534
FXUS63 KABR 111151 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
651 AM CDT Fri Sep 11 2026

.KEY MESSAGES...

- Above normal high temperatures in the 80s today. A sharp
  cooldown is expected Saturday through early next week with
  highs in the 60s to low 70s. These temperatures are about 5 to
  10 degrees below normal.

- A Red Flag Warning is in effect for parts of south central
  South Dakota. A combination of dry fuels, wind gusts up to 40
  miles per hour, and afternoon humidity around 20 percent will
  create critical fire weather conditions. Grassland Fire
  Danger will reach High for all counties west of Brown and
  Spink Counties and Very High west of the Missouri River.

- There is a Slight (Level 2 of 5) to Marginal (Level 1 of 5)
  risk for severe storms late this afternoon into this evening
  over northeastern South Dakota and western Minnesota. Main
  severe threats include hail up to 2 inches in diameter and
  wind gusts of 60 to 75 miles per hour. A tornado cannot be
  ruled out either.

&&

.UPDATE...
Issued at 649 AM CDT Fri Sep 11 2026

See below for an aviation forecast discussion for the 12Z TAFs.

&&

.DISCUSSION...
Issued at 211 AM CDT Fri Sep 11 2026

A cold front is set to pass through the region this afternoon,
turning winds to the northwest. Under the cold air advection regime,
wind gusts may reach as high as 40 miles per hour, with perhaps a
stray gust up to 45 miles per hour. Confidence on gusts reaching 45
miles per hour (Wind Advisory criteria) is somewhat low at this
point. HREF and REFS both do not give much credence to the
possibility (<10% this afternoon) but NBM probabilities show a
couple of hours of 10-20% chances to hit 45 miles per hour over
north central South Dakota. Regardless of the exact probability,
confidence is not high enough to issue a Wind Advisory today. The
headline with a bit higher confidence is a Red Flag Warning, which
is being issued with this forecast package for Jones, Lyman, and
Buffalo counties. This are will see a period of humidity below 20
percent this afternoon, which when combined with winds will create
critical fire weather conditions. Further north humidity increases
to 20-40%, which is still enough for elevated fire weather concerns
and High to Very High Grassland Fire Danger this afternoon.

The other point of concern with the cold front passing through will
be convection over northeastern South Dakota and western Minnesota
this afternoon. The latest model guidance trends towards storms
firing over this area sometime between 20-22Z before quickly
progressing eastward and out of the Aberdeen CWA as they intensify.
This will leave a fairly short window in which severe weather could
impact the area. Should storms fully develop within the Aberdeen
forecast area, hail and wind will be the most likely severe threats.
Hail in particular could prove to be significant, with a CAPE/Shear
combo of roughly 3000+ J/kg and 30-40 knots in place. Also
supporting the hail threat are mid-level lapse rates around 7.0-7.5
C/km in the area. On the wind side of things, much of the area out
ahead of the front will have upwards of 1000 J/kg of DCAPE in place
and low-level lapse rates near dry-adiabatic to aid in gusts
reaching the surface. Also can`t quite rule out the potential for a
tornado with these storms. Favorable ingredients include strong
MLCAPE, helicity as high as 200 m2/s2, and low-level turning within
the hodographs. The actual value of low-level shear leaves something
to be desired (only about 20 to 25 knots, with perhaps some small
pockets of a more ideal environment of 30 knots), but the main
limiting factor to tornado potential will be LCLs over 1000m in most
locations. However despite these limitations, it is not out of the
question for these ingredients to line up in such a way that allows
for tornadic development, but confidence is not high. It should be
noted as well that a number of CAMs keep convection out of the
Aberdeen CWA entirely. This is likely due to the limiting factor of
a cap in place. The Potential Temperature difference between the
surface and the warm layer is only about 5K at best, and there seems
to be a bit of a spread in model confidence on the ability of that
cap to be overcome or worn down through the day. All this to say
that while this would definitely be a less likely outcome, it would
not be entirely out of the question for the cap to hold and the
Aberdeen area sees little to no convection today. The latest severe
outlook from the Storm Prediction Center covers the areas east of
the James River in a Slight to Marginal Risk.

Temperatures behind the cold front will drop, with highs in the 60s
across the forecast area expected over the weekend. These highs 5-10
degrees below mid-September normals are expected to persist through
at least the start of next week. The departing upper-level trough`s
right entrance region will move over the Northern Plains early
Sunday, bringing a jet streak overhead. This will lead to some
potential for rain showers Sunday morning across much of the
forecast area. By Sunday afternoon, a brief ridge and surface high
pressure center will build into the region, but both are expected to
be fairly short-lived.

Chances for rain return early next week as another upper-level
trough moves over the Northern Plains. Divergence aloft from a jet
streak will be the driving force for this system, as well as some
help from an associated cold front. The below normal temperatures
already in place out ahead of the front will help to form a fairly
strong cap in place and likely significantly limiting deep
convection through the profile. This in turn will all but eliminate
chances for severe weather during this period, an assessment that
mid-range severe probability models agree with. Still, non severe
showers to perhaps a stray thunderstorm will be possible due to the
divergence aloft (~50-60 knots of speed shear from roughly 700mb to
300mb). Latest NBM probabilities of seeing half an inch of rain or
greater still range from 30-50% through 00Z Tuesday, which is a
slight downward trend from 24 hours ago. Other long range ensembles
trend more towards the 10-30% range for that same half inch
threshold.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 649 AM CDT Fri Sep 11 2026

Terminals KABR,KATY,KPIR,KMBG

VFR conditions forecast for all terminals. Winds from the south
southwest shift to northerly with a frontal passage today. KATY
could continue to see some LLWS for a couple more hours this
morning.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning from 10 AM this morning to 7 PM CDT this
     evening for SDZ045-048-051.
MN...None.

&&

$$

UPDATE...10
DISCUSSION...BC
AVIATION...10