textproduct: Boise

DISCUSSION

Cool and unstable conditions persist today as a broad upper level trough remains the dominant feature over the Pacific Northwest. A weak shortwave passage later today moving along the Oregon Coast into California will facilitate scattered snow showers across southeast Oregon and along the Idaho/Nevada border. Overall, up to 2 inches of snow is possible especially across the higher terrain. In the lower elevations, including the Treasure Valley and Snake River Plain, mostly dry conditions are expected.

The upper level trough continues inland early Friday bringing the last round for showers to the region. Light snow showers will be possible Friday morning across the entire area including the Snake River Plain. Accumulations though will be minimal with less than 0.2 inches expected. This shift will allow heights to begin rising over our area by Friday afternoon, signaling the start of a brief drying trend for the start of the weekend.

AVIATION

Generally VFR through the day as LIFR mountain fog dissipates this afternoon. Scattered mtn snow showers will bring brief IFR/mtn obscuration in the afternoon. Surface winds: SE-NE 5- 15 kt. Winds aloft at 10kft MSL: S 5-15 kt.

KBOI...VFR under mid-high clouds. Although, a 10% chance of light snow Friday morning and accompanying IFR conditions. Light SE surface winds through the day.

Weekend Outlook...Generally VFR conditions. Local IFR fog in mtn valleys Saturday and Sunday mornings. Surface winds Saturday and Sunday SE 5-15 kt with gusts up to 20 kt, except in highlands and the Snake Plain where gusts up to 30 kt are possible.

PREV DISCUSSION

SHORT TERM...Today through Saturday night...The area remains under a broad cool trough digging out east today through Friday. Temperatures will remain on the colder side this morning and climbing into the lower 40s for valleys today and tomorrow. High surface moisture will favor the development of mountain valley fog this morning through the early afternoon.

A weak shortwave trough will dig into the Great Basin from the OR coast later today, bringing another round of convective snow showers mainly over southeast OR and the central ID mountains. The system will shift further east Friday, bringing a more defined band of snow showers Friday early morning through afternoon. Minimal accumulations of 1 to 2 inches are expected for the West-Central ID mountains by late Friday. A period of light snow is possible for the lower valleys Friday morning.

By Friday night, most areas will start seeing a drying trend as an amplified ridge begins building into the region over the weekend. A warming trend is expected to begin Saturday, with valley daytime temperatures expected to climb into the upper 40s. Clearing skies will pave way for cold overnight lows in the teens and 20s Friday through Saturday. Strong troughing from a potent upper low digging into the Pacific Northwest coast will bring gusty southeast winds for most areas Saturday afternoon, with the highest concentrated near Baker County OR and the Mountain Home area of ID.

LONG TERM...Sunday through Thursday...A deep trough off the West Coast will keep our region under a mild SW flow on Sunday and Monday. Temperatures will peak around 10 degrees above normal on Monday which will put lower elevations in the upper 50s. Precipitation chances increase across SE Oregon and the mtns of SW Idaho on Monday as the trough draws deeper moisture northward. Monday night/Tue will be the period of heaviest rain/snow rates as mtn top level flow reaches 30-50 mph and precipitable water values push past the 90th percentile. During this period, snow levels will reside around 5kft MSL across e-central Oregon and w-central Idaho, to between 6-7kft MSL along the NV border. This will keep the potential for heavy snow in the higher terrain of the w-central and Boise mtns in Idaho (mainly east of Idaho City/Garden Valley and Hwy 55 corridor). Valleys will see precipitation chances push above 60% as the ridge flattens out in response to the approaching trough. Some uncertainty in for Wed/Thur, but the 00Z deterministic solutions have trended drier behind the exiting trough. The NBM/forecast is holding onto broad precipitation chances, but would expect it to catch up with this trend if the 12Z solutions remain dry. After Monday's highs, temperatures for Tue-Thur will hold near normal.

BOI WATCHES/WARNINGS/ADVISORIES

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