797
FXUS63 KABR 271739
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1239 PM CDT Fri Mar 27 2026

.KEY MESSAGES...

- Highs in the 60s and 70s Saturday through Monday will be 15 to
  as much as 30 degrees above normal for this time of year.

- Winds will shift to southerly Saturday, with gusts of 35 to 45
  mph. Higher winds will be over northeastern SD, with the favored
  downslope areas of the Sisseton hills potentially exceed 60 mph.

- Our continued dry conditions, relative humidity of 15 to 30
 percent, and the strong winds will combine to create very high to
 extreme Grassland Fire Danger Index values Saturday for all but
 portions of north central SD.

&&

.UPDATE...
Issued at 746 AM CDT Fri Mar 27 2026

The ongoing forecast remains on track. The main concern is
overnight into Saturday afternoon for winds and fire weather. The
key messages have been updated.

&&

.DISCUSSION...
Issued at 143 AM CDT Fri Mar 27 2026

Complex scenario regarding fire weather conditions with surface high
pressure moving over central/north central South Dakota this
morning, and into the east this evening. This leaves us with a cold
airmass but initially efficient mixing. As we move through the
afternoon winds should weaken despite daytime driven mixing. NAM
BUFKIT winds for Summit area peak around 25-30kts 2-3 pm with
unidirectional flow aloft. Thereafter mixed winds begin to slowly
drop. This is the most mixy part of the east though. Despite the
cold temperatures (highs in the 30s/40s)...dewpoints in the single
digits/teens means afternoon humidity drops to 20% across
central/western South Dakota and 40% up across the far northeast.

As that high pressure continues east, during the evening and
overnight, the gradient increases to about 14mb across the state.
1/2km winds increase, with the NAM peaking around 50 to 55kts across
central/north central South Dakota at 09Z, transitioning east into
the James valley and increasing to 55+kts by 12Z, and topping out at
65kts over the Sisseton hills with a downslope component. Those
winds mix out by 15Z as the core of the gradient shifts into far
eastern/southeastern South Dakota. There is uncertainty as to how
long that lingers in the far southeast CWA (Watertown south and
east) where we currently have the Fire Weather Watch with the NAM
lingering longest and the GFS suppressing the gradient a little more
rapidly southwards. Thats mainly a question of end timing for any
fire weather headlines moving forwards we will need to address. For
the daytime conditions however, warm advection will somewhat impeded
a full mixing of these winds save for the downslope region, but that
still leaves us with a fairly sizable fraction and NAM BUFKIT mixed
down winds for Watertown are 40+kts. HREF mean is up around 60mph
and NSSL WRF is up around 70mph.

In regards to dewpoints, the GFS is more mixy typically and should
be fairly representative of the lower bounds, with initially
dewpoints around -10C (low teens) to start the day, but all the
models show a bit of a advection of some `higher` dewpoint airmass,
closer to the mid 20s. NBM has a good representation of this
transition, though probably not with as tight a gradient as some the
CAMS suggest.

And of course its dry during all this. Upper flow is mostly zonal
with broad shallow ridge across the central CONUS. A weak shortwave
crosses the northern tier of the CONUS for late Monday/Tuesday. The
surface low associated with this feature develops overhead. NBM
probabilities of moisture is around 25% for 0.01 and only about 10%
for a tenth of an inch. The system that follows for later in the
week is a broader, deeper trough for the northwestern CONUS, which
would support a low to the north and one possibly for the Southern
Plains. NBM has higher probabilities for moisture of appreciation
(about 40% for 1/4 inch).

As for temperatures for next week, there is a frontal passage
associated with the Tuesday system. Until the frontal passage,
Sat/Sun and Monday 850mb temperatures are about a standard deviation
above climo. That means, according to NBM highs, Saturday will be 15
to 25F above climo, closer to 15 to 20 for Sunday and 20 to 30 above
for Monday. The cooler airmass Tuesday/Wednesday/Thursday puts us
closer to average.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1238 PM CDT Fri Mar 27 2026

Terminals KABR,KATY,KPIR,KMBG

MVFR ceilings initially at ATY will be improving as clouds scatter
out over the next 2 hours. The main concern will be increasing
winds behind the exiting surface high overnight through Saturday
morning. Low level wind shear will start at 07Z at MBG/PIR and
then between 09-11Z at ABR/ATY with winds above the surface
gusting 40-55kts. The strongest surface winds will be through the
morning hours, diminishing in the afternoon from west to east.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning from 10 AM to 9 PM CDT Saturday for SDZ007-008-
     011-019>023.

     Wind Advisory from 7 AM to 5 PM CDT Saturday for SDZ007-008-011-
     019>023.

     Red Flag Warning from 10 AM to 7 PM CDT Saturday for SDZ017-018-
     036-037-048-051.

MN...Red Flag Warning from 10 AM to 9 PM CDT Saturday for MNZ039-046.

&&

$$

UPDATE...06
DISCUSSION...07
AVIATION...06