Sunrise 5:35 AM   Sunset 8:12 PM Moonrise 4:25 AM   Moonset 5:32 PM

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FXUS66 KPDT 051026 AFDPDT

Area Forecast Discussion National Weather Service Pendleton OR 326 AM PDT Sun May 5 2024

SHORT TERM
Today through Tuesday...The center of the closed upper level low is moving through NW Nevada this morning and will be over SW Idaho by this afternoon. Moisture continues to wrap around the low coming into eastern Oregon from Idaho mainly impacting NE and north central Oregon and portions of southern Washington. This will continue through the morning but as the low moves towards SW Idaho this afternoon this moisture flow gets cut off and leaving leftover moisture lingering over the forecast area. As the low moves into Idaho this will allow a northwest flow to push into the Pacific Northwest and begin to push the lingering moisture eastward beginning this afternoon and continuing overnight. This flow will maintain some showers along the Cascade crest and portions of the east slopes. Meanwhile this flow will place the Blue mountains under a favorable upslope flow enhancing precipitation over the eastern mountains that begins to taper off late tonight. This event is still on track to produce some significant and beneficial precipitation amounts to the forecast area today and overnight with the main focus now shifting to the eastern portion of the forecast area, the Blue Mountain Foothills and eastern mountains. Snow levels over central Oregon will remain around 3000 to 4500 feet today with some more accumulation snow accumulations in the mountains for which Winter Weather Advisories continue. Snow levels over the eastern mountains will lower tonight to around 3500 feet by Monday morning meaning there will be some minor accumulation snow as well.

A shortwave in the northwest flow is expected to arrive on Monday which will once again increase precipitation across the forecast in the form of showers with a slight chance of thunderstorms over the eastern mountains. This will be followed by linger mountains showers on Tuesday that come to an end Tuesday night as a ridge of high pressure begins to build into the region from the west.

Other concern for today will be the increasing westerly winds associated with exiting low pressure system and the developing northwest flow. Expect westerly windy conditions to reach wind advisory levels of 25 to 35 mph with gusts up to 50 mph across north central Oregon from the Columbia River Gorge eastward to the Foothills of the Blue Mountains. Winds will decrease slightly tonight but still remain breezy to windy through Monday and Tuesday with further issuances or extension of wind advisories being possible..

LONG TERM
Wednesday through Sunday...Significant weather concerns in the long term will be limited to warming temperatures and dry conditions as high pressure becomes the primary weather feature across our region.

In regards to the overall synoptic pattern, aforementioned high pressure will be the primary feature of our region, though the low pressure and troughing currently moving across today will have an influence as well. Ensemble guidance indicates a ridge of high pressure will begin moving over the PacNW on Wednesday, while low pressure moves into the middle of the US. As the ridge continues to stretch into the Northern Rockies and Canada on Thursday and Friday, part of the low will separate from the primary source and retrograde into a separate, weaker low over California/Nevada. This will allow the ridge to continue strengthening over the PacNW and possibly over the entire West Coast by the weekend. Primary discrepancies in ensemble guidance revolve around the weak low that moves back over California, as around 60% of the GFS members have this low stronger than other ensemble guidance, even bringing a portion of it into Southern Oregon, which would be a cooler solution compared to other ensembles, but with the majority of members including the multi- model ensemble indicating strong ridging for the majority of the PacNW, this remains an outlier solution.

With this synoptic pattern, expect a quick warming trend and dry conditions through the long term. Temperatures on Wednesday should still be on the cooler side, around 2-5 degrees below normal, but rapidly become 2-5 degrees above normal on Thursday, and by the weekend could be reaching as high as 10-20 degrees above normal. The NBM indicates a 30-90% chance of highs greater than or equal to 80 degrees next Saturday for our lower elevation zones, and a 30-50% chance of highs greater than or equal to 90 degrees for the Columbia Basin by next Sunday. NWS HeatRisk values still only show around a category 1, or minor, level of heat for our area, primarily affecting those extremely sensitive to heat, especially when outdoors, and heat-related highlights remain very low (less than 5%). Goatley/87



AVIATION
06z TAFs...Light to moderate rain showers will impact all sites through the period, leading to MVFR and even IFR conditions at times as showers lead to reduced cigs and even lowered vsby's at times. The bulk of the rain associated with this ongoing weather system is expected to occur during the overnight hours, with locally heavy showers possible for PDT and ALW around sunrise Sunday. Elsewhere, showers will be of a lighter intensity, however cigs for most of the period are expected to be bkn-ovc between 2 and 7 kft. Rain chances will end earliest across sites near the Cascades, spreading eastward throughout the period, before rain is largely expected to end for all sites by nightfall Sunday night.
Winds will remain gusty at times as well, peaking during the day Sunday as many sites see westerly gusts up to 35 kts, especially DLS and PDT. Evans/74



PRELIMINARY POINT TEMPS/POPS
PDT 49 41 57 38 / 100 80 70 30 ALW 52 43 59 41 / 100 90 70 30 PSC 59 46 64 44 / 100 50 30 10 YKM 62 39 62 37 / 80 10 20 0 HRI 56 43 62 42 / 100 40 40 10 ELN 58 41 56 37 / 60 10 20 10 RDM 49 34 52 30 / 70 10 60 30 LGD 46 37 52 36 / 100 90 90 60 GCD 43 34 51 33 / 100 80 90 80 DLS 58 45 57 44 / 90 20 60 20

PDT WATCHES/WARNINGS/ADVISORIES
OR...Wind Advisory until 11 PM PDT this evening for ORZ041-044-507- 508-510.

Winter Weather Advisory until 11 PM PDT this evening for ORZ506.

Winter Weather Advisory until 11 AM PDT this morning for ORZ509.

WA...Wind Advisory until 11 PM PDT this evening for WAZ024-521.

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