Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 201120 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
620 AM CDT Tue Jun 20 2017

.SHORT TERM...(Today through Thursday Afternoon)
Issued at 405 AM CDT Tue Jun 20 2017

High pressure moving overhead today, and as this feature moves east,
we see return flow and a 40kt low level jet developing in south
central South Dakota. This will be the focus for elevated convection
with around 1000 j/kg MUCAPE. Shear is unidirectional out of the
northwest, at 50-60kts, so storms that develop could be severe with
a hail threat focused across central South Dakota.

As the day progresses and elevated convection moves east and weakens
we are set up with a low pressure center over southern Canada and a
front extending to the south across the forecast area. Flow will be
southerly ahead of this feature with mixed dewpoints in the upper
50s/low 60s, but with 700mb temperatures from +9 to +13C from north
to south. That cap looks to push east while the frontal passage is a
little slower thanks to westerly flow at 700mb so we still have the
potential for surface based convection. The convective environment
will feature MLCAPE values topping out around 1500j/kg with 40kts 0-
6kt shear. Most of the turning in the low levels is shallow and flow
is mostly westerly so anticipate any storms that develop to move
rapidly eastwards.

Its important to note the duality of this frontal system as the GFS
depicts more of a dry line with a cooler airmass in southeast flow
at 850mb, while to the west we see warmer temperatures with
favorable mixing in northwest flow and drier air, with the cold
advection lagging about 100km to the northwest.

The front will also stall just to the south, and with zonal flow
aloft we actually see some return flow/isentropic lift in the mid
levels and warm advection clouds and showers for Thursday

.LONG TERM...(Thursday Evening through Monday)
Issued at 405 AM CDT Tue Jun 20 2017

The long term starts off with a broad trof digging into and across
the Northern Plains. An expanding and amplifying ridge over the
western conus should allow for the trof to gradually develop/deepen
east toward the Great Lakes. Energy aloft diving southeast over the
region will provide for a chance of rain both Friday and Saturday,
along with cool temperatures. The latter part of the weekend should
be mostly dry as that energy heads off to the east. Severe weather
chances look minimal during the entire time period.

The mid level trof over the region will provide for a cool weekend
over the region with temperatures averaging out below normal.
Temperatures will begin to recover next week.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday Morning)
Issued at 620 AM CDT Tue Jun 20 2017

Vfr conditions are expected at all terminals through today.




SHORT TERM...Connelly
AVIATION...TDK is the U.S. government's official web portal to all federal, state and local government web resources and services.