Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 221945

Area Forecast Discussion
National Weather Service Aberdeen SD
245 PM CDT Tue May 22 2018

.SHORT TERM...(This Evening through Wednesday)
Issued at 243 PM CDT Tue May 22 2018

The forecast concerns include the threat for severe storms later
tonight, and again Wednesday afternoon.

A warm front will slowly lift northward over the region later this
afternoon through tonight. Showers and thunderstorms should develop
along the front around 0Z near the NE/SD border. With marginal
instability along the the nose of a 30 knot LLJ could yield a few
stronger storms tonight. A few CAMS suggest a broken line of storms
lifting northward over much of the CWA tonight through Wednesday
morning before diminishing. Others indicate east central SD and
north central SD receiving the brunt of the pcpn tonight. With a
slow storm motion expected, locally heavy rainfall could be the main
threat with tonight`s weather.

Pcpn over this CWA should exit the area by 15Z Wednesday with mostly
dry and warm temperatures expected through the mid afternoon hours.
By the afternoon hours, a few CAMS are suggesting convection
developing along a weak front, or better the Missouri and James
Valley. With plenty available instability and shear, strong to
severe storms are possible. However, the overall timing and
placement of storms on Wednesday remains unclear.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 243 PM CDT Tue May 22 2018

Upper level ridging will slide east of the area Wednesday night and
Thursday, as a shortwave trough tracks across the Northern Plains
through early Friday. Ridging then rebuilds over the region and
remains dominant through the remainder of the period, with another
shortwave trough approaching the western high plains next Tuesday.

An elongated surface low will be over the Rockies Wednesday evening,
then begins to push eastward, becoming the focus for shower and
thunderstorm development Wednesday night across the western and
central part of the CWA, then again Thursday afternoon and evening
across the central and eastern part of the CWA. Instability drops
off pretty quickly Wednesday evening, with minimal amounts of bulk
shear, but there will be some low level jet support, so cannot rule
out a few strong to severe storms developing. Thursday will see
slightly higher amounts of shear and fairly impressive amounts of
MUCAPE in the afternoon, with the northeastern CWA looking to be the
prime area for strong to severe storms, before both shear and
instability drop in the evening, with again little in the way of low
level jet support. The Friday through Sunday time period looks dry
under the strong upper ridge, then will just see the potential for
scattered shower and thunderstorm activity Monday and Tuesday under
slightly unstable conditions with the CWA situated between low
pressure to the west and high pressure to the northeast.

Temperatures will be fairly warm through the period, with highs in
the mid 80s to mid 90s, and overnight lows mainly in the lower to
mid 60s.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 1234 PM CDT Tue May 22 2018

Prevailing VFR conditions are expected for all terminals through
the valid TAF period. A warm front lifting northward over the
region tonight will bring a change of showers and thunderstorms.
MVFR to IFR conditions are possible with these storms. Timing of
thunderstorms is best between 3Z and 9Z.




LONG TERM...Parkin
AVIATION...SD is the U.S. government's official web portal to all federal, state and local government web resources and services.