Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 260346
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1046 PM CDT Mon Mar 25 2024

.KEY MESSAGES...

- Major Spring storm begins to wind down across the region,
  with all snow expected to continue west of I-29, and a mix of
  all precipitation types along and east of I-29.

- Blizzard and Winter Storm Warnings have been transitioned to a
  Winter Weather Advisory late this evening.

- Expanded the Winter Weather Advisory to include the rest of
  the area for the expected mixed precipitation, which will
  leave behind light snowfall and a light glaze of ice.

&&

.UPDATE...
Issued at 901 PM CDT Mon Mar 25 2024

Have transitioned the Blizzard and Winter Storm Warnings for our
counties in south central SD and along the Hwy 14 corridor to a
Winter Weather Advisory. Although winds have been gusting to
around 45 mph at times and will continue to do so through the
night, visibility as remained well above one quarter mile.
Across the area, an additional inch or less of snow is expected
into Tuesday morning, with locally higher amounts possible in
southwestern MN. Could see a glaze to a tenth of an inch of ice
across northwestern IA, with mixed precipitation and temps
near/just above freezing. Have seen some fog reducing visibility
to half a mile or less across portions of southwestern MN as
well.

Main concerns through the night remain the hazardous travel
conditions, as snow and slush on roadways freezes with temps
falling into the teens and 20s tonight into tomorrow morning.
Those with travel plans should continue to check road and
weather conditions before heading out.

&&

.DISCUSSION...
Issued at 347 PM CDT Mon Mar 25 2024

Our strong spring storm continues to impact the area, with the
highest precipitation chances and amounts now behind us. Areas
generally west of a line from Yankton, SD to Sioux Falls, SD to
Marshall, MN will continue to see chances for snow, while areas
along and just east of that line will see snow with chances for
freezing rain and ice pellets mixing in, and areas in NW IA and
adjacent will largely continue to see rain throughout the day. On
the extreme northern point of the inverted trough, a narrow corridor
of thunderstorms have developed in western Iowa, but with the
surface front having moved through our Ida/Cherokee/Buena Vista
counties, not expecting these thunderstorms to impact our area.

As the 925/850mb frontogenesis currently extends from southwest
Minnesota through northwest Iowa and into northeast Nebraska, mid-
afternoon radar is showing our precipitation northwest of the front
starting to decrease. This is due to the moisture advection starting
to decrease in the wrap-around flow, with the deformation band also
weakening. We`ll see renewed chances for precipitation this evening
into the overnight period as the vorticity lobe from the upper level
low  moves overhead, with a surface high pressure moving towards the
region from the northwest. This surface high will be shoving the
rain/snow line eastwards throughout the overnight period, with the
thermal profiles determining what the precipitation types will be.
As we`ve been observing, areas along the rain/snow line have been
mixing in freezing rain and/or sleet at times, so expect this mixed
precipitation to occur overnight as it moves eastwards. Given that
the transition from rain to snow will take a few hours, have
expanded the winter weather advisory to account for the light
ice/sleet accumulations in addition to the light snowfall. With both
the blizzard and winter storm warnings continuing into the Tuesday
morning, we encourage you to remain prepared for slick roads,
reduced visibilities, or a combination of both. If you must commute,
remember: Ice and Snow, Take it Slow!

By Tuesday morning, the surface low will have moved off to our east,
which will continue the strong north-northwesterly winds with gusts
30 to 40 mph. Given the strong winds, there remains some uncertainty
on how "blowable" the freshly fallen snow is, but based on some
public feedback we are hearing it is rather wet/heavy/mushy. So, not
expecting this snowpack to be able to be lofted, and with snowfall
decreasing throughout the morning hours, the headlines look to
remain in good shape to expire at 7 AM Tuesday. With the continued
north-northwesterly winds, highs for Tuesday will be in the mid 20s
to lower 30s, and the breezy winds resulting in wind chills topping
out in the 5-15 degree range.

The surface high continues to drift southeastwards, with the center
of the high looking occur right overhead by the end of the day on
Wednesday. This will result in mostly sunny skies and light winds,
with temperatures likely in the mid 20s lower 30s for those that saw
a decent amount of snow, and in the mid 30s to lower 40s for those
that didn`t. Upper level ridging into Thursday will keep us dry and
warm, with some shortwaves into Friday bringing the possibility of a
weak surface low pressure into the region and our next chance for
precipitation. Ensemble clustering analysis doesn`t offer much
assistance in determining additional details, largely due to their
fairly even split of having 35/31/24/10% of members respectively.
Have thus left the NBM pops as is, which keeps 20-40% pops largely
for areas east of I-29 on Friday.

Zonal flow sets up for the weekend, though we`ll have to see where a
stationary frontal boundary sets up from previous surface low to see
what our temperatures end up being. Some indications we could see
additional precipitation chances on Sunday from some weak
shortwaves, but again confidence is not high in solutions that far
out at this time.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1038 PM CDT Mon Mar 25 2024

MVFR and lower ceilings expected with stratus through much of
the period, improving to lower VFR by Tuesday evening. An area
of snow stretches from south central SD into northeastern SD and
southwestern MN, with a secondary area of mixed precip across
northwestern IA. Expect this precip to continue to pivot over
the area overnight, with precipitation eventually turning to
snow in northwestern IA. Precipitation should exit the region
by mid morning (around 15z), although flurries may linger into
the late morning across southwestern MN.

Strong northwest winds gusting to 35 knots may create blowing
snow and additional visibility restrictions with falling snow,
into the IFR category. Areas with more snowfall as well as
those at higher elevations may see visibility briefly
fall to less than one mile. Expect conditions to improve
through the day into Tuesday evening as winds decrease.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 7 AM CDT Tuesday for SDZ038>040-
     050-052>071.
MN...Winter Weather Advisory until 7 AM CDT Tuesday for MNZ071-072-
     080-081-089-090-097-098.
IA...Winter Weather Advisory until 7 AM CDT Tuesday for IAZ001>003-
     012>014-020>022-031-032.
NE...Winter Weather Advisory until 7 AM CDT Tuesday for NEZ013-014.

&&

$$

UPDATE...SG
DISCUSSION...APT
AVIATION...SG


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