Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 231919
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
219 PM CDT Sat Mar 23 2024

.KEY MESSAGES...

- Major Spring storm arriving late tonight and continuing
  through Monday night. All precipitation types likely as well
  as a little thunder. The worst conditions should be along
  highway 14 into central SD.

- Upgraded highway 14 from Marshall to Huron then south into
  central SD to a winter storm warning. Left all other
  headlines as is. May need a watch for I-29 near Sioux Falls
  towards Sioux City later Monday afternoon and night as the low
  wraps up and strong forcing develops along with strong winds.
  Not out of the question to potentially need a blizzard
  warning at some point in time if snow is blowable enough.

- Increased winds on the backside of the system Sunday night
  into Monday, gusts close to 50 mph possible.

&&

.DISCUSSION...
Issued at 218 PM CDT Sat Mar 23 2024

Overall the weak band of snow this evening should mostly be near
parts of highway 14 and near and east of the Buffalo Ridge south
towards Ida Grove. Accumulations will be minor as will the impacts.

Later tonight very strong thermal and moist advection will take
place bringing a large area of precipitation into the area Sunday
morning. Some weak elevated instability will be possible and could
allow for a few rumbles of thunder. Models soundings do hint that
Sunday afternoon and evening will be the best chance for thunder
with elevated CAPE values of 300-500 J/kg given strong lapse rates
in the mid levels and increased low level temperatures and moisture.
The main concerns and challenges for Sunday will be precipitation
type. Every location will see a varying degree of these challenges,
with mainly snow in central SD Sunday and Sunday night, a period of
sleet or freezing precipitation near and south of I-90 in the
morning before turning to rain in the afternoon and night, then near
and north of I-90 mainly snow with some mixed precipitation moving
in late morning into the early afternoon then some rain and snow in
the afternoon and evening. The best chance to remain mainly snow
will be within about 25 miles of highway 14 and points north. Some
of the latest models are wrapping more warm air farther north which
even locations along highway 14 from about I-29 east could see a
period of rain or freezing rain in the afternoon and evening.

Monday will see a dry slot wrap northwest with some pretty strong
forcing and some elevated instability to work with, in the form of
about 500 J/kg CAPE in northwest IA advecting northwest. The
importance of this forcing and instability really play a role in
precipitation rate. And I say precipitation as we are still seeing
the low level thermal profile, about 5000 feet AGL to the surface,
waver with just about any type of precipitation possible. West of I-
29 should be mostly snow with increasing winds through the day.
Blowing snow will likely develop as winds start to increase with
gusts to 40 to 50 mph. Monday into Monday night will see the best
chance for blizzard conditions. Late Monday afternoon into Monday
evening the final surge of pv aloft with a fairly storng dry slot
will surge north and likely allow a final band of potentailly
heavier precipitation to develop. This will be near I-29 and is what
could necesitate an expansion of headlines a little farther south
Monday night.

Storm total liquid QPF still expected to be somewhere in the range
of 1.50-3.00" with this slow moving, very dynamic system. The EC
ensemble, GEFS and Canadian ensembles all indicate means of 2+
inches liquid. In fact the 10th percentile, meaning 90 percent of
model runs are higher, is 1.00-1.33" from southeast SD into
southwest MN. The highest probability for 12+ inches of snow
continues to be near highway 14 and especially into southwest MN.

Upper level ridging builds in behind this system Wednesday into
Thursday. Temperatures will be somewhat dependent upon snow cover,
but expect below normal temperatures on Wednesday then above normal
Thursday all but the deeper snowpack locations. Should be dry both
days.

System expected to move through on Friday with the better dynamic to
the north. Precipitation chances are on the lower side but worth
watching given how much precipitation is expected Sunday and Monday.
Friday and Saturday both look to be on the mild side but still
recovering over the deeper snowpack.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1144 AM CDT Sat Mar 23 2024

Mostly VFR conditions through the evening. Some spotty MVFR
conditions where patchy light snow exists, mainly near and east
of highway 81. Much stronger forcing arrives overnight and
continues into Sunday. IFR conditions will become likely on
Sunday morning with all types of precipitation possible,
including rain, freezing rain, sleet and snow. The morning will
see the better chance for freezing precipitation, especially
south of I-90, while areas north of I-90 will see a better
chance for mainly snow. Through the morning the freezing rain
will likely transition to mainly rain as temperatures warm into
the 30s.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from 7 AM to 7 PM CDT Sunday for
     SDZ062-067.
     Winter Weather Advisory from 1 AM to 1 PM CDT Sunday for
     SDZ050-063>066-068>070.
     Winter Storm Warning from 4 AM Sunday to 7 AM CDT Tuesday for
     SDZ038>040-052-053-057>059.
     Winter Storm Watch from Sunday evening through Tuesday morning
     for SDZ050-063>065-068.
     Winter Storm Watch from late tonight through Tuesday morning
     for SDZ054>056-060-061.
MN...Winter Weather Advisory from 7 AM to 7 PM CDT Sunday for
     MNZ089-090-098.
     Winter Storm Warning from 7 AM Sunday to 7 AM CDT Tuesday for
     MNZ071-072.
     Winter Storm Watch from Sunday morning through Tuesday morning
     for MNZ080-081-097.
IA...Winter Weather Advisory from 7 AM to 7 PM CDT Sunday for
     IAZ001.
NE...Winter Weather Advisory from 1 AM to 1 PM CDT Sunday for
     NEZ013.

&&

$$

DISCUSSION...08
AVIATION...08


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