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000
FXUS63 KFSD 162341
AFDFSD

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

.KEY MESSAGES...

- A Tornado Watch has been issued through 7 PM for portions of
  far southeastern SD, far northeastern NE, and northwestern IA.
  The severe weather threat will likely continue through 7 PM
  before dissipating.

- The Wind Advisory will continue though 7 PM today with gusts
  between 35-45 mph possible at times.

- Periods of light to moderate rainfall will continue through
  Wednesday morning. Additional accumulations between
  0.25"-0.75" are expected with isolated pockets of up to 1 inch
  possible. Isolated flash flooding will also be possible
  especially across portion of northwestern IA.

- More precipitation chances (60%-90%) return by Wednesday
  night into Thursday with the highest chances focused south of
  Hwy-18.

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

&&

.DISCUSSION...
Issued at 324 PM CDT Tue Apr 16 2024

A wet and dreary day will continue! Taking a look across the area,
the dry slot continues to push into northwestern IA and portions of
southwestern MN as the surface low continues to pivot northeastwards
towards our area. Looking at the sounding near KSUX, about 1000-1800
J/kg of instability and 20-30 kts of bulk shear are available for
scattered showers and thunderstorms to develop across northwestern
IA. A few storms could become severe with large hail up to quarter
size and damaging winds up to 65 mph being the primary threats. With
low cloud bases and enhanced stretching potential expected with
developing storms, there is a chance for a few isolated tornadoes as
well. With all this in mind, a tornado watch was issued for portions
of far southeastern SD, far northeastern NE, and northwestern IA
through 7 PM this evening. The severe threat will likely continue
across northwestern IA through about 7pm before gradually
diminishing.

Shifting gears to tonight, moisture will continue to wrap around the
surface low bringing more light to moderate showers and
thunderstorms across the area. While this activity should stay below
severe limits, a few stronger updrafts could end up producing some
period of moderate rainfall. As a result, additional accumulations
of 0.25"-0.75" of an inches are expected with the some low potential
(<30%) for up to 1 inch on either side of the surface low. With
all this in mind and several sites already reporting accumulations
between 1-2 inches, some isolated flash flooding will be possible
especially across portions of northwestern IA and far northeastern
NE. Lastly, breezy easterly winds ahead of the surface low will
become more northwesterly behind the system. With a few sites
reporting gusts up to 40 mph, the plan is to hold on to portions
of the Wind Advisory along and east of I-29 through 7 PM.
Nonetheless, we`ll trim counties out of the advisory as needed.

Looking into Wednesday, the rain chances will continue to push to
the northeast with the surface low through the mid-morning. Quieter
conditions will temporarily return from the late morning onwards as
a mid-level ridge moves into the region. However, northwesterly
surface winds will increase as the SPG tightens with gusts between
30-40 mph expected. This along with lingering cold air advection
aloft will lead to a slightly cooler conditions compared to the
previous day with highs expected to peak in the upper 50s and lower
60s. Otherwise, more precipitation chances (30%-70%) will likely
return from Wednesday night into Thursday as a weak mid-level
wave interacts with a developing surface low over Nebraska and
Kansas. While the better rain chances will certainly be south of
I-90, most ensemble guidance continues to show the highest
confidence (60%-90%) along and south of the Hwy-18 corridor with
at least a tenth of QPF or greater expected at time. Nonetheless,
the precipitation chances will likely continue into the early
afternoon hours on Thursday before pushing southeastwards with
the cold front.

Heading into the extended period, a cold front will swing through
the region throughout the day on Thursday pushing any lingering
precipitation to the southeast by Thursday afternoon. Mostly
quieter conditions return as broad troughing continues to
progress across the northern plains. Northwesterly surface flow
along with lingering cold air advection (CAA) aloft will
continue to gradually decrease our overall temperatures through
Saturday with daily highs sitting in the upper 40s to low 50s
across the area. Things could potentially begin to trend warmer
from Saturday night onwards as a surface high builds in behind a
departing shortwave. A switch to southerly flow along with
increased warm air advection (WAA) aloft will lead to a gradual
increase in temperatures with highs gradually increasing from
the mid to upper 50s on Sunday to the low to mid 60s by Monday.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 640 PM CDT Tue Apr 16 2024

Current satellite shows a vertically stacked low pressure system
sitting over the area to begin the TAF period. As this low pressure
system pushes to the northeast, winds will turn to out of the
northwest and restrengthen with gusts up to 30-40 knots. The
strongest gusts will lie across the Missouri River Valley. Scattered
showers will also continue across the area through the evening hours
and persist into the overnight hours before pushing northeast of the
area. Ceilings are currently a mix of VFR/MVFR/IFR but will become
all MVFR/IFR as the low moves off to the northeast.

Gusty northwest winds will continue through the day tomorrow but
will be on a decreasing trend. Ceilings will raise to VFR levels by
the afternoon hours. The VFR conditions will finish out the TAF
period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...Wind Advisory until 7 PM CDT this evening for MNZ071-072-080-
     081-089-090.
IA...Wind Advisory until 7 PM CDT this evening for IAZ002-003-013-
     014-021-022-032.
NE...None.

&&

$$

DISCUSSION...Gumbs
AVIATION...Meyers