171
FXUS65 KBOI 181540
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
940 AM MDT Sat May 18 2024

.DISCUSSION...Relatively stable conditions prevail across the
region this morning, with high cirrus clouds over Baker County,
OR and the West Central Mountains. Temperatures will be slightly
above normal today, with the frontal passage still anticipated
later tonight (11 pm MDT-3 am MDT). Winds will pick up this
evening, especially along the Snake River Valley with brief
gusts to 30-35 mph, with ridgetops seeing gusts to 45 mph. This
front will cool temperatures for tomorrow by about ten degrees,
beginning the slight cooling trend next week. Light
precipitation across the West Central Mountains still looks
possible (30% chance), although hi-res model guidance now
suggests it will stay mostly to the north of the county warning
area. No forecast updates necessary.

&&

.AVIATION...VFR with some high clouds over the region. Surface
winds: light and variable this morning, becoming SW to NW 5-15
kt with afternoon gusts to 20-30 kt. Then, NW gusts up to 30- 40
kt spreading through the Snake Plain from KBKE/KONO to
KMUO/KTWF this evening/overnight with cold front. Winds aloft at
10k ft MSL: W 20-35 kt.

KBOI...VFR. Increasing high clouds. Winds light and variable,
becoming NW 5-10 kt around Sat/21Z. Increasing to 10-15 kt with
gusts 20-30 kt around Sun/05Z, due to cold front.

Sunday Outlook...VFR. Increasing clouds for northeast OR and w-
central ID mountains Sunday, and 20-50% of showers. Snow levels 4500-
5500 ft MSL. Surface winds: W to NW 10-20 kt on Sunday. Local gusts
to 25-30 kt in the Snake Plain.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Monday night...An upper-level
trough situated just north of the forecast area today will
continue to bring breezy conditions and below-normal
temperatures. Winds are expected to lighten this afternoon,
with valley temperatures reaching the low to mid-70s.

This evening, an approaching shortwave and its associated cold
front will move across southeast Oregon and into southwest Idaho
by early Sunday morning. The front will bring brief gusty
winds, with gusts up to 45 MPH. The strongest winds are
anticipated between Baker City and Ontario from 6 PM MDT to
midnight, and from Ontario to Mountain Home from midnight to 5
AM MDT. Breezy conditions will persist from Mountain Home
through the Western Magic Valley from about 3 AM MDT until
sunset on Sunday. While the latest guidance indicates increased
wind speeds, they remain below advisory levels. Temperatures
will drop to approximately 10 degrees below normal for this time
of year. Additionally, there is a 30% chance of showers in the
West Central and Boise Mountains of Idaho, with light snow
possible above 6000 feet.

The shortwave and cold front will exit the region by Sunday
night. However, the upper-level trough will remain, expanding
southward across the entire forecast area by Monday. This shift
will increase instability and moisture, supporting a 30% chance
of convective showers in the afternoon and evening over the
higher terrain. Though overall instability and dynamics are
relatively weak, its still sufficient to support a 15% chance
for thunderstorms. Breezy northwest winds will persist,
maintaining below-normal temperatures across the area.

LONG TERM...Tuesday through Saturday...Dry conditions with
slightly warmer temperatures are expected with a brief, weak
ridge Tuesday. Winds will become breezy Tuesday night into
Wednesday as the next trough arrives over the Pacific Northwest.
Shower chances will increase over east Oregon and southwest
Idaho Wednesday, with the best chance (60-80%) of precipitation
occurring over the central Idaho terrain. In addition,
instability will increase Wednesday afternoon and promote a
slight chance (15%) of thunderstorms across the area.
Temperatures are anticipated to drop several degrees below
normal with the trough, with snow levels lowering to
approximately 5500-6500 ft MSL by late Wednesday. As a result,
snow accumulations are possible at high elevations through early
Thursday. Models begin to vary significantly on the path and
evolution of this trough, and subsequent troughs, for the
remainder of the week. However, the overall pattern will support
unsettled and cooler than normal conditions.

&&

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

&&

$$

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DISCUSSION...SA
AVIATION.....SA
SHORT TERM...JDS
LONG TERM....SH