962
FXUS63 KFSD 051644
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1144 AM CDT Fri Jul 5 2024

.KEY MESSAGES...

- Diurnal showers/weak storms will rotate southward across the
  area this afternoon, dissipating by sunset. Rainfall will be
  spotty and light, but isolated lightning may impact outdoor
  activities.

- Unsettled weather continues Saturday-Monday, with periods of
  scattered showers/storms, mainly focused during the afternoon
  to early evening by Sunday-Monday. A few strong to severe
  storms are possible Saturday afternoon, with large
  hail/damaging winds the primary threats.

- Cooler than normal temperatures for early July through the
  early part of next week, but trending closer to normal by the
  end of the week.

&&

.DISCUSSION...
Issued at 343 AM CDT Fri Jul 5 2024

TODAY-TONIGHT: Well-defined upper low spinning over central
Minnesota early this morning is expected to make slow eastward
progress toward the western Great Lakes by this evening. We remain
in northwest flow on the back side of this low, with cool and moist
mid-levels contributing to weak instability as we modestly warm into
the 70s this afternoon. Expect to see scattered showers or weak
thunderstorms develop and rotate southward across the area through
the afternoon, diminishing rather quickly as we approach sunset and
lose surface heating.

Most locations should remain less than 0.10" rainfall, though HREF
does show streaks of low-moderate (20-40%) probability of exceeding
0.25". However, these higher values appear to be overly influenced
by more robust development in the FV3 which is not seen in other
HREF members, so confidence in higher rainfall amounts is low.

SATURDAY-MONDAY: This period will be dominated by a broad trough
sagging into the northern Plains, with various shortwaves sliding
through the base of the trough. First, and perhaps the strongest
wave will swing through the area Saturday afternoon, providing some
upper level support during diurnal peak of instability. Models show
broad area of MLCAPE 1000-1500 J/kg, with a modest deep layer shear
of 30-40kt as the wave slides through, the latter mainly focused
through the southwest half of our forecast area. This could support
a few stronger storms capable of large hail, though mid-level lapse
rates are on the weak side, so thinking quarter to perhaps half
dollar size in a more organized storm. Forecast soundings indicate
a dry sub-cloud layer which could support isolated damaging wind
gusts, but tornadoes appear unlikely given high LCLs seen in the
soundings. Stronger storms could also produce locally heavy rain,
but given progressive storm movement, widespread heavy rainfall is
not expected. Timing of stronger storms should be focused from mid
afternoon until about sunset, with the wave sliding east and
instability quickly waning thereafter.

Sunday-Monday we remain within the broad trough. Modest afternoon
instability could support scattered showers/storms driven by the
diurnal heating. However, shear is severely lacking so would not
expect severe storms during this period.

TUESDAY ONWARD: The early week trough makes a push east by midweek,
allowing a dominant upper ridge over the western CONUS to at least
attempt to build into the Dakotas for the latter half of the week.
Still some differences among models in how far east the ridge and
associated warmer air will build beneath this ridge, influenced by
the remnants of tropical system Beryl sliding northeast through the
southern Plains toward the mid-Mississippi Valley late next week.
Ensembles do show increasing probabilities of temperatures topping
80F during this period, though, so there is hope of temperatures
trending closer to normal. This tropical remnants should keep any
meaningful moisture blocked from reaching our area, so rainfall
chances look to be on the low side.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1140 AM CDT Fri Jul 5 2024

Isolated diurnally driver showers and thunderstorms are
expected to develop this afternoon, with the slightly better
chances east of Interstate 29. Coverage is expected to be
limited at TAF sites. Any showers or storms will dissipate by
sunset this evening. Additional scattered shower and
thunderstorm development will then be possible over central SD
on Saturday morning. Occasionally gust northwesterly winds
through this afternoon, then winds become light and variable
tonight into Saturday morning.

&&

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

&&

$$

DISCUSSION...JH
AVIATION...JM