302 
FXUS63 KFSD 052046 RRA
AFDFSD

Area Forecast Discussion...RESENT
National Weather Service Sioux Falls SD
223 PM CDT Sat Sep 5 2026

.KEY MESSAGES...
 
- Thunderstorms again expected after 4am Sunday with risks 
  continuing through Sunday afternoon. Ping pong ball size hail 
  and 40-60 mph will be possible.
 
- Higher risks for locally heavy rain will develop by mid-day
  Sunday, with potential for pockets of 2-4" of rain and
  localized amounts to 6". Localized flash flooding may be
  possible through Sunday afternoon.

- A shifting pattern may bring higher rain chances, slightly 
  cooler temperatures, and a severe weather risk Monday evening 
  and early overnight. This risk could continue Tuesday 
  afternoon south of I- 90.

- Dry and continued above normal temperatures are favored for 
  most of next week. 

&&

.DISCUSSION...
Issued at 218 PM CDT Sat Sep 5 2026

THIS AFTERNOON: We're slowly recovering the airmass post convection 
this afternoon, though continued overrunning of the convective 
outflow to our south has persisted in developing additional 
cloud cover in northeast Nebraska and northwest Iowa. 
Temperatures will continue to rise and it appears we'll reach 
into the upper 80s to lower 90s once again. Across NW Iowa
temperatures have been cooler, but a late day temperature surge
is still possible if clouds clear. Dew points will also recover
slowly and should end up into the upper 60s to 70s by this 
evening. The resultant heat index values climb back to the 95 to
102 range in quite a few locations. 

TONIGHT: We'll be watching modest theta-e advection kicking off 
additional showers and thunderstorms over the western High Plains 
later this afternoon and early evening. This activity will 
likely struggle as it tries to reach central South Dakota later 
this evening. Greater concerns begin to develop after midnight 
as the LLJ intensifies. The majority of guidance is now showing 
two areas of concern...one along the Minnesota river valley and 
Buffalo Ridge where some increased convergence and influence of 
mid-lvl vorticity could spark elevated storms. A second area 
over western/central Nebraska and central South Dakota where a 
potentially stronger mid- lvl area of vorticity enters the state
and begins to slowly drift east northeast. Elevated convection 
in both of these areas would favor brief marginally severe hail 
and a few 40-60 mph wind gusts. The biggest uncertainty is the 
time of development which may range from 4am to 7am. 

SUNDAY:  While there isn't a lot of certainty in meteorology, my 
confidence is growing that we'll be dealing with some type of 
impactful weather during the day.  Already ongoing convection at 
daybreak may continue to spread both east (from western complex), 
and southeast (from elevated Ridge convection)...an interesting 
artifact of being stuck under the mid-lvl ridge axis.  Occasionally 
strong updrafts may still produce isolated severe weather through 
the morning as this activity meanders. Soundings by mid-day either 
side of the I-29 corridor show a nearly uncapped environment which 
could signal some potential for ongoing elevated storms to tap into 
the surface layer and intensify.  Shear remains quite marginal, but 
2000-2500 J/KG MLCAPE and decent mid-lvl lapse rate could suggest 
some large hail and downdraft potential.  While extremely low 
probabilities...the low LCL and chaotic SFC wind pattern could lead 
to a few funnels.  Gradual cold pool development and continued 
southeast shift in the upper vort max should push this convective 
cluster southeast and out of the CWA by early evening. 

Another concern, which may end up being the biggest concern will be 
heavy rain.  As evident this morning, the environment overhead 
remains rich for locally heavy rainfall with several areas of 4-6" 
of rain.   A similar situation will be in place tomorrow with 
another deep warm cloud layer, high PWAT, and slow storm motion (AOA 
10-15 knots) event.    REFS/HREF 6 hr PMM through 00z all indicate 
localized totals of 2-4"...however as shown by last night's 
data...the many of the totals were closer to the ensemble max.  In 
this case the potential shifts to higher localized values of 3 to 
5"+.  All this to say that these high end amounts may be quite 
spatially variable which makes pinning down a potential flood 
watch more difficult. Areas from Mitchell to Tyndall are by far 
the most susceptible to flooding, with 3 hr FFG in most other 
areas between 2.5-3.25". Will allow next shift to take a closer 
look and try to pin point any areas of concern as data focuses 
in on the potential. 

SUNDAY NIGHT: Any MCS that develops Sunday afternoon should exit the 
area early in the evening leaving subsidence in it's wake. There 
still remains a 30-40 knot LLJ that will develop and may produce 
scattered convection into the James river valley into Monday 
morning. 

MONDAY-TUESDAY:  The mid-lvl ridge axis slides east by Monday, with 
deeper troughing moving into the PACNW and Northern Rockies.  Lee-
side troughing develops a surface boundary over the western Dakotas 
early on Monday with an increasing SPG bringing gusty winds to the 
CWA Monday afternoon.  Temperatures may also warm back towards the 
90s ahead of the front.  While we'll have to watch return flow and 
boundary layer moisture along the boundary, there may be sufficient 
pooling of moisture to overcome lingering capping by late in the 
afternoon in central South Dakota.  Should storms develop, then a 
narrow focus for severe convection may extend into the western half 
of the CWA into the early overnight hours. Depending on the extent 
of coverage of storms, the aforementioned front may dip into 
northern Nebraska and Iowa by Tuesday. Convection may again 
develop along this boundary with some increased severe weather 
potential focused mostly in the southern third of the CWA. 

WEDNEDAY-FRIDAY: The rest of the work week favors slightly cooler 
temperatures and drier conditions as high pressure moves into the 
Plains. Temperatures will remain slightly above seasonal normals in 
the lower to middle 80s. 

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1208 PM CDT Sat Sep 5 2026

Outside of limited MVFR to mostly VFR conditions near Highway
20, mostly clear skies should prevail into the overnight hours.
We'll gradually see increasing mid-lvl and upper clouds as
convection develops both in western and central South Dakota,
but also in southwest and southcentral Minnesota after midnight. 

Modest agreement in model data suggesting thunderstorms converge
towards I-29 late in the morning bringing potential impacts to
the corridor through the afternoon.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

DISCUSSION...Dux
AVIATION...Dux