152
FXUS65 KBOI 270249
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
849 PM MDT Fri Apr 26 2024

.DISCUSSION...This evening, a weak trough lingers over the area
while a low pressure system reorganizes over Utah. This setup
will result in isolated showers and thunderstorms across
southeast Oregon. As the low pressure system strengthens in
Utah, expect easterly flow aloft to persist, leading to
scattered showers across the West Central and Boise mountains of
Idaho, as well as the Western Magic Valley, until Saturday
afternoon. Furthermore, the strong surface pressure gradient
will prolong gusty northwesterly winds through Saturday.

From Saturday through Monday, anticipate springtime conditions
to persist, with a series of weak troughs and cold upper-level
low- pressure systems traversing the Northern Rockies. While
these systems aren`t expected to bring significant
precipitation, surface winds could pose concerns, particularly
on Monday and Tuesday. The EC EFI index indicates anomalously
higher wind forecasts for Monday compared to the past 5 weeks,
suggesting an above-average chance of stronger winds early next
week.

The current forecast adequately accounts for showers this
evening and windy conditions persisting until Tuesday, so no
updates are necessary at this time.

&&

.AVIATION...Generally VFR. Isolated showers diminishing in SE
Oregon tonight, but remaining over central/south-central Idaho
through much of Saturday. Snow levels 5500-7000 ft MSL.
Mountains obscured in showers. Surface winds: generally W to NW
10-20 kt. Gusts to 25-30 kt from KONO to KTWF/KJER tonight
through Saturday. Winds aloft at 10kft MSL: W to NW 10-25 kt.

KBOI...VFR with scattered to broken mid/high clouds. Shower
activity over surrounding foothills is not expected at terminal
tonight. Surface winds: NW 10-20 kt with gusts to 25-30 kt this
evening. Gusts dropping off overnight, then returning to 25-30
kt around Sat/16Z.

Sunday Outlook...Patchy mountain valley fog/low stratus in the
morning. Otherwise, mostly dry and VFR. Surface winds generally
SW to NW 5-15 kt, then variable 5-10 kt after sunset. Afternoon
gusts to 20-25 kt around KMUO/KTWF/KJER.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Sunday night...Scattered rain
showers have developed this afternoon in Baker and Malheur
Counties in Oregon and in the Owyhee Mountains in Idaho as
an upper trough comes in from the northwest. Showers will
develop over higher terrain in the rest of our CWA later
today and marginal instability will support isolated
thunderstorms (10-20 percent coverage) through sunset. Gusty
northwest winds will blow through the night and Saturday,
decreasing only slightly between midnight and dawn. The windiest
area will be the Snake Basin from Mountain Home eastward where
speeds 20 to 30 mph and gusts 35 to 40 mph will be found. Rain
and snow showers will continue in central and south- central
Idaho Saturday and Saturday night (snow level 6000 feet MSL),
ending Sunday as the upper trough moves into the central and
southern Rockies. Drying Sunday night under a weak upper ridge
ahead of the next deep trough approaching from the Gulf of
Alaska.

LONG TERM...Monday through Friday...The 12Z runs of the
deterministic models have come into much better agreement
through Thursday night. They depict an upper trough moving by
to our north Monday and a second one Tuesday into Tuesday night.
Together, these will keep a chance (generally 15-40%) of
showers, mainly in the north, through Tuesday night. Isolated
thunderstorms are also in the forecast in the north Mon/Tue
aft/eve. Temps will be around 5 degrees below normal. We`ll see
relatively dry northerly flow aloft Wed night into Thu, gently
backing to NW late Thu and continuing into Friday. This will
bring just a slight chance (10-20%) of showers to the northern
higher terrain. Temps in the NBM seemed to be influenced too
much by time-lagged members, and were adjusted cooler to be
more in line with newest GFS and EC MOS guidance.

&&

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

&&

$$

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