Le Mars, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

205
FXUS63 KFSD 141143
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
643 AM CDT Mon Apr 14 2025

.KEY MESSAGES...

- Colder with scattered showers/thunderstorms this afternoon.
  Some storms may contain tiny hail. There is a also a very low
  (<20%) potential for a rain/snow mix in higher elevations of
  east central South Dakota/southwest Minnesota.

- Northwest winds remain gusty today. Widespread gusts 40 to 45
  mph are expected, but showers/storms have potential to bring
  down pockets of 50+ mph winds. A Wind Advisory has been issued
  for all areas from 11 am through 7 pm today.

- Increased rain chances (40-60%) are seen by Thursday-Thursday
  night. Scattered storms are possible, but uncertainties remain
  on northward extent of potential for strong to severe storms.

&&

.DISCUSSION...
Issued at 425 AM CDT Mon Apr 14 2025

TODAY: Gusty northwest winds remain at the forefront of today`s
challenges. Our anticipated overnight surge of stronger gusts
has come and gone and winds will ease slightly through daybreak
to mid morning. Attention then turns to an advancing shortwave
rotating around the back side of the mid-upper trough as it
moves slowly east into the Great Lakes/southwest Ontario. Much
colder air has settled into the region, especially aloft with
sub-zero 850mb temperatures over most of the forecast area
today. This is resulting in low convective temperatures with
additional lift provided by the aforementioned shortwave which
will drop south across the area this afternoon. Expect isolated
to scattered showers to expand southward during the early to mid
afternoon, slowly diminishing as we approach sunset and the wave
moves off to the southeast. The low freezing level topped by a
tall but very skinny CAPE profile could support graupel/small
hail with more robust showers along with a threat of lightning.
Our higher elevations in east central South Dakota/southwest
Minnesota may also see the surface-based "warm" layer cool
enough with the convective activity to maintain a rain/snow mix
at times, though accumulation is not expected.

As far as wind speeds, general synoptic mixing would flirt with
advisory-level wind gusts with soundings generally supporting
mixed layer momentum transport around 30-35+kt. However, taller
showers/storms would tap into stronger winds and potentially
bring localized gusts topping 50 mph to the surface. As such,
have issued a Wind Advisory from late morning through about
sunset across the forecast area. The colder air mass along with
scattered showers should keep humidity levels above critical
levels for most areas this afternoon. However, locations along
the Missouri River Valley are expected to see lesser coverage
of showers as humidity values drop to 25-30% this afternoon and
have transitioned the Fire Weather Watch to a Red Flag Warning
in these areas.

TONIGHT-WEDNESDAY: Relatively quiet period as weak upper level
ridging bringing warmer and drier air back to the region. Winds
will be on the lighter side Tuesday, especially west of I-29
where humidity levels are at their lowest. Elevated fire danger
returns Wednesday as southerly flow begins to increase, but at
this time conditions look to remain shy of critical levels.

THURSDAY-THURSDAY NIGHT: This becomes our next period of focus
as the pattern evolves to southwest flow aloft. Warm advection
and a lead shortwave sliding northeast Thursday morning could
produce elevated showers or storms during the latter half of
Wednesday night into Thursday morning. At this time it appears
the potential for strong to severe storms with this activity is
low, though steep lapse rates above 850mb could support small
hail. More questions as to how things will then evolve through
the afternoon and evening, with models showing less agreement
than was seen at this time yesterday. Decent consensus showing
increasing mid-upper level winds leading to increasing deep
layer shear across Nebraska/Iowa by late in the day. However,
placement of the surface warm front is uncertain (could be near
or south of Highway 20, or lift as far north as Highway 18 in
northwest Iowa). A stout capping inversion may limit potential
of stronger storms from developing north of the boundary, so
while rain chances are moderate (40-60%), confidence in details
regarding stronger storms is low.

FRIDAY-SUNDAY: Models diverge on how the upper level pattern
will evolve as we progress into next weekend. Decent agreement
that cooler air will again settle southward Friday, but just how
cold and how long it will persist is in question. Attention
then turns to a trough ejecting out of the southern Rockies.
More aggressive solutions could spread rain back into the region
by Sunday, while weaker/slower solutions favor a dry weekend
with rain chances holding off until Monday or perhaps sliding
east of the area altogether.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 641 AM CDT Mon Apr 14 2025

Low-level stratus will continue to impact our area to start the
period, but MVFR ceilings should begin gradually lifting from west
to east through the morning hours. MVFR stratus may linger a bit
into the afternoon for mainly southwest Minnesota. Scattered showers
look to develop this afternoon into the early evening, bringing
ceilings down to MVFR to near-MVFR at times. Otherwise broken to
overcast ceilings between 35-60 kft will be the norm this afternoon.
Isolated thunderstorms cannot be ruled out within this activity, but
chances are too low to warrant mentioning in the TAFs at this time.
We`ll be watching trends closely throughout the day. Rain chances
exit off to the east this evening, taking most of the clouds with it
and leaving mainly clear skies to end the TAF period.

Northwest winds continue to be an issue today, with gusts as high as
30-40 kts at times area-wide this afternoon. Those showers that are
possible today could also mix down 40+ kt gusts to the surface.
Winds will gradually diminish after sunset and will be much
lighter to end the period.

&&

.FIRE WEATHER...
Issued at 425 AM CDT Mon Apr 14 2025

Northwest winds gusting 40-45 mph are expected to develop again
by late this morning. Colder temperatures and scattered showers
will result in higher humidity levels (35-50%) for much of the
area, keeping fire danger below critical levels. However, areas
along the Missouri River Valley will see drier air with lower
chances of shower activity. Relative humidity as low as 25-30%
along with the gusty winds will create critical fire weather
conditions and a Red Flag Warning will be in effect from 1 PM
through 8 PM today. Please note that any showers will bring a
potential for erratic stronger gusts, perhaps topping 50 mph,
which could further enhance fire spread.

Lighter winds will ease the fire danger on Tuesday. However,
breezy south winds and dry air will again produce High to Very
High grassland fire danger Wednesday. The week will end with
increasing humidity levels as rain chances increase across the
area Thursday into Thursday night.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from 11 AM this morning to 7 PM CDT this evening
     for SDZ038>040-050-052>071.
     Red Flag Warning from 1 PM this afternoon to 8 PM CDT this
     evening for SDZ050-063-068>071.
MN...Wind Advisory from 11 AM this morning to 7 PM CDT this evening
     for MNZ071-072-080-081-089-090-097-098.
IA...Wind Advisory from 11 AM this morning to 7 PM CDT this evening
     for IAZ001>003-012>014-020>022-031-032.
     Red Flag Warning from 1 PM this afternoon to 8 PM CDT this
     evening for IAZ031.
NE...Wind Advisory from 11 AM this morning to 7 PM CDT this evening
     for NEZ013-014.
     Red Flag Warning from 1 PM this afternoon to 8 PM CDT this
     evening for NEZ013-014.

&&

$$

DISCUSSION...JH
AVIATION...Samet
FIRE WEATHER...JH