Sunrise 6:40 AM   Sunset 8:44 PM Moonrise 12:00 AM   Moonset 7:32 AM

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FXUS65 KBOI 270927 AFDBOI

Area Forecast Discussion National Weather Service Boise ID 327 AM MDT Sat Apr 27 2024

SHORT TERM
Today through Monday night...An area of showers associated with a mid-level circulation/deformation zone in eastern Idaho is near the eastern fringe of our forecast area early this morning. The western edge of the showers is near Jerome and Gooding and is expected to slowly shift eastward, exiting east of the area by mid-morning. A weak upper trough to our west is expected to reach SW Idaho this afternoon. Scattered to numerous showers develop with the trough in central Idaho while remaining dry across SE Oregon and the remainder of SW Idaho. A weak surface low in central Idaho will enhance the pressure gradient for windy conditions in southern Idaho from Mountain Home to Twin Falls. There is a 20-60 percent chance of showers in the West Central Mountains (mainly east of McCall)
tonight as another weak upper trough moves through northern Idaho. West-southwest flow aloft will bring drier conditions on Sunday, although it will be breezy across most SE Oregon and SW Idaho. Little change in temperatures are expected over the weekend, averaging within a couple degrees of normal.

A strong and fast-moving cold front is anticipated to move through on Monday. Windy conditions develop by the afternoon, and it could be very windy across s-central Idaho - including the Camas Prairie, Upper Treasure Valley, and Western Magic Valley where a Wind Advisory may eventually be warranted. An upper trough lags behind the front, bringing a chance of showers to mainly the higher elevations. Snow levels fall to around 4000-5000 feet and there may be snowfall accumulations in the higher elevations of Baker County and central Idaho.
Preliminary totals of 1 to 3 inches are possible, with locally higher amounts north of McCall. Much cooler temperatures (5-10 degrees lower) arrive with the cold front. The winds and showers diminish Monday night.

LONG TERM
Tuesday through Saturday...An upper level low will deepen over the Pacific Northwest on Tuesday, bringing slightly below normal temperatures to the region and a slight chance of precipitation to the region. For Tuesday into Wednesday, there's a low chance of precipitation in the valleys (10-20% chance)
with much higher confidence in precipitation over higher terrain in Baker County-West Central Mountains (50-60% chance). Snow levels will drop to 3500-4500 feet across the area by Tuesday evening-Wednesday morning, so some precipitation over the mountains will briefly fall as snow. Minor accumulations are anticipated, with areas below about 7000 feet seeing less than an inch. The surface and upper level pressure gradient will tighten as the low digs into the region, bringing gusty westerly winds to the region on Tuesday and Wednesday, especially in the Snake River Valley. The low will then move to the east by late Wednesday, as northwest upper level flow returns for Thursday and a ridge looks to build in over the region on Friday. This northwest flow will bring dry conditions and slightly warmer temperatures as a warmer and drier air mass looks to creep in from the southwest.

Model agreement remains high through Thursday, but differences exist in the storm track by early Friday. Some deterministic and cluster solutions show a shortwave trough moving through the region by the end of the week, while others show a ridge building in. This brings a wide spread to the potential temperatures and precipitation for the region on Friday and Saturday. The NBM favors higher temperatures than most of the individual forecast models on the Wednesday-Friday period, so have lowered these temperatures in the extended slightly to reflect the higher probability for lower temperatures.

AVIATION
Generally VFR with localized MVFR/IFR this morning near KBKE-KBNO. Some patchy valley fog and low clouds in southeast Oregon this morning as high clouds clear to the east.
Isolated rain/snow showers over the Camas Prairie/Magic Valley this morning, diminishing after Sat/16Z. Snow levels 6000-7500 ft MSL. Mountains obscured during showers. Surface winds: variable less than 10 kt, except W to NW 10-20 kt with gusts to 20-30 kt in the Snake River Valley. Winds increasing to W 10-20 kt with gusts 20-30 kt everywhere by Sat/20Z. Winds aloft at 10kft MSL: N to NW 10-20 kt.

KBOI...VFR with scattered mid-high clouds and a few low stratus clouds in the morning near the foothills. Surface winds: NW 10-20 kt with gusts to 25-30 kt this evening. Gusts dropping off overnight, then returning to 25-30 kt around Sat/16Z.

Sunday Outlook...Mostly dry and VFR. Surface winds generally SW to NW 5-15 kt, then variable 5-10 kt after sunset. Afternoon gusts to 20-25 kt around KMUO/KTWF/KJER.

BOI WATCHES/WARNINGS/ADVISORIES
ID...None.
OR...None.

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