Mostly dry conditions will continue through the week as temperatures climb steadily toward the upper 80s and near 90 degrees over Memorial Day weekend, before a significant pattern change brings cooler temperatures, gusty winds, and increasing precipitation chances early next week.
The region will remain on the western edge of upper-level troughing through Thursday. While organized precipitation will stay to the east, daytime instability will support widespread cumulus buildups over the mountains each afternoon. There is a slight chance that showers could develop from the cumulus field across east-central Oregon and west-central Idaho mountains each afternoon, with localized gusty winds possible from showers or more robust cumulus. Shower chances briefly increase to 15 to 25 percent in the west-central Idaho mountains and south-central Idaho zones Wednesday night in response to a passing shortwave trough. Otherwise, conditions will be dry and temperatures will continue climbing, leaving behind any frost and freeze concerns for the Snake River Plain.
A ridge of high pressure will build over the western United States by the end of the week, bringing generally clear, warm, and dry conditions through the holiday weekend. Temperatures will run about 10 to 15 degrees above normal, with the ridge reaching peak strength on Sunday. High temperatures will approach 90 degrees in the Treasure Valley on Sunday, making for an exceptionally warm Memorial Day weekend.
By Monday, an upper-level low moving into the Pacific Northwest will begin to increase precipitation chances. The upper-level trough will move inland on Tuesday, with about half of the weather models showing the trough evolving into a closed low over the Pacific Northwest by Tuesday or Wednesday. In either scenario, temperatures will cool down 10 to 20 degrees by Tuesday, with increasing winds and a 20 to 30 percent chance of showers and thunderstorms.
Tonight
Mostly clear, with a low around 45. NW wind becoming calm in the evening.
Wednesday
Mostly cloudy in the morning, then gradually becoming sunny later in the day. Milder, with a high near 75. Wind becoming NW 5-10 mph in the afternoon.
Wednesday Night
Mostly clear, with a low around 47. North wind 5-10 mph.
Thur
sday
Sunny & warmer, with a high near 78. NW wind 5-10 mph, with gusts as high as 20 mph.
Thursday Night
Partly cloudy, with a low around 49. NW wind becoming light and variable after midnight.
Friday
Sunny & warmer, with a high near 81.
Friday Night
Clear, with a low around 50.
Saturday
Sunny & unseasonably warm, with a high near 88.
Saturday Night
Mostly clear, with a low around 55.
Sunday
Sunny & continued unseasonably warm, with a high near 89.
Sunday Night
Mostly clear, with a low around 56.
Memorial Day
Mostly sunny early then increasing clouds before evening. Continued very warm, with a high near 87.
Monday Night
A 20 percent chance of showers. Partly cloudy, with a low around 47.
Tuesday
Partly cloudy, breezy & much cooler with a 20 percent chance of showers., with a high near 70.
