weather through the extended, but with less confidence on where high temperatures will ultimately land. -Alviz && .AVIATION...High pressure lingers over the region with VFR conditions through the next 24 hours. Winds will be generally north to northwesterly. Areas along the coast, and from KSLE southward to K77S within the Willamette Valley will see slightly stronger winds. Around KEUG, there is a 10% chance that gusts could reach as high as 30 kt but trending towards more of a 20 kt gust forecast. Around 5000 ft ASL, wind speeds will be high initially this morning (around 35 kt), then will ease through the afternoon to around 20 kt from the northwest. PDX AND APPROACHES...VFR with no concerns. Mainly wind driven forecast changes, but in general northerly winds through the day with a 10% chance of gusts up to 25 mph after 06Z Friday. -Muessle/Batz && .MARINE...High pressure over the region will lead to clear skies and fairly persistent winds. Will see a northerly wind through the next few days which will ramp up around 5 PM Thursday. From PZZ272/252 southward, gusts could reach speeds up to 30 kt. This is generally due to heating changes through the day. Seas will hover right around 10 ft at 13 seconds. Have extended the small craft advisory for the northern waters as seas have remained elevated and winds will ramp up again in several hours. Conditions will begin to ease on Saturday as a very weak front nears the waters. This front appears to have limited impact, but cannot rule out some gustier conditions here or there. Seas will lower to around 5 to 7 ft at 12 seconds. -Muessle && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 11 PM PDT this evening for PZZ251- 271. Small Craft Advisory until 6 AM PDT Friday for PZZ252-253-272- 273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland