Sunrise 6:40 AM   Sunset 8:44 PM Moonrise 12:00 AM   Moonset 7:33 AM

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FXUS65 KBOI 270249 AFDBOI

Area Forecast Discussion National Weather Service Boise ID 849 PM MDT Fri Apr 26 2024

DISCUSSION
This evening, a weak trough lingers over the area while a low pressure system reorganizes over Utah. This setup will result in isolated showers and thunderstorms across southeast Oregon. As the low pressure system strengthens in Utah, expect easterly flow aloft to persist, leading to scattered showers across the West Central and Boise mountains of Idaho, as well as the Western Magic Valley, until Saturday afternoon. Furthermore, the strong surface pressure gradient will prolong gusty northwesterly winds through Saturday.

From Saturday through Monday, anticipate springtime conditions to persist, with a series of weak troughs and cold upper-level low- pressure systems traversing the Northern Rockies. While these systems aren't expected to bring significant precipitation, surface winds could pose concerns, particularly on Monday and Tuesday. The EC EFI index indicates anomalously higher wind forecasts for Monday compared to the past 5 weeks, suggesting an above-average chance of stronger winds early next week.

The current forecast adequately accounts for showers this evening and windy conditions persisting until Tuesday, so no updates are necessary at this time.

AVIATION
Generally VFR. Isolated showers diminishing in SE Oregon tonight, but remaining over central/south-central Idaho through much of Saturday. Snow levels 5500-7000 ft MSL.
Mountains obscured in showers. Surface winds: generally W to NW 10-20 kt. Gusts to 25-30 kt from KONO to KTWF/KJER tonight through Saturday. Winds aloft at 10kft MSL: W to NW 10-25 kt.

KBOI...VFR with scattered to broken mid/high clouds. Shower activity over surrounding foothills is not expected at terminal tonight. Surface winds: NW 10-20 kt with gusts to 25-30 kt this evening. Gusts dropping off overnight, then returning to 25-30 kt around Sat/16Z.

Sunday Outlook...Patchy mountain valley fog/low stratus in the morning. Otherwise, mostly dry and VFR. Surface winds generally SW to NW 5-15 kt, then variable 5-10 kt after sunset. Afternoon gusts to 20-25 kt around KMUO/KTWF/KJER.

PREV DISCUSSION
SHORT TERM
Tonight through Sunday night
Scattered rain showers have developed this afternoon in Baker and Malheur Counties in Oregon and in the Owyhee Mountains in Idaho as an upper trough comes in from the northwest. Showers will develop over higher terrain in the rest of our CWA later today and marginal instability will support isolated thunderstorms (10-20 percent coverage) through sunset. Gusty northwest winds will blow through the night and Saturday, decreasing only slightly between midnight and dawn. The windiest area will be the Snake Basin from Mountain Home eastward where speeds 20 to 30 mph and gusts 35 to 40 mph will be found. Rain and snow showers will continue in central and south- central Idaho Saturday and Saturday night (snow level 6000 feet MSL), ending Sunday as the upper trough moves into the central and southern Rockies. Drying Sunday night under a weak upper ridge ahead of the next deep trough approaching from the Gulf of Alaska.

LONG TERM
Monday through Friday
The 12Z runs of the deterministic models have come into much better agreement through Thursday night. They depict an upper trough moving by to our north Monday and a second one Tuesday into Tuesday night.
Together, these will keep a chance (generally 15-40%) of showers, mainly in the north, through Tuesday night. Isolated thunderstorms are also in the forecast in the north Mon/Tue aft/eve. Temps will be around 5 degrees below normal. We'll see relatively dry northerly flow aloft Wed night into Thu, gently backing to NW late Thu and continuing into Friday. This will bring just a slight chance (10-20%) of showers to the northern higher terrain. Temps in the NBM seemed to be influenced too much by time-lagged members, and were adjusted cooler to be more in line with newest GFS and EC MOS guidance.

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

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