textproduct: Boise

KEY MESSAGES

- High temperatures 5 to 15 degrees above normal through Wednesday.

- Shower and thunderstorm chances return starting Tuesday afternoon, and increasing Wednesday through Friday.

- Cooler temperatures by the end of the week and into the weekend.

SHORT TERM /Through Wednesday Night/

An upper low off the Oregon coast will continue to track south over the next day. Our area will see southerly winds aloft continue for Tue/Wed. This keeps temperatures 10-15 degrees above normal, or low-mid 70s in the valleys and upper 60s in the mtns. The southerly flow will also draw up moisture, which will be reflected by 20 degree dew point temperature rises and precipitable water values pushing past the 90th percentile. This moisture will be fuel for shower and possible thunderstorm development starting late Tuesday afternoon, and continuing beyond Wednesday night. Daytime heating along with elevated instability will support afternoon/evening development over the w-central ID mtns and along the northern NV border late Tuesday. An embedded wave lifting through the area Tuesday night will extend a low chance of showers (and possibly a rumble of thunder) across much of the area. A low chance of showers and thunderstorms returns to the w-central Idaho mtns and areas along the NV border Wednesday afternoon/evening. Wednesday night will see precipitation chances increase from south to north as the closed low pushes onto the s-central CA coast and a secondary wave approaches the Pac NW.

LONG TERM /Thursday through Monday/

Widespread showers will be the story Thursday into Friday, as the low lifts northeast over our area from California. While cloud cover will help limit daytime instability, cooling aloft will allow for weak instability to develop, resulting in a slight chance of embedded thunderstorms. Any thunderstorms will result in localized heavier rainfall rates/totals underneath the core. At least for Thursday, southerly flow aloft will keep snow levels on the higher side (9-10kft MSL), giving rain its opportunity to shine as the dominate precipitation type. Over the course of Thursday through Friday, guidance continues to trend upwards on total accumulations, with lower elevations ranging from 0.15-0.50 inches (lowest in eastern Oregon), mountain valleys ranging from 0.50-0.80 inches, and highest elevations up to 1.25 inches; with the bulk of the precipitation falling late Thursday into early Friday. While this will be more stratiform and long duration in nature, steep terrain/burn scars may experience increased runoff and land movement.

A cold front on Friday will bring a rather sharp end to the precip and a cooldown as it moves across our area from west to east. Temperatures comes Friday will drop around 5 degrees below normal. Another, probably more notable, consequence of the cold front will be the gusty west-northwest winds that will accompany it. Friday afternoon, winds across ridge tops and open terrain will gust to 20- 35 mph. The strongest winds, however, will blow in the Snake River Plain east of Mountain Home where gusts will reach 35-45 mph. Lowering snow levels on Friday behind the front will allow for a transition to snow/wintry mix for elevations above 6.5 kft MSL. Although this switch will be at the tail end of the precipitation, so only a dusting of snow is expected along high elevation passes such as Banner Summit.

Pattern uncertainty increases behind this system, however Saturday at the very least should be dry with temperatures warming to near normal again. While ensemble consensus is another trough digging down to the west coast come Sunday, there is considerable uncertainty in how this low interacts with the departing on and when/if it get brought inland over our area.

AVIATION /18Z Monday through Tuesday/

Issued 1017 AM MDT MON OCT 19 2026

VFR under high clouds. Locally reduced visibility due to smoke from prescribed fires. Surface winds: S-E 5-15 kt, with localized gusts to around 20 kt this afternoon in SE Oregon. Generally becoming light and variable overnight. Winds aloft at 10kft MSL: S-SW 10-25 kt.

KBOI...VFR. Surface winds: SE 6-12 kt with afternoon gusts 15-20 kt, becoming light and variable overnight.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None.

OR...None.