157
FXUS63 KFSD 142332
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
632 PM CDT Mon Jul 14 2025

.KEY MESSAGES...

- Hot, humid weather continues through Tuesday with highs in the
upper 80s to upper 90s. A cooldown comes for Wednesday through
Friday with highs only in the 70s to lower 80s.

- Scattered thunderstorms are expected to develop in central South
Dakota and Nebraska Tuesday afternoon, tracking east Tuesday
evening. A few strong to severe thunderstorms may develop with this
activity, bringing heavy downpours, hail up to golf ball size, wind
gusts up to 70 mph, and perhaps a tornado or two. The greatest
threat comes 5 PM to 9 PM.

- Periodic (<50%) rain chances continue through Wednesday night and
again through the upcoming weekend and early next week.

&&

.DISCUSSION...
Issued at 229 PM CDT Mon Jul 14 2025

TONIGHT: Hot, humid weather continues overnight amidst a warm air
advection and a light south wind. A weak ridge-riding shortwave will
triggered scattered storms in western SD this evening, tracking into
northeast SD overnight. Given very weak deep layer shear, upper
ridge influence, and a very dry subcloud layer, seems unlikely to
see any impacts from this activity aside from a very low chance of
virga or sprinkles. Temperatures will only fall into the 60s to near
70 degrees overnight.

TUESDAY: Tuesday brings another hot, humid day with dew points
rebounding to the mid 60s to mid 70s. Models have high confidence in
scattered Tstorms developing near a cold front draped from the NE
Panhandle to south central SD to west central MN late Tuesday
afternoon. A moderately unstable airmass with 7-8 C/km mid level
lapse rates and a stronger approaching mid level wave in zonal flow
should be sufficient to produce scattered strong to severe Tstorms.
Initially expect cells to develop in/near south central SD, but 20-
35 kts of 0-6km deep layer shear mostly parallel to the front
suggests storms favors multicells growing upscale into a linear
complex. Big questions are 1) how far east storms initially develop
(Huron-Gregory vs Pierre-Kadoka), 2) coverage (isolated vs
scattered) and severity (or lack thereof) for additional storms
developing east of the James River Valley overnight (seems
likely but perhaps not severe), and 3) whether the resultant MCS
will track southeast near the MO River corridor (less likely)
or dive further south directly into central NE (more likely).
Pwat values of 1.5- 1.75" favor heavy downpours with any storms.
HREF LPMM suggest pockets of 1.5-2.5 inches of rain are
possible, especially in south central SD, but discrepancies in
the ensemble data lend to low confidence in rainfall amounts
near and southeast of a Tracy to Sioux Falls to Yankton line.
Regardless, the main threats still appear to be locally heavy
downpours, wind gusts up to 70 mph, large hail up to half dollar
size, and to a lesser extent perhaps a brief tornado. HREF UH
tracks and less favorable environmental conditions further east
suggest severe weather threat should gradually wane through the
overnight hours.

WEDNESDAY AND THURSDAY: Closer proximity of a northern stream
longwave trough and persistent stratus brings a notable cooldown for
Wednesday, with highs 10-15 degrees cooler than Tuesday (mid 60s to
lower 80s). We may also see lingering showers and/or drizzle with
abundant cloud cover dictating how much insolation-related heating
we can achieve. Coupled with a breezy north wind, this looks to
be a fairly dreary day for any outdoor activities. Should get
drier mid to upper level air in Thursday behind the upper
trough, making for a cool day with more sunshine.

FRIDAY THROUGH EARLY NEXT WEEK: A more active, zonal flow pattern
aloft brings periodic rain chances through next weekend and early
next week as Southeast ridging regresses westward and ridge-riding
shortwaves slide through the North Central part of the CONUS. As
highlighted in the CPC 6 to 10 day outlook, there`s some signal for
a wetter pattern with multiple rounds of convection early next week
with 90th percentile (NAEFS-relative) precipitable water content
coupled with a stronger, northern stream longwave trough digging
in.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 631 PM CDT Mon Jul 14 2025

VFR conditions begin the TAF period. Light southeasterly winds
persist late this afternoon. While conditions are quiet,
thunderstorms have developed west of the Missouri River and are
pushing southeastwards. These storms currently are most likely to
weaken as they approach the Missouri River and thus have left out of
KHONs TAF. However, these storms will be closely monitored and
amendments will be made if they hold together east of the river.
The low level jet (LLJ) will strengthen tonight, resulting in low
level wind shear (LLWS) along and west of I-29. Should see the LLWS
wane as the LLJ weakens early tomorrow morning.

Breezy southerly winds are expected during the day tomorrow with
gusts up to 20-25 knots. A cold front will be pushing into the area
tomorrow afternoon. While turning winds to out of the north in its
wake, this front will also develop showers and thunderstorms along
it, including at KHON. These showers and storms will finish out the
TAF period.

&&

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

&&

$$

DISCUSSION...BP
AVIATION...Meyers