FXUS66 KPDT 092116 AFDPDT Area Forecast Discussion National Weather Service Pendleton OR 216 PM PDT Sun Jun 9 2024 .SHORT TERM...Today through Tuesday... Bottom Line Up Front (BLUF) 1. Thunderstorms over south central OR and along the eastern mountains today. 2. Sub advisory winds Tuesday. 3. Near normal to normal temperatures return. Current radar is showing a few cells moving across the area putting down some rain. The line of precipitation has shifted eastward with the frontal boundary. Ground observations show that 0.03 inches of rain has fallen over the Ochoco-John Day Highlands and has continued to move northeastward. We had a nice cell move over Pendleton a bit ago and dumped roughly 0.03 inches of rain so far. These showers will continue off and on through the evening. Hi-res models are in good agreement with the upper level synoptic pattern through tonight. An upper level ridge has shifted east of the region as the leading edge of an upper level trough makes its way onshore. Mid level moisture will enhance as the southwesterly flow intensifies ahead of the the upper level trough. This synoptic set up will lead to thunderstorm probabilities across southern Deschutes, Crook and Grant Counties. The SPC has a general thunderstorm outlook across the CWA. As the upper level trough continues to push onshore, thunderstorm ingredients will continue through this evening and move along the Ochoco-John Day Highlands and across the eastern mountains into Wallowa County. There is also a slight chance (<25%) of thunderstorms along the Cascades and portions of far northern Kittitas County. Model derived soundings for the Cascades with MUCAPEs of 300-600 J/kg, lifted index of -3 to -4, however, the lapse rates are low at 7.4 J.kg and bulk shear is week at 20 kts. Confidence in thunderstorms occurring over the aforementioned area is low (10%). Looking at the eastern mountains however, model derived soundings continue to show MUCAPE of 400-600 J/kg, lapse rates of 8.4 C/km, lifted index of -3 to -4, PWATs of 0.78 inches and bulk shear nearing 40kts. The strongest of the ranges being in Union and Wallowa Counties. Confidence in thunderstorms continuing to occur over the eastern mountains is moderate (30-50%). The upper level trough pushing across the Cascades, model derived pressure gradient tool shows that there is a tightening of the surface gradients along the Cascades of 9 to 11 mb as another shortwave ripples across the region causing a surface pressure gradient across the Cascades. Due to this, ensembles are picking up on increased winds, especially through our wind prone areas. There is over a 60-75% chance the Simcoe Highlands and portions of the Gorge seeing gusts of 45 mph or greater, 70% through the lower Kittitas Valley and a 65% along the foothills of the Blues. Will continue to monitor the winds as the system draws near. Lastly, temperatures will slowly moderate back to near normal through Tuesday. However, EFI is picking up on above average temperatures along the eastern mountains on Tuesday. Regardless, temperatures will moderate a few degrees through the period. Over 55% of the ensembles have temperatures above 75 degrees today with a few isolated location in the Basins seeing low 80s while the higher terrains will see temperatures in the upper 60s to low 70s. Temperatures will remain much the same daily through the period. Bennese/90 .LONG TERM...Wednesday through Sunday...Dry westerly flow will prevail over the Pacific Northwest through early Friday. Then the flow will become more southwesterly in response to an approaching trough. As the trough approaches, there will be some rain over the Washington Cascades on Friday, with other locations remaining dry. The rain will progress to the Oregon Cascades on Saturday and into the eastern mountains by Sunday. However, most of the rest of the area will remain dry. There still is considerable uncertainty as to the exact strength and position of the upper trough with the latest ECMWF deterministic run keeping the trough over southwestern Canada while the GFS brings the trough further south across the Pacific Northwest. The ensemble clusters don't show much of a favorite until Saturday then 37% of the clusters show support for the GFS solution with the low in the Pacific Northwest. This would support the deeper/further south solution. The tightening pressure gradient will bring breezy to windy conditions on Friday and continued breezes on Saturday, especially across the Columbia Basin, Gorge, Kittitas Valley, Yakima Valley, Simcoe Highlands and Foothills of the Blue Mountains. Ultimately, where the low/trough set up will help determine how windy it may get. The ECMWF EFI is not excited about the wind gust potential on Friday, and given the ECMWF more northerly track of the low it would likely be less windy. The NBm probabilities of winds >=39 mph range from 70 to 100% in the above areas. Given all the uncertainty though, and the time range, things could change. Probabilities of winds >=47 mph are 40-60%, though higher in the Kittitas Valley. Additionally, with the trough moving across the region, by Saturday, temperatures will end up 5 to 10 degrees below normal. Wednesday will see highs slightly above normal, from near 80 degrees to the lower 80s. Thursday will be warmer with temperatures above normal generally in the mid to upper 80s. By Friday, the change starts with highs ranging from the mid 70s to mid 80s. Saturday will see highs from the mid 60s to the mid 70s. Sunday's highs will be similar to those on Saturday. && .AVIATION...18Z TAFS...VFR conditions are expected through the TAF period. There will be isolated SHRA/TSRA around through the afternoon that could impact virtually any TAF site. The best chances are (20-30%) are at YKM, ALW, RDM and BDN. Given the low chances, will not include in the individual terminals and will handle with amendments as needed. Any activity should decrease after 10/03Z. Winds will gust to around 25 kts at DLS/RDM/BDN before decreasing this evening. Other sites will generally be 10 kts or less, though there could be a local increase in and around any SHRA/TSRA. && .PRELIMINARY POINT TEMPS/POPS... PDT 55 79 56 81 / 0 0 0 0 ALW 59 81 60 84 / 0 0 0 0 PSC 59 85 60 87 / 0 0 0 0 YKM 53 84 55 81 / 10 0 0 0 HRI 58 84 60 84 / 0 0 0 0 ELN 55 78 56 74 / 0 0 0 0 RDM 47 79 50 79 / 0 0 0 0 LGD 51 76 53 79 / 10 0 0 0 GCD 49 78 53 82 / 10 0 0 0 DLS 57 81 59 77 / 0 0 0 0 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. && $$ SHORT TERM...77 LONG TERM....90 AVIATION...77