762
FXUS63 KFSD 020843
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
343 AM CDT Tue Jul 2 2024

.KEY MESSAGES...

- Below normal temperatures continue today and through most of
  the week with high temperatures on the order of near
  seasonable to 5 to 10 degrees below average.

- A cold front passing through the area today could provide
  another round of strong to severe storms and heavy rain along
  and southeast of a Spencer, IA to Sioux City, IA line.
  However, confidence is low (<=30%) in this happening.

- An active pattern aloft will continue periodic rain chances
  for the rest of the week and weekend.

&&

.DISCUSSION...
Issued at 342 AM CDT Tue Jul 2 2024

The previous light rain showers have pushed off to the east early
this morning leaving low level stratus in its wake. Given light
winds across the forecast area, some very patchy fog has developed
in a few locations. Should see continued patchy fog persist through
the rest of the overnight and early morning hours.

A cold front is beginning to push into the forecast area early this
morning. The front will move through the area rather quickly,
pushing all the way through most of northwest Iowa come the
afternoon hours. Some low level stratus looks to hang around the
area through the early afternoon hours which may put a hamper on
high temperatures. Due to this possibility, have tempered high
temperatures a bit, with highs now expected to warm to the upper 70s
to low 80s rather then purely into the 80s. Dew points will be
lowering in the wake of the passing cold front but moisture looks to
pool along and just ahead of the front. This will push dew points
into the low 70s which will make for another round of showers and
thunderstorms. Convection looks to fire along the front as the base
of an upper level trough encroaches on the front. This will place
the right entrance region of the upper level jet right over the
front which will provide adequate instability and shear for
potential strong to severe storms. Some questions remain regarding
severe weather potential though as the front will most likely be out
of the forecast area by the mid afternoon hours, thus keeping any
severe weather chances at bay. There remains a small chance (<=30%)
chance that convection could fire along the front as it is just
about the exit the forecast area. Should this scenario come to
fruition, locations along and southeast of a Spencer, Iowa to Sioux
City Iowa could see strong to severe storms for a few hours before
the storms push east of the area. This area could also see a quick
inch of rain as well from the storms. Non-severe storms and showers
are expected develop along the 850-700 mb front late this morning
into the afternoon hours as the vort max with the wave catches up to
the elevated boundary. Only light rain is expected with these
showers with amounts from a few hundredths to a tenth or two
expected. Any chance for rain will come to an end this evening
leaving dry conditions for the overnight hours. Low temperatures
will fall to the upper 50s to low 60s overnight.

Wednesday will begin on the dry side as a surface ridging quickly
slides through the area. However, southwesterly return flow on the
backside of the ridge will set up through the afternoon hours. High
temperatures will warm back to seasonable with highs in the 80s
expected. The return flow will not advect in high moisture air
though as the higher theta-a air will reside on the front edge of
the previously mentioned surface ridge. However, dew points look to
moisten up to about 60 degrees F across portions of north central
Nebraska and south central South Dakota. With an upper level jet
remaining parked over the Northern Plains and an approaching mid
level wave from the west, showers and thunderstorms are again
expected. Convection looks to develop along the warm front along the
Nebraska/South Dakota border during the afternoon hours but
questions remain how far east can the storms progress. Deep layer
shear is sufficient at around 40 knots but instability will be on
the low side, only around 700-1,000 J/kg of CAPE keeping severe
potential questionable. As of now, think storms may be on a downward
trend as they approach the Missouri River valley during the evening
hours.

Medium range guidance has come into better agreement in a closed low
passing through the Northern Plains on Thursday/Independence Day.
This will keep high temperatures on the cool side with highs in the
70s expected. Thermal profiles will be on the order of moist neutral
and with enough saturation to support scattered showers across the
area. Thunderstorms are also possible as the cooling from the low
will steepen mid level lapse rates enough to generate some
instability. However, with the upper low overhead, cold air funnels
may be possible. The showers and storms look to persist into the
overnight hours but on a downward trend as the upper low pivots off
to the east. Low temperatures will fall to the upper 50s and 60s
overnight.

The upper level low continues to push off to the east of Friday,
leaving cool northwest flow in its wake. The cooler airmass in place
will continue below average high temperatures with highs in the 70s
expected. Some light precipitation is possible throughout the day
given wrap around moisture from the exiting low. Ensembles support
this as they show a 50-80% chance for exceeding a tenth of an inch
of rain throughout the day.

Upper level ridging builds across the western CONUS during the
weekend, placing northwest flow aloft across the Northern Plains.
Typically, upper level subsidence lies downstream of a ridge,
resulting in dry conditions. However, ridge riding shortwaves could
result in additional shower and storm chances through the weekend
and into next week. Tough to say when and where just yet so will
continue to keep an eye on trends. Have left model blended PoPs
through this period as well to account for the uncertainty. High
temperatures will remain near to below seasonal in the 70s and
80s.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1050 PM CDT Mon Jul 1 2024

Showers and isolated thunderstorms continues to move across our
eastern portions of the area, with MVFR/IFR cigs under majority of
the showers and storms. These showers/storms will continue to push
off to our east over the next couple hours, with the severe threat
largely done. In between the showers and the cold front further off
to the west, some patchy fog is possible given the recent rainfall,
with visibilities possible below a mile. Have kept mention of fog
limited to MVFR at both KHON and KFSD, which will need to be
monitored overnight.

&&

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

&&

$$

DISCUSSION...Meyers
AVIATION...APT