116
FXUS65 KBOI 032023
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
223 PM MDT Fri May 3 2024

.SHORT TERM...Tonight through Sunday night...Dry, warmer, and
increasingly windy weather overnight and Saturday ahead of an
approaching north Pacific cold front. Southeast through southwest
winds will increase in southern CWA zones Saturday, reaching 30
mph with gusts to 45 mph, enough for a Wind Advisory in the
Upper Treasure Valley and western Magic Valley, and the southern
half of Harney County. These winds will help boost temps to near
70 degrees Saturday in the southern Idaho valleys, and 60s in
the rest of Idaho, but only 50s and 60s in Oregon as rain will
begin there around midday. A deep upper low in the north Pacific
will come inland along the OR/CA border late Saturday then due
east along the southern OR border Saturday night and southern
Idaho border Sunday. This is an ideal track for pcpn in our CWA.
The rain will be moderate to heavy late Saturday through
Saturday night as the cold front moves eastward across our CWA.
Totals will be .50 to 1.25 inch in the mountains, and .30 to
.60 inch in the valleys. Snow level will drop sharply behind the
cold front all the way to valley floors in Oregon, and 3500 to
4200 feet MSL in western Idaho Sunday morning. But by then most
of the pcpn will be ending so snow totals will only be a couple
inches, except above 7000 feet where a foot may fall. Behind
the cold front Sunday`s high temps will be some 20 degrees
lower than on Saturday, only in the 30s and 40s in the mountains
and 40s to lower 50s in the valleys. Sunday will also be windy
but not as windy as Saturday, and from the west or northwest.
Lighter rain and snow showers will continue Sunday night as
moisture wraps around the eastward-moving upper low. Thunderstorms
were taken out of the forecast, except for a 15 to 20 percent
chance in southern Twin Falls County Sunday afternoon.

.LONG TERM...Monday through Friday...Northwest flow aloft will
prevail as a deep low moves eastward out of the area. Embedded
in the flow, another trough will move into the area late Monday
and early Tuesday. As this trough moves into already moist and
cold air, it will extend the chances (50-70%) of precip through
the early parts of the long term. With snow levels still between
5000-6000 ft MSL, a chance for mtn valley mixed precip will
exist, while mtns continue to favor snow. At the same time,
Monday afternoon instability supports a slight chance of
thunderstorms in the W-Central Mtns of Idaho and the ID/NV
border. Precipitation chances will taper off between Tuesday
and Wednesday as the trough exits the area, but a slight chance
for showers will remain over central Idaho through Thursday
morning.

Models continue to agree on a period of calmer weather kicking off
on Thursday, as a ridge of high pressure builds north of our area.
The exact position of the high varies, but the forecast remains the
same: warmer, drier, calmer by the end of next week. Temps will
rise from 10-15 degrees below normal on Tuesday to near normal
on Thursday/Friday.

&&

.AVIATION...VFR with scattered mid and high level clouds through
early Sat morning. Sat/12z a north-south oriented band of moderate
precipitation begins to enter Harney county. Winds at 2000ft will
increase significantly as it approaches, and as sfc winds lag
behind a 6-10 hour LLWS threat exists at TAF sites NW of MUO and
in SE OR. Surface winds: Becoming SE 10-20 kt, winds increasing
Sat morning to SE 15-25 kt gusts to 25-35 kt. Winds aloft at
10kft MSL: S 15-25 kt.

KBOI...VFR through the period, clouds generally building. LLWS
threat exists Sat/06z through Sat/15z as surface winds struggle to
keep up with rapidly increasing 2000ft winds. The timing of the LLWS
threat may not be exact, but should cover the entire period of
concern. Winds becoming SE 10-15 kt Friday afternoon. Winds are set
to increase significantly early Sat morning to SE 15-25 kt with
gusts to 25-35 kt.

Weekend Outlook...A band of widespread precipitation will move
into SE Oregon mid-morning Saturday, then into SW Idaho Saturday
afternoon and will continue across the region through Sunday.
High confidence (<100%) for rain at all sites as the precip band
moves through. A 20% chance of thunderstorms Saturday afternoon
in s-central Idaho. Snow levels 6000-7000 ft MSL, lowering to
4000-5000 ft Sunday. Lowered snow levels on Sunday means a
switch to mixed precip in mtn valleys and snow in mtns. IFR and
widespread mountain obscuration Saturday night through Sunday.
Surface winds: SE 15-25 kt with gusts 30-40 kt Saturday
afternoon, W 5-15 kt with gusts to 20-30 kt Sunday.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory from 9 AM to 6 PM MDT Saturday IDZ014-016.
OR...Wind Advisory from 8 AM to 5 PM PDT Saturday ORZ061.

&&

$$

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SHORT TERM...LC
LONG TERM....JM
AVIATION.....JM