000
FXUS63 KFSD 161746
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1246 PM CDT Tue Apr 16 2024

.KEY MESSAGES...

- Wind Advisory has been issued for most of the forecast area
  into this afternoon. Strong easterly winds sustained at 20-30
  mph with gusts up to 45 mph are expected, but will decrease
  from west to east through the afternoon.

- Rainfall continues through Wednesday morning. Additional
  rainfall 0.50 to 1.50" through tonight, highest along/east of
  Hwy 81. Pockets of 3+ inches total rainfall possible.

- Rainfall rates could exceed 1 inch per hour at times. Isolated
  to scattered urban flash flooding may occur. Ponding in low lying
  areas is also likely.

- Isolated to scattered severe thunderstorms will be possible
  late this morning. The greatest threat with the strongest
  storms will be large hail.

- Moderate (40%-80%) precipitation chances return Wednesday
  night into Thursday. Focused south of I-90.

- The breezy conditions will continue along with more seasonal
  conditions from the midweek into the weekend.

&&

.DISCUSSION...
Issued at 332 AM CDT Tue Apr 16 2024

TODAY (Tuesday): Water vapor imagery shows the surface low
pressure system that will continue to impact our area over the
next 24 hours spinning over the Colorado/Kansas/Nebraska
borders. This low pressure system is expected to continue its
northeastward trek, bringing the region beneficial rainfall.
Showers and thunderstorms that formed along the South
Dakota/Nebraska boarder continue to move north-northeastward.
The better environment for severe weather remains to our south
over Nebraska and Iowa. However there exists enough instability
in the form of 400-800 J/kg of MUCAPE and around 30 kts of 1-3
km bulk shear to support storms strong enough to produce hail
from dime to quarter sized, wind gusts 50+ mph, and lightning
through Tuesday morning. Though the risk is low, cannot rule out
a brief tornado or two.

Strong easterly winds sustained at 20-30 mph and gusts of 45-55 mph
have been occurring during the overnight hours and will
continue through Tuesday night. A Wind Advisory has been issued
for portions of southeastern South Dakota, northeastern
Nebraska, northwestern Iowa, and southwestern Minnesota and
continues until 7 PM today.

CAMS indicate the possibility of a secondary band of stronger
storms forming along the cold front/triple point as it rotates
over the area Tuesday morning. The most likely scenario is
storms will begin as isolated cells, and then quickly grow
upscale into a line due to the forcing being mostly parallel
with the front. The biggest question with this line is will the
environment be able to destabilize enough to support severe
storms? If it does, the most likely threat with these storms
remains hail from dime to half dollar size, wind gusts up to 50
mph, and locally heavy rainfall. Following the band of heavier
rain we will see scattered brief lulls as the dry slot moves
over the area. On the back side of the low we will once again
see some rain showers, but expect these to be lighter.

Looking at rainfall: rainfall rates under stronger storms could
approach 1 to 2 inches per hour. WPC excessive rainfall outlook has
portions of southeastern South Dakota, northwestern Nebraska, and
northwestern Iowa in a slight risk (level 2 of 4) as a result.
Expecting widespread rainfall totals of 1 to 2.5 inches with
isolated pockets of 3+ inches, especially in the counties along
the Missouri River. Scattered urban street flooding is possible,
as well as rises in small creeks and streams. While this
rainfall will result in overall river rises as well, large
rivers are low enough that we are not expecting river flooding
at this time.

WEDNESDAY-THURSDAY: Another upper level trough will be pushing into
the Northern Plains Wednesday evening. A cold front tied to this
upper wave will be pushing through the area, cooling temperatures in
its wake. Along with the cooler temperatures, the front will bring
another chance for rain with it. Ensembles generally support this
but have a wide variance in the location of the highest chance for
rain. This chance for rain looks to be tied to locations south of I-
90 but the highest probabilities for exceeding an tenth of an inch
or more vary between I-80 and the highway-20 corridor. For now, have
stuck with model blended PoPs to account for this uncertainty.
Chances for rain look to persist into Thursday morning before
pushing southeast of the area. With a new, cooler airmass in place,
Thursday will be a cooler day with high temperatures into the 50s.

FRIDAY AND Beyond: The cooler conditions look to be here to
stay as the previously mentioned upper level wave is slow to
push east of the area. Northerly flow along with the cooler
conditions will continue through the rest of the work week and
persist into the weekend. High temperatures will remain in the
50s while low temperatures fall to the 20s and 30s.

A second upper level trough looks to push into the Northern Plains
early next week but this wave`s evolution is uncertain since medium
range guidance depicts varying evolutions of the wave. This wave
could bring another chance of rain with it as ensembles show a broad
30-50% chance for exceeding a hundredth of an inch of precipitation.
This wave does look to bring some warmer temperatures with it via
the warm air advection (WAA) out ahead of it, possibly bringing high
temperatures back to seasonable for the beginning of next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1235 PM CDT Tue Apr 16 2024

Mostly MVFR and IFR conditions will continue across the area
this TAF period mostly due to developing showers and
thunderstorms. Taking at satellite imagery, MVFR to IFR stratus
continues to sit over the area ahead of a surface low this
afternoon. As the low rotates to the north-northeast into the
evening hours, areas across portions of northwestern IA and far
northeastern NE should break free of the low-level deck which
will lead to the development of more showers and storms through
the late evening. Periods of light to moderate showers will
continue into Wednesday morning. Otherwise, breezy easterly
winds will decrease as the low approaches then shift towards the
northwest overnight. Wind speeds will gradually increase with
gusts between 30-35 kts possible to end the TAF period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 5 PM CDT this afternoon for SDZ039-040-
     054>056-061-062-066-067-070-071.
MN...Wind Advisory until 5 PM CDT this afternoon for MNZ097-098.
     Wind Advisory until 7 PM CDT this evening for MNZ071-072-080-
     081-089-090.
IA...Wind Advisory until 5 PM CDT this afternoon for IAZ001-012-020-
     031.
     Wind Advisory until 7 PM CDT this evening for IAZ002-003-013-
     014-021-022-032.
NE...Wind Advisory until 5 PM CDT this afternoon for NEZ014.

&&

$$

DISCUSSION...AJP
AVIATION...Gumbs