062
FXUS63 KABR 282316
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
616 PM CDT Mon Sep 28 2026

.KEY MESSAGES...

- There is a marginal risk (level 1 out of 5) for severe
  thunderstorms this evening into the early overnight hours.
  There is a potential for a few stronger storms with 1" hail
  and wind gusts up to 60 mph.

- Rain over central SD will expand across northeastern SD and
  west central MN tonight, before exiting east during the day
  Tuesday.

- There is a 25-65% chance of rainfall over 0.5" this evening
  through the day Tuesday, and around an 85% chance over north
  central SD between the Missouri and James Rivers. Heavy rain
  is possible with any stronger storms over mainly central SD,
  with localized flooding especially over areas that received
  heavy rain today.

&&

.UPDATE...
Issued at 550 PM CDT Mon Sep 28 2026

Went ahead and issued a flood watch for areas/counties that had
earlier today received heavy rainfall. Storms continue to look
likely and soil conditions saturated. Outside the watch area,
while heavy rain is possible, will be more cautious given CAMS
and BUFKIT profiles would support a 25kt storm motion and
training would be required.

See below for an update to the aviation discussion...

&&

.DISCUSSION...
Issued at 246 PM CDT Mon Sep 28 2026

Radar estimates of 2 to nearly 5" of rain fell over far northeastern
Corson/northwestern Campbell Counties during the morning to early
afternoon hours, with an estimated 2-3.5" over portions of western
Dewey County. These areas will be a concern with additional shower
or thunderstorms producing steady or heavy rain tonight into early
Tuesday morning. PW values averaging 1.45" will increase to near
1.7" 00-03Z Tuesday over central SD, before shifting to areas that
have experienced little to no rain over the past 24 hours. The daily
mean PW from the SPC sounding climatology page is around 0.7", with
the our values nearing the daily max values.

Winds out of the south gusting 15 to 30 mph will slowly weaken this
evening. Expect rain to continue over central South Dakota into
Tuesday morning. There is a marginal risk, or level 1 out of 5, for
severe thunderstorms over portions of central South Dakota this
evening into the early overnight hours, where a few stronger storms
with 1" hail and wind gusts up to 60 mph will be possible. Heavy
rain is possible with any stronger storms, with localized flooding
especially over areas that have already received heavy rain. The mot
likely time period for strong to near severe storms will be from 23
Monday-06Z Tuesday. Rain will expand across northeastern South
Dakota and west central Minnesota early Tuesday morning, before
coming to an end Tuesday afternoon as an area of low pressure
crosses west to east across South Dakota. The winds out of the south
will shift out of the northwest during the day. There is a 25-65%
chance of rainfall over half an inch from the evening hours through
the day Tuesday, with around an 85% chance over north central South
Dakota between the Missouri River and James River. Plenty of low
level moisture will remain. For example, relative humidity will
bottom out in the 60 to 80 percent range Tuesday east of the
Missouri River, and still not fall much below 50 percent west of the
Missouri River.

Fog will likely be a concern Wednesday morning over northeastern SD
into west central MN per the NAM and ECMWF ENS visibility meteograms
page, and if the trend continues, will be added to our ongoing
forecast.

Looking farther out, there is some uncertainly on the
strength/timing of ridging over the western U.S., with either more
zonal flow or ridging as we move into early next week. Stay tuned.
Currently we are expecting temperatures of 5-10F below normal for
this time of the year starting Thursday. Other than a 20% chance of
light rain Saturday morning over northeastern SD, dry weather is
forecast Wednesday through early next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 550 PM CDT Mon Sep 28 2026

Terminals KABR,KATY,KPIR,KMBG

Initially VFR conditions, but storms near the start of the TAF
period, with chances expanding out from there through the
overnight hours. Lower CIGS and VISBY from fog follow during the
morning hours with a return to VFR late in the TAF period.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Flood Watch until 3 AM CDT /2 AM MDT/ Tuesday for SDZ003-004-
     015.
MN...None.

&&

$$

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