049
FXUS63 KABR 030240 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
940 PM CDT Tue Sep 2 2025

.KEY MESSAGES...

- Widely scattered strong to severe storms possible into early
  evening across portions of east central South Dakota. Marginal
  risk (threat level 1 of 5) includes hail up to quarter size and
  winds near 60 mph.

- Smoke, both aloft and near the surface, is forecast to impact
  the region later tonight into Wednesday and then again Thursday
  and Thursday night.

- Below normal temperatures are expected after today. For the
  most part, highs will be in the upper 50s to lower 70s from
  Wednesday through next Monday. These temperatures are 10 to 20
  degrees below normal. Low temperatures Thursday morning and
  again Saturday morning may dip into the upper 30s for some
  locations.

&&

.UPDATE...
Issued at 924 PM CDT Tue Sep 2 2025

The cold front has slid south of our area, now situated from
Brookings, SD to Marshall, MN and further east toward Minneapolis.
Northerly winds and cold air advection have commenced and showers
and thunderstorms are ongoing across parts of North Dakota. The
showers and isolated thunderstorms will slide into our area
tonight. The only update with the evening forecast package was to
refine timing of POPS based on current trends. Smoke/haze is also
being reported along the North Dakota/Canada boarder and the HRRR
is persistent in progging near surface smoke over our region
Wednesday afternoon.

UPDATE Issued at 642 PM CDT Tue Sep 2 2025

See the updated aviation discussion below.

&&

.DISCUSSION...
Issued at 333 PM CDT Tue Sep 2 2025

Cold front continues to make southward progress into northern SD
this afternoon. Lift and instability (MLCAPE ~2000 J/KG) out ahead
of the front across the eastern CWA is leading to initial
development of convection across the far northeast counties. Could
see additional development into the early evening hours further
south across the eastern CWA as the front continues moving
southward. Best shear is lagging the front and only have about 25 to
maybe 30 knots of deep layer shear. Mid-level lapse rates could be a
bit better also. All that said, still appears to be a marginal risk
for severe storms across the eastern CWA into the early evening
hours.

For the overnight, mid-level wave noted upstream on water vapor will
move southward into the region, bringing additional showers. There`s
really no instability to speak of, so just looking at general
showers with perhaps some embedded thunder. Already seeing showers
on upstream radars across ND, a sign of things to come for the
overnight.

Smoke will be another thing to watch tonight through Wednesday as it
looks to be spreading across the CWA from the north by morning.
Upstream obs where visibility is generally 5-8SM is where HRRR has
smoke concentrations around 20-25ug/m^3. By Wednesday morning, HRRR-
smoke has these levels of concentration and higher (30-35ug/m^3)
setting up over the CWA. Continued mention of "areas of smoke" in
the forecast late tonight through tomorrow. Still seeing signals in
the models of smoke clearing out from north to south during the
afternoon.

Focus then shifts to the strong north-northwest winds expected on
Thursday behind another passing cold front. Models showing a surface
low moving southeast through the area on Thursday, with a tight
pressure gradient developing late morning (central SD) into the
afternoon hours (eastern areas). NBM probability of 24-hr (ending at
06Z Friday) max gusts over 45 mph exceeds 60 percent along and west
of the James River, and even greater than 90 percent over western
into north central SD. Will need to monitor for what`s becoming an
increasing need for a wind headline.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 642 PM CDT Tue Sep 2 2025

Terminals KABR,KATY,KPIR,KMBG

Light rain showers ongoing across North Dakota will drop southeast
into parts of central and northeast South Dakota tonight, mainly
after 06Z. Not expecting much of an aviation impact, if anything,
a brief ceiling reduction to MVFR, but not prevailing. Winds will
also switch to the north and gusts will increase to 10-20 kts.
Smoke, both aloft and near the surface, is forecast to impact the
region later tonight into Wednesday. Will monitor upstream
observations for how widespread and dense smoke becomes and future
forecasts will provide further detail.


&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...Serr
DISCUSSION...TMT
AVIATION...Serr