269
FXUS63 KFSD 061159
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
559 AM CST Fri Mar 6 2026

.KEY MESSAGES...

- Isolated small hail up to quarter size could be possible in
  northwest Iowa through mid-morning. Similar conditions this
  afternoon to early evening, with slightly higher potential for
  50 mph winds.

- Rain/Drizzle will transition to a wintry mix then snow from
  west to east today through this evening. A glaze to over 0.10"
  of ice (greatest in southwest Minnesota), flash freeze, and
  areas of 1-3" of snow (greatest in south-central South Dakota.

- Above normal temperatures will dominate the week ahead with
  occasional low precipitation chances.

&&

.UPDATE...
Issued at 330 AM CST Fri Mar 6 2026

As of 3 AM, cold front has progressed into our far western
counties, currently located near to just east of Huron to Platte
SD line. This is a little quicker with temperatures dropping
more sharply behind the front than previously forecast. HRRR
seems to have the best handle on this and have blended more of
the HRRR into temperatures going forward into this afternoon.

There have been no changes to the severe weather outlook this
morning, though a faster frontal timing may temper the northwest
extent of any risk, so please monitor for updates through the
day.

Previous shift had already accounted for somewhat faster frontal
timing with adjustments to precipitation types/expansion of the
Winter Weather Advisory for today/tonight, and made only minor
tweaks to p-type transitions/amounts this morning. Although
these updates resulted in some light ice accumulation in our far
southeast, confidence in this icing potential for Sioux City to
Storm Lake remains low and no adjustments to the Winter Weather
Advisory are planned early this morning. Next shift will want
to look closely at latest guidance to determine whether a short
advisory for icing will be needed in these areas. Fortunately,
the overall air mass remains relatively mild with even the 10th
percentile NBM showing temperatures climbing above freezing by
Saturday afternoon with many areas in the upper 30s to mid 40s.
So aside from potential impacts of more substantial snow cover
(2-3" possible in south-central South Dakota), travel impacts
from overnight icing may ease by the latter half of Saturday.

Issued at 821 PM CST Thu Mar 5 2026

We`re continuing to see low-mid level moisture surge northward
across Nebraska and western Iowa this evening.The OAX/UEX/FSD
VWP show the LLJ increasing towards the 35 to 40 knot range.
Short term CAMs continue to increase scattered shower and
thunderstorm coverage by midnight along the MO river valley and
into NW Iowa. While there is considerable effective shear, a
fairly thin and tall MUCAPE profile only approaching 800 J/KG
may limit strong storm potential. Freezing level AOA 10K FT are
also seasonally high. That said the greatest potential will
develop after 3am and may continue through 8am. Mostly small
hail will be likely, but a very isolated storm could produce
quarter size hail.

Further west we`re already seeing the cold front expected to
move southeast late Friday, stretching across central South
Dakota. One big change from guidance earlier today is surging
colder air much faster to the Southeast. After initial rain
moves northeast through Iowa this morning, we should see
development of drizzle followed by renewed showers along and
west of the James River by mid-morning as a tightening frontal
circulation develops. A slight low-lvl ridge may actually back
the baroclinic zone westward in the morning, leaving a greater
risk of freezing drizzle/rain to develop west of the James River
by mid-morning.

Once deeper troughing ejects northeast into the Plains, we`ll
again see redevelopment of convection along the advancing cold
front, likely just along the far southeastern edge of the CWA.
Further west, forcing along the low-lvl frontal zone will
increase further, inducing fairly widespread wintry mix that
will turn to snow into the late evening and overnight.

Given the soundings, and likely faster surge of colder air
southeast, have increased ice coverage over most areas to a
glaze to tenth of an inch. Have also increased snowfall amounts
slightly and increased the potential for sleet (and a non-zero
risk for thundersleet in the evening). Adjusting these elements
has led to advisory expansion and adjustments in timing for
Friday.

One thing to note is that if we see a quick 1-3" of snow, then
temperatures on Saturday may also trend lower.

&&

.DISCUSSION...
Issued at 337 PM CST Thu Mar 5 2026

Mid to upper clouds are building in ahead of an approaching wave
this afternoon. Breezy southerly winds will gradually decrease
through the evening. Lows for tonight will fall into the low 30s to
mid 40s, with the warmest temperatures over northwestern Iowa.
Tonight WAA and an increasing LLJ may be enough to trigger showers
and thunderstorms, most likely beginning after midnight. Some of
these could be strong to severe with 500-1000 J/kg of tall and thin
MUCAPE, and 40+ kts of 0-6 km bulk shear. ESAT tables indicate
precipitable water to be at >99% for climatology from 06.06Z through
07.06Z. Considering this, rainfall could be heavy at times under
stronger thunderstorms. By Friday morning rain totals of 0.2" to
0.4" are possible for eastern South Dakota with the highest as you
move east. Areas in southwestern Minnesota and northwestern Iowa may
see 0.5 to 0.75" in total. As far as the severe threat is concerned,
despite some convective parameters being on the favorable side the
weak instability may limit severe storms to just one or two isolated
thunderstorms. The main threat with any that do become severe will
be heavy rain, hail up to the size of a quarter (1 inch), and
possibly wind gusts in excess of 60 mph. The main area of concern is
for areas east of I-29 in northwestern Iowa and eastern Nebraska.
Severe risks diminish around daybreak Friday.

