Scientific Forecaster Discussion
fxus63 kabr 250840
Area forecast discussion
National Weather Service Aberdeen South Dakota
340 am CDT sun Jun 25 2017
Short term...(today through Tuesday afternoon)
issued at 339 am CDT sun Jun 25 2017
Clouds have finally broken up for the most part across the eastern
County Warning Area. Surface high also settling into the region with light winds
across central South Dakota. Temps are falling through the 40s for most areas,
and would not be surprised to see a few upper 30s by sunrise across
central South Dakota into the James Valley.
For later today, upper level disturbance will slide southeast across
the Dakotas. This system produced scattered showers across southern
Canada on Saturday. Cam solutions all show widely scattered showers
or thundershowers developing/moving into the area this afternoon.
Instability is very limited, but minimal amounts of MLCAPE do exist
across the eastern County Warning Area. Have extended pops further west based on
several cam solutions showing development as far west as the
Surface high pressure will settle in once again tonight, bringing
another night of chilly temperatures. Overall, the atmosphere looks
drier, so more confidence in mostly clear skies through the night
which will allow for temps to plunge once again into the lower 40s.
This high pressure will remain in the area on Monday, which will
bring mainly light winds and dry conditions.
Tuesday is looking warm and windy with increasing low level
moisture. Dewpoints will be in the increase as southerly low level
flow increases ahead of an approaching cold front. Pressure gradient
tightens nicely and have increased wind speeds above that of
superblend. Seemed like a classic case where we can safely go higher
with wind speeds. Any convection on Tuesday will likely hold off
until later in the day and be confined to the western County Warning Area closer to
the frontal boundary. More widespread precip will likely hold off
until Tuesday night.
Long term...(tuesday evening through saturday)
issued at 339 am CDT sun Jun 25 2017
The extended period begins with upper level ridging over the region,
which quickly gets pushed to the east Tuesday night by a shortwave
trough and its associated energy. After a brief period of zonal flow
Wednesday night, another trough will slide across the region
Thursday and Friday before northwest flow sets up on Saturday.
At the surface, a frontal boundary will be over the western part of
the state Tuesday evening, with precipitation likely ongoing or just
getting started over parts of the County Warning Area. The precipitation will likely
continue through Tuesday night, with some strong to severe storms
possible in association with MUCAPE values of 1500-3000 j/kg, shear
of 40-60 knots, and a 40 to 60 knot low level jet. The system pushes
east on Wednesday, with precipitation coming to an end in the
morning. Additional precipitation chances associated with a low
pressure system set to track across the Central Plains Thursday and
Friday will likely just be some general showers and thunderstorms
with weak instability and shear at best. High pressure slides back
over the area Saturday, resulting in mostly dry conditions.
Temperatures will be near to slightly below normal through the
period, with highs mainly in the mid 70s to lower 80s. Overnight
lows will be mainly in the 50s.
Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1224 am CDT sun Jun 25 2017
VFR conditions are expected overnight and through the day Sunday.
Winds will continue to diminish overnight and become light and
variable for the western sites. As a shortwave moves through the
region on Sunday, isolated thunderstorms will be possible. Still
too uncertain on areal extent and timing to add a mention in the