Heron Lake, Minnesota Weather Forecast Discussion

570
FXUS63 KFSD 060303
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
1003 PM CDT Fri Sep 5 2025
.KEY MESSAGES...
- Patchy frost will be possible Saturday and Sunday mornings,
  especially Sunday morning. The best chance will be in east
  central SD and southwest MN.
- Next week there are occasional chances for showers and
  thunderstorms, though confidence on timing is low at this
  time. The better chances will be on Monday with a small chance
  for severe storms.
&&
.DISCUSSION...
Issued at 212 PM CDT Fri Sep 5 2025
As the sun sets, diurnally driven cumulus will gradually diminish,
but model soundings do linger a small moist layer around 4-6 kft
through the night so some cumulus could linger overnight. However
the majority should dissipate. With clearing skies and lighter winds
temperatures will be on the cooler side Saturday morning, likely in
the upper 30s to lower 40s. With winds expected to remain around 5-7
mph full radiational cooling is not expected.
Saturday should see cumulus develop in the morning with that small
moist layer with northwest winds about 10 to 15 mph. Another cool
day with highs in the mid and upper 60s.
High pressure fully settles into the area by Sunday morning which
should be the coldest morning with the best chance for patchy frost.
Expect lows in the mid to upper 30s in many locations.
With high pressure in place on Sunday and abundant sunshine a very
pleasant and cool day is expected. Highs generally in the upper 60s
to lower 70s.
Sunday night fairly strong elevated warm advection spreads across
the area. At this time moisture looks a bit scant, but elevated
instability could creep up around 1000 J/kg if enough moisture can
get into the 850-700 mb layer. This could produce scattered showers
and thunderstorms with a low threat for severe storms.
Monday will see significant warming as deeper southerly flow
develops. Models very agreeable on developing 1000-2000 J/kg CAPE by
Monday afternoon into the evening with weak shear, providing the
area with a marginal environment for severe storms. The main factor
will be what appears to be a fairly stout inversion which could keep
updrafts from developing. However with a weak wave expected to move
through some cooler air aloft could help erode any capping, so will
need to keep a chance for thunderstorms in the forecast during this
time. Highs will generally be in the 80s.
Quite a bit of disagreement on Tuesday behind the wave moving
through on Monday. It does look like some ridging will build across
the area so a better chance of remaining dry than seeing and showers
or storms.
Wednesday into Friday most models are fairly aggressive at building
a strong upper level ridging across the Plains which should keep
normal to above normal temperatures in place. With stronger westerly
flow not too far to the west a few thunderstorms will be possible
during this time, especially Thursday night into Friday when the
models begin to break down this ridge.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 955 PM CDT Fri Sep 5 2025
Scattered 8-10K ft AGL ceiling will continue to drift through
the region into mid-morning Saturday. Winds continue to turn
light and variable and will remain so into mid-morning. Some
very localized valley/river fog may be possible, especially in
NW Iowa, at daybreak Saturday.
Similar to Friday, afternoon diurnal CU will develop, but
coverage is likely to be lower than experienced today. VFR
ceilings are expected and a quick decay of clouds will take
place by the evening.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...08
AVIATION...Dux

NWS FSD Office Area Forecast Discussion