441
FXUS63 KABR 211135
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
635 AM CDT Fri Jun 21 2024

.KEY MESSAGES...

- A Flood Watch remains in effect through Friday night for southern
  portions of the forecast area, mainly south of Hwy 212.

- The next round of precipitation is expected later today (50-80%).
  Severe storms are possible, primarily across eastern and southern
  South Dakota, with a low probability that severe storms cross into
  the CWA. Otherwise, looking at a random coverage of showers and
  storms through the afternoon, evening and overnight.

- The weather pattern turns mostly dry early next week as
  temperatures and humidity climb significantly with daytime
  readings in the mid 80s to mid 90s.

&&

.SHORT TERM /TODAY THROUGH SATURDAY AFTERNOON/...
Issued at 401 AM CDT Fri Jun 21 2024

Most of the rainfall is now southeast of Watertown, though isolated
weak convective elements exits smattered across the CWA this early
morning. The warm front/inverted trough doesn`t look like it will
move very much, despite a deepening surface low over western
Nebraska later today, and may end up drifting deeper into southeast
South Dakota for the activity later this afternoon. That puts us on
the stable side of the front, with stratus evident at all our
ASOS locations. So thunderstorm activity should expand in coverage
though the course of the day as another southwest flow shortwave
comes though the Dakotas, however with moist adiabatic profiles
and skinny CAPE, the severe weather threat looks extremely limited
with the exception of the far south/southeast portions of the
CWA. CAMS, as should be expected with the weakly forced
environment, are showing rather random coverage of storms across
the CWA for later today. The HREF 2-5km updraft helicity also
points to storms along the southern portions of the CWA showing
mid-level rotation. Thus, cant rule out the isolated severe
weather threat for today. Will leave the flood watch in place for
now, though confidence in additional flood potential has
decreased. The only caveat here is the flood guidance is low with
portions of the watch area only needing an inch to half inch
additional moisture to re-start the process, and PWATS remain 2-3
standard deviations above climo.

While CAMS show activity diminish, especially across central/north
central South Dakota tonight, there is another weak wave that scoots
across as the flow transitions to more zonal. Saturday, however,
should remain mostly dry, with the exception to potentially up in
north central South Dakota late in the short-term period (Saturday
evening) with a wave that zips across southern Canada, along with an
80kt jet streak. Westerly flow through the profile would support an
isolated risk, fast moving cells type environment thanks to about
1000j/kg MLCAPE and 0-6km shear of about 35kts of shear.

&&

.LONG TERM /SATURDAY EVENING THROUGH THURSDAY/...
Issued at 401 AM CDT Fri Jun 21 2024

The main focus in this period will initially concentrate on
temperatures followed by the next chances for precipitation set to
periodically affect the forecast area next week. The upper flow
pattern will begin to orient itself into a less active phase early
next week as an upper ridge is progged to shift into the Northern
Plains. This will lead to a stretch of dry conditions that should
last at least a couple of days before the next disturbance moves in.
Temperatures will begin to respond as the ridge moves overhead with
readings well above normal for late June. A couple of rainfall
opportunities could present themselves next week as the upper ridge
gets knocked down to a certain extent by passing shortwave energy
across the Northern Plains.

Sfc high pressure will be building east-southeast across the Dakotas
on Sunday, giving the region a relatively quiet end to the weekend
weather-wise. This sfc ridge is set to shift east of our region on
Monday, setting up return flow as that upper ridge axis is about
over the top of our forecast area. Temperatures will respond
significantly as a much warmer air mass is drawn in. 850mb
temperatures are progged to top out from +25C to +30C across our
forecast area on Monday. NBM progs the probabilities of seeing max
temperatures of 90 degrees or higher at a 75 to 95 percent chance
from the James Valley and points west through central SD. We`ll
currently side with the middle of the road with forecasted highs in
the upper 80s to mid 90s east to the low to mid 90s west are
roughly around the 50th percentile.

Cooler temperatures will move back in the remainder of the period
through midweek. Another mid level shortwave trough is progged to
track across southern Canada into the Western Great Lakes on
Tuesday. A frontal passage Monday night into Tuesday could lead to a
few widely scattered showers and thunderstorms. At this point, this
system doesn`t appear that it will provide any widespread moisture
across the CWA. The upper ridge is anticipated to re-assert itself
across the Northern Plains by midweek. This should lead to dry
conditions and summer like temperatures and humidity. More shortwave
energy will try and traverse over the top of the ridge axis by the
end of the period as an upper low or trough crashes into the PacNW
and Western Canada. This could provide the next window of
opportunity for rainfall by late Wednesday into Thursday.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 633 AM CDT Fri Jun 21 2024

Terminals KABR,KATY,KPIR,KMBG

MVFR VISBY due to fog is occurring at KPIR, while low CIGS and
impacting both KPIR and to a lesser extent KMBG. Through the
course of the day we can expect showers and generally weak
thunderstorms to form and potentially move close to any one of our
terminals, though the highest probability for seeing VCTS is for
the KATY area. Winds will remain primarily out of the east-
northeast.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Flood Watch through Saturday morning for SDZ018>020-022-023-036-
     037-048-051.

MN...None.
&&

$$

SHORT TERM...Connelly
LONG TERM...Vipond
AVIATION...Connelly