Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 240343 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1043 PM CDT Wed May 23 2018

Issued at 1022 PM CDT Wed May 23 2018

Pops/Wx/QPF have been the primary focus of evening updates.
Earlier thunderstorms that went up on the northward moving warm
front had plenty of instability but not much deep layer shear.
Still, anywhere from pea-sized hail to 1 inch hail happened with
these storms. For the rest of tonight, the focus is shifting to
the thunderstorms working up out of swrn SoDak and western NE.
Slightly better deep layer shear exists over the western half of
SoDak and still plenty of instability (including high amounts of
DCAPE - strong wind gust potential) for storms to work with.
Surface observing equipment dotted over portions of western into
central SoDak are indicating 55 to 65 mph wind gusts are occurring
or possible for, perhaps, a couple more hours through late this

UPDATE Issued at 630 PM CDT Wed May 23 2018

See below for an aviation forecast discussion for the 00Z TAFs.


.SHORT TERM...(This Evening through Thursday)
Issued at 318 PM CDT Wed May 23 2018

The threat for severe storms over the next 30 hours will be the main
forecast challenge.

As of 19Z, an area of low pressure is located near Pierre with a
warm front draped east-southeast across the region. With dew
points in the 60s, surface based cape values exceed 3K J/KG.
While 0-6 KM bulk shear values are lacking, deep layer shear is
around 25-30 knots. CAMS still support convection developing in
south- central SD within the next few hours. These storms should
track northeastward through this evening, pushing into North
Dakota around 3Z. With high DCAPE values, damaging winds are
possible with these storms. Hail is also possible.

After the first round of convection this evening, attention then
turns westward. Thunderstorms currently developing over Wyoming
should push across western SD after 0Z, potentially reaching our CWA
around 3Z. These storms should progress eastward across the CWA with
diminish intensity expected. There could be lingering pcpn in the
eastern CWA Thursday morning.

The NAM, as well as the HREF seems to suggest a break in convection
Thursday morning through Thursday afternoon before additional storms
develop along a cold front. As of now, convective initiation looks
best along the James River Valley after 21Z. There storms should
push eastward across the rest of the CWA Thursday evening.

.LONG TERM...(Thursday Night through Wednesday)
Issued at 318 PM CDT Wed May 23 2018

A shortwave trough and surface cold front should be on their way out
of the area by Thursday evening, taking a very moist environment
with them. Before that happens, thunderstorms are possible across
eastern SD and west central MN through Thursday evening. An unstable
atmosphere will provide the potential for strong updrafts with any
activity. Shear does not look to be too favorable, however large
hail and damaging winds will be possible. By Friday, a Western U.S.
upper level ridge begins makings its presence known by spreading
east towards our across our CWA, resulting in much above
temperatures. This will be the story through Memorial Day Weekend
into early next week as well. Models indicate highs in the 90s
during this time. Meanwhile, a large and slow-moving upper-level
trough across the western U.S. will churn towards the High Plains.
Pieces of energy may begin ejecting northeastward by late Saturday,
leading to on-and-off thunderstorm chances. The trough itself may
begin working into the High Plains by Tuesday/Wednesday, leading
generally better precip chances.


.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 630 PM CDT Wed May 23 2018

VFR conditions are expected over the next 24 hours. Any exception
would be during thunderstorms, which are possible across the area
through early this evening and then again later tonight (mainly
KPIR/KMBG). After a break in precipitation chances Thursday
morning, thunderstorm chances return across the area (mainly
KABR/KATY) Thursday afternoon and evening.

There will also be a low level jet around tonight, which could
create some low level wind shear at times.




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