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529
FXUS63 KABR 270550 AAB
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1250 AM CDT Thu Jun 27 2024

.KEY MESSAGES...

- Showers and storms (20-70% chance) will be on the increase late
tonight in parts of central South Dakota before spreading north
and east through the day on Thursday.

- A second round of storms is expected for late Thursday afternoon
through late Thursday night (50-90% chance). An enhanced risk (3 out
of 5) for severe storms covers the west river counties of this CWA
(Corson/Dewey/Stanley/Jones) for late Thursday afternoon through
early Thursday evening. Slight/Marginal risk potential extends
further east to the James River valley Thursday evening/overnight.

- Friday severe weather potential is conditional; hinging on cold
frontal position/timing. Currently, the Prairie Coteau into western
Minnesota is included in a marginal risk (1 out of 5).

- Another opportunity for showers and thunderstorms will arrive
later Sunday into Monday (40-80% chance of measurable rain), as a
low pressure system moves through the region.

&&

.UPDATE...
-- Changed Discussion --
Issued at 1239 AM CDT Thu Jun 27 2024

The aviation discussion has been updated below for the 06Z TAFS.

UPDATE Issued at 608 PM CDT Wed Jun 26 2024

Hi-res models have slowed down precipitation onset tonight. May
need to move intro of pops until after 6z, but will first see how
showers over the Black Hills this evening evolve. Otherwise, the
forecast remains on track this evening.
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&&

.SHORT TERM /THIS EVENING THROUGH THURSDAY NIGHT/...
Issued at 214 PM CDT Wed Jun 26 2024

At 2 PM CDT, skies were mostly sunny and temperatures were
warming through the 70s for most locations. On the front/south
side of an area of surface high pressure, most areas are
experiencing winds with a north to northeast component for
direction while sustained winds are generally between 5 and 15 mph
with some occasional gusts up to 20 to 25 mph.

Not a whole lot has changed since yesterday, regarding precipitation
chances tonight into Thursday, other than the timing of things
slowing down some. At this time, it appears that there is very
little in the way of rain chance over the CWA prior to 06Z Thursday.
But then, between 06Z and 12Z Thursday, the best nocturnal 700hpa
WAA and 850hpa moisture advection look to sync up and elevated
showers/embedded thunderstorms should really start to blossom. But,
again, areal coverage-wise, most of the precipitation is probably
west of the James River valley through 12Z Thursday. Then,
precipitation chances spread eastward into Minnesota through early
afternoon on Thursday.

The focus then changes to Thursday afternoon through the end of
Thursday night, when strong to severe thunderstorms could happen.
SPC increased the severe thunder risk by adding an enhanced (3 out
of 5) to the northern high plains, including the west river counties
of this CWA. The marginal/slight risk (1-2 of 5) areas remain in
place over the Missouri River and James River valleys of the CWA for
Thursday evening. Based on current model progs, convection could
hold together while crossing the Missouri River valley (~03Z-05Z)
before slowly fizzling out further east as a result of running into
a more stable environment. Instability throughout and west of the
Missouri River valley is progged at 1000-3000J/kg mlCAPE. And,
overall, deep layer and low level shear progs are supportive of
hail, wind and tornadoes, including supercellular structures (both
discrete and embedded in linear convective mode), with an eventual
emphasis later in the evening more toward bowing line segment/squall
line strong winds potential as the low level jet develops.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 214 PM CDT Wed Jun 26 2024

Not a whole lot of change to the long term pattern over the last 24
hours, with the period starting with an upper trough and associated
surface low moving through and departing the region on Friday. High
pressure will then move in between the departing trough and
approaching ridge, bringing below normal temps for the weekend,
before the next trough and low pressure system arrive for Sunday and
the beginning of next week.

Surface low will be located in eastern ND at the start of the
period, with a front extending south through eastern SD. Expect some
lingering shower/thunderstorm activity to be ongoing, but pushing
east through the morning hours. That should depart by mid day and
expect largely dry conditions with the mid level drying behind the
front. Could be some diurnally driven convection in southwest SD
towards late afternoon that may sneak into our I-90 corridor in the
evening, but a low probability (10-20%) at this time. Did notice
that the energy associated with the upper trough looks to be a touch
farther south than yesterday for the Friday night period, but at
this point, the probabilities of precipitation point to most of it
staying to the north after the front pushes through. Do expect some
gusty winds both Friday ahead of the secondary front and Friday
night behind it. For Friday, we`re in a neutral advection setup in
the low levels during the day, but still looking like deep mixing to
700mb, leading to wind gusts in the 20-30kt range, greatest over the
north central. The best cold air advection arrives overnight into
Saturday morning (slightly delayed from yesterday), so winds may be
able to overcome the normal diurnal influences and keep some
gustiness at times through the night.

Behind the secondary cold front, Saturday will be below normal for
temperatures, with highs in the low-mid 70s. This is driven by the
below normal 850mb temps over the region (5-9C 25-75th percentile
from ensembles), which puts values below the 10th percentile of the
KABR sounding climo for this time of year. Ahead of high pressure
moving in during the late afternoon and night, will have the
potential for an area of low clouds moving in for potentially a good
portion of Saturday, especially over the northeast half of the area.
Still a lot of spread in the ensembles at this point, but definitely
trending towards at least a period of cloudier conditions on
Saturday.

Focus then turns to the next system arriving later Sunday into
Monday. Overall, looks to be pretty similar to the tonight into
Thursday night system, with initial warm air advection precip in
central SD on Sunday, along with increasing increasing southerly
winds ahead of the low. Still high probabilities of winds exceeding
34kts (39 mph) on Sunday, 70-97% along and west of the Missouri
River, which fits with the going NBM deterministic forecast. There`s
even greater than 50% probabilities in the western Corson/Dewey
counties of 50 mph winds, so the going advisory level winds there
seems reasonable at this point. The initial warm air advection
precip will push to the east-northeast with time Sunday night across
the rest of the area, then the main focus for severe weather will be
Monday as the surface low moves into the central Dakotas. Still
variability in where the low will track, but it seems to be a little
farther south than tomorrow`s system. Thus, we`ll have plenty of
shear, but the nose of best instability will be focused a little
farther south and peaking in western-central SD. CSU ML probs still
pointing towards a 15% severe risk for the eastern Dakotas on Monday
out ahead of the low.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
-- Changed Discussion --
Issued at 1239 AM CDT Thu Jun 27 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are still expected to persist into the early
morning hours at all 4 TAF sites. Showers and thunderstorms will
begin to develop and spread across central South Dakota before
daybreak with MVFR/IFR cigs/vsbys setting in at KPIR/KMBG with
the onset of the rainfall. These conditions will spread east into
KABR/KATY terminals by mid morning. Expect these conditions to
prevail through the majority of this remainder of this forecast
period.
-- End Changed Discussion --

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...Wise
SHORT TERM...Dorn
LONG TERM...SRF
AVIATION...Vipond