172
FXUS65 KBOI 290242
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
842 PM MDT Tue May 28 2024

.DISCUSSION...Several sub-severe thunderstorms moved through the
region this afternoon, with several reports of around 50 mph
winds, very heavy rain, and several thousand without power in
the Boise metro area and near Garden Valley, ID. Storms are
still active across the Treasure Valley, with a particularly
strong storm about to move into Ontario, OR as of 8:30 pm MDT.
Temperatures plummeted in the Lower Treasure Valley from near
90F to mid 60F as the afternoon storms passed. Isolated
thunderstorms and showers will continue through midnight for
most of the region, except into the early morning for the West
Central Mountains and Weiser River Basin. The cold front is
still just west of Boise, but it appears to have passed
Caldwell-Nampa due to the breezy northwesterly winds. This cold
front will cool temperatures sufficiently tonight into tomorrow,
with much cooler high temperatures, breezy westerly winds, and
a low chance(<10%) of high terrain showers expected tomorrow. No
forecast updates necessary.


&&

.AVIATION...Scattered showers and thunderstorms continue
areawide through 29/06Z, and will be capable of heavy rain, small
hail, and gusty outflow winds up to 40 kt. Conditions will be mainly
VFR, with brief reductions to MVFR/IFR in thunderstorms and heavier
rain showers. A cold frontal passage tonight will support showers
mainly in/near the West Central Mtns after 29/06Z. Post-frontal
winds will remain gusty through Wednesday. Surface winds: NW 10-20
kt with gusts to 30 kt, except E to NE 5-15 kt east of KMUO until
the front moves through (roughly 29/07Z for KJER/KTWF). 10k ft MSL
winds: SW 15-25 kt, becoming W 15-25 kt by 29/15Z.

KBOI...A 40% chance of showers and a 20% chance of thunderstorms
through 29/05Z. Winds NW 12-20 kt with gusts to 25-30 kt, decreasing
slightly 10Z-10Z.
&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Thursday night...Active weather
ramping up this afternoon and evening as a cold front approaches
the area. Warm southwest flow remains over the area, with
temperatures near 90F at Mountain Home this afternoon. Isolated
showers and thunderstorms have formed across southwest ID this
afternoon, keeping temperatures slightly cooler for portions of
southwest ID, but partial clearing this afternoon should help
temperatures rebound, and enhance instability for showers and
storms. Showers and storms will increase in coverage late this
afternoon into the evening hours. Morning sounding at BOI had a
nice inverted V sounding, with DCAPE of 1100 J/kg. DCAPE values
of 1200-1500 J/kg this afternoon will promote environment
capable of producing gusty winds up to 60 mph with any showers
or storms that form, along with areas of blowing dust. Forecast
storm motion is also 10-20kts, so heavy rain with ponding of
water possible, especially in the west central ID mountains.
Cold front moves through this evening bringing northwest winds
behind the front. Showers linger over the central ID mountains
into Wednesday morning, with temperatures cooling around 15-20
degrees compared to today. Breezy northwest winds continue
Wednesday and Thursday, especially during the afternoon.

LONG TERM...Friday through Tuesday...Models continue to be in
relatively good agreement on the large-scale pattern through
Tuesday. The most notable differences can be found in the
progression of two troughs embedded in an otherwise zonal
westerly flow. The first trough passes through on Saturday, but
only amplifies after a majority of the moisture has already
moved east. Our area will see mostly cloudy skies and a 10-20%
chance of showers over the West Central Mountains Saturday
afternoon. The second trough passes on Monday/Tuesday and has a
decent gradient and moisture flow, but mostly to the north of
our area. This will allow a slightly higher 20-30% chance of
precipitation, but only over our northern zones including Baker
and Valley counties. The EFI isn`t flagging any majorly
anomalous weather over the long term, which reflects the overall
pattern well. Temps will be about normal on Friday and
Sunday/Monday after the first trough, but 5 degrees above normal
otherwise. Clusters after the long term period are confident
that a strong high will build, bringing very warm temperatures.

&&

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

&&

$$

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DISCUSSION...SA
AVIATION.....SP
SHORT TERM...KA
LONG TERM....JM