139
FXUS65 KBOI 051509
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
909 AM MDT Sun May 5 2024

.DISCUSSION...At 9 AM MDT upper low clearly seen in eastern
OR on water vapor satellite imagery, with moisture streaming
northward from eastern NV into south-central Idaho, then into
Baker County and Harney County, and relatively dry air near the
OR/ID border. The upper low is moving slowly eastward and the
wrap-around moisture will bring showers back across all CWA
zones tonight, with snow level 3500 to 4200 feet MSL. The Magic
Valley may see wet snow early Monday morning. Then drying from
the west Monday as the low continues eastward, but westerly
winds will increase, especially in the central Snake Basin. We
are considering issuing a Wind Advisory for Monday afternoon.
After that, models show another Pacific trough and more showers
Monday night, drying Tuesday. Temps will stay cold through
Wednesday, then warm the rest of the week as a Pacific upper
ridge moves to the WA/BC coast. Current forecast covers things
well. No updates.

&&

.AVIATION...Numerous rain and snow showers creating MVFR/IFR and
local LIFR. Mountain obscuration. Snow levels 3500-4500ft, lowest
over central OR, except 5000-6000ft MSL over central ID mountains.
Surface winds: NW-SW 10-20 kt. Winds aloft at 10kft MSL: variable
10-20 kt becoming W-NW 20-30 kt by 00z/Mon.

KBOI...VFR thru 16z/Sun then periods of MVFR to IFR in rain
showers. A break in shower activity expected 11z-18z/Mon, with
a return to VFR. Surface winds: SE 5-10 kt, becoming W-NW 5-15
kt after 16z/Sun. Then W-NW 10-20 kt with gusts to 25-30 kt
between 06z-12z/Mon.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Tuesday night...Precipitation will
wrap around a closed low as it tracks through northern NV today.
This will put the focus of heavier precipitation across the
w-central mtns early this morning and over SE Oregon through the
day and into this evening. Cold air on the back side of the low
is quickly dropping snow levels across SE Oregon and the Owyhee
mtns this morning, setting up potential for accumulating snow
down to 4kft MSL. Expect 3 to 8 inches above 5000 feet and over
a foot possible across Steens Mtn. In SW Idaho snow levels will
remain between 4500 feet along the ID/NV border to 5500 feet
over the w-central mtns through this evening. The precipitation
on the back side of the low will shift eastward tonight as the
low crosses the Rockies. This will bring a break to the rain/snow
across SE Oregon while increasing precipitation coverage and
lowering snow levels across SW Idaho zones. By Monday morning
snow levels of 3500-4500 feet could bring a mix of rain/snow or
brief changeover to snow in the Snake Plain east of Boise. Low
temperatures will remain above freezing so valley sites below
4500 feet will stay wet. Mountains will pick up additional
snowfall overnight and see a further boost as a trailing upper
wave brings another round of valley rain and mtn snow Monday
into Tuesday. Westerly flow aloft will bring breezy winds each
afternoon through Tuesday. The western Magic Valley will see the
strongest winds and could be in line for a Wind Advisory on
Tuesday. Temperatures are 10-15 degrees below normal through
Tuesday.

LONG TERM...Wednesday through Sunday...An upper level trough
will remain over the western US through Thursday, keeping
temperatures cooler than normal. Temperatures will be around
10 degrees below normal on Wednesday before warming to near
normal by Thursday. An upper level ridge is forecast to build
over the Pacific NW and southwest Canada on Friday into the
weekend. Record breaking high temperatures are possible over
portions of the Pacific NW, but the center of the ridge will
be north and west of our area, where the warmer temperatures
are. Temperatures rising to around 5-10 degrees above normal
for Saturday and Sunday. A weak trough lingers over the Great
Basin Saturday and Sunday, with a threat of afternoon
thunderstorms and slightly cooler temperatures. Forecast
confidence is low on the strength of the trough and the
placement.

&&

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

&&

$$

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DISCUSSION...LC
AVIATION.....SH
SHORT TERM...DG
LONG TERM....KA