290
FXUS63 KABR 210119
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
819 PM CDT Mon Apr 20 2026

.KEY MESSAGES...

- Record or near record warm temperatures in the upper 80s to
  lower 90s are expected Wednesday. Winds out of the south will
  gust 30 to 40 mph and relative humidity will fall into the 15
  to 30 percent range. The strong winds and warm/dry conditions
  will combine to create very high grassland fire danger index
  values.

- There is a 30-70 percent chance of showers and thunderstorms
  Wednesday night into Thursday, mainly throughout central and
  north central South Dakota.

- Strong sustained west winds 25 to 35 mph with gusts up to 50
  mph are expected on Thursday. These windy conditions may last
  all the way through Friday into Friday night, especially along
  and north of U.S. Highway 212.

- After a warm start to the day Thursday, cold air will
  establish control of the temperature forecast from Thursday
  afternoon through the end of the weekend. High temperatures
  Friday through next Monday are expected to be near to around 5
  degrees below normal; low temperatures 5 to 10 degrees below
  normal (below 32F).

&&

.UPDATE...
Issued at 819 PM CDT Mon Apr 20 2026

The Red Flag Warning for far northeastern South Dakota and west
central Minnesota has been allowed to expire. No significant
changes are anticipated to the near-term forecast for the rest
of the evening.

&&

.DISCUSSION...
Issued at 120 PM CDT Mon Apr 20 2026

At 1 PM CDT, skies are sunny/mostly sunny and temperatures are
warming into the 60s and 70s (20 to 25 degrees warmer than this
hour yesterday). Winds are south at 15 to 25 mph with gusts up
to 40 mph at times. Relative humidity values are falling through
the 20 to 30 percent range as well.

Northwest flow aloft is forecast to persist through Wednesday. A
cold front will pass southward through the forecast area tonight,
but there will not be much of a cool down expected on Tuesday given
the rather limited time for low level CAA tonight into Tuesday
morning. Today`s really dry airmass gets shunted down into far
southern South Dakota/Nebraska on Tuesday, and by peak
heating/mixing on Tuesday, the I-90 corridor of this CWA could be
dealing with relative humidity as low as 15 to 20 percent, although
the east-southeast wind expected in that area on Tuesday is not
expected to gust to 25+mph.

A strong low level jet develops Tuesday night and persists into
Wednesday night in response to the strong low level WAA expected
over the central/northern plains heading into Wednesday. Presently,
there is no notable tongue of Gulf moisture surging up into the CWA
on Wednesday. With 925hpa and 850hpa temp progs supporting upper 80s
to mid 90s (which are record or near record high temps) on
Wednesday, and a dry airmass advecting back into the CWA on strong
(20 to 35+mph sustained/40-45 mph gusts) southerly winds, the CWA is
primed for very high or higher Grassland Fire Danger indexes.
Circling Wednesday as a potential Fire Weather Watch day once
today`s Red Flag Warning event is over.

The upper level steering flow will switch around to the
west/southwest Wednesday night as a large/cold upper level
low/longwave trough heads east across the nation`s mid-section. Both
the NAM and GFS in BUFKIT showcase more than enough mid-level
moisture (at or above 2km) availability Wednesday night into
Thursday morning to support thunderstorm mention (Elevated CAPE at
or above 750J/kg). At times, deep layer (cloud bearing) shear
appears to produce straight-line hodographs at or above 35 knots. So,
there is that potential for updrafts to rotate/split. Wouldn`t be
surprised if some hail is produced Wednesday night into Thursday
morning. Still fairly cold aloft, too, in April, when convection
happens, adding to the favorability of updrafts to be able to make
hail. The probability of one quarter inch or more of rainfall
occurring Wednesday afternoon through Wednesday night is 20 to 35
percent and is presently centered on Sully, Hughes and Hyde
Counties.

Still looks like the upper low will run up against an upper level
steering flow blockade as it makes its way through Montana/the
Dakotas into southern Canada. A rather blocky steering flow
pattern is set for the end of the week into the weekend, which
should stall this upper low`s progression across NOAM. There
continues to be a signal in both the deterministic GSM`s and all
the various ensemble model camps for rather strong westerly-
component winds to develop on Thursday, at least across the
northern two-thirds of the CWA, continuing through Friday night
before diminishing.

Becoming anomalously cold Friday and Saturday in the wake of this
large upper low, while the strong westerly-component winds are
occurring. Thursday is expected to be the transition day from warm
at the start of the day to getting cold at the end of the day.
Beyond that, the rest of the 7-day forecast boasts of high
temperatures only reaching the 50s (so long as post-system
stratus/strato-cu isn`t widespread over the region), with night-time
temperatures falling below the freezing mark Thursday night through
Sunday night.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 620 PM CDT Mon Apr 20 2026

Terminals KABR,KATY,KPIR,KMBG

Expect VFR conditions to continue over the next 24 hours with winds
around 15kts or less.

&&

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

&&

$$

UPDATE...06
DISCUSSION...10
AVIATION...06