678
FXUS65 KBOI 220304
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
904 PM MDT Tue May 21 2024

.DISCUSSION...A shortwave trough ahead of a deep upper low will
move through tonight, bringing widespread rain and high
elevation (above 7000 feet MSL) snow to the area. Precipitation
amounts tonight of up to 0.25 inch are expected in the valleys
and up to 0.50 inch in the mountains. The trough will move east
Wednesday morning, but the upper low will be approaching with a
cold front set to move across our area. Instability will
develop as the low approaches, resulting in additional showers
and isolated to scattered thunderstorms continuing through
Wednesday. Additional precipitation amounts through Wednesday
will vary due to the showery nature of the precipitation, but a
general 0.10 to 0.50 inch of additional precipitation can be
anticipated. Winds will be gusty behind the front, strongest
across southeast Oregon and far southwest Idaho Wednesday
afternoon where gusts to 45 mph are possible. Showers will taper
off Wednesday evening as the low moves overhead, but any
remaining showers will turn to snow above 4500-5000 feet.
Forecast remains on track and no updates anticipated this
evening.

&&

.AVIATION...Rain will increase across SE Oregon this evening,
moving into SW Idaho after Wed/06Z resulting in low-VFR and
local MVFR conditions in valleys. Areas of IFR/LIFR in mountains
obscuring higher terrain. Showers continuing Wednesday with
isolated to scattered thunderstorms. Snow levels 6500-7500 ft
MSL through Wednesday morning, lowering to 4500-5500 ft by
Thur/00Z. Surface winds: SE-SW 5-15 kt tonight, becoming W-NW
15-25 kt on Wednesday with gusts to 35 kt along and behind a
cold front. Winds aloft at 10k ft MSL: W 20-35 kt.

KBOI...VFR this evening. Rain beginning Wed/09-11Z with periods
of MVFR ceilings and visibility. Steady rain becoming showers
by 13Z with isolated thunderstorms developing late morning into
early afternoon. Winds: SE this evening up to 10 kt, becoming NW
and breezy overnight. Gusts to 30 kt Wednesday afternoon.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Thursday night...A strong upper
level system will move towards and then through the area tonight
and Wednesday. This will bring plenty of precipitation along
with a cold front. There is also a chance of thunderstorms
behind the front beginning Wed morning and lasting through the
afternoon. The front will enter our Oregon zones early Wed
morning, move through the Boise area around noon, and make it
through the western Magic Valley around 6 PM MDT. Showers will
occur both ahead of and behind the front, from this evening
through tomorrow. Precipitation totals are expected to range
from 0.01 to 0.30 in lower elevations, up to 1 to 1.5 inches in
higher elevations. Snow levels will start out around 7000 ft
MSL, and fall to 4500-6000 by late Wed afternoon. With snow
showers lingering in the mountains into Thu night, total
snowfall above around 7000 ft MSL will range from 6-12 inches,
with the highest totals above 8000 ft. Temperatures Wednesday
will be 15-20 degrees below normal, and it will be breezy
(gusts 30-40 mph), especially over southeast Oregon and in/near
the Treasure and Magic Valleys. However, at this time, it does
not appear as if a wind advisory is warranted. Thursday will be
breezy in the western Magic Valley, with gusts to 25-35 mph, and
temperatures will be 10-15 degrees below normal. We will dry out
Thursday night as NW flow behind the departing system backs to
zonal.

LONG TERM...Friday through Tuesday...A weak short wave trough
will move through Friday, spreading clouds across the area, but
very little if any precipitation. A stronger system will move in
Saturday. Details on the exact path of this system are not clear
yet, but our best bet is the center will pass by to our north.
This would give us a good cold front along with showers mainly
in the higher elevations of the northern part of the CWA. Snow
levels are forecast to range from 6-7000 ft MSL. Upper level
ridging is expected to build into the area late Sunday night and
Monday, bringing dry and warmer conditions. Tuesday, we may get
a passing glance from another upper level trough, but
uncertainty is high. After climbing a few degrees above normal
Monday, temps might be 10 degrees above normal by Tuesday.

&&

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

&&

$$

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DISCUSSION...ST
AVIATION.....ST
SHORT TERM...SP
LONG TERM....SP