Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 271657

Area Forecast Discussion
National Weather Service Aberdeen SD
1157 AM CDT Sat May 27 2017

Issued at 1147 AM CDT Sat May 27 2017

Only minor adjustments to keep up with some warmer temperatures in
the northeast as the inversion mixes out rapidly with thinning
clouds, and to POPs as the weak wave moves across our
south/southeast counties while dissipating. Winds here at KABR are
also a bit stronger then originally anticipated and have adjusted
accordingly, but the rest of the area is still around the 10mph

Still anticipating isolated to scattered shower/thundershower
activity later today as NAM BUFKIT profiles show steep low level
lapse rates while a mid level warm layer cools allowing for
shallow convection. If we can get showers to develop, NAM BUFKIT
profiles show that bases will be above the freezing layer, so we
could see some gustier winds with showers. Whether we will build
enough vertical development (into the hail growth zone) remains to
be seen, but will keep in mention of thunder for the afternoon.


.SHORT TERM...(Today through Monday Afternoon)
Issued at 345 AM CDT Sat May 27 2017

Large scale lift out ahead of the approaching trough is bringing a
large area of precipitation from far south central SD southward into
KS. Across our CWA, precip has been rather spotty thus far over the
southwest counties. There has been a bit of an uptick with the radar
returns across southwest SD recently, so expect these showers to
continue to advance into the CWA over the next several hours, with a
push east-northeastward through the morning. Northern SD looks to
stay dry from this morning`s event, and will have to await
redevelopment of showers/thundershowers later this afternoon and
evening for any chances at picking up rainfall. Although, any
activity later this afternoon and evening still looks widely

With upper level low pressure spinning across southern Canada Sunday
into Monday, cyclonic flow aloft along with steep lapse rates and
embedded vort maxima will keep potential for afternoon showers going
both Sunday and Monday. But again, coverage looks to be widely
scattered, and with limited instability, not expected any strong or
severe storms.

.LONG TERM...(Monday Evening through Friday)
Issued at 345 AM CDT Sat May 27 2017

At the start of the period, there are two predominant upper features
of interest over the western two-thirds of the CONUS: a large upper
level ridge over the Rocky Mountains and a large upper level closed
low system over Ontario; a blocky pattern to say the least. This cwa
will still be experiencing some of the influence of cooler (near to
below normal) conditions steered southward into the region from that
upper low on Tuesday. But beyond that, much of the period continues
to maintain a warming trend as the upper level ridge begins to
translate eastward into the region. The evolution of polar jet
westerlies influence on the western CONUS upper level ridge will
continue to need monitoring as this highly amplified pattern
gradually de-amplifies. With the 00Z deterministic GFS/ECMWF and
Canadian models all handling that de-amplification process a little
differently, they all have some slightly different outcomes for
timing/coverage of precipitation chances. The GFS has precipitation
developing out ahead of and underneath the ridge axis on Thursday.
The Canadian is a bit slower and pushes shortwave energy all the way
through the ridge axis, bringing precipitation chances into the CWA
Thursday night. The ECMWF, similar to the Canadian but slower,
brings precipitation chances into the CWA on Friday. So still some
ironing out to do w.r.t. precipitation chances, and Superblend
correctly keeps the forecast dry until Thursday when low pops are
introduced. Low pops can then be found smattered all throughout the
rest of the period.


.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
Issued at 649 AM CDT Sat May 27 2017

VFR conditions are expected through tonight at all four terminals.
Morning showers at KPIR will likely shift east and become early
afternoon showers at KATY, if they don`t fizzle out first. Then,
later this afternoon into this evening, all four terminals, but
especially KMBG, KABR and KATY, could be dealing with an isolated
to widely scattered shower or weak thunderstorm.




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