Damaging Wind in Idaho, September 18, 2023

Area Forecast Discussion
National Weather Service Pocatello ID
235 PM MDT Mon Sep 18 2023

.SHORT TERM...TODAY THROUGH TUESDAY NIGHT...
A series of shortwave troughs will bring modestly breezier
conditions and a chance of isolated to widely scattered
afternoon/evening showers and thunderstorms to southeast Idaho today
and Tuesday. Today, the HREF consensus continues to favor the
corridor from the Central Mntns NE into Clark/Fremont counties, and
the corridor from Cassia County ENE across the srn highlands, Bear
Lake, and the Caribou Highlands, for the best chance of
thunderstorms through about 8 PM. Overall CAPE and shear parameters
and not favorable for severe weather, but dry low-levels with DCAPE
over 1,000 J/kg and steep low-level lapse rates may support gusty
winds of 40 to 50 MPH with some cells (propagating outward and
weakening with outflows), so have added mention of such to the
forecast. Tuesday, the southern and eastern highlands will be
favored. 01

.LONG TERM...WEDNESDAY THROUGH NEXT MONDAY...
On Wednesday, our main low will begin deepening and setting up
shop across central/eastern Washington and Oregon. We will see
showers and thunderstorms developing during the day, with the
general trend for the afternoon putting the bulk of things across
the southern and eastern highlands, extending back into portions
of the Snake Plain and south end of the Magic Valley. We could see
some locally heavy rain with thunderstorms and gusty winds.
Thursday and Friday still look fairly wet and colder across our
area. Snow levels are still looking to drop to 8500-9500ft during
colder times of the day and perhaps a bit lower with any heavier
pockets of precipitation. Snow totals over the 72 hour period
ending Friday night, any snowfall will be light and really high
elevation. We are still seeing a low end potential for over 6" for
places like Mt Borah. Rainfall amounts still are hitting
0.30-0.60" for lower valleys and around 1" for most mountain
ranges. Our highest ranges (Bear River, Big Holes, Sawtooths, Lost
River, etc.) are still pushing close to 1.5" in places. We will
eventually dry out over the weekend, but any warm up looks to be
pretty slow. Keyes

&&

.AVIATION...
A series of shortwave troughs will bring modestly breezier
conditions and a chance of isolated to widely scattered
afternoon/evening showers and thunderstorms to southeast Idaho today
and Tuesday. VCTS has been expanded to all TAF sites this afternoon,
but confidence in a direct thunderstorm hit to any terminal is low
as the most favored corridors will reside south of KBYI and KPIH,
and north of KSUN, KIDA, and KDIJ. Thunderstorm outflows with wind
gusts over 40 MPH cannot be ruled out. Winds will veer from SSE to
SW at KSUN this afternoon for a crosswind at the runway. Some
shower/thunderstorm activity is expected again Tuesday
afternoon/evening favoring the srn/ern highlands, predominantly
south/east of the TAF sites except for possibly KDIJ. In general,
we're still looking ahead to Wednesday afternoon and beyond for a
better potential for aviation impacts over a several day period, as
a decent storm system arrives with widespread clouds, showers/rain,
and localized high-elevation snow. 01

&&

.FIRE WEATHER...
As expected, showers and isolated storms have formed over the
mountains. Most of this will remain over the mountains into this
evening, although there are some indications we could see some
outflow boundaries across the Snake Plain and Magic Valley...which
means we can't rule out a storm or 2 along those boundaries.
Gusts over 40 mph are possible along with a brief burst of rain. A
few light showers/sprinkles remain in the forecast overnight and
Tuesday morning for the south end of Zone 410, as well as most of
413, 425 and 427. Another low and trailing front will impact
central and eastern Idaho Tuesday. This will help kick off another
round of showers and storms in the afternoon, south of a Teton
Pass to Murphy Hot Springs line. Brief downpours and gusts over 40
mph are expected with stronger storms. It will be a more breezy
day, with gusts 15-30 mph common across our area, with a corridor
of gusts to 35 mph from around Sun Valley northeast across the
central mountains east of US- 93 and at mid/upper slopes. A
similar pocket of wind gusts is forecast for Craters and the INL.
It still looks like later Wednesday through Friday looks wet and
cooler, especially Thursday and Friday. Any type of accumulating
snow over that 72 hour period looks to be above 8500ft and light,
likely melting during warmer parts of the day. There is still a
low chance for over 6" in the central mountains for elevations
like Mt Borah. Rainfall amounts for lower valleys are still
pinging in the 0.30-0.60" range and up to 1" for many mountainous
locations. Our highest ranges (Bear River, Big Holes, Sawtooths,
Lost River, etc.) are still pushing close to 1.5" in places. Keyes

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.

&&

Preliminary Local Storm Report
National Weather Service Pocatello ID
239 PM MDT Mon Sep 18 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0220 PM     Tstm Wnd Gst     18 NNE Berenice         44.07N 112.84W
09/18/2023  M51 MPH          Clark              ID   Mesonet

            Mesonet station BLU - Blue Dome.

&&

KSmith

Preliminary Local Storm Report
National Weather Service Pocatello ID
247 PM MDT Mon Sep 18 2023

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0230 PM     Tstm Wnd Gst     13 WNW Monteview        44.03N 112.75W
09/18/2023  M51 MPH          Clark              ID   Mesonet

            Mesonet station PC374 - Reno Gulch.

&&

KSmith