093
FXUS63 KABR 130438
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1138 PM CDT Wed Jun 12 2024

.KEY MESSAGES...

- After 10 PM CDT, an additional round of near 30% chances of
  showers and thunderstorms will sets up over central SD and
  persist into Thursday morning.

- Temperatures will be closer to normal Thursday and Thursday
  night, along with dry conditions.

- A more active weather pattern sets up on Friday afternoon and
  continues into early next week. This will bring multiple
  opportunities for showers and thunderstorms to the region (near
  50% chance). While there is an opportunity for severe weather
  most days, the greatest chance for severe weather (15%) is
  highlighted by the Storm Prediction Center on Monday in eastern
  SD.

&&

.UPDATE...
Issued at 802 PM CDT Wed Jun 12 2024

Severe Thunderstorm Watch 405 has been cancelled, as storms have
moved out of the area. Convection has quickly diminished after
00Z, with only a few clouds lingering from Clark to Watertown and
Clear Lake. Will update the forecast to diminish the clouds faster
than originally anticipated. Otherwise, the forecast remains on
track.

&&

.SHORT TERM /THIS EVENING THROUGH THURSDAY NIGHT/...
Issued at 223 PM CDT Wed Jun 12 2024

At 2 pm CDT, temperatures were warming through the 80s, and in
several places were already nosing up into the low 90s. Skies were
generally partly to mostly sunny. Winds out ahead of a surface cold
front analyzed from northern Brown County southwestward into Buffalo
County were southwest around 10 to 15 mph, with some occasional
higher gusts, while behind the front, winds have shifted to the
northwest and are running closer to 15 to 25 mph with occasionally
higher gusts. The last remaining pesky convection from earlier this
morning finally fizzled out over Hand County.

Severe storm potential remains basically unchanged. The deep layer
shear this afternoon/evening supports supercell thunderstorms. The
low level shear is weak and basically rules out the possibility of
tornadoes in this CWA. But, the instability is quite large, with SPC
RAP instability forecast to increase to and then hold around 2000-
3000J/kg of MLCAPE through 23Z. Hail CAPE is still advertised at 750-
1050J/kg and low/mid level lapse rates are quite steep. Downdraft
CAPE is forecast to be around 1100-1750J/kg, so there is definitely
a supercell downdraft/strong wind concern. But, the biggest concern
is for very large hail (1.75in to 2.50in hail) over the far
eastern CWA, mainly east of a line from Hecla to Waubay to Clear
Lake between 21Z and 02Z. West and south of that line depiction,
areal coverage of the mid-level capping inversion (+10C or warmer)
looks to reside and should basically preclude the potential for
convection. Plus, without a clearly defined shortwave (PVA) moving
through, it will be harder to get updrafts to go and be sustained
(just a 110+knot upper level jet streak in the region, but not in
the proper quadrant for supportive lift) as there is a capping
inversion (albeit weaker) still to be overcome even in the far
northeast corner of the CWA. On a mesoscale note, there is outflow
air (an OFB) moving north of SD Hwy 20 this afternoon from
earlier convection. This boundary (plus any other boundaries that
may be around farther east from earlier convection that can`t be
detected by the 88D) will have to be monitored as one more source
of focused low level forcing/lift for convective initiation as it
moves further away from the warmer/stronger mid-level capping in
place.

Elevated showers/storms are still possible overnight within the
trailing/southward-shifting mid-level baroclinic zone over the
region and that impressive upper jet streak in play. Precipitation
potential should be waning considerably by 15Z Thursday.

Most of Thursday should be dry and a bit cooler than Wednesday`s
readings in the 90s. Thursday night should be dry as well with high
pressure over the region.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 223 PM CDT Wed Jun 12 2024

The upper ridge that will develop over the northern part of the
CONUS on Thursday will quickly push east and over the Dakotas on
Friday and then into the Great Lakes on Saturday. This will set our
region up for an unsettled weather pattern for the long term part of
the forecast, as the ensemble clusters are very consistent on an
upper trough gradually moving through the Pacific Northwest this
weekend and stalling over the Mountain West through at least the
first half of next week. This will lead to southwesterly flow aloft
over our region, and a series of upper level disturbances and
associated surface lows moving through. While this whole period
isn`t going to be a washout (and some locations may see limited
precipitation), there will be several opportunities for
precipitation and most locations have 30-60% rain chances through
the extended.

Starting with Friday, high pressure will be in place at the start of
the day while a surface low develops in eastern WY through the
afternoon. This will lead to increasing southeasterly flow and in
turn moisture/instability. Best instability plume is off to the west
of our CWA, but could see storms persisting eastward into our CWA
(storm motions to the ENE at 20kts), but diminishing with time as
the MUCAPE diminishes towards the Missouri River. Still could see
some weak showers pushing east across northern SD overnight, while
the better forcing focuses farther south into southeastern SD and
associated with a better shortwave lifting northeast through NE and
into IA/MN Friday night into Saturday. That area has the best
precipitation potential, but we still should see some potential for
heavier rain on the northwest side and over east central SD (15-35%
chance of 0.5" of rain in 24hrs ending at the end of the daytime
Saturday). Farther northwest, a cold front or surface trough looks
to move through during the Sat into early Sun period (uncertainty
remains in ensembles on timing/intensity). We do see instability
increase ahead of this trough/front, but also the potential for
capping with a good warm nose at 850-700mb. Shear does look to be
less impressive on Saturday in our area (20-25kts ahead of the
front/trough and better into wrn ND were there are increased CSU ML
probs of 15%), so overall severe threat does look lower during this
time.

Sunday will depend on where the front/trough that moves through Sat-
Sat night stalls out. Latest ensemble trends have it stalling in the
NE/IA/MN/southeast SD area, so largely to the southeast of our CWA.
That should limit the precipitation potential for our area on
Sunday.

Precipitation chances do increase on Monday, with ensemble clusters
showing increasing instability on the inverted surface trough
(previously mentioned weekend front/trough that stalls) stretching
from the low in eastern CO and through southeast SD and into MN.
Some differences in the location of the trough, so exact details are
too uncertain at this point and it`s possible the trough stays south
of us. But where that instability/lift sets up, we have ample shear
in place (40-55kts) and would support severe storms when/where they
develop. Thus, the Day 6 15% severe risk from SPC looks to be
reasonable at this time. This is also highlighted in EC-Ens EFI
values (0.6-0.7) in the CAPE-Shear realm across much of our CWA,
which aligns where the overlap of the better instability/shear is
located. Finally, 00Z GEFS based CSU ML severe probs also
highlighting this period with 15% probs over eastern SD into
central/southern MN. In addition to the severe storm potential, NBM
probabilities of 0.5" of rain on Monday increase to 30-40% over much
of the CWA, with the highest values over the east. Even greater
uncertainty on where the overall setup of instability/shear will be
for Tues/Wed, but it does look to slowly shift farther to the
east/southeast with time.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1138 PM CDT Wed Jun 12 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected to continue over the next 24 hours.
Light showers are nearing central SD (mainly the MBG area) and
will expand across much of the forecast area. Added VCSH to MBG as
this is the most likely to experience light rain or a potential
weak thunderstorm during the early overnight hours.

&&

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

$$

UPDATE...KF
SHORT TERM...Dorn
LONG TERM...SRF
AVIATION...KF