WARM FALL WEATHER HANGS ON THROUGH WEDNESDAY
October warmth continues across the Treasure Valley through Wednesday, with afternoon temperatures running roughly 10 to 15 degrees above normal.
Boise-area highs should reach the mid to upper 70s Tuesday and Wednesday, following mild overnight temperatures in the upper 40s and lower 50s.
Tuesday and much of Wednesday will remain relatively quiet in the valley, but changes will already be developing around the region. Increasing moisture from the south will bring scattered afternoon and evening showers and possibly a thunderstorm to the west-central Idaho mountains and areas near the Nevada border.
By Wednesday night, shower chances increase from south to north as the approaching storm begins moving toward our area.
WIDESPREAD RAIN ARRIVES THURSDAY
Thursday is the big transition day.
Widespread showers are expected as the upper-level low lifts northeast from California. A few embedded thunderstorms will also be possible, and any thunderstorms could produce locally heavier rainfall.
Rainfall amounts Thursday into Friday could reach:
- 0.15 to 0.50 inches in the lower elevations, with the lowest totals in eastern Oregon
- 0.50 to 0.80 inches in mountain valleys
- Up to 1.25 inches at the highest elevations
The bulk of the precipitation is expected Thursday and Thursday night.
Snow levels will initially remain high, around 9,000 to 10,000 feet Thursday, meaning this will primarily be a rain event.
MUCH COLDER AND WINDY FRIDAY
The storm exits with a noticeable punch Friday.
A cold front will sweep from west to east, bringing an end to most of the rain along with a dramatic temperature change. After highs in the 70s earlier in the week, Treasure Valley temperatures are expected to reach only the upper 50s Friday.
Winds will also increase behind the front. Gusts could reach 20 to 35 mph across exposed terrain and ridge tops.
The strongest winds are expected in the Snake River Plain east of Mountain Home, where gusts could reach 35 to 45 mph Friday afternoon.
Snow levels fall to around 6,500 feet behind the front. A brief change to snow or a wintry mix is possible at the highest elevations, although only a dusting is expected around high mountain passes such as Banner Summit.
CHILLY FRIDAY NIGHT, THEN A DRY SATURDAY
Skies clear Friday night as colder air settles into Southwest Idaho.
Temperatures around the Treasure Valley could fall into the mid-30s by Saturday morning, making it the chilliest night of this forecast period.
Saturday looks dry with sunshine and a high around 58 degrees. Temperatures recover into the lower to mid-60s Sunday and Monday.
Forecast confidence decreases by Sunday as another trough may develop along the West Coast, but its eventual track and impacts on Idaho remain uncertain.
Tonight
Partly cloudy, with a low around 47. Light wind.
Tuesday
Mostly sunny, with a high near 76. Light wind.
Tuesday Night
Partly cloudy, with a low around 50. Light wind.
Wednesday
Mostly sunny, with a high near 77. Light wind.
Wednesday Night
A 40 percent chance of showers, mainly after midnight. Mostly cloudy, with a low around 52. Light wind.
Thursday
Showers likely developing, with thunderstorms also possible after noon. Mostly cloudy, with a high near 71. Chance of precipitation is 70%.
Thursday Night
This will be the wettest period... Showers and possibly a thunderstorm before midnight, then showers likely. Low around 45. Chance of precipitation is 80%. New precipitation amounts between a quarter and half of an inch possible.
Friday
Poss showers before noon then partly sunny, breezy & much cooler, with a high near 57.
Friday Night
Mostly clear with areas of frost, with a low around 35.
Saturday
Mostly sunny & quite cool, with a high near 58.
Saturday Night
Partly cloudy, with a low around 41.
Sunday
Mostly sunny & milder, with a high near 64.
Sunday Night
Partly cloudy, with a low around 41.
Monday
Mostly sunny, with a high near 62.
