textproduct: Boise

DISCUSSION

Rain has finally tapered off across the Boise metro area this evening, with over an inch of rain recorded at the office today. This breaks the daily precipitation record of 0.76 inches, previously set in 2014. Precipitation will likely pick back up overnight over most locations, with a steady stream of moisture from the southwest. Snow levels around 5000-7000 feet MSL will keeping the precipitation type in most populated areas in a rain-snow mix. Higher elevation roadways will likely be snow covered with an additional 1-3 inches of accumulation anticipated tonight. Precipitation coverage will decrease tomorrow as cooler air moves in from the northwest, but showers will keep precipitation chances elevated especially over the Magic Valley and Central Mountains. More wet weather with above normal temperatures is anticipated through Wednesday, but a shift back to cooler seasonal conditions is expected by this weekend. Updated precipitation chances across the region to reflect the ongoing rain in eastern Oregon, otherwise no updates.

AVIATION

MVFR-LIFR conditions will continue into early Monday as a plume of moisture along a warm front remains aimed at the region. The heaviest precipitation will begin to move more to the east, with Oregon terminals seeing improvement first, and all but mountain area terminals seeing distinct improvement after 10-12Z. Snow levels around 5k-7kft MSL. Surface winds: SE-SW 5-15 kt. Winds aloft at 10kft MSL: W-SW 40-70kt.

KBOI...Low clouds and precipitation to continue through 10-12Z. LIFR ceilings are possible through that time, with visibility generally greater than 6SM. VFR is expected after 12-14Z through the afternoon. Surface winds SE around 5 kt through 18Z, SE 5-10 kt after that.

PREV DISCUSSION

SHORT TERM...Tonight through Tuesday night...Will let the current Wind Advisory in the Southwest ID Highlands continue until 5 PM MST as scheduled. The warm front has reached our nrn zones, about as far north as it will go. The front will stall tonight, then shift southward again Monday as upper winds become westerly or WNW-ly, but it will hardly qualify as a cold front. The atmospheric river (AR) from the Pacific subtropics into our CWA has broadened and is no longer the concentrated stream it was before. By late Monday the frontal zone should extend from sw Montana through our central CWA zones into nw Nevada. Lingering rain will tend to focus along the frontal zone, mainly in the Boise Mountains. Later Monday night the front will shift northward again as a warm front, and models again increase pcpn along the front. By Tuesday morning the front should extend from near Salmon through our northern CWA zones into central Harney County and sw OR, with the AR also becoming more concentrated. That means high PoPs again Tuesday in our central and northern zones, and warming and drying in south-central ID. Temps will rise again--getting well into the 50s in the Magic Valley.

LONG TERM...Wednesday through Sunday...A longwave trough off the Pacific Northwest coast will continue to steer moisture into the region, sustaining an active pattern throughout the extended period. Precipitation chances Wednesday through Friday are around 30-70%, lower in valleys and higher in mountains. Snow levels will start generally high at 6-7 kft MSL, gradually decreasing to 4-5 kft MSL by Saturday. This late-week period will see 3-8 inches of snow in mountains above 5 kft MSL, up to 10 inches above 7 kft MSL. Most valleys will get around 0.1" of rain, with mountains receiving 0.5-1" of rainfall/liquid equivalent. Peak temperatures are expected to remain 10-15 degrees above normal throughout the extended period, highest on Wednesday, so snow in mountain towns may be preceded by rain and then a wintry mix in the later hours. Due to the expected drop in snow levels into the 3000-4000 ft range, Thursday and Friday should see a considerably higher likelihood of snowfall over most mountain areas. For late Friday through Sunday there is considerable guidance uncertainty over whether the coastal upper low will bring mild, moist southwesterly flow, or cooler and drier northwesterly flow to our area. For now, the cooler and drier pattern is favored, with only a 10-25% chance of precipitation over the mountains Saturday.

BOI WATCHES/WARNINGS/ADVISORIES

ID...None. OR...None.