122
FXUS63 KFSD 161124
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
624 AM CDT Tue Jul 16 2024

.KEY MESSAGES...

- Scattered showers with isolated thunderstorms will be
  possible through this evening. An isolated severe weather risk
  will be possible mostly across our southcentral SD counties.

- Near to below normal temperatures will continue through the
  weekend as cooler air funnels into the region.

- Confidence continues to grow in more widespread rain chances
  over the weekend. However, the details remain far from
  certain.

&&

.DISCUSSION...
Issued at 335 AM CDT Tue Jul 16 2024

The Short Term (Today & Tonight):

A cooler day is ahead! Taking a look across the area, cooler air
continues to funnel into the region behind yesterday`s cold front.
As a result, many area`s will wake up to temperatures in the low to
mid 60s to start the morning as a surface high gradually sides into
the area. Looking a radar, a few scattered showers continue to
develop across portions of western ND and southcentral SD in
response to bits of isentropic lift associated with the rotating
Hudson Bay trough in Canada along with support from the right
entrance region of an upper-level jet. While these developing
showers could make it into areas west of the James River and north
of I-90 this morning, the general expectation is for these showers
to gradually dissipate by the early afternoon as they approach the
more stable airmass (surface high) sitting over our area. Nonetheless,
lingering CAA advection along with light northeasterly flow
will likely help our temperatures drop below our seasonal
normals for the day as highs only reach the mid to upper 70s to
low 80s with the warmest conditions along the Missouri River.

Our focus will likely turn to the Missouri River Valley by the early
afternoon as a few isolated showers and thunderstorms develop ahead
of a subtle shortwave diving into southcentral NE. While the better
convective chances will likely occur just south of our area in
southcentral NE, there is a narrow but decent chance for an isolated
stronger storm or two over our southcentral SD counties closer to
21z. With up to 1500-2000 J/kg of MLCAPE and 35-40 kts of deep layer
shear to work with, developing storms could quickly become severe
with large hail up to golf ball size and damaging winds up to 60 mph
possible. With all this in mind, SPC continues to outline the
Missouri River Valley in a Marginal Risk (Level 1 of 5) for severe
weather. From here, expect any developing activity to progress
southeastwards before dissipating this evening. Lastly, expect a
much cooler night as colder air continues to makes it way to
the surface. With this in mind, overnight low will decrease
to the mid to upper 50s and low 60s across the area.

The Long Term (Wednesday-Monday):

Heading into the midweek, much quieter conditions will continue
through Thursday as mid-level ridging quickly moves in to replace
the departing upper-level wave. With lingering cold air
advection (CAA) aloft and ample mixing at the surface, expect
temperatures to continue their cooling trend through Thursday as
highs gradually decrease into the low to upper 70s and low 80s
on both days with overnight lows in the 50s to low 60s. By
Friday, a warm nose will begin to develop on the backside of the
mid-level ridge as 850 temps approach 20 degrees C. While this
won`t likely translate to a tangible increase in surface
temperatures, the warm mid-levels will likely serve as fuel for
the approaching clipper wave as it dives southeastwards into
our area from the international border.

Intermittent periods of scattered showers and thunderstorms will
likely develop from Friday into Saturday as the open wave wraps up
into a closed low. With borderline convective temperatures and long-
skinny CAPE profiles (500-1000 J/kg); the severe weather threat
should be rather limited. However, PWATs up to 1.75 inches and warm
cloud layer depths of up to 11kft do suggest the potential for
pockets of heavy rainfall. With all this in mind, a wet and dreary
weekend is ahead to say the least. As the closed low begins to drift
southwards by Sunday expect any lingering activity to gradually
dissipate throughout the day with much quieter conditions expected to
return by Monday. Lastly, with the increased precipitation
chances (30%-60%) over the weekend; temperatures will likely
continue to hover just below normal with highs expected to be
in the mid to upper 70s and low 80s.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 609 AM CDT Tue Jul 16 2024

VFR conditions conditions with occasional MVFR conditions will
be possible this TAF period mostly due to developing showers and
thunderstorms. Taking a look at satellite imagery, VFR stratus
continues to fill into the area as a few lingering shower
gradually dissipate west of I-29. Expect another round of
showers to approach the area this morning from the northwest
then gradually weaken as it approaches the I-90 corridor.
Otherwise, light and variable winds will become light northerly
to northeasterly by this afternoon with few isolated showers and
thunderstorms possible by this evening to end the TAF period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

DISCUSSION...Gumbs
AVIATION...Gumbs