287
FXUS65 KBOI 050248
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
848 PM MDT Sat May 4 2024

.DISCUSSION...Heavy rain bands are expected to persist across
the forecast area into Sunday morning as a cold front moves
through. While surface winds have generally calmed, gusts of up
to 45 MPH have been observed with the stronger showers this
evening.

The cold front is currently advancing eastward across Baker and
Malheur Counties, with radar showing heavy rain bands along the
Idaho/Oregon Border and more precipitation moving north from
northern Nevada. Precipitation observations align closely with
forecasts, with sites like Rome, Oregon reporting 0.11 of rain
in one hour. Valley locations are anticipated to receive up to
0.75 of rain, while higher terrain could see up to 1.00
through Sunday. The cold front will continue its northeastward
movement late tonight, with the low center shifting into
northwestern Nevada and then progressing east along the Nevada
border towards northwest Utah by late Sunday night. This
trajectory will sustain periods of precipitation throughout
Sunday. While snow levels are initially high, they are expected
to lower to around 4000 feet across southeast Oregon late Sunday
morning. There is a 70% chance of light wet snow accumulation
(up to 0.5) Sunday morning across Harney and southern Malheur
County. Snow levels are forecasted to remain above 6000 feet
across Southwest Idaho, resulting in 2-4 of snow on mountain
peaks.

Overall, guidance remains consistent, and minor adjustments to
precipitation totals have been made to reflect ongoing trends.
An update will be released shortly to provide the latest
information.

&&

.AVIATION...Precipitation becoming increasingly widespread
tonight. Mainly VFR with mid-level ceilings and light rain, but
becoming MVFR for a few hours at each site as a heavier precip
band moves west to east. Snow levels 7-9kft MSL, lowering to
4-6kft behind the precip band Sunday morning. Local IFR in
mountain snow as snow levels drop. Mountains obscured.
Precipitation becomes scattered after Sunday morning. Surface
winds: Variable 5-10 kt becoming W-NW 10-20 kt tonight. Winds
aloft at 10kft MSL: Generally SW 10-30 kt, but with significant
direction and speed variability through Sunday evening.

KBOI...Mainly VFR and light rain with mid-level overcast skies.
Tonight a few hours of MVFR are possible as the heaviest part
of the rain band moves through. The heavier band is through by
~Sun/09z, with rain becoming scattered through the rest of
Sunday. Winds are generally 5-15 kt out of the W-NW, but Sunday
morning a brief period of variable winds exists.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Monday night...Major north Pacific
storm now inland in OR and CA, preceded in our CWA by gusty
southeast to southerly winds. Current Wind Advisory in the
Upper Treasure Valley, Western Magic Valley, and Harney County
is set to expire at 3 PM MDT /2 PM PDT/.  Latest MOS guidance
supports that expiration time with winds forecast to diminish.
The Pacific storm`s cold front will then move into our CWA with
moderate to heavy rain late today through tonight, with the
front reaching central Idaho early Sunday morning. Latest
forecast rain amounts through Sunday remain consistent with
previous forecast: .15 to .50 inch in the Oregon valleys, .50
to 1.00 inch in the Oregon mountains, .40 to 1.00 inch in the
Idaho valleys, and .80 to 1.75 inch in the Idaho mountains.
Pcpn should decrease to lighter rain and mountain snow showers
Sunday and Sunday night, then increase again Monday night as a
weaker Pacific trough comes inland. The extra pcpn will add
another .15 to 25 inch to the amounts stated above. Latest
models now show little chance (less than 10%) of thunderstorms
through Monday morning, but a 20 percent chance Monday afternoon
and evening throughout our CWA. High temperatures Sunday will
only be in the 40s to lower 50s. For Idaho that means about a 20
degree drop from today. Monday will be also be cold with the
main upper trough still nearby (but east of our CWA).

LONG TERM...Tuesday through Saturday...After Monday`s system,
we will be left with moist NW flow aloft and steadily decreasing
chances of showers going from Tuesday through Tuesday night.
The big story Tuesday will be strong winds, with gusts 30-50
mph possible. The strongest gusts are expected to develop from
around Mountain Home south and east into the western Magic
Valley. Wednesday, the only chance of precipitation worth
mentioning (15-30%) will be in eastern Valley County as
relatively dry northerly flow aloft builds in. Winds will
still be breezy, but much weaker than Tuesday. Ridging aloft
to our north, combined with a low to our south, will result in
(relatively rare) easterly flow Thursday and Friday. Models
begin to differ significantly late Friday and Saturday, but
odds are we will be dry with temperatures near or a little
above normal.

&&

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

&&

$$

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DISCUSSION...JDS
AVIATION.....JM
SHORT TERM...LC
LONG TERM....SP