641
FXUS65 KPIH 262034
AFDPIH

Area Forecast Discussion
National Weather Service Pocatello ID
234 PM MDT Fri Jul 26 2024

.SHORT TERM...Tonight through Saturday Night.
Early afternoon satellite imagery shows a departing cold front
over the WRN Great Plains as a H5 trough shifts over the PacNW and
NRN Rockies, bringing with a drier and cooler airmass in addition
to increased wildfire smoke regionwide. Even given this drier
environment in place today, PWATs around 0.50-0.80" will support
isolated to scattered shower and thunderstorm development across
ERN Idaho with the HREF model showing a 20-60% chance of thunder
along and east of I-15 into Wyoming with less than a 20% chance
elsewhere. The convective environment today will support around
800-1200 J/kg of SBCAPE, 1000-1500 J/kg of DCAPE, 20-30 kts of 0-6
km shear, and 8- 9 degree/km 700-500 mb lapse rates. This
environment will support strong thunderstorms that will be capable
of producing wind gusts to 40-60 mph, small hail, and brief heavy
rain. Highs today will be in the 80s to low 90s with breezy
synoptic winds supporting gusts to 20-40 mph.

A H5 low off the coast of NRN California this afternoon will move
onshore tonight into Saturday and as it does, pick up a plume of
monsoon moisture along the way. This moisture will build into SE
Idaho starting Saturday morning with isolated to scattered showers
and thunderstorms possible during the morning hours SE of the
Snake Plain. These shower/thunderstorm chances will expand
regionwide by the afternoon hours with the HREF model showing a
40-90% chance of thunder across our entire CWA with an emphasis on
a 70-90% chance across the Snake Plain into Montana, Wyoming, and
Utah. In similar fashion to today, the convective environment
Saturday will support 300-800 K/kg of SBCAPE, 1000-1500 J/kg of
DCAPE, 25-35 kt 0-6 km shear, and 7-9 degree/km 700-500 mb lapse
rates. This environment will again support strong outflow wind
gusts in that 40-60 mph range (locally stronger), small hail, and
heavy rain. In addition, the SPC has outlined much of our region
in a MARGINAL RISK (5-14% chance) of severe thunderstorms across
much of SE Idaho for Saturday. Shower and thunderstorm coverage
will drop after sunset with isolated activity lingering around the
Yellowstone/Grand Teton NP region. Highs Saturday will be in the
70s and 80s which will mark the coolest day in our region since
July 4th given this system`s passage. MacKay

.LONG TERM...Sunday through next Friday.
Sunday, expect southwest flow aloft as a weak wave passes well
north of our area. Expect breezy winds on the surface with gusts
of around 20 to 30 mph along with isolated, mostly afternoon
mountain thunderstorms. Temperatures will be around normal on
Sunday. Expect breezy southwest flow aloft to continue on Monday
bringing afternoon gusty conditions. Little to no thunderstorms
are expected on Monday. Temperatures look to rise slightly above
normal on Monday. Tuesday into Wednesday models show a weak wave
move through the area bringing breezy winds and mostly isolated
thunderstorms. Temperatures look to drop down to normal to
slightly below normal on Tuesday and Wednesday.

Late Wednesday into late next week high pressure builds back into
the area. Expect dry and hot conditions Thursday and Friday.
Temperatures will be 8 to 12 degrees above normal with lower
elevations in the mid to upper 90s. A few areas may hit 100
degrees on Friday. Wyatt

&&

.AVIATION...For the 18Z TAFS through 18Z Saturday.
Expect VFR conditions and breezy winds this afternoon for all TAF
sites. Our area has breezy southwest flow aloft behind an exiting
cold front today. There is enough moisture and instability for
thunderstorms this afternoon, mainly in the mountains across our
east and southeast. Only have vicinity thunderstorms for KDIJ this
afternoon as the HREF model shows a 50 to 60 percent chance of
thunderstorms. Any thunderstorms on station could bring brief MVFR
conditions. The only other likely TAF site that may have
thunderstorm impacts is KPIH. There is a 20 to 30 percent chance
of thunderstorms for KPIH from the HREF model. However,
thunderstorms look to develop just southwest of KPIH over the
Portneuf mountains near Inkom this afternoon. Have held off on
vicinity thunderstorms for this afternoon for KPIH for now.

Saturday morning into Saturday afternoon, expect thunderstorm
impacts for all sites with a trough moving through southwest flow
aloft. Gusty outflow winds of around up to 35 to 50 mph are
likely. Gusts up to 60 mph are possible, especially for KBYI.
Thunderstorms on station are possible as well, especially for
KBYI, KPIH, KIDA, and KDIJ. Wyatt

&&

.FIRE WEATHER...
Following a departing cold front yesterday, RED FLAG WARNINGS
remain in effect for FWZ 410, 422, 475, and 476 for a combination
of low RH in the teens and wind gusts to around 25-40 mph. In
addition today, isolated showers and thunderstorms will be
possible across FWZ 410, 411, and 413 with an emphasis on stronger
storms supporting gusty outflow winds in that 40-60 mph range,
heavy rain, and frequent lightning.

For Saturday, another system rolls in from the Pacific and as a
result we have gone ahead with RED FLAG WARNINGS for all zones
outside of 422 for a mix of scattered wet and dry thunderstorms
which will go in effect from 1200 to 2200 everywhere outside of
FWZ 413 which will be from 0600 to 2200 given the threat of
morning convection. Again, stronger storms will support gusty
outflow winds in that 40-60 mph range, heavy rain, and frequent
lightning but given PWATs around 0.50-0.80" range, the potential
for isolated dry thunderstorms will exist.

Following this systems exit to our NE on Sunday, isolated to
scattered showers and storms will linger in 410, 411, 413, 427,
and 476 but coverage will drop across our region in comparison to
Saturday. High pressure begins to build into early next week as a
H5 trough passes over the NRN Rockies on Tuesday. As a result,
conditions will remain mostly dry early next week outside of
isolated showers and storms in Lemhi County with the primary focus
on elevated winds peaking each afternoon which will support near
critical to critical fire weather conditions given RHs in the
teens and 20s. Following the exit of that trough, a H5 ridge axis
will shift overhead and will lead to a warming trend through next
week as conditions return to being very dry. MacKay

&&

.AIR QUALITY...
The HRRR smoke model shows a large plume of smoke from Oregon and
California wildfires as well as a large wildfire about 50 miles
south of Mountain Home working through through our area today.
Meanwhile smoke from the Bench Lake Fire will overspread much of
the Central mountains. Air quality in our northwest areas, Eastern
Magic Valley, Shoshone, northern Arco desert, and southern Snake
Plain fell to the "unhealthy" stages today. There are multiple Air
Quality advisories out including Cassia, Lincoln, Minidoka,
Custer, and Butte counties. There will likely be additional
counties added to the Air Quality advisories today.

Wildfire smoke will likely hang around through the weekend and
possibly into early next week across the Snake Plain, Magic
Valley, Lower Snake plain, and Central mountains. There could be
some improvement Saturday afternoon across eastern Idaho as storms
develop. These storms will allow for vertical mixing and may
temporarily clear the atmosphere for a few hours. Expect continued
degraded air quality on Sunday with less confidence heading into
early next week. Wyatt

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 10 PM MDT Saturday for IDZ410-411-
425-427-475-476.

Red Flag Warning until 10 PM MDT this evening for IDZ410-422-475-
476.

Red Flag Warning from 6 AM to 10 PM MDT Saturday for IDZ413.

&&

$$