Wildfire in Idaho, September 1 to 30, 2021

Area Forecast Discussion
National Weather Service Pocatello ID
922 PM MDT Tue Aug 31 2021

.UPDATE...
Winds across the Red Flag Warning zones have dropped below
critical thresholds per latest sfc mesonets. Relative humidity
values remain below 15% across portions of the Arco Desert, but
they are slowly trending up compared to 2 hours ago and should
continue to do so as the boundary layer cools. Therefore, we have
allowed the Red Flag Warning to expire on-time for the day. Winds
continue to look sub-criteria for Wednesday, but the midnight
shift will fully reevaluate the fire wx situation. - KSmith

&&

.PREV DISCUSSION... /issued 202 PM MDT Tue Aug 31 2021/

SHORT TERM...Tonight through Thursday night. Satellite imagery
today highlights the smoke inundation into the area, associated
with persistent southwest flow through Thursday. This similar
pattern is likely to remain through mid-week. We have seen winds
today with gusts over 30kts across the Snake Plain, and conditions
are expected to remain slightly breezy in our valley locations
each afternoon/evening through ahead of the passage of an upper
level trough Friday. Taking a look at the remnants of Tropical
Storm Nora working through the region, precipitation chances
generally remain in the far southeast corner of the state with
minimal precipitation accumulation expected. Short-term models
are still not certain on precipitation locations or totals, but
have been reflecting an eastern track for the bulk of the
precipitation into Wyoming and Eastern Utah, with trends not
currently supporting any widespread events for the Eastern and
Southeast Highlands. This is generally supported by upper level
southwest flow that limits the precipitation track northward.
There is a greater chance for scattered rain showers and isolated
thunderstorms Thursday and Thursday night, with minimal impacts
expected.
CM/DMH

LONG TERM...Friday thorugh Tuesday. Expect the long term to be a
quiet period dominated by high pressure with the only possible
shower activity in the afternoon in the eastern highlands. The
upper level ridge will build in by early next week. Temperatures
will be a bit below normal Friday but warm over the weekend to
near or slightly above seasonal norms for early September. Winds
not expected to be overly strong in the long term period but may
see some breezy conditions late weekend into Monday.
GK

AVIATION...
Main impacts today will be how much smoke reduces visibility and
strength of winds.  Expect general sustained winds of 10 to 20 knots
at all sites through 03Z with gusts 20 to 30 knots at all sites.
Winds will die down to under 10 knots after 03z.  Expect the diurnal
increase Wednesday but should be lighter than today with 10 to 15
knots sustained and 15 to 20 knot gusts expected after 18Z.
Occasional visibilities down to 4 or 5 statue miles at any site
possible tonight but should stay at 6 miles at most sites.
GK

FIRE WEATHER...
Red Flag Warning for zones 410 and 422 continues through 9 pm as
winds have increased this afternoon with most areas gusting 20 to 35
mph in those areas.  Only precipitation chances will be isolated
thunderstorms Tuesday and Wednesday afternoons in zone 413.  Dry
conditions are expected Friday through next Tuesday with generally
low humidity and low humidity with poor recoveries expected.  May
see an increase in the winds late in the weekend into next week but
below red flag criteria.
GK

AIR STAGNATION...
Persistent southwest flow is expected, and bringing along with it
smoke from large-scale western wild fires. Significant changes
from this is not expected until at least Friday, ahead of the
passage of an upper level trough. This development is likely to
result in associated north/northwest flow, bringing some relief
for smoke in the area by the start of the weekend.
CM/DMH

&&

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