textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Hot temperatures through tomorrow, with temps 10 to 15 degrees above normal Thursday along with increasing southerly winds. - Cold front passage Friday with cooler temperatures heading into this weekend and a chance of precipitation across northern portions of the forecast area Friday.

- Cooler conditions continue through the weekend and early next week.

SHORT TERM /Through Friday Night/

Issued 233 AM MDT WED SEP 23 2026 Dry west to southwest flow will be over the area today with the flow aloft becoming more southwesterly by Thursday ahead of a strong longwave Pacific trough. Thus, temperatures will generally warm today, and then increase sharply from today to Thursday. Temperatures will be 10-15 degrees above normal on Thursday, with many lower valleys forecast to see maximum temperatures in the low-mid 90s. Ahead of the approaching trough, winds in the Snake Plain will increase to SE 15 to 25 mph with gusts up to 35 mph. Elevated fire weather conditions will develop Thursday afternoon across SE Oregon and SW Idaho due to hot, dry, and windy conditions in southerly flow. Breezy to windy conditions will continue Thursday night ahead of the Pacific trough and approaching cold front.

The cold front is still on track move through the area Friday afternoon. While the front is mostly dry, save for precipitation to the north, pre- and post-frontal winds will be strong. Southwesterly pre-frontal winds will increase with gusts to 25-45 mph, strongest south and west of the Snake Plain and along ridgetops. As the front moves through the area, winds will switch to the northwest, with post-frontal gusts remaining elevated at 25-40 mph. As the associated trough swings north of our area, the best precipitation chances/totals will stay generally north of our area. In our area, the best chances of precipitation (20-40%) will be in northern portions of Baker and Valley Counties. The temperature effects of this front will be most felt in eastern Oregon, where it will move through earlier in the afternoon, with a nearly 20 degrees temperature difference between Thursday afternoon and Friday afternoon highs. Above normal temperatures will persist friday across SW- Idaho, with max temps in lower elevations reaching the low to mid-80s.

LONG TERM /Saturday through Wednesday/

Issued 233 AM MDT WED SEP 23 2026 Temperatures will cool to 5-15 degrees below normal area-wide come Saturday. A trough digging off the west coast will pass- over the area late Sunday/early Sunday along with an associated cold front. While this trough and front will be weaker than that of Friday, it will help keep cooler conditions and breezy west/northwest winds in place into the start of the next week. Moisture availability is in question for this next system. With an active eastern Pacific, tropical moisture could work it's way back up to support precipitation chances. However, return flow will be limited with the quick one-two punch of these systems. Right now, am leaning towards another dry frontal passage with moisture remaining south and east of our area. Long-range guidance doesn't handle the energy transfer with tropical systems the best, but things should become more clear in the days to come.

AVIATION /12Z Wednesday through Thursday/

Issued 509 AM MDT WED SEP 23 2026 VFR. Patchy fog/low stratus near the Magic Valley and in S-Central ID mountain valleys. Surface winds: variable under 10 kt this morning remaining variable or SE through the afternoon. Winds aloft at 10kft MSL: SW 5-15 kt.

KBOI...VFR. Surface winds: S-SE 3-8 kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.