734
FXUS63 KFSD 071110
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
610 AM CDT Sun Jul 7 2024

.KEY MESSAGES...

- Patchy fog again developing early this morning. Widespread
  dense fog is not expected, but areas of visibility below a
  mile are possible.

- Unsettled weather continues through the first half of this
  week with spotty afternoon to early evening showers/storms
  Sunday through Wednesday. Severe weather is not expected.

- Cooler than normal temperatures for early July through the
  early part of next week, but trending warmer and more humid by
  the end of the week.

&&

.DISCUSSION...
Issued at 355 AM CDT Sun Jul 7 2024

TODAY-WEDNESDAY: The first half of this week will be dominated by
a slow moving northern stream trough in the mid-upper levels. The
main trough axis resides from northern Minnesota through eastern
South Dakota into Nebraska today and slides further east into the
Upper Mississippi Valley on Monday. With the trough overhead today,
expect to see scattered showers/thunderstorms expand in coverage
through the mid-late afternoon and early evening, diminishing
again after sunset. Lack of deep layer shear and weak mid level
lapse rates should keep storms non-severe, with lightning and
perhaps brief heavy rain the main threats.

While the above transition with the northern stream upper trough
is occurring, tropical cyclone Beryl will be making landfall on
the Texas coast, and the track of its remnants over the following
couple of days may have some impact on our weather through midweek.
Modest consensus in latest deterministic models, and even in the
broader ensemble view, takes the remnants of Beryl northeast toward
the mid-Mississippi Valley, potentially connecting with the northern
stream trough as it slides a bit further east into the Great Lakes.
This ultimately slows the eastward progression of the trough, which
keeps portions of our forecast area under weak cyclonic flow through
Wednesday. Not seeing a significant impact on temperatures, with
daily highs holding in the upper 70s-mid 80s through Wednesday.
However, the cyclonic flow provides additional weak lift in support
of low chances for diurnal/afternoon showers and thunderstorms,
mainly near and east of the US Highway 81 corridor. NBM seems a
little low on its coverage of low pops based on the more recent
models, so have bumped up and/or expanded coverage of 20-30 pops
for the afternoon hours Monday through Wednesday. Similar to today,
shear remains quite weak through this period, so severe storms are
not expected.

THURSDAY-SATURDAY: As we progress through the latter part of next
week, the upper ridge makes a stronger push eastward. While this
should favor dry weather with regards to precipitation, it will also
allow summertime heat and humidity to return to the region. We see
temperatures trending upward through this late week period, with low
(20-30%) probabilities of temperatures topping 90F in our far west
by Friday, with moderate-high (50-80%) probabilities pushing into
the James River Valley on Saturday. Along with the increasing heat,
a transition to southerly low level flow will draw higher dew points
northward. Ensembles indicate moderate (~50%) probabilities for dew
points topping 70F Friday, and moderate-high (60-80%) probabilities
of the same by late Saturday. Those with heat sensitivities will
want to monitor trends for this late week-next weekend period and be
prepared to take precautions to avoid heat illness.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 610 AM CDT Sun Jul 7 2024

Areas of fog reducing visibility to less than a mile in some
locations north of I-90 at sunrise (though not impacting TAF
sites). This should dissipate by 13Z-14Z.

Scattered showers and thunderstorms are expected to develop
this afternoon (07/19Z-21Z), diminishing by sunset or shortly
thereafter (08/01Z-03Z). Light winds will prevail through the
period, variable during the overnight/early morning, favoring
west to northwest at or below 12kt during the late morning and
afternoon. Storms may bring some stronger gusts and brief MVFR
visibility.

&&

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

&&

$$

DISCUSSION...JH
AVIATION...JH