Wildfire in Idaho, September 1 to 30, 2024

Area Forecast Discussion
National Weather Service Pocatello ID
227 PM MDT Sat Aug 31 2024

.SHORT TERM...Tonight through Sunday night. Very dry pattern
continues through short term as upper ridge remains in place. The
high pressure will keep temperatures quite warm, though smoke
inundation will hold temperatures down where it is thickest,
mainly across the central mountains. Upper flow turns southwest
during the day Sunday, with slight increase in winds mainly across
upper elevations. Weak shortwave passage afternoon/evening begins
to allow moisture to creep into southern zones, leading into
thunderstorm chances for Monday. More details in the Long Term
discussion below. DMH

.LONG TERM...Monday through next Saturday.
High temperatures will trend toward the cooler side of normal for
the first half of next week, generally 80s and below, as an upper
low in the Pacific moves onshore and works through Idaho on Tuesday
and Wednesday. At this time, thunderstorms look to start off mostly
dry and even showers likely won't produce much measurable
precipitation with ensembles indicating precipitable water (PWAT)
values ranging only around half an inch to three quarters of an inch
Monday into Tuesday. Thunderstorm coverage will become increasingly
scattered heading into later Monday. While breezy winds will
accompany the front, magnitudes currently do not look very
impressive for the Monday/Tuesday period, with gusts ranging 20 to
30 mph outside of gusty thunderstorm outflows. Behind the departing
low, a ridge of high pressure will rebuild from the west with
temperatures returning to right around normal by late week. Cropp

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.AVIATION...Haze and smoke from regional wildfires are
resulting in reductions to VIS at times at KBYI and KSUN, especially
during the early morning hours before the inversion breaks prior to
increased heating and mixing. Otherwise, VFR conditions are
supported by dry conditions and light winds through early Sunday.
Chances for showers and thunderstorms return as early as Sunday
afternoon ahead of the next Pacific low. Winds begin to pick up
Sunday afternoon with gusts to around 15 kts. The HREF max wind gust
potential suggests high end gusts could reach around 25 kts before
increasing further on Monday. Cropp

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.FIRE WEATHER...Very dry conditions continue into Sunday, with
daytime humidities generally 5-15% and poor recovery at higher
elevations overnight. Flow aloft turns southwest during the day
Sunday, allowing for a slight increase in winds at higher
elevations. Winds remain below critical thresholds, though the
very low humidities and high Haines of 5-6 may combine for near
critical conditions especially near existing fires. There is a
very low outside chances (< 10%) of a dry thunderstorm across the
south half of the forecast area late afternoon/evening, mainly
south of a line from Shoshone to Soda Springs, but not enough to
include in the forecast at this time. Much better thunderstorm
chances exist during the day Monday, with scattered or greater
thunderstorm coverage for much of the day. Have issued a Fire
Weather Watch for Monday for Noon-10PM, though update to a Red
Flag Warning may flex the time as confidence grows in thunderstorm
timing. Storms will likely start dry but transition towards
wetting storms as the day progresses, and may continue past
midnight for areas along the Wyoming border. Upper trough shifts
through the region Tuesday into Wednesday with continued threat
for thunderstorms mainly high elevation areas. Temperatures
decrease slightly Tuesday, with locally gusty winds. Ridge of high
pressure rebuilds for the latter portions of the week into the
weekend. DMH

&&

.AIR QUALITY...
Overnight inversions and limited mixing and light winds under high
pressure have resulted in several days of degraded air quality due
to smoke from regional wildfires. However, increased south/southwest
flow tomorrow ahead of the next low pressure system will aid in
clearing out some of the smoke. Air Quality Advisories are in effect
for Blaine and Lincoln Counties through Sunday afternoon and for
Custer County through Tuesday afternoon. Air quality in Blaine and
Lincoln Counties is "Unhealthy" to "Very Unhealthy" and forecast to
improve to "Moderate" to "Unhealthy for Sensitive Groups" by
tomorrow. In Custer County, air quality is currently "Unhealthy" and
forecast to improve to "Unhealthy for Sensitive Groups" between
today and tomorrow. Cropp

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.PIH WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Monday afternoon through Monday evening
for IDZ410-411-413-422-425-427-475-476.

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