A surface low pressure will move through the region dragging a cold
front with it early Friday morning. Strong CAA in the 925-850 mb
layer rapidly decrease temperatures there 10-15 degrees C. This will
help to bolster gusty northerly winds behind the front. Areas along
and west of the James River Valley will experience the strongest
gusts of 30-40 mph. Through the day stronger winds push east of I-29
but will be slightly lower at 20-30 mph. In addition rain showers
and weak thunderstorms will become scattered to numerous through the
day as the main vorticity lobe of the wave moves northeast. With
this comes an increase in instability and renewed chances for
strong to severe thunderstorms for areas east of I-29 in
northwestern Iowa. The main threats will once again be brief
heavy downpours, hail to the size of a quarter, and to a lesser
extend damaging wind gusts of 60+ mph. An additional 0.1 to
0.25" are possible with the highest again being east of the
SD/MN/IA border. Eventually rain will change over to freezing
rain/drizzle or sleet to a wintry mix before becoming all snow
overnight.

The timing of the change over remains uncertain due to timing
differences in the cold front passage in the short term guidance.
About half of the guidance has the front over central South Dakota
around to shortly after midnight tonight. While the other half
indicate a slower passage around or shortly after 6 am Friday. This
6 hour difference continues as the front progresses through eastern
South Dakota and into western Minnesota and Iowa. This leaves
uncertainty in ice and snow totals very high at this time. One thing
that does appear more certain at this time is an area of prolonged
freezing rain and drizzle for portions of east central South Dakota,
southwestern Minnesota, and northwestern Iowa. Here there may be
between 0.1 to 0.2 inches of ice accumulations before switching
over to snow. For this reason, a Winter Weather Advisory has
been issued from 3 pm Friday through 9 am Saturday morning. Snow
moves clear of the area by late morning Saturday.

Saturday afternoon skies will clear and we will warm into the 40s to
50s. Sunday a high pressure skirts to our south, turning winds
southwesterly and increasing WAA. Highs will warm into the 60s and
winds will be diurnally breezy gusting 20-25 mph. Flow aloft becomes
slightly more zonal for Monday. A short wave passes along the US/CAN
border which will give a weak push of CAA that cools highs to the
50s for areas north of I-90, 60s to the south both Monday and
Tuesday. Wednesday brings another chance for rain with cooler highs
in the 40s. Then things dry out and warm again into the 50s and 60s
for the remainder of the week.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 557 AM CST Fri Mar 6 2026

Complex forecast this morning with a variety of weather expected
over the next 24 hours. Beginning the day with thunderstorms and
brief heavy rain in portions of northwest Iowa, mainly from KSUX
to KSLB, but could lift slightly farther north before exiting to
the east by 15Z.

Farther west, a cold front has pushed east of Highway 281 and
will continue to progress east through this afternoon. While not
much precipitation across this area currently, have seen reports
of -DZ increasing along with LIFR-VLIFR ceilings/visibility in
fog.

As the cold front pushes east and surface temperatures fall
below freezing, will see increasing potential for icing with
freezing rain/drizzle, with a transition to snow expected later
in the afternoon and tonight as colder air aloft moves in. The
low stratus is expected to clear KHON-KAGZ by late in this TAF
period; otherwise low MVFR-IFR ceilings will persist.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from 6 PM this evening to 9 AM CST
     Saturday for SDZ062-066-067-069>071.
     Winter Weather Advisory from noon today to 9 AM CST Saturday
     for SDZ040-055-056-060-061-065-068.
     Winter Weather Advisory from 9 AM this morning to 3 AM CST
     Saturday for SDZ038-039-050-052>054-057>059-063-064.
MN...Winter Weather Advisory from 6 PM this evening to 9 AM CST
     Saturday for MNZ081-089-090-098.
     Winter Weather Advisory from noon today to 9 AM CST Saturday
     for MNZ071-072-080-097.
IA...Winter Weather Advisory from 6 PM this evening to 9 AM CST
     Saturday for IAZ001>003-012>014.
NE...None.

&&

$$

UPDATE...Dux/JH
DISCUSSION...AJP
AVIATION...JH