Spencer, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

697
FXUS63 KFSD 101931
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
231 PM CDT Tue Jun 10 2025

.KEY MESSAGES...

- Morning showers and isolated thunderstorm Wednesday give way
  to increased risks for thunderstorms south of I-90 Wednesday
  between 3pm and 10pm. Conditional risks for severe weather
  with large hail (1.5") and isolated strong wind pockets (60-70
  mph).

- Thunderstorm risks continue into Thursday morning, slowly
  shifting northward. Persistent marginal hail risks along with
  some potential for locally heavy rainfall are expected. Exact
  locations remain uncertain, though favor areas along and north
  of I-90 in to SW Minnesota.

- Forecast has trended more unsettled for Thursday with warmer
  temperatures and risks for isolated to scattered severe storms
  in the afternoon/evening.

- Temperatures rise through the upcoming weekend, bringing
  additional thunderstorm risks by Sunday and into next week.
  Monitor for strong storm potential.

&&

.DISCUSSION...
Issued at 227 PM CDT Tue Jun 10 2025

THIS AFTERNOON:  Hot and dry conditions continue to build into the
Tri-state area as surface winds turn west to southwesterly.  High
temperatures are likely to top the 90 degree mark along and
west of I- 29. Smoke aloft continues to remain thin, and is not
having any impact on temperatures given the degree of mixing.

TONIGHT: Rather messy westerly mid-lvl flow begins tonight, with the
first of many subtle vorticity maxima exiting the Rockies and moving
into the Dakotas later tonight. While low-mid lvl moisture is
considerably lacking tonight, a 30 to 35 knot southerly LLJ will
begin to transport moisture into South Dakota overnight.  The
combination of mid-lvl dPVA and convergence on the LLJ should
isolated to scattered high based showers and isolated thunderstorms
stretching west to east across the state (mainly along or north of I-
90) through the night. Meanwhile a surface front already sinking
into north central SD this afternoon, will continue to push
southeast overnight reaching the Highway 20 corridor by daybreak
Wednesday.

WEDNESDAY:  The aforementioned front will become a focal point for
convection later Wednesday afternoon and evening.  Meaningful
surface moisture (dewpoints higher than 60F) currently over
Oklahoma, will begin to transport northward overnight, reaching this
boundary and seeping slightly north of the boundary through
Wednesday morning. CAMS all fairly confident on a mid-lvl
impulse arriving into eastern SODAK by mid-afternoon, which when
combined with the arrival of convective temps, should be enough
to spark isolated to scattered convection within a narrow
corridor of 1800- 2500 J/KG MLCAPE. With stronger westerly
residing north of I-90, the primed area for convection will be
on the southern edge of stronger effective shear. Nevertheless
30 to 35 knots of shear may be enough to promote a few multicell
clusters to even a storm or two with supercellular
characteristics moving east to northeast. The prime hazards
will be 1.5-1.75" hail, with lingering mid-lvl dry air
suggesting pockets of strong wind gusts in the immediate
vicinity of the front. Overall tornado parameters remain low
near Highway 20, however if a storm would happen to cross north
over the boundary, stretching could be enough to produce a brief
weak tornado. If storm coverage projections increase, then
overall severe risk levels may also increase.

WEDNESDAY NIGHT: Storms should use up MUCAPE fairly quickly in the
evening, with the greater severe weather risk diminishing by 9pm.
However, then we`ll watch for the northward retreat of the low-lvl
front and increase of the LLJ after dark. Signals in model guidance
continue to suggest that elevated convection will begin to
increase in coverage late in the evening, though uncertainty on
if this area will be south or north of I-90 continues. The
rapid influx of moisture Wednesday night (PWATS AOA 170% of
normal), combined with modest LLJ convergence on the 850
boundary, lingering 1000-1200 J/KG MUCAPE, and slightly parallel
storm motion along the boundary would promote both a marginal
hail risk but moreso a heavy rain risk. HREF LPMM suggest
potential for 2-4" rain totals in very localized pockets.
Currently focused highest PoPs near or north of I-90, with focus
for heaviest rain in SW Minnesota.

THURSDAY:  A stronger mid-lvl trough ejects out of the Rockies early
Thursday.  Model guidance remains split on just how far north the
850 and surface front will retreat in the morning, with some
guidance pushing the front all the way to northern SODAK, and others
holding it closer to I-90.  This may have a significant impact on
the forecast overall with southern solutions locking in more
persistent moderate rain through the day and cooler overall
temperatures. Northern solutions unlock a stronger warm sector,
keep most of Thursday dry, and bring a much greater risks for
severe storms to areas west of the James River and along the
Buffalo Ridge in the afternoon. The ECMWF and it`s ensembles
remain further south with the GFS/CMC ensembles both further
north with the elevated front. Regardless of solution, available
moisture remains strongly elevated, and any convection should
produce high rainfall rates. Greatest excessive rainfall risks
are likely to remain north of I- 90.

FRIDAY-SATURDAY: Troughing should move east of the area on Friday,
with a slight cooldown during the daytime hours and a northerly
wind.  Ridging moving back into the Plains for Saturday, along with
high pressure over the Great Lakes, will keep temperatures near
seasonal normals Saturday.

SUNDAY-MONDAY: Quite a bit of uncertainty remains in the forecast
for the end of the weekend and start of next week, though guidance
continues to support an overall increase in the regional severe
weather risks. Increasing mid-lvl ridging through the Central
Plains will begin on Sunday, allowing one or more subtle waves
to cross the ridge. Given moisture return, this might be a
favorable MCS setup for the Dakotas, along with above normal
temperatures. It`s also possible to see some elevated convection
on the nose of the moisture return Sunday morning.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1153 AM CDT Tue Jun 10 2025

VFR conditions with light elevated smoke layer continue into the
evening hours. A broken mid-lvl cloud deck will form over the
northern half of South Dakota later this evening and overnight,
with widely scattered showers moving along Highway 14 into early
Wednesday. The passage of a weak cold front will bring easterly
winds to most of the CWA north of Highway 20 by mid-morning
Wednesday.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

DISCUSSION...Dux
AVIATION...Dux