Lyonville South Dakota Weather Forecast Discussion

886
FXUS63 KFSD 121151
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
651 AM CDT Sun Oct 12 2025
.KEY MESSAGES...
- Breezy conditions today (gusts 25-35 mph, locally up to 40
  mph) and warmer temperatures could lead to elevated fire
  weather concerns. However, higher relative humidity values and
  rain chances will help prevent a more widespread fire weather
  threat.
- After a warm day today with highs in the mid-70s to low-80s,
  expect a return to near to below normal temperatures to start
  the work week.
- An active pattern may promote continued rain chances
  throughout much of this week starting on Tuesday, but
  confidence in any details is low at this time.
&&
.DISCUSSION...
Issued at 412 AM CDT Sun Oct 12 2025
Showers continue to move through the area this morning, aided
by a 850 mb LLJ of 50-60 kts. Not all the rain has reached the
ground due to a dry sub-cloud layer, but continued rainfall and
the southerly LLJ should help moisten up the low levels through
this morning to allow for better ground coverage by daybreak.
Still, not expecting a lot this morning, with most spots seeing
less than a tenth of an inch of rain. If a storm can develop
within this weakly unstable environment, than perhaps you could
see up to .15" or so. For today, a trough will eject through the
northern Plains and help drag a cold front through the area.
Additional shower development is possible this afternoon and
evening along the cold front and in the immediate post-frontal
environment before the low-levels dry up again. The best chance
of this redevelopment will be along and east of I-29 where the
low-levels will be a bit more saturated and so some spots may be
able to pick up another few hundredths to a tenth of an inch of
rain. So all told, most areas will see anywhere between 0.05 to
0.15," today, with locally higher amounts of 0.2" possible in a
spot that sees a thunderstorm. Severe weather is not expected.
Highs will be warm today in the mid-70s to low-80s due to strong
southerly flow ahead of the front and the fact that we will
likely see more breaks in the cloud cover than compared to
yesterday. It will be breezy today, with gusts up to 30-35 mph,
with some spots locally seeing a gust up to 40 mph. These winds
could lead to an elevated fire weather threat in spots, but
higher relative humidity values and rain chances will help
prevent a more widespread fire weather threat. Winds will drop
off quickly after sunset and any rain will come to an end from
west to east this evening into early tonight as the low- levels
dry up again. Cooler air filters in behind the frontal passage
and so temperatures will drop into the mid-30s to mid-40s,
coldest north of I-90 and west of I-29. There could be some
patchy areas of frost by tomorrow morning mainly along the
Highway-14 corridor from the Brookings-area into central South
Dakota in the Chamberlain-area.
Heading into tomorrow, another upper-low and its associated
trough will dive into the Pacific Northwest. Downstream of this,
guidance indicates a weak upper-wave moving in from western
Nebraska into our area. There could be a few light showers associated
with this tomorrow morning after sunrise, but dry low- level
air should win out and so kept PoP`s very low (10% or less) for
areas south of I-90. Another wave looks to move in later
tomorrow into tomorrow night. Once again, a stout layer of sub-
cloud dry air will be in place, but guidance indicates better
coverage and more persistent showers which will likely saturate
the low-levels enough to increase rain chances heading into
Tuesday. Models are a bit split in how much rain we could see
into Tuesday, so will keep the 30-50% PoPs from the NBM in for
now.
For Wednesday into Wednesday night, a low pressure system will develop
out of the Rockies and lift northeastward into the western Dakotas,
with a cold front draped southward from it. This will help
increase rain chances for our area especially Wednesday night
into Thursday, but confidence is low as details on development
of this system are highly uncertain owing to it being several
days out. Switching gears to temperatures this upcoming work
week, temperatures will be near to below average through
Tuesday, but another warm-up may be in tap for the middle of the
week as some ridging aloft may build back into the area as we
will be on the northern periphery of an upper-level high
pressure system centered over Texas. Temperatures may cool-off
again heading into next weekend as most guidance shows ridging
being replaced with general troughiness.
&&
.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 650 AM CDT Sun Oct 12 2025
Scattered showers and isolated storms are moving through areas along
and east of I-29 to start the period and will continue pushing east-
northeast through the morning hours. Can`t entirely rule out
isolated lightning strikes at KFSD with some of the higher radar
returns through about 13z, but should remain sparse. Additional
showers are expected to develop this afternoon into the evening
hours, but should remain quite scattered in nature and thus the
PROB30 groups at KFSD and KSUX will do at least for now. Can`t
entirely rule out some drops to MVFR CIGS with this late day
activity, but not enough of a chance to include in the TAFs. There
may be some radar returns between roughly 22Z and 00Z near
KHON, but did not include a PROB30 group for it because there
will be plenty of dry air below the cloud deck to allow for any
rainfall to evaporate on its way down.
Winds will be gusty today as a southerly 50-60 kt LLJ continues
across the area, leading to LLWS concerns to start the period. The
LLJ should gradually wind down throughout the day from west to east.
Winds at the surface will peak around 30-35 kts through this
afternoon before also gradually winding down into the evening. A
cold front will be moving through the area from west to east late
this morning through the afternoon, turning winds from the
south/southeast to the northwest.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...Samet
AVIATION...Samet

NWS FSD Office Area Forecast Discussion