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Area Forecast Discussion
Issued by NWS Pendleton, OR
Issued by NWS Pendleton, OR
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159 FXUS66 KPDT 131725 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 1025 AM PDT Sat Jul 13 2024 Updated Aviation Discussion .AVIATION...18z TAFs...VFR conditions expected. Sites will see mostly clear skies and light, terrain-driven winds less than 12 kts, save for DLS which will see gusts up to 25 kts at times this afternoon. Area haze and smoke may also cause some obscurities in the horizon as well. Evans/74 && .PREV DISCUSSION... /issued 321 AM PDT Sat Jul 13 2024/ SHORT TERM...Today through Monday... Key Points: 1) Critical fire weather conditions expected throughout the weekend including dry and unstable conditions and abundant lightning for southeastern Oregon, and breezy winds/low RH`s for the Cascade Gaps into the Columbia Basin. 2) Heat remains present with heat advisory continuing throughout the weekend. Models indicate the overall pattern will remain fairly consistent through the weekend into early next week as a deep upper level high centered over the Four Corners stretches out ridging across our region while troughing just offshore in the Pacific helps to produce a westerly to southwesterly flow pattern. This will keep us hot and dry overall while smaller shortwaves rounding the ridge will produce both periods of breezy winds as well as the potential for some isolated thunderstorm activity in southern Oregon that may be able to work its way up towards our region on Sunday. CAMs continue to keep the most plentiful thunderstorm activity south of our region today and Sunday with the passage of the shortwave activity. Forecast soundings show very dry conditions until the 500 mb level as well, but the 700-500 mb lapse rates today are upwards of 9-9.5 C/km. With plentiful instability, fire weather concerns have remained high in the Strawberry/Southern Blue Mountain zones today. By Sunday CAMs present more convection potential up into our zones with portions of Central OR up through southern Wallowa County seeing isolated storms at times. But with low to mid levels still dry, expecting these will be mostly dry thunderstorms with lightning and gusty outflow winds the possible hazard. For more information on the fire weather potential, see Fire Weather section below. Onto the continued heat, the NBM has widespread 60-95% chance of highs 100+ for the Yakima Valley, Central Oregon, Columbia Basin, and foothills of the Blue Mountains. Probabilities do drop on Sunday as the passing shortwave impulse should help to deter some of the ridging, but 40-90% chance still remains for the Yakima Valley, Columbia Basin, and foothills of the Blues. There remains high confidence in HeatRisk values of moderate to locally major, giving good confidence to the ongoing heat advisory. Probabilities drop by Monday, but don`t get too excited - highs still remain widespread 90`s to near 100 in the Columbia Basin, so relief will only be by a few degrees at best. Goatley/87 LONG TERM...Tuesday through Saturday...Models continue to be in good agreement regarding placement of key weather features during the long term periods. Mainly that the weather pattern over the western USA will continue to be dominated by a large scale ridge of high pressure. The center of the ridge will initially be over the Four Corners area but slowly shift west to be closer to Las Vegas late in the week. Question becomes whether there will be enough moisture wrapping around the ridge to become concerned about possible thunderstorms. As of now the probabilities of thunderstorms remains less than 10% on any given day over the long term forecast periods. The ridge placement does guarantee that high temperatures will continue to run 10 to 15 degrees above normal throughout the long term period. This will continue to put much of the forecast area in the moderate HeatRisk category with a low chance (20-30%) of occasional major HeatRisk. FIRE WEATHER...Instability continues to remain prevalent across central and southeastern Oregon with Haines values of 6 widespread in this region. A red flag warning for hot dry and unstable was issued for OR-642 to account for this and the Falls Fire ongoing in this zone; however, any new startups that occur across OR-611, 640, 644, and even 645 will see extreme fire behavior potential as instability is strong in these regions as well. On Sunday, CAMs remain scattered on thunderstorm potential, but each show some form of activity making its way into the region. A fire weather watch remains in effect for OR-642 for this potential as this is the most likely zone that storms will be possible in with abundant lightning. Winds and RH`s still remain borderline for our fire weather watch across the Cascade gaps and into the Columbia Basin on Sunday. But with fuels very dry and RH values into the teens alongside sustained winds of 15-25 mph, critical fire weather concerns remain highly plausible. The NBM has a 60-100% chance of sustained winds 20+ mph from the Cascade Gaps through the Columbia Basin and even into the foothills of the Blues, which gives moderate to high confidence (60-70%) that these breezes will coincide long enough with minimum RH values to have a significant effect on fire potential. Have continued the fire weather watch for this area with the expectation it will likely be upgraded today. Goatley/87 && .PRELIMINARY POINT TEMPS/POPS... PDT 100 63 98 59 / 0 0 0 0 ALW 103 68 101 66 / 0 0 0 0 PSC 104 66 102 65 / 0 0 0 0 YKM 102 64 100 61 / 0 0 0 0 HRI 104 66 102 66 / 0 0 0 0 ELN 100 66 96 63 / 0 0 0 0 RDM 99 55 96 54 / 0 0 10 0 LGD 99 61 96 58 / 0 0 0 0 GCD 103 62 98 58 / 0 0 10 20 DLS 100 66 97 64 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Heat Advisory until 10 PM PDT Sunday for ORZ041-044-049-503- 505>508-511. Fire Weather Watch from Sunday afternoon through Sunday evening for ORZ641. Red Flag Warning until 8 PM PDT this evening for ORZ642. Fire Weather Watch from Sunday morning through Sunday evening for ORZ642. WA...Heat Advisory until 10 PM PDT Sunday for WAZ024-026>029-521. Fire Weather Watch from Sunday afternoon through Sunday evening for WAZ690-691. && $$ SHORT TERM...87 LONG TERM....91 AVIATION...74