Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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697 FXUS66 KPDT 271613 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 913 AM PDT Thu Jun 27 2024 .MORNING UPDATE...Water vapor imagery this morning shows troughing over the forecast area, which will lead to breezy winds and light mountain showers today. Mountain showers will primarily impact the Washington Cascade crests, as the airmass over the eastern mountains and Oregon Cascades looks to be too dry to support any meaningful shower development. Thunderstorms are not anticipated. Meanwhile, the passing of the trough will cause winds to gust up to 35 mph this afternoon across primarily the Basin and Cascade Gaps, with a stray gust over 40 mph possible through our more wind-prone areas such as the Gorge and Kittitas Valley. Scaled back on PoPs along the Washington Cascades based on latest CAMs runs this morning, which were showing less PoPs than what was in the latest forecast. Evans/74 && .PREV DISCUSSION... /issued 418 AM PDT Thu Jun 27 2024/ SHORT TERM...Today through Saturday...Sensible weather concerns should be limited during the short term thanks to a transitory weather pattern with breezy and seasonably cool conditions today followed by a steady warm up through the beginning of the weekend. Ensemble guidance is in good agreement on the overall pattern, showing an upper low over the borders of Washington and Canada currently progressing eastwards today, followed by a quick transitory ridge taking its place Friday through early Saturday before another low approaches the Canadian coastline, with a cold front and attendant trough beginning to enter our region early Sunday. With this pattern, expect another breezy day today as the pressure gradients remain tightened thanks to the passing system and post- frontal environment. Peak wind gust chances reaching or exceeding 45 mph over the next 24 hours are around 30-60% outside of the high terrain near the Kittitas Valley and Simcoe Highlands. This suggest we should see widespread gusts 25-35 mph today, with breezes locally reaching 40-45 mph but remaining isolated enough that wind products will not be warranted. Temperatures are also notably cooler today, with Spring-like highs for the entirety of the area. In fact, the NBM only shows probabilities of reaching or exceeding 80 degrees today for Hermiston up through the Columbia Basin, with around a 30-60% probability. This means the majority of the high temperatures for our population centers should run in the low to upper 70`s, with locations such as Tri-Cities and Hanford right around 80. Finally, lingering showers are noted across the eastern mountains of Oregon as well as across the Cascades. Precipitation should taper off for the eastern mountains through this morning, but continue across the crests of the Cascades through this afternoon, exiting by the evening hours. Under a transitory ridge, conditions then calm tomorrow through Saturday morning. Temperatures rise around 2-6 degrees Friday and again on Saturday, placing us near or slightly below normal and then a few degrees above by Saturday. Otherwise sensible weather concerns should be mostly nil with calm conditions on Friday and a few mountain showers beginning overnight Saturday into Sunday with the approach of the next trough and cold front, and breezy winds around 20-30 mph through the Cascade Gaps during the evening and overnight timeframe as well. Goatley/87 LONG TERM...Sunday through Thursday...The main sensible weather concerns through the extended forecast will revolve around breezy to locally windy conditions during and post a trough passage Sunday and Monday. Otherwise, the remainder of the period looks to see near seasonable temperatures with little precipitation and locally breezy conditions. Ensemble guidance starts in good agreement with an upper trough and attendant surface cold front pushing across the PacNW Sunday through early Monday. The cold front passage Sunday will bring increased winds across the forecast area, which will continue through Monday as a tightened cross Cascade pressure gradient persists. Chances for the peak wind gust to meet or exceed 45mph in a 24hr period are between 60-80% for areas of the Simcoe Highlands, Kittitas valley, Cascade gaps, southern Blue mountain foothills, and the OR Columbia Basin for both Sunday and Monday. The increased winds combined with dry conditions will result in elevated fire weather concerns both days. Otherwise, the trough and cold front passage will bring isolated to scattered showers across the WA Cascade crest, northern Blues, and the Wallowas Sunday into early Monday. Increasing instability with modest low level lapse rates across Wallowa county will also facilitate the development of isolated thunderstorms Sunday afternoon and evening (chance 15-20%). Behind the upper trough, there is generally good agreement between ensemble solutions for ridging to develop upstream in the northeast Pacific through early Tuesday. However, late Tuesday and beyond, ensembles come in to disagreement with solutions ranging from ridging amplifying offshore with northwest flow aloft (ECMWF ensemble) to a broad shallow trough centered along the northern Rockies (GFS ensemble). Impact-wise, the difference in the solutions will mean either a quicker warming period through the midweek (ECMWF ensemble), or slower warming period through the midweek (GFS ensemble). As of the most recent NBM run, chances of hitting or exceeding 90 degrees across the Basin and Yakima valley Wednesday is only 30-45%, and only 40-55% on Thursday. Confidence in going temperature forecast at this time is only low- moderate (25-40%). Meanwhile, either solution will result in dry conditions settling back across the region with locally breezy winds through the Cascade gaps in the afternoons (confidence 60%). Lawhorn/82 AVIATION...12Z TAFs...VFR conditions to prevail through the period. Light winds have developed at sites RDM/BDN/YKM, with winds of 12-15kts at all other sites through the morning. Winds will increase again through the morning to 12-20kts with gusts up to 30kts through the afternoon and early evening. Light winds will develop late this evening at all sites. SCT-BKN mid to high level cloud decks will diminish through the day, with clear skies developing overnight. Lawhorn/82 && .PRELIMINARY POINT TEMPS/POPS... PDT 73 48 80 54 / 0 0 0 0 ALW 77 52 84 57 / 0 0 0 0 PSC 80 53 84 60 / 0 0 0 0 YKM 76 47 82 55 / 0 0 0 0 HRI 78 51 85 56 / 0 0 0 0 ELN 70 49 81 55 / 10 0 0 0 RDM 73 41 80 48 / 0 0 0 0 LGD 70 45 78 52 / 0 0 0 0 GCD 73 45 81 51 / 0 0 0 0 DLS 74 52 84 58 / 10 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...74 LONG TERM....82 AVIATION...82