A cold front will bring another wave of widespread rain and embedded thunderstorms tonight, delivering the most significant rainfall totals of the event before conditions improve dramatically for the weekend. However, another round of wet weather will return Sunday night through Labor Day as Hurricane Marie's moisture gets steered into the region.
More rain tonight ahead of changes for holiday weekend in Scott Dorval's video forecast
Tonight: Heaviest Rain of the Event
A cold front approaching from west-central Oregon will cross the forecast area overnight into Friday morning, bringing another wave of widespread rain and embedded thunderstorms along with breezy westerly winds. Tonight's rainfall will be the most significant of the entire event for the Treasure Valley, with a 90 percent chance of precipitation and additional amounts of a tenth to a quarter inch possible on top of what has already fallen this week.
Updated Cumulative Rainfall Totals Through Friday Evening:
| Location | Total Rainfall Through Friday Evening |
|---|---|
| Treasure Valley (Boise area) | 0.25 to 0.33 inches total |
| West-Central Idaho Mountains | 1.00 to 1.25 inches total |
| East Central Idaho Mountains | 0.33 to .75 inches |
| Southeast Oregon | 0.50 to 1.00 inches total |
| Western Magic Valley / Camas Prairie | Less than 0.10 inches total |
Fire Season Relief: A Historic Development
This rainfall event is delivering the most significant moisture to the Treasure Valley and central Idaho since spring, and the impacts on the fire season are already being felt. Mountain areas receiving 1 to 1.5 inches of rainfall will see dramatic reductions in fire behavior and spread rates. Fuel moisture levels, which had been critically low after weeks of record heat, will increase substantially. Fire danger ratings across much of the region will drop from critical to moderate or low levels, providing firefighters with a significant tactical advantage.
Spirit of Boise Balloon Classic: Friday and Saturday Outlook
Friday morning will bring patchy fog before 10 a.m. and a slight chance of showers, making conditions marginal for balloon operations. However, skies will clear through the afternoon. Saturday looks like the best day of the event, with patchy morning fog clearing by 10 a.m. and mostly sunny skies developing with a high near 74 degrees. Balloon Classic attendees should plan for Saturday as the highlight day of the event.
Labor Day Weekend Day-by-Day Outdoor Guide
Saturday: The best day of the holiday weekend. Patchy morning fog clears by 10 a.m. before mostly sunny skies develop. High near 74 degrees with light winds. Excellent conditions for outdoor activities, hiking, camping, and the Balloon Classic.
Sunday: Mostly sunny with a high near 75 degrees. Another good day for outdoor activities, particularly in the morning and early afternoon. Shower and thunderstorm chances increase significantly Sunday night with a 60 percent chance of precipitation as the Pacific upper low steers inland and Hurricane Marie's moisture approaches.
Labor Day: A 50 percent chance of showers with patchy morning fog and a high near 69 degrees. Conditions will be noticeably cooler and wetter than a typical Labor Day. Keep outdoor plans flexible and have a backup plan. The central Idaho mountains will see the heaviest rainfall Monday as the low core passes directly over the area.
Looking Ahead: Drier and Warmer Tuesday Through Thursday
Below-normal temperatures will persist through early next week due to upper troughing and widespread cloud cover. However, drier conditions and warmer temperatures are expected Tuesday through late next week, with highs climbing from 76 degrees Tuesday to 82 degrees Thursday. Another Pacific upper low may return scattered precipitation Thursday, depending on the amount of Pacific moisture steered into the area.
Tonight
Showers, mainly before 5am. Low around 51. Northwest wind 5-10 mph becoming calm after midnight. Chance of precipitation is 90%. New precipitation amounts between a tenth and quarter of an inch possible.
Friday
A slight chance of showers before 1pm, then a slight chance of showers after 4pm. Patchy fog before 10am. Otherwise, cloudy through mid morning, then increasing sunshine, with a high near 68. Light wind.
Friday Night
Showers likely, mainly after 5am. Mostly cloudy, with a low around 50. Light and variable wind. Chance of precipitation is 70%.
Saturday
Patchy fog between 8am and 10am. Otherwise, mostly sunny, with a high near 74. Light and variable wind.
Saturday Night
A 20 percent chance of showers after midnight. Partly cloudy, with a low around 53.
Sunday
Mostly sunny, with a high near 75.
Sunday Night
A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after midnight. Mostly cloudy, with a low around 52. Chance of precipitation is 60%.
Labor Day
A 50 percent chance of showers. Patchy fog between 8am and 9am. Otherwise, partly sunny, with a high near 69.
Monday Night
Mostly clear, with a low around 48.
Tuesday
Sunny, with a high near 76.
Tuesday Night
Partly cloudy, with a low around 51.
Wednesday
Mostly sunny, with a high near 79.
Wednesday Night
Partly cloudy, with a low around 55.
Thursday
Mostly sunny, with a high near 82.
