Lismore, Minnesota Weather Forecast Discussion

817
FXUS63 KFSD 131856
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
156 PM CDT Sat Sep 13 2025
.KEY MESSAGES...
- Temperatures remain well above normal through the weekend and
  into early next week.
- Convection chances remain low into Sunday morning, however
  chances do increase Sunday afternoon into Sunday night. A few
  storms will be possible in central SD tonight.
- Conditional risks for isolated severe storms develop Sunday
  afternoon into the evening. Marginal hail and brief strong
  wind gusts are the primary risks.
- Next reasonable risk for rain arrives Tuesday and continues
  through Wednesday, with cooler temperatures the second half of
  next week.
&&
.DISCUSSION...
Issued at 152 PM CDT Sat Sep 13 2025
THIS AFTERNOON:  Surface low continues to linger west of the James
River this afternoon, with cooler and more stable air pulling into
far South Central South Dakota. Further east, temperatures continue
to soar through the 80s and into the 90s as a secondary warm
front accelerates north towards Highway 14. Deeper mixing
throughout the Tri-State area, and impacts of drying vegetation
and recent lack of rain, is dropping dew points into the lower
60s, This dew point drop offset with higher temperatures is
resulting in heat index values near the middle to upper 90s.
TONIGHT: Convection risks begin to increase over western South
Dakota and Nebraska this evening as an upper wave pivots northward
through the Plains.  Generally most of the convection risks are
likely to stay west of the CWA, with an outside risk of an elevated
thunderstorm lifting northward through South Central South Dakota
towards or after midnight.  Further east, winds may briefly turn
light and variable at times, potentially leading to minor
fog/stratus in the higher elevations of the Ridge.
SUNDAY-SUNDAY NIGHT:  Models remain mostly in agreement through
Sunday, with minor timing differences remaining in arrival of
vorticity lifting northward through the Plains at mid-day.  Outside
of lingering morning showers west of the James River, variable
mid- upper cloud cover is anticipated further east into the
early afternoon hours. This cloud cover brings some uncertainty
on just how unstable we`ll grow across the CWA in the afternoon.
CAMS have backed off on overall MLCAPE values, only approaching
800-1200 J/KG of thin CAPE in most areas by 2-4pm. However the
increasing synoptic lift, slight surge in 850mb winds, and
boundary layer confluence (east of the James River) may lead to
the development of isolated to scattered storms by mid-late
afternoon. Greater focus is likely to take place along and west
of the James River, where instability may actually be lower, but
convergence higher. With freezing levels AOA 13-14K feet and
mid-lvl lapse rates only near 6 C/KM, feel that hail size should
be limited. However modest effective shear of 35 to 45 knots,
with increasing 925:850mb flow, and slight dry layer at 700 mb
could promote a few stronger wind gusts in multi-cell to briefly
supercellular storms. Again though, instability remains very
questionable. Should a bit more 0-5km CAPE form, given the
increase in LVL helicity near the western boundary, a brief TOR
could not be ruled out. The loss of daytime heating should lead
to a continue downtrend in convection by and after sunset, with
dry conditions moving into the region overnight.
MONDAY: The upper trough pivot over North Dakota on Monday, with
broad southwesterly surface flow lingering over the Tri-State area
on Monday.  Temperatures again rise into the 80s and for most areas
no convection is anticipated outside of lingering early day showers.
TUESDAY-FRIDAY: Longwave troughing remains centered from central
Canada into the Rockies through the middle of the week. By Tuesday
an extended surface front from eastern North Dakota through Central
South Dakota and into Western Nebraska. The buildup of
instability Tuesday afternoon could lead to a few thunderstorms
along this front in the western CWA, through the lack of shear
should preclude widespread severe weather. This aligns with the
very low probabilities of severe weather depicted by machine
learning severe weather guidance.
The track and orientation of the upper trough by Wednesday will
determine the lingering risks for convection into the
Wednesday/Thursday timeframe. There remains quite a bit of
difference between the ECMWF/GFS/CMC mostly centered around the
timing of the trough and any embedded waves within it. Precipitation
chances remain spread through the end of the week, but it
certainly doesn`t look like the entire 2nd half of the week
will be filled with rain, but more sporadic rain chances.
Confidence is much higher that we`ll see a drop in temperatures
Wednesday onward with highs near to slightly below normal in the
70s.
&&
.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1200 PM CDT Sat Sep 13 2025
VFR conditions expected into the overnight hours. Southerly
winds may occasionally turn gusty as a few afternoon CU develop.
In South Central South Dakota, the intrusion of cooler westerly
air will allow lower stratus to persist into mid-afternoon.
Tonight, a low end risk for scattered showers and thunderstorms
in central South Dakota may bring lowering ceilings to the HON
area, otherwise VFR conditions are likely elsewhere with a
variable to southerly wind.
We`ll have continued cirrus in the sky on Sunday morning, with
perhaps some lingering mid-lvl clouds moving into areas west of
the James River. A few showers may also accompany these clouds,
but greater rain chances look to hold off until Sunday
afternoon. Winds will likely turn gusty by mid-late morning
Sunday as mixing rapidly increases.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...Dux
AVIATION...Dux

NWS FSD Office Area Forecast Discussion