Hail and Damaging Winds in Idaho, August 13, 2024

Area Forecast Discussion
National Weather Service Pocatello ID
338 AM MDT Tue Aug 13 2024

.SHORT TERM...Today through Wednesday Night.
Early morning satellite imagery shows a cold front currently
situated in NRN Nevada and ERN Oregon with this frontal boundary
expected to work over SRN Idaho today. This will support isolated
to scattered showers and thunderstorms throughout the day before
dry conditions return overnight tonight with a focus later today
on the potential for strong to severe thunderstorms to develop.
The Storm Prediction Center has highlighted all of ERN Idaho in a
MARGINAL RISK (5-14% chance) for severe thunderstorms with
stronger storms today capable of producing wind gusts to 40-60
mph, large hail, heavy rain, and frequent lightning. The Weather
Prediction Center has also outlined ERN Idaho in a MARGINAL RISK
(5-14% chance) of excessive rainfall leading to flash flooding
given the higher PWATs and rainfall amounts/rates expected.

This will all be possible courtesy of today's convective
environment with the HREF ensemble showing 600-1200 J/kg of
SBCAPE, 25-35 kts of 0-6 km shear, 7-9 degree/km 700-500 mb lapse
rates, and PWATs around 0.80-1.2" across ERN Idaho. The HRRR model
maximum hail size today shows stronger supercells being capable
of producing hail up to 1-1.5" in diameter. Given the focus
further east today, the highest precipitation amounts today will
be focused across ERN Idaho where the NBM 50th percentile shows
around 0.10-0.50" of rain with less than 0.10" elsewhere. Taking
into account a high-end scenario, the 90th percentile shows totals
across ERN Idaho in that 0.50-1.00" range with up to around
0.10-0.50" elsewhere. Highs today will be seasonably cool courtesy
of increasing cloud cover and zonal flow aloft with highs in the
low 70s to mid 80s. Winds will remain breezy given the cold front
with gusts outside of thunderstorms peaking around 20-40 mph. This
front will also help to introduce increased wildfire smoke from
the CNTRL Mountains to the rest of our CWA later today with the
HRRR smoke showing the highest concentrations up around Custer and
Lemhi Counties. Have gone ahead with adding the mention of smoke
to the CNTRL Mountains through the day, further expanding it this
evening.

For Wednesday, look for another round of isolated to scattered
showers and thunderstorms throughout the day with activity
increasing after sunrise and continuing through sunset. Rainfall
totals look to be on the lighter side in comparison to Tuesday
aided by 0.50-0.80" PWATs filling back in on the back side of the
cold front. The NBM 50th percentile shows around T-0.10/0.20" with
higher totals again focused across ERN Idaho with the 90th
percentile showing amounts in that 0.50-0.75" range again across
ERN Idaho. Dry conditions will return after sunset with our next
system remaining on track to arrive Thursday, keeping our active
weather pattern going. Highs on Wednesday will be very similar to
Tuesday in the low 70s to mid 80s with overnight lows both tonight
and Wednesday night in the 40s/50s outside of some 30s for our
colder mountain basins. MacKay

.LONG TERM...Thursday through next Tuesday.
The ECMWF and NBM models bring a trough through the area on
Thursday with the GFS model bringing the trough through on late
Thursday into Friday and farther north, not impacting our area as
much. Have high precipitation chances in our forecast currently,
going with the NBM and ECMWF models. Friday and Saturday models
show drier southerly to southwesterly flow into our area with a
larger upper level low off the Pacific coast. Sunday into early
next week models still show the upper level low still off the
Pacific coast with southerly to southwesterly flow into our area.
However, models are showing moisture moving into our area Sunday,
Monday, and Tuesday bringing back isolated, mostly afternoon,
showers and thunderstorms.

Expect isolated to scattered showers and thunderstorms Thursday
afternoon across the area. Models still show isolated showers and
thunderstorms Friday afternoon, mainly over the Montana Divide and
the northern Eastern Highlands across the Wyoming border.
Saturday currently looks dry across the area. Sunday, Monday, and
Tuesday afternoons models bring back isolated, mainly afternoon,
mountain showers and thunderstorms. For Sunday models have backed
off on thunderstorm coverage, but still show isolated
thunderstorms over the mountains across the Eastern Highlands near
the Wyoming border.

Temperatures look to be around normal, mid to upper 70s for
mountains and mid to upper 80s for lower elevations. Saturday
looks to be the warmest day, with some temperatures in lower
elevations likely hitting 90 degrees. Wyatt

&&

.AVIATION...For the 12Z TAFS through 12Z Wednesday.
A cold front will through this afternoon. Expect vicinity showers
for all TAF sites this morning transitioning to vicinity
thunderstorms for all TAF sites this afternoon into early evening.
KPIH and KDIJ have the best chances of thunderstorms on station.
Have Tempo groups for thunderstorms for KPIH and KDIJ. Expect
gusts of 30 to 40 mph for outflows for mainly KBYI, KPIH, KIDA and
KDIJ. Gusts up to 50 mph are possible, especially for KPIH and
KDIJ. Hail on station is possible too, especially for KPIH and
KDIJ. Wyatt

&&

.FIRE WEATHER...
A cold front passing over SRN Idaho today will support isolated
to scattered showers and thunderstorms regionwide throughout the
day with a RED FLAG WARNING in effect from 1000 to 2100 MDT for
FWZ 410, 411, 413, 475, and 476 where coverage of thunderstorms
remains highest. Stronger storms today (primarily across ERN
Idaho) will be capable of producing wind gusts to 40-60 mph, large
hail, heavy rain, and frequent lightning. Given the focus further
east today, the highest precipitation amounts today will be
focused across ERN Idaho where the NBM 50th percentile shows
around 0.10-0.50" of rain with less than 0.10" elsewhere. Given
the variability of convection, we will end up seeing locally
higher and lower totals. Dry conditions will return overnight
tonight with a H5 shortwave trough working over the Continental
Divide for Wednesday leading to another round of isolated to
scattered showers and thunderstorms.

Daily shower and thunderstorm chances will continue for Thursday
as activity becomes increasingly isolated and shifts north for
Friday before predominantly dry conditions are back for the
weekend under the increasing influence of high pressure.
Seasonable to seasonably cool temperatures are expected through
Friday ahead of warmer temperatures building back in for the
weekend. Outside of very isolated shower and thunderstorm activity
this weekend primarily in the mountains, the axis of monsoon
moisture looks to shift back into our region for early next week
as a slow moving H5 low moves into the NE Pacific. This will
support an uptick in activity starting Monday. MacKay

&&

.AIR QUALITY...
Air quality is degraded over our northern areas due to fires just
west of Stanley. An air quality advisory is out for Custer county
today through Thursday. For our southern areas, the HRRR smoke
model shows continued air quality improvement for most of today,
Tuesday, due to showers and thunderstorms and clearer air moving
into the area with southwesterly flow ahead of a cold front. For
our northern areas, the HRRR model shows air quality getting worse
this afternoon with stronger winds from a cold front moving
through today. For the rest of our area, the HRRR model does show
air quality degrading this evening (Tuesday) into Wednesday due to
a wind direction change behind the cold front that moves through
this afternoon. So air quality improvement for our southern areas
today will be short-lived. Wyatt

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 10 AM this morning to 9 PM MDT this
evening for IDZ410-411-413-475-476.

&&