465
FXUS63 KABR 132300 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
600 PM CDT Mon Apr 13 2026

.KEY MESSAGES...

- Isolated strong storms possible this evening. Marginal Risk
  (Level 1 of 5) for severe weather across north central and
  northeast South Dakota. Large hail up to 1 inch in diameter and
  strong wind gusts of 60 mph are the main threat. Slight risk (2
  of 5) extends just into far eastern South Dakota through west
  central Minnesota. Hail of 1 to 1.5 inches in diameter and wind
  gusts of 60 mph are the main threats in that area.

- A warming trend will take place through the week, peaking on Thursday
  with highs in the upper 70s to low 80s (20 to 25 degrees above
  mid-April normals). A strong cold front will bring colder air
  back into the region Friday/Saturday, with temperatures dropping
  to 10 to 15 degrees below normal.

&&

.UPDATE...
Issued at 556 PM CDT Mon Apr 13 2026

Cancelled the Red Flag Warning early this evening as RH in the
affected area is above 40 percent and winds have fallen below 20
mph.

&&

.DISCUSSION...
Issued at 136 PM CDT Mon Apr 13 2026

Low stratus deck and pockets of dense fog has stuck around longer
than expected this morning, leading to an expectation of
temperatures much lower than previous forecasts, especially in the
north. Central South Dakota may still see temperatures in the 70s,
but over north central and northeastern South Dakota as well as
western Minnesota the expectation is now that highs may struggle to
hit 60 degrees. This temperature reduction will have consequences
for this afternoon and evening`s fire weather conditions and
potential severe weather threat.

Tackling the critical fire weather conditions first, the Red Flag
Warning is still in place from 18Z this afternoon through 01Z
Tuesday for Stanley, Jones, and Lyman counties. With the delay in
the low clouds clearing out this morning, the resulting slight high
temperature drop compared to previous forecasts will push minimum
afternoon humidity up a bit. Parts of Jones and Lyman counties are
still expected to reach below 20 percent, but concern further north
into Stanley county is beginning to wane due to humidity ranging
from 25 to 40 percent across the county now expected. Wind gusts
also appear somewhat marginal this afternoon in that area, but a
tightening pressure gradient (supporting a flip to a westerly
direction) will still get gusts up to 25-30 miles per hour for a
couple of hours. So while confidence is decreasing, the area may
still still reach Red Flag conditions. Even if Red Flag conditions
aren`t met to the letter, relatively dry fuels in the area combined
with the aforementioned humidity and wind conditions will support
High Grassland Fire Danger regardless.

There are two main areas of concern for severe weather today, the
first of which coming over northeastern South Dakota and western
Minnesota. Convection is expected to develop along a frontal
boundary, which recent guidance has trended southward. Due to this
southward shift, recent runs of CAMs have been much less impressed
with the setup, and most keep storm initiation to the southeast of
the forecast area. There remains a scenario in which a storm develop
along and then up the front, moving north as an elevated storm.
Should this occur, the ingredients at the mid- to upper-levels
appear to be mostly in place to sustain storms this far to the
north. Strong mid-level lapse rates between 7 and 8 C/km and ample
shear upwards of 45 knots support favorable hail conditions, but the
missing ingredient in the area is the MUCAPE, which remains more
favorable closer to the front to the south (reaching at most 1000
J/kg in parts of eastern South Dakota within the Aberdeen forecast
area). All this to say that while convective initiation does not
appear favorable over the Aberdeen forecast area, still can`t rule
anything out at this point. Anticipating hail of 1"-1.5" at the most
at this point, with damaging winds also possible, though they may
have trouble mixing down to the surface with any elevated storms.

A secondary severe weather threat is located over north central
South Dakota this evening. Hi-res CAMs are almost more impressed by
this setup, which is a bit of a reversal in the expectations put
forth by previous forecasts. Development is once again expected
along the front as it curves back north. With the front in the area
convective initiation may be a bit easier, although the limitations
from the lingering cloud cover may still prove fatal to prospective
storms. Should something get going along the boundary, shear upwards
of 40 knots, 500-700mb lapse rates around 7-7.5 C/km, and marginal
MUCAPE (again about 500-1000 J/kg at the highest) may sustain a
brief hail threat. After detaching from the boundary, MUCAPE will
quickly run out as storms push north and east, limiting the
expectations for a sustained threat this evening in north central
South Dakota.

There is once again a signal for fog development overnight tonight,
mainly over northeastern and north central South Dakota. Strong
humidity recovery combined with light winds provide the favorable
conditions, with the main caveat being wind gusts upwards of 10
knots potentially dispelling some of the fog. However if conditions
can stay calm (which under a weakening pressure gradient, chances of
weaker winds should improve through the night), one mile visibility
or lower may develop in the early morning hours.

Briefly looking in the extended period, the broad upper-level setup
keeps jet streaks and higher wind speeds aloft to the east of the
northern plains for the next few days. The possible exception to
this is a shortwave clipping eastern South Dakota on Wednesday, but
presently precipitation chances peak around 20-30%. Otherwise, a
warming trend is expected through Thursday, with highs reaching 20-
25 degrees above normal (highs in the upper 70s to low 80s) by that
point. Fire weather may be a concern Thursday as well, with the heat
bringing low afternoon humidity, combined with southerly winds
gusting to 20-30 miles per hour in the afternoon.

Ensemble clusters appear to be in agreement on a favorable setup for
an end of week system to move into the northern plains. A longwave
trough over the western CONUS will develop a low pressure center
into the region. Early looks at ensemble meteograms show that with
colder air being allowed to filter in from the trough, snow is very
much a possible precipitation type, particularly on the back end of
the system with lingering precipitation behind a cold front.
Ensemble means show roughly one inch of snow through the weekend.
Northwesterly winds will also pick up behind the cold front, with
the latest NBM giving a broad roughly 10-30% over the area to reach
Wind Advisory criteria of 45 miles per hour. However taking into
account known biases in the NBM, those probabilities are likely a
bit underdone.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 556 PM CDT Mon Apr 13 2026

Terminals KABR,KATY,KPIR,KMBG

MVFR/IFR stratus persists across the east. While there may be some
clearing this evening for a few hours, expect the stratus field to
expand again tonight along with some fog redevelopment. An
isolated lightning strike cannot be ruled out over the next couple
of hours near KATY.

&&

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

$$

UPDATE...20
DISCUSSION...BC
AVIATION...20