National Weather Service Area Forecast Discussion for Long Beach, WA USA
000 fxus66 kpqr 161050 afdpqr Area Forecast Discussion National Weather Service Portland, OR or 342 am pdt tue aug 16 2022 .synopsis...high pressure across the great basin will expand into our area through mid week to promote a hot wednesday and thursday, with more seasonable temperatures likely to return by the upcoming weekend. && .discussion... key messages: * above normal temperatures will occur inland through thursday. wednesday and thursday continue to appear the hottest days. * high heat risk is forecast for much of the population across the north and central willamette valley, clark county, and the columbia gorge/upper hood river valley on wednesday. moderate heat risk is forecast for sensitive groups thursday. * a thunderstorm threat will exist for the higher oregon cascades wednesday evening through thursday evening. there is the potential for the thunder threat to expand more to the west wednesday night. detailed discussion (through next monday)...at 3 am, water vapor satellite shows elevated moisture streaming northeastward along the pacnw coastline and into the olympics, indicating a weak shortwave trough which deterministic guidance suggests will pass to our north through the morning. in its wake, ridging will build in from the great basin to bring increasing 500hpa heights and resultant warming. today temperatures will be above normal for the interior lowlands, but not significantly so. highs are forecast to peak in the upper 80s to low 90s, which is only around 6 to 10 degrees above normal for mid august; for instance, the average high at pdx for august 16th through the 22nd is 82 degrees. wednesday, we heat up further and many areas will thus enter the high heat risk category as high temperatures reach the 95 to 103 range across the interior. nbm is now giving around an 80% that temperatures will exceed 95 and nearly a 50% chance that highs will reach the triple digits in salem on wednesday. thursday looks similarly hot, though uncertainty in the temperature forecast is greater. the nbm interquartile range (iqr), or mid-50 range, spans 92 to 102 on thursday in salem, whereas the range extended from 97 to 102 on wednesday. this indicates the probability for temperatures at or above 102 is the same (around 25%) on both days, while the likelihood of temperatures at or greater than 97 is significantly lower on thursday compared to wednesday (in fact, it drops from ~75% to ~55%). even so, the chances for setting a record high temperature on thursday currently appear higher than the chances for doing so on wednesday in the northern and central willamette valley. see below for record highs (and their chances of being broken) on both days. wednesday thursday pdx: 105 (1%) pdx: 99 (34%) salem: 105 (7%) salem: 102 (17%) eugene: 97 (42%) eugene: 98 (27%) much of the spread in thursday`s high temperatures forecast can be explained by the models` spread in whether and where convection will occur wednesday evening/night. forecast soundings from the nam continue to suggest ample elevated instability across the entire area, though strong capping will make it difficult for convective initiation without a sufficiently strong trigger - and on this point models do not agree. the deterministic ec, gfs, and cmc each show an area of enhanced, mid-level cyclonic vorticity racing north-northwestward across nw oregon wednesday evening, but the strength of the feature is just not nailed down. the nam shows a weak pv1.5 signature, and in fact suggests a more well defined tropospheric fold with the parent trough thursday evening; not surprisingly, the namnest suggests little convective activity wednesday. meanwhile, the hrrr portrays a few blobs of higher reflectivities spreading from the cascades across the willamette valley, as does the high resolution fv3. for now, we`ll keep the thunder mention in the lane co. cascades on wednesday, as that is where the nbm and sref have the highest probabilities for thunder (at around 20%) and where the ec deterministic depicts lightning activity. we`ll choose to believe the bulk of the ensemble guidance which keeps the remainder of the area qpfless. thursday, a westerly component is added to the flow as a negatively tilted trough approaches our area from the northwest. models still do not agree on how late in the day this will happen, though. the gfs keeps southeasterly 700mb flow over nw oregon through mid afternoon, which could promote convective activity across the cascades, foothills, and even willamette valley if convective initiation occurs early enough in the day (or it`s continuing from wednesday night). however, the ec and cmc steer the flow back to westerly a little sooner, which would imply convection that develops in the cascades would be driven quickly east of the crest. this seems like the more likely scenario, but again it will bear watching. since thunder chances were highest (approaching 25% in spots) along the high cascades according to both the sref and nbm, the slight chance mention in the forecast is confined to that area. with the arrival of the aforementioned upper trough friday morning, a strong marine push is expected, and this may ultimately cool temperatures even more than what guidance currently suggests. the nbm is giving highs in the mid 80s across most of the interior lowlands, but one would not be surprised if it ends up even cooler if marine stratus holds on into the early afternoon. either way, it will feel much better than wednesday and thursday for those who don`t enjoy the heat. temperatures look to remain near to slightly above normal through the weekend as the area remains under southwest flow between the great basin high and a large trough over the eastern pacific. -bumgardner && .aviation...12z tafs: typical summer pattern, as high pressure sits offshore with moderate northerly flow across region. gusts 20 to 25 kt along the coast for the afternoon and evening. air mass remains stable, with just occasional thin high clouds. do have shallow marine layer, with ifr stratus along the coast punching well into the valleys of the willapas and coast range. some ifr/low mvfr stratus along the lower columbia river and cowlitz valley as well, with this stratus around the portland/vancouver metro til 17z. all stratus will break up and dissipate by 18z inland, and by 20z along the coast. sidenote: expect pockets of smoke to continue south and east of albany, mostly due to the fires in upper mckenzie valley. for detailed pac nw aviation weather information, go online to: https://weather.gov/zse kpdx and approaches...vfr with variable high clouds today. marine stratus, with cigs 800 to 1200 ft, will continue to form over clark county through 13z, and spread over the east part of metro. think pdx stays with scattered to broken clouds, but more broken to overcast as move to east and north of field. this stratus will dissipate through 17z. /rockey && .marine...high pressure will remain anchored offshore over the next several days, with thermal low pressure along the south oregon coast into northwest california. this will maintain moderate northerly pressure gradients over the south oregon coastal waters, resulting in a prolonged period of northerly winds over the coastal waters. northerly winds will be strongest during the mid to late afternoon and evening hours each day, especially to the south of cascade head. a small craft advisory is up for the coastal waters this afternoon and evening, but have extended that through wed evening. gusts 20 to 25 kt expected, with the gusts strongest and more frequent to south of cascade head. seas should generally 4 to 6 ft, with the choppiest seas likely to occur to the south of newport. not much change thu through sat, through winds will be lighter, running 10 to 15 kt. seas stay 3 to 6 ft overall. for information about upcoming marine zone changes, go online to: https://www.weather.gov/pqr/marinezone && .pqr watches/warnings/advisories... or...heat advisory from noon wednesday to 10 pm pdt thursday for cascade foothills in lane county-cascades in lane county- central columbia river gorge-central willamette valley- greater portland metro area-lower columbia-northern oregon cascade foothills-northern oregon cascades-upper hood river valley-western columbia river gorge. wa...heat advisory from noon wednesday to 10 pm pdt thursday for central columbia river gorge-greater vancouver area-i-5 corridor in cowlitz county-south washington cascade foothills-south washington cascades-western columbia river gorge. pz...small craft advisory from 2 pm this afternoon to midnight pdt wednesday night for coastal waters from cape shoalwater wa to florence or out 60 nm. && $$ www.weather.gov/portland interact with us via social media: www.facebook.com/nwsportland www.twitter.com/nwsportland
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