textproduct: Boise

UPDATE

Updated aviation discussion.

KEY MESSAGES

- Well above normal temperatures through next week.

- Chance of daytime showers and thunderstorms Sunday through Tuesday. Greatest coverage likely Monday afternoon/evening.

SHORT TERM /Through Monday Night/

Issued 317 AM MDT SAT MAY 2 2026 An elongated closed low off the Oregon coast will dig further off the West Coast through Monday. Water vapor satellite imagery showing plenty of moisture transported on southerly flow wrapping around the east side. For today this will result in mostly mid-high level cloud cover. Shower and thunderstorm development will initiate over central Oregon this afternoon, with isolated cells drifting into western Harney County by evening, bringing little if any rain and a chance of gusty outflow winds to 35 mph. The chance for showers and thunderstorms will increase to 10-20% along the northern NV border on Sunday. The w-central ID mtns will see cumulus buildups as well, and for now hold a 10% chance for areas east of Lowman-Yellowpine, but wouldn't be surprised to see a cell or two pop-up over higher peaks. The upper low center is still modeled to turn east and track into the central CA on Monday. This track will place southern areas in a more favorable environment for shower/storm development, and expand the potential northward into central Idaho. The chance of precipitation increases to 40-60% along the NV border, with a 20-30% chance into the Snake Plain (east of Boise) and w-central ID mtns mainly east of Idaho City-Warm Lake. The more widespread threat would continue to be gusty outflow winds, with localized heavy rain and hail potential from stronger storms that develop. High temperatures are 10-15 degrees above normal through Monday.

LONG TERM /Tuesday through Saturday/

Issued 317 AM MDT SAT MAY 2 2026 The positively-tilted upper-level low/trough will continue moving east across the Great Basin on Tuesday. Moisture on the northern flank of the low will continue shower and thunderstorm chances for Tuesday, primarily over Southwest Idaho. Thunderstorms may produce brief heavy rain, small hail, and gusty winds. Widespread breezy to gusty N/NW winds are also expected Tuesday as the low passes. As the trough moves out, an upper-level ridge quickly builds into the Pacific NW, keeping conditions warm and dry Wednesday through Friday. Ensembles are hinting at a rex block pattern, with lower pressure aloft in southern California. If this were to materialize, warm and dry conditions could be seen for an extended time. Temperatures will reach 10-15 degrees above normal by Thursday, with lower valley highs in the low to mid 80s. By Friday into Saturday, some model guidance indicates a weak shortwave trough will provide ridge breakdown over the area. While this seems like more of an outlier than the predominant solution, it creates two scenarios. This uncertainty results in a 10-20% chance of showers and thunderstorms with temperatures remaining well-above normal.

AVIATION /18Z Saturday through Sunday/

Issued 1148 AM MDT SAT MAY 2 2026

VFR. High clouds will increase throughout the day, with patchy valley smoke in the West Central and Boise Mountains overnight. Low chance (20% chance) in afternoon virga showers with blowing dust and gusty outflow winds near KBNO. Surface winds: SE-E 5-15 kt, then variable less than 10 kt overnight. Winds aloft at 10k ft MSL: S-E 5-15 kt.

KBOI...VFR with increasing high clouds throughout the day. Surface winds: NW 4-8 kt this afternoon becoming SE 5-10 kt overnight.

Sunday Outlook...Generally VFR with isolated showers and thunderstorms tomorrow afternoon over SE OR and high terrain in SW ID. Gusty and erratic outflow winds with blowing dust are likely near showers and thunderstorms. Surface winds: NW-NE 5-15 kt.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.