Area Forecast Discussion
Issued by NWS Portland, OR
Issued by NWS Portland, OR
751 FXUS66 KPQR 061006 AFDPQR Area Forecast Discussion National Weather Service Portland OR 303 AM PDT Sat Jul 6 2024 .SYNOPSIS...Prolonged heatwave continues for all of SW Washington and NW Oregon today, with the beaches being just about the only exception. Strong high pressure aloft will support the hot weather through Tuesday evening, after which a robust push of onshore flow should bring temperatures closer to early-mid July norms. Trickle of onshore flow may bring some cooling into the coastal valleys Sunday, but inland areas and elevations above 1000 ft are unlikely to feel significant relief. No rain is in sight through next weekend. && .DISCUSSION...Today through next Saturday...Not a lot of changes made to the forecast this morning, as NW Oregon and SW Washington remain within the grip of a prolonged and dangerous heat wave. Will see pattern continue through at least Monday, with hot afternoons/early evenings, with temperatures reaching 100 to 105 deg for most interior lowlands, but in the middle 80s to middle 90s in the Cascades and the Coast Range/Willapa Hills. But, with thermal trough over the region, will not see all that much in way of winds. So, will feel rather hot. At least humidity will be down, with afternoon minimums of 15-25% for most. But, this comes with a price. With hot temperatures and low humidity, one can easily become dehydrated. So, everyone should keep hydrated to avoid more serious injuries from heat, as well as avoiding more strenuous activities between 11 am and 6 pm. Got animals? Consider if they have adequate shade and water, and perhaps consider taking them out earlier in the day or in the evening as it starts to get a bit cooler. Keep in mind that their paws can burn on hot surfaces like concrete and asphalt; another reason to take them out during the cooler morning hours. Speaking of cooling, it will take some time for temperatures to fall in the evenings. Many lowlands areas may not see temperatures drop back under 90 until 8 pm (especially in more urban areas). Overnight lows will fall back to the upper 50s to middle 60s for many areas, but, does appear will generally stay the warmest in the urban areas where overnight lows will stay in the upper 60s to lower 70s. As such, may take a while for any refreshing coolness to take hold, and that may be not until 2 or 3 am, or not at all for some of the hotter Portland neighborhoods. Elevated terrain will remain warm at night as well, with some RAWS stations possibly not falling much below 80 degrees each night. Will see a slight uptick of onshore flow Saturday night, enough to drop the coast back to more pleasant temperatures for Sunday. This onshore flow may be enough to knock down morning lows a bit. But, air mass remains dry and warm, so this so-called coolness will be fleeting. With the thermal trough sitting over the Willamette Valley on Sunday, will see another hot day on Sunday, but with lighter winds. Bit cooler along the coast, with highs in the 70s to middle 80s along the coast for Sunday into early next week. Again, will have hot afternoon/early evening temperatures across the region (away from immediate coastal areas) into early next week. As such, the duration of the heat will be memorable. For the Willamette Valley, the record most days in a row of 100+ deg is 5 days, set in mid-July 1941 at Portland airport. Many areas in the Willamette Valley/Clark County have seen 4 days in row a few times, such as back in August 2023, or 2015 or in 1981. This year, it looks like 3-4 days of 100+ deg heat is a good bet, but will see if the record 5 days is reached. A lot will depend on temperatures on Tuesday. Current thoughts are that will have last hot day on Tuesday (across the interior). As such, will extend the current Excessive Heat Warning and Heat Advisory through Tuesday evening. Warmest days look to be the Monday and Tuesday. Highest potential of the the highest heat looks focused on areas around the Portland/Vancouver metro and then to the east (through the Columbia Gorge) and to the south (throughout the Willamette Valley). Here are the odds of reaching 100+/105+ deg at select cities, based on data as of Saturday morning: Sat Sun Mon Tue July 6 July 7 July 8 July 9 100 105 100 105 100 105 100 105 ======================================================== Kelso 40% 1% 70% 5% 70% 25% 65% 30% Portland* 85% 20% 95%30% 95% 55% 95% 60% Salem 95% 50% 95%50% 95% 75% 95% 75% Eugene 95% 30% 95%40% 95% 50% 90% 30% Hood River 80% 5% 90%20% 95% 65% 95% 85% The % of reaching 110 or higher is <5% for all areas, except is 5-20% on Monday and Tuesday in the Willamette Valley. *Portland is for Greater Portland/Vancouver metro area Will see onshore flow increase Tuesday night into Wednesday, as the thermal trough shifts east of the Cascades. This will bring back westerly winds to the west side of the Cascades, with a modest cooldown for the interior for Wednesday. Overall, temperatures on Wednesday look to be in the upper 80s to middle 90s, but even cooler temperatures for Thursday, as look to stay in the 80s. Latest WPC cluster analyses suggest a 70-80% chance of positive 500 mb height anomalies lingering through next weekend, which would tend to keep the marine layer on the shallow side and limit the effectiveness of onshore flow to bring cooling east of the Coast Range. Therefore, don`t expect temperatures to fall back below seasonal normals anytime soon. Rockey/Weagle && .FIRE WEATHER...Hot and dry weather will rapidly dry out vegetation over the coming days. Unfortunately overnight relative humidity recoveries appear poor over the higher terrain for several nights moving forward, further working to chip away at fuel moisture. Forecast guidance still suggests winds will be lighter today and Sunday, but it will still be very hot, dry, and unstable near the surface with thermal low pressure overhead. Those working out on the line any day through Tuesday should pay special attention to staying hydrated, as the expected conditions can easily cause heat-related illness or worse.Weagle && .AVIATION...High pressure with northwest flow aloft leading to clear sky VFR conditions through the period. Diurnally driven winds will be somewhat lighter on Saturday as the ridge axis shifts closer to the coast and relaxes the gradient, but 10-15 kt NW winds are still likely to develop at the coastal terminals after 18z Sat. PDX AND APPROACHES...VFR with clear skies through the period. Northwest winds will be lighter around 5-7 kt on Saturday. /DH && .MARINE...High pressure over the waters is expected to weaken today as an area of low pressure well offshore lifts northward. Thermally induced low pressure remains over southern Oregon into California, maintaining northerly winds across the coastal waters. This will lead to weaker pressure gradients over the weekend with wind gusts up to 20 kt. Therefore, will allow the Small Craft Advisory to expire this morning. High pressure is expected to build over the waters again on Monday with SCA level winds likely returning by the afternoon. Seas will be predominately wind- driven resulting in wave heights below 6 ft through early next week. /DH && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Excessive Heat Warning until 10 PM PDT Tuesday for ORZ104>125. Heat Advisory until 10 PM PDT Tuesday for ORZ126>128. WA...Excessive Heat Warning until 10 PM PDT Tuesday for WAZ202>210. Heat Advisory until 10 PM PDT Tuesday for WAZ211. PZ...Small Craft Advisory until 2 AM PDT early this morning for PZZ251>253-271. Small Craft Advisory until 8 AM PDT this morning for PZZ272-273. && $$ www.weather.gov/portland Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland