Sunrise 6:31 AM   Sunset 8:51 PM Moonrise 3:29 AM   Moonset 2:37 PM

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FXUS65 KBOI 031016 AFDBOI

Area Forecast Discussion National Weather Service Boise ID 416 AM MDT Fri May 3 2024

SHORT TERM
Today through Sunday night...Any lingering showers wrapping around an exiting upper trough will dissipate by mid-morning. The exiting trough is replaced by an upper ridge this afternoon, resulting in dry weather and temperatures 5-10 degrees warmer than yesterday.

Upstream, a deep Pacific low will approach the NW coast on Saturday. This system will be punctuated by heavy precipitation and gusty winds as it pushes into the region late Sat/Sun. The winds will increase out of the S-SE on Saturday in advance of the low. Widespread sustained winds of 20-30 mph with gusts to 40 mph are expected. Locally stronger winds could set up over SE Oregon Saturday and in portions of the Snake Plain east of Boise that would require headlines.

A band of heavier precipitation will form ahead of a cold front that will push into SE Oregon Saturday afternoon, then cross into SW Idaho by evening. Marginal instability and surface energy will support a 15% chance of thunderstorms over s-central Idaho Saturday. Storms that do form will have a favorable shear profile and could become strong. The front will bring a wind shift to the NW Saturday night that will be reinforced by flow aloft on Sunday. Precipitation will continue on Sunday as it wraps around the low center which is forecast to track through northern NV. The probability for precipitation totals of over 0.25" has increased to greater than 80% across SE Oregon and SW Idaho through Sunday. The axis of heavier precipitation remains near the OR/ID border where the chance of exceeding an inch of liquid through Sunday is 15-30%. Snow levels ahead of the front will rise to 6-9kft Saturday evening, falling quickly behind the front Sunday morning. This could bring accumulating snow to SE Oregon as snow levels briefly drop to around 3000 feet early Sunday. Otherwise much of the accumulating snow is above 5500 after the frontal passage.
Precipitation continues in the mountains through Sunday night while valleys trend drier.

LONG TERM
Monday through Friday...Northwest flow continues in the wake of the exiting trough on Monday. Models show trailing shortwave energy that will keep a chance of showers over the region through Tuesday. An upper ridge will build along the coast Wednesday, gradually folding inland through Friday.
Deterministic and ensemble solutions are in good agreement with with this pattern change. Afternoon instability will support a 15-30% chance of showers over the mountains while lower elevations remain dry. Temperatures through Wednesday are 10-15 degrees below normal, warming to near normal Thur/Fri.

AVIATION
VFR. A few lingering showers over SW Idaho early this morning will dissipate by 15Z. Local valley fog/stratus could lower conditions to IFR through 18Z. Mountains will see scattered to broken cumulus field with bases 3500-5500ft AGL.
Surface winds: variable or NW 5-15 kt, then S to SE 5-15 kt Fri afternoon. Winds aloft at 10kft MSL: NW to NE 15-25 kt, veering to S after Fri/15Z.

KBOI...VFR and clearing Friday. Light NW or variable winds, becoming SE 5-10 kt after Fri/21Z.

Weekend Outlook...Widespread precipitation moves into SE Oregon mid-morning Saturday, then into SW Idaho Saturday afternoon and will continue across the region through Sunday. A 20% chance of thunderstorms Saturday afternoon in s-central Idaho. Snow levels 6000-8000 ft MSL, lowering to 4000-5000 ft Sunday. IFR and widespread mountain obscuration Saturday night and Sunday.
Surface winds: SE 15-25 kt with gusts 25-35 kt Saturday afternoon, W 5-15 kt with gusts to 25 kt Sunday.

BOI WATCHES/WARNINGS/ADVISORIES
ID...None.
OR...None.

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