Annex, OR Weather

Update

Updated aviation discussion.

Key messages

- Light rain and high elevation snow today across southwest Idaho.

- Widespread rain and high elevation snow late Saturday into Sunday, with the highest precipitation amounts across southern Idaho. A slight chance of thunderstorms Saturday evening.

- Cooler with gusty winds Sunday, then dry and warmer Monday through Wednesday. Slight chance of precipitation late week.

.SHORT TERM /Through Sunday Night/: Issued 321 AM MDT FRI OCT 30 2026 An upper low remains off the Washington coast early this morning. With ridging over the northern Plains, our area sits in southwest flow aloft. Embedded within the flow, a weak system will lift north across our area today. This will bring scattered rain and high mountain snow showers to southwest Idaho late this morning into the afternoon, while drier air to the west keeps southeast Oregon mostly dry. Weak instability across south- central Idaho will support a 10% chance of thunderstorms this afternoon in the Magic Valley. Showers will end by the evening with dry conditions overnight. Precipitation amounts will be light, with less than 0.10 inch expected in the lower valleys and 0.10 to 0.25 inch in the central Idaho mountains, and light snow accumulations above 7000 feet. Highs today will be near normal with valley highs in the mid to upper 50s. Winds will be light in most areas. Skies will partially clear tonight, allowing patchy fog to develop especially where precipitation falls today.

On Saturday, the low will elongate southward down the coast before moving inland Saturday night into Sunday. Additionally, a cold front will strengthen over central Oregon and move east across our area. The low will tap into subtropical moisture over the Desert Southwest, with southerly flow ahead of the low transporting the moisture north into our area. A few showers will arrive during the day on Saturday, but the bulk of the moisture will arrive Saturday night into Sunday. The chance of precipitation will rise Saturday evening to around 60-90% in most areas with showers increasing from the south, transitioning to steadier precipitation overnight. There will be enough instability for a slight (15-25%) chance of thunderstorms late Saturday afternoon and evening across southern Idaho, capable of producing heavier precipitation. Temperatures and winds Saturday will be similar to today.

Showers will taper off from west to east on Sunday as the low moves across the area. Snow levels will be 6500-8000 feet MSL through Saturday night, falling to 5500-6500 feet behind the cold front Sunday morning. Light precipitation amounts are expected across southeast Oregon. Higher totals are generally anticipated across southwest Idaho, with 0.25 to 0.50 inch of rain likely in the lower valleys. However, there is a 10-20% chance of an inch or more of rain across the Boise Metro. The highest totals are expected in the mountains east of Boise with 0.50 to 1 inch of precipitation (locally higher amounts possible), which translates to several inches of heavy, wet snow above 7000-8000 feet and light snow accumulations down to 6000 feet. Highs will be 5 to 10 degrees cooler on Sunday with gusty winds developing in the afternoon behind the cold front. Gusts will be strongest east of Boise through the Magic Valley and continue overnight, where gusts 30 to 45 mph will be possible.

.LONG TERM /Monday through Friday/: Issued 321 AM MDT FRI OCT 30 2026 An upper level ridge will build across the region early next week, returning dry conditions and warmer temperatures. However, the decreasing sun angle and developing weak inversion conditions will keep highs near to only slightly above normal. A weak low should disrupt the ridge on Thursday with potential for another trough on its heels on Friday. These systems will bring a 10-30% chance of showers to the area. Temperatures cool slightly at higher elevations while holding nearly steady at lower elevations. Winds will generally be light through the week.

.AVIATION /12Z Friday through Saturday/: Issued 553 AM MDT FRI OCT 30 2026 Mainly VFR under mid to high clouds. Light rain with snow above 6500-7500 ft MSL will increase from the south this morning, mainly across SW Idaho, with MVFR ceilings across higher terrain. A 10% chance of thunderstorms in the Magic Valley this afternoon. Mountains obscured in precipitation. Patchy valley fog developing tonight. Surface winds: SE-SW 5-10 kt with gusts to 20 kt across higher terrain. Winds aloft at 10kft MSL: S-SW 15-25 kt.

KBOI: VFR. Light rain moving in from the south late this morning, ending by mid afternoon. Surface winds: variable to SE 4-8 kt.

Weekend Outlook: Isolated to scattered showers through Saturday afternoon, becoming widespread Saturday night. Isolated thunderstorms across S Idaho late Saturday afternoon and evening. Precipitation continuing through Sunday, tapering off from W-E. VFR-MVFR in rain showers, IFR-LIFR in mountain snow. Mountains obscured in precipitation. Snow levels: 6500-8000 ft MSL Saturday, lowering to 5500-6500 ft MSL Sunday. Surface winds: SW-SE 5-10 kt Saturday, then W-NW 10-20 kt with gusts to 20-30 kt behind a cold front Sunday.

Watches, warnings and advisories

ID: None.

OR: None.