textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- A cold frontal passage brings very gusty winds, blowing dust, a chance of showers and thunderstorms, and cooling conditions today.

- Thunderstorms will develop late this morning, with a risk of strong outflow winds up to 65 mph in the Western Magic Valley this afternoon.

- Just above normal temps through Friday before another cooldown this weekend, conditions stay dry and breezy.

SHORT TERM /Through Friday Night/

Issued 256 AM MDT WED MAY 13 2026 A significant pattern shift is underway as a deep Pacific trough pushes a strong cold front through southeast Oregon and southwest Idaho today. After yesterday's record breaking heat, temperatures will drop 20 to 25 degrees behind the front. Highs today will range from the mid 60s in southeast Oregon to the low 80s in the Magic Valley ahead of the frontal passage.

The airmass has already begun to destabilize this morning with isolated thunderstorms observed across the West Central mountains as of 1 AM. Showers and thunderstorms will expand in coverage late this morning across southeast Oregon and southwest Idaho along and ahead of the front. While many areas will see gusty outflow winds (40-50 mph), the most favorable environment for organized convection will be across the Western Magic Valley this afternoon. Better instability and shear will reside there ahead of the passing cold front between 2 PM and 4 PM, as highlighted in the SPC day one outlook. These fast moving storms will be capable of transporting momentum downward to the surface, supporting the potential for dry microbursts with gusts up to 65 mph.

Very windy conditions will develop area wide along and behind the cold front. A Wind Advisory is in effect for much of southern Idaho where gusts up to 55 mph are possible. High res models suggest the potential for blowing dust in areas that remain dry before precipitation arrives. Though most fuels are still greening up, the combination of an extended hot and dry period followed today with strong winds, a dry boundary layer, and lightning supports an elevated risk for wildfires across south-central Idaho.

Showers will linger into Wednesday night and Thursday morning, particularly over the northern mountains as the upper level trough axis moves through. Snow levels will drop to around 6000 to 7000 feet by early Thursday morning. Thursday will be much cooler with breezy west winds continuing, though speeds will be lower than today. High temperatures will struggle to reach seasonal normals, topping out in the 60s for most valley locations.

The region will remain under a dry west northwest zonal flow through Friday. This will lead to stable conditions and plenty of sunshine. Temperatures on Friday will begin a slight recovery, warming back into the upper 60s and lower 70s, which is near normal for mid May. Lows Friday night will be chilly, dropping into the 30s and 40s across the area.

LONG TERM /Saturday through Wednesday/

Issued 256 AM MDT WED MAY 13 2026 A large trough will begin digging across the region from off the coast of British Columbia Saturday through Sunday, bringing a significant cooling trend that will drop daytime temperatures 5 to 10 degrees below normal for the weekend. Not much precipitation is expected from this system over our area. Saturday will see a 10-20% chance over the northernmost mountain areas of our CWA. There is considerable guidance uncertainty over the precip amount for Sunday. For now, we are mainly expecting a 30-50% chance over high terrain areas on the southwest/west-central ID side. From Monday through midweek, our area will mostly stay under a dry west-northwest zonal flow. Temperatures will mostly hover near seasonal normals but may take on a slight upward trend towards the end of the extended period.

AVIATION /12Z Wednesday through Thursday/

Issued 514 AM MDT WED MAY 13 2026 VFR with scattered showers and isolated thunderstorms until late morning. A strong cold front will pass through the area early afternoon, bringing strong W-NW winds over all areas and scattered showers/thunderstorms over central mountains and Magic Valley. Surface winds S-SW 10-20 kt this morning, then WNW 20-30 kt with gusts 30-40 kt after frontal passage in the afternoon. Strongest gusts 40-50 kt near KMUO, KTWF, and KJER. Periods of LLWS possible near the approaching front. Winds aloft at 10kft MSL: SSW 20-25 kt, then W-NW 25-30 kt after Thu/00Z.

KBOI...VFR with high clouds and scattered vicinity showers. Strong cold frontal passage this afternoon 17Z-19Z, with strong winds expected. Surface winds ESE 8-12 kt this morning, becoming WNW 20-25 kt with gusts to 35 kt after 17Z. Winds lowering to 10-15 kt after sunset.

BOI WATCHES/WARNINGS/ADVISORIES

ID...Wind Advisory from 9 AM this morning to midnight MDT tonight for IDZ012-014>016-028>030. OR...Wind Advisory from 9 AM MDT /8 AM PDT/ this morning to midnight MDT /11 PM PDT/ tonight for ORZ064. Wind Advisory from 9 AM MDT /8 AM PDT/ this morning to 6 PM MDT /5 PM PDT/ this evening for ORZ061-063.