Damaging Wind in Idaho, July 13, 2024

Area Forecast Discussion
National Weather Service Pocatello ID
240 PM MDT Sat Jul 13 2024

.SHORT TERM...Tonight through Sunday Night.
Early afternoon satellite imagery shows a strong H5 ridge of high
pressure overhead centered over the Four Corners region which
will continue to bring hot and very dry conditions to our region.
Also worth mentioning is the increase in wildfire smoke and haze
overhead which will continue to lead to smoky and hazy skies with
the current air quality generally in that "moderate" category.
Weak monsoon moisture transport over SRN Idaho associated with
moisture working clockwise around this area of high pressure has
led to an uptick in clouds with radar imagery showing
predominantly clouds and or virga so far this afternoon with the
closest thunderstorms down in NRN Utah and Nevada. The HREF model
probability of thunder through tonight shows less than a 10%
chance across our entire region with around a 10-20% chance along
the Utah, but we will see that very isolated 5-10% chance today
dependent on if we see any organization. High temperatures today
will be in the 90s to low 100s before temperatures slightly cool
for Sunday by around 3-5 degrees as a shortwave trough ushers in
more isolated to scattered coverage of thunderstorms for Sunday.
As a result, the current HEAT ADVISORIES and EXCESSIVE HEAT
WARNINGS remain on track to expire tonight in coordination with
our neighboring offices.

As that aforementioned H5 shortwave trough passes overhead for
Sunday, PWATs around 0.30-0.60" on Saturday will increase to 0.60-
1.00" on Sunday which will lead to an uptick in shower and
thunderstorm potential regionwide. The HREF model picks up on this
increasing trend showing a 30-60% chance of thunder for
everywhere outside the CNTRL Mountains where a 10-30% chance will
exist. The convective environment Sunday afternoon will support
around 300-700 J/kg of SBCAPE, 20-30 kt 0-6 km shear, and 8-9
degree/km 700-500 mb lapse rates. As a result, the primary hazards
tomorrow will center around gusty outflow winds and any new fire
starts given PWATs will be in that typical range we see a mix of
wet and dry storms. Outside the CNTRL Mountains, the HREF model
shows a 50-70% chance of winds greater than 34 mph with ensemble
maximum wind gusts in that 40-60 mph range given elevated DCAPE.
Very isolated showers and storms will continue overnight Sunday
into Monday as a secondary H5 shortwave building in early next
week helps to keep convection going. MacKay

.LONG TERM...Monday through next Saturday.
The continued heat will be the main long term impact through next
Saturday. A weak upper level short wave riding on top of the
ridge will bring the coolest day of the period on Monday with
highs in the lower 90s low elevations and mid 70s to mid 80s in
the mountains. Will also have isolated thunderstorms with the
system mainly in the mountains. The ridge axis rebuilds over Idaho
Tuesday and remains overhead with weak oscillations east and west
into next weekend. Some moisture may get trapped in the region
and isolated showers and thunderstorms are in the blended data
daily, but significant rainfall is not expected and nearly all
activity forecast for the central, southern and eastern mountains.
High temperatures will remain well above normal with low
elevations mid to upper 90s and mountains lower 80s to lower 90s
in the Tuesday through Saturday time period. Monday will be the
breeziest day with up valley 10 to 20 mph sustained and gusts 20
to 30 mph in the Snake River Plain. With the building upper level
ridge much lighter winds expected Tuesday through Saturday. GK

&&

.AVIATION...For the 18Z TAFS through 18Z Sunday.
Will have VFR through Sunday with mainly mid level and high cloud
cover as some monsoonal moisture continues to push in from the
southwest. Extremely dry so do not have and thunder in the TAFs
today in vicinity, but will be a much better chance late Sunday
afternoon. Winds generally around 10 knots this afternoon at all
sites with some occasional gusts up to 20 knots. Expect similar
winds Sunday afternoon. GK

&&

.FIRE WEATHER...
Under the continued influence of a H5 ridge of high pressure
centered over the Four Corners Region, hot and very dry conditions
continue today with breezy wind gusts peaking around 25-35 mph.
As a result, a RED FLAG WARNING is in effect for FWZ 475 and 476
with near critical to critical fire weather conditions possible
elsewhere given a very dry air mass in place with winds
approaching or reaching critical levels at times. While we are
seeing an increase in clouds today on the leading edge of some
weak monsoon moisture transport, conditions will remain dry
outside of a very isolated 5- 10% chance of thunderstorms this
afternoon and evening.

Attention tomorrow turns to an approaching H5 shortwave trough
lifting NE out of the Great Basin. This trough will help to
introduce a NBM 15-35% chance of thunderstorms everywhere outside
the CNTRL Mountains where a 10-25% chance will exist. The HREF
model is a bit more aggressive with these probabilities, putting
about a 30-60% everywhere outside the CNTRL Mountains where a
10-30% chance exists. A mix of isolated to scattered wet and
mostly dry thunderstorms are expected tomorrow with a RED FLAG
WARNING in effect for FWZ 413 and 427 given the best scattered
coverage of storms in theses areas. Elsewhere however, we are also
continuing to monitor the potential for expansion of this RFW
dependent on further forecasts but keep in mind isolated wet and
dry thunderstorms will be possible regionwide tomorrow. The
primary hazards with storms tomorrow will center lightning and
outflow wind gusts to around 40-60 mph. 30

Thunderstorm chances will continue again into Monday before
decreasing in coverage and shifting SE for Tuesday as a slightly
cooler air mass settles in early next week. The majority of long
range model guidance continues to show a ridge of high pressure
building back in by midweek next week which will lead to a warming
trend as conditions remain mostly dry. We are still expected
afternoon isolated showers and thunderstorms each day through much
of next week with a focus over the higher terrain. MacKay

&&

.AIR QUALITY...
Wildfire smoke from regional wildfires across the Intermountain
West continues to lead to degraded air quality in that "Moderate"
to "Unhealthy for Sensitive Groups" category across much of SRN
Idaho. The latest HRRR smoke model keeps wildfire smoke in our
area through the weekend which will continue to lead to hazy and
smoky skies overhead below about 500 mb. MacKay

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until midnight MDT tonight for IDZ051>054-061-062-
065>068-070-075.

Red Flag Warning from noon Sunday to midnight MDT Sunday night
for IDZ413-427.

Excessive Heat Warning until midnight MDT tonight for IDZ055>059.

Red Flag Warning until 9 PM MDT this evening for IDZ475-476.

&&