Area Forecast Discussion

KEY MESSAGES

- Dry and warm trend will continue through early next week

- Locally breezy north to northeast winds Saturday and Sunday

- Breezy to locally windy conditions developing Tuesday and Wednesday, leading to elevated fire weather conditions

DISCUSSION

Today 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 today 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 either day are only 20-40%.

Sunday, ensemble cluster guidance is in good agreement that the upper level ridge offshore will move closer to the PacNW, which will introduce chances (40-70%) of hitting 90 degrees across portions of the Columbia Basin and eastern Gorge.

Monday through Wednesday: 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 (70-85%) of widespread max temperatures in the 90s Monday. 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%). Medium range and ensemble guidance has backed off the potential of hitting 100 degrees on Tuesday, with the NBM showing a 10-20% chance (it was 30-50% 24 hours ago) across the lowest areas of the Columbia Basin. While chances of Major HeatRisk developing Tuesday have dropped considerably (10-20%), ensemble guidance does show an increase in Major HeatRisk chances (15-45%) Monday along the eastern Gorge, Yakima Valley, and WA Columbia Basin.

Wednesday, uncertainty grows in the evolution of the synoptic pattern, with about 40% of ensemble cluster members favoring a shortwave trough impacting the region (cooler and breezy conditions), while the remaining members show a quasi-zonal flow aloft (mild and breezy conditions). Lawhorn/82

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

VFR conditions are forecast at all sites for the next 24 hours. Winds will be diurnally driven with periodic afternoon and early evening gusts of around 15 kts at all sites, except DLS where higher gusts of 15-25 kts are likely (70 percent confidence). Mostly clear skies are anticipated.

FIRE WEATHER

Dry and warming trend through early next week. RHs will drop into the teens to low 20s through Saturday, then teens through Wednesday. Locally breezy north to northeast winds develop over the weekend, with localized elevated fire weather conditions. Breezy to locally windy conditions develop Tuesday into Wednesday as the upper ridge breaks down, resulting in widespread elevated fire weather conditions across the lower elevations.

Preliminary Point Temps/PoPs

PDT 49 80 49 84 / 0 0 0 0 ALW 53 81 54 84 / 0 0 0 0 PSC 51 85 53 88 / 0 0 0 0 YKM 51 85 53 87 / 0 0 0 0 HRI 52 84 52 87 / 0 0 0 0 ELN 48 78 49 82 / 0 0 0 0 RDM 44 82 44 83 / 0 0 0 0 LGD 44 77 45 80 / 0 0 0 0 GCD 43 82 43 83 / 0 0 0 0 DLS 55 84 56 89 / 0 0 0 0

PDT WATCHES / WARNINGS / ADVISORIES

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