Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 232020

Area Forecast Discussion
National Weather Service Aberdeen SD
320 PM CDT Wed May 23 2018

.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 3 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 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1244 PM CDT Wed May 23 2018

VFR conditions are expected this afternoon. Any exception would
be during thunderstorms, which are possible across the area this
late afternoon and evening. Thunderstorm chances return across the
area Thursday afternoon, however they should be limited mainly to
northeastern South Dakota.




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