Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 212359 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
659 PM CDT SAT MAY 21 2016

Issued at 656 PM CDT SAT MAY 21 2016

The aviation discussion has been updated below.


.SHORT TERM...(This Evening through Monday Night)
Issued at 315 PM CDT SAT MAY 21 2016

The potential for severe storms late Sunday afternoon through Sunday
evening will be the main forecast concern.

a large upper level trough of low pressure over the Pac NW will
slowly lift northeastward into SC Canada by 0Z Monday. This
system...along with a surface low pressure and associated front
will slowly slide across the western Dakotas around 0Z monday.
This front will interact with a moist...albeit narrow boundary
layer where cape values should reach 2K J/KG. The best area of
cape is located along the Missouri River Valley. This is where
some hi-res models suggest strong to potentially severe
thunderstorm development. That said...both the NAM and GFS are
suggesting the Missouri River Valley could see stratus through
most of the day which should limit the convective potential. The
12Z NSSL WRF highlights limited convection fairly well. Somewhat
interesting...nearly all models suggest weak elevated showers
Sunday...which seems unlikely given 700 MB temps of plus 8C.
Overall...the severe potential Sunday looks rather limited.
Stronger storms are possible Sunday night as a healthy LLJ
develops. Hail and damaging winds will be the main threat. Locally
heavy rainfall will also be possible.

Additional strong storms are possible along and east of I-29 Monday
afternoon as the front will be slow to exit the cwa. Cape parameters
remain fairly high...and shear is decent enough to support strong

.LONG TERM...(Tuesday through Saturday)
Issued at 315 PM CDT SAT MAY 21 2016

A fairly active forecast is taking shape during the long term. A
very broad positive tilt trof is expected to exist from south
central Canada southwest into the extreme southwest CONUS. A wavy
but weak frontal boundary will persist on the southern edge of the
westerlies through most of the forecast time period. Every day or so
a surface wave will track northeast across the central
CONUS...producing scattered showers and thunderstorms over much of
the Central and even parts of the Northern Plains. Details in this
particular flow pattern are hard to pin down and thus a broad brush
approach will have to be used for pops/pcpn. Temperatures overall
should favor near to perhaps slightly below normal during the four
to seven day time period.


.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 656 PM CDT SAT MAY 21 2016

VFR stratus has spread across much of western and central SD this
evening. Expect ceilings to drop into the MVFR category through the
night at the KMBG/KPIR TAF sites. Winds will continue to decrease
through the night as well...although maintained the possibility of
LLWS at KABR and KATY overnight. Also carried a VCSH mention in the
KPIR for early Sunday morning...although precip chances remain low
at this point.


.ABR Watches/Warnings/Advisories...


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