284
FXUS63 KFSD 070736
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
236 AM CDT Sun Sep 7 2025

.KEY MESSAGES...

- Patchy frost is possible this morning, especially for areas
  along Highway 14, southwestern Minnesota, and northwestern
  Iowa. A Frost Advisory is in effect for this area until 9am
  today. Otherwise, mostly clear skies and highs in the upper
  60s to mid 70s.

- Chances for isolated to scattered thunderstorms Monday. Some
  could be strong to severe.

- Additional chances for thunderstorms in the latter half of
  next week. Warmer temperatures in the 70s and 80s will be at
  or slightly above normal.

&&

.DISCUSSION...
Issued at 235 AM CDT Sun Sep 7 2025

TODAY AND TOMORROW: Patchy frost is possible this morning as low
temperatures fall to less than 36 degrees F in some areas. Roughly
areas along Highway 14 and portions of southwestern Minnesota and
northwestern Iowa have the highest chance of seeing frost. As a
result, a Frost Advisory is in effect until 9 am this morning.

High pressure continues to move into the region from the north
throughout the day, keeping conditions dry. Though there will be a
chilly start to the day, sunny skies, slightly breezy southerly
winds, and WAA in the mid-levels will help us warm into the mid 60s
to mid 70s. As we move into Sunday evening, a weak mid-level wave
will push into the area from the west. Model soundings indicate a
shallow layer of moisture will be present in the mid-levels. As the
surface low and warm front lift northeast the low-level jet
increases, and this forcing may be strong enough to spawn a few
isolated and elevated thunderstorms early Monday morning. Confidence
in location and timing of Monday morning storms is low due to low
model agreement. Have kept NBM PoPs as they are as a result.

Lows by Monday morning will be much warmer than the previous two
days, in the 50s with some 60s possible in south central South
Dakota. Showers clear out by mid-Monday morning as the low
progresses northeast. Conditions the rest of the day should be dry
and significantly warmer thanks to continued WAA on southerly winds.
Highs will climb into the mid to upper 70s east of the James River
Valley, and into the mid 80s to the west. Lows by Tuesday morning
will be in the upper 50s to 60s.

Late Monday night into early Tuesday morning another round of storms
is possible as a surface trough axis begins to move through the
region. Moisture advects in from the south through the day,
increasing instability. By the late afternoon 1500-2000 J/kg of CAPE
will be present along with steep mid-level lapse rates of 7.5-8 deg
C/km. Deep layer shear is lacking at only 20-25 kts. In addition,
the environment will be strongly capped, potentially limiting
updraft initiation. If we manage to break the cap storms will most
likely initiate over central South Dakota in the late afternoon to
evening time frame. Storms will then most likely become elevated as
the progress east through the evening and into the overnight.
Despite the capping and weak shear, a few of these storms could
become strong to severe thanks to the generally unstable
environment. Risks would most likely include hail to the size of a
quarter, and wind gusts to 60 mph.

TUESDAY AND THE REST OF THE WEEK: Showers clear out by late Tuesday
morning as an upper ridge builds in aloft. Dry and warm for Tuesday
afternoon with highs in the upper 70s to mid 80s. A ridge rider
impulse may result in storms again Tuesday late evening into early
Wednesday morning. But mid-range guidance is in very low agreement,
so confidence is also low. Dry during the day Wednesday with highs
again in the upper 70s to mid 80s. Additional shortwaves move
through the pattern the rest of the week, keeping chances for rain
in the forecast. Thermodynamic profiles indicate there is some
strong to severe potential with these, but uncertainty is too high
to speculate on details at this point. Highs for Thursday and Friday
will be in the upper 70s to mid 80s.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1011 PM CDT Sat Sep 6 2025

VFR conditions with light winds continue through the night.
Sunset satellite imagery clearly showed a thin smoke layer
aloft, so will include a high based ceiling in TAF through mid-
morning Sunday.

A few diurnal CU possible again Sunday afternoon, with some
indications that a scattered mid-lvl deck may begin to form and
move northeast Sunday evening.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Frost Advisory until 9 AM CDT this morning for SDZ038>040-
     052>056.
MN...Frost Advisory until 9 AM CDT this morning for MNZ071-080-089-
     090-097-098.
IA...Frost Advisory until 9 AM CDT this morning for IAZ001>003-
     012>014-021.
NE...None.

&&

$$

DISCUSSION...AJP
AVIATION...Dux