Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 221601
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1001 AM MDT Fri Mar 22 2024

.DISCUSSION...Partly cloudy today underneath a weakening upper
level ridge. This is response to an approaching upper level low
expected to bring precipitation on Saturday. However, ahead of
this system, warm and mostly dry conditions will continue.
High- res showing a few showers developing later this afternoon
over south-central Idaho. Have added low pops across the higher
terrain of south-central Idaho this afternoon to account for
this shift. Otherwise, the forecast remains on track with
precipitation on Saturday with the cold frontal passage. Update
will be out shortly.

&&

.AVIATION...Mainly VFR and dry with mid and upper level clouds.
Widespread rain/snow Saturday morning and obscured mountains as
a cold front moves in. VFR/MVFR in rain showers, and MVFR/IFR
in snow showers. Snow levels 6-7 kft MSL. After a brief pause in
precip around noon, afternoon/evening scattered showers
develop. Surface winds: S-SE 5-15 kt, with gusts 20-30 kt
developing this afternoon across SE OR. Winds aloft at 10kft
MSL: SW 15-25 kt.

Weekend Outlook...Showers will continue into Sunday, with snow
levels dropping to 4-5 kft MSL behind the front. Surface winds SW-NW
10-20 kt Saturday into Sunday. Winds generally strongest each
afternoon, with gusts to 30 kt in the higher elevations and across s-
central ID.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Sunday night...Today will be the
last warm and dry day likely through the end of March as a
major pattern change takes place this weekend. An upper level
ridge will pass overhead today as a deep Pacific trough
approaches the coast, with southwest flow aloft developing.
Temperatures will warm about 5 degrees from Thursday, reaching
the upper 60s in the Treasure Valley. Mid to high level clouds
will continue to stream into southeast Oregon and southwest
Idaho today with breezy southerly winds developing across south-
central Oregon.

A cold front will move inland tonight, reaching the Idaho border
early Saturday morning and the Magic Valley by late morning.
Rain and snow will develop along the front, with snow levels
falling from 6000-7000 feet MSL ahead of the front to 4500-5500
feet behind the front. Several inches of snow are expected in
the mountains above 6000 feet, while mountain valleys see a
rain/snow mix with little snow accumulation. Showers will
develop Saturday afternoon as cold air aloft associated with the
trough moves in. There will be a low (less than 15%) chance of
thunderstorms as well. Showers will decrease Saturday night with
the loss of daytime heating. The trough will slowly cross the
region on Sunday, with showers increasing Sunday afternoon
(especially over the mountains) as marginal instability
develops. Temperatures Saturday and Sunday will be 10-15 degrees
cooler than today, which will be near normal for late March.
West to northwest winds will be breezy both days, strongest on
Sunday where gusts of 25-40 mph will be common. The strongest
winds will be across the Magic Valley where there is about a
50% chance of peak wind gusts 50 mph or greater.

LONG TERM...Monday through Saturday...An unsettled wet and cool
pattern will remain in place through the long term period. Northerly
upper level flow will bring seasonable temperatures and intermittent
precipitation to the region on Monday through Tuesday. A weak ridge
will build in quickly late Tuesday, bringing a brief period of dry
conditions and slightly warmer temperatures. Snow levels look to be
around 3500-5000 feet through Wednesday, with most higher elevations
seeing snow through the middle of the week. The Snake River Valley
will likely have morning low temperatures in the mid 30s to low 40s,
so precipitation will fall as rain through the period. The best
chance (<5% chance) for snow in the Snake River Valley will be
Monday morning, with morning lows in the mid 30s at most. Very minor
accumulations of snow would shift quickly to rain by Monday
afternoon. Higher elevation snow accumulations will be around 6-10
inches from Monday to Thursday, with locally higher amounts over
ridgetops. Model agreement weakens by midweek, as deterministic and
ensemble solutions vary on the progression of a deep upper level cut
off low into the Pacific Northwest. Despite the difference in
timing, there is widespread agreement in extensive
precipitation across the region after Thursday. Models then vary
widely after Friday, with disagreement in location of cold air
and moisture.

&&

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

&&

$$

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DISCUSSION...JDS
AVIATION.....JM
SHORT TERM...ST
LONG TERM....SA


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