textproduct: Pendleton

KEY MESSAGES

- Drying and warming trend through early next week

- Locally breezy northerly winds developing over the weekend

DISCUSSION

Today: Satellite imagery this afternoon shows an upper shortwave trough has exit the region, with mainly cloudy to partly cloudy conditions across the eastern half of the forecast area. Behind the shortwave exit, winds have started to weaken and radar shows showers are diminishing across the eastern mountains. This will be the trend through the remainder of today, with dry conditions and light winds returning late this evening.

Thursday through Sunday: The region will sit between an amplifying upper level ridge offshore and a broad trough centered over the northern Great Plains through the weekend. Conditions will remain dry across the forecast area through this period, while diurnally driven winds develop Thursday and Friday. Over the weekend, ensemble guidance is in good agreement of shortwave troughing diving down the northern Rockies, which will clip the PacNW. This will shift surface winds to the north and northeast Saturday and Sunday, with locally breezy winds (10-20 mph) developing from the Columbia Basin into central OR in the afternoons. This will lead to elevated fire weather conditions across portions of the OR Columbia Basin Saturday and Sunday afternoons, though chances of Red Flag thresholds being met are only 25-40% Saturday and 35-50% Sunday.

Sunday, ensemble cluster guidance is in good agreement that the upper level ridge offshore will move closer to the PacNW, which will introduce chances (30-50%) of hitting 90 degrees across portions of the Columbia Basin and eastern Gorge.

Monday and Tuesday: Most recent ensemble cluster guidance is in good agreement that the upper level ridge will slide inland Monday, limiting wind concerns but also increasing the warming trend across the lower elevations, with mod-high confidence (65-80%) of widespread low to mid 90 degree high temperatures developing Monday afternoon. With the ridge axis moving overhead, winds will become light, which will limit fire weather concerns to the very dry conditions in the lower elevations.

By Tuesday, great agreement remains in the upper ridge breaking down as it moves further inland, bringing the peak of the warming trend in the afternoon as well as introducing breezy to locally windy conditions to the intermountain PacNW (confidence 60-70%). Looking to the NBM, there is a 30-50% chance of 100 degree temps developing Tuesday afternoon along the I-82 corridor from Hermiston to Yakima, as well as in the Walla Walla valley and eastern Gorge. Currently, probabilistic HeatRisk guidance shows a 10-40% chance of Major HeatRisk developing across the Columbia Basin and eastern Gorge Tuesday. If this trend continues, heat products may need to be issued for some portions of the Columbia Basin early next week. Lawhorn/82

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

VFR conditions to prevail through the period. Breezy winds (12-18kts with gusts 18-25kts) will continue at most sites through the remainder of the afternoon, with winds becoming light through the remainder of the period. Lawhorn/82

Preliminary Point Temps/PoPs

PDT 41 78 49 80 / 0 0 0 0 ALW 47 79 53 81 / 0 0 0 0 PSC 44 82 50 85 / 0 0 0 0 YKM 44 82 50 84 / 0 0 0 0 HRI 43 81 51 84 / 0 0 0 0 ELN 40 77 47 77 / 0 0 0 0 RDM 34 80 43 83 / 0 0 0 0 LGD 38 78 44 78 / 0 0 0 0 GCD 36 81 43 82 / 0 0 0 0 DLS 47 81 54 82 / 0 0 0 0

PDT WATCHES/WARNINGS/ADVISORIES

WA...None. OR...None.