Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 282035

Area Forecast Discussion
National Weather Service Aberdeen SD
335 PM CDT Wed Jun 28 2017

.SHORT TERM...(This Evening through Thursday Afternoon)
Issued at 335 PM CDT Wed Jun 28 2017

Shower/thunderstorm activity already taking place in Wyoming/
Montana/far western South Dakota late this afternoon with the
approach of the next short wave trough. This activity will continue
to develop/move east through tonight and Thursday as the short wave
moves into our region. With weak instability, dont expect any severe
weather with this system. Have in good chances of showers/storms
starting after midnight out west and spreading east through
Thursday. Otherwise, below normal temperatures are expected on
Thursday with highs in the 70s.

.LONG TERM...(Thursday Evening through Wednesday)
Issued at 335 PM CDT Wed Jun 28 2017

Upper trough axis will be just west of the CWA at the start of
the long term period, stretching from Lake Winnipeg and southwest
to far northwestern Colorado. This upper trough will slide
southeast through the region through Friday evening and provide
the best opportunity for rain during the long term portion of the
forecast.  As the upper trough moves through, a trailing cold
front will drop southeast across the CWA during the day on
Friday. Will show the highest pops moving through Thursday night
with the initial shortwave and lingering convection and again
during the day on on Friday over the eastern half of the CWA.
Will continue to include thunder chances with the showers on
Friday with afternoon MLCAPE values rising to 500-1000 J/kg, but
don`t expect any severe weather due to the tall/skinny CAPE
(NCAPE values don`t exceed 0.05) and 0-6km bulk shear values are
less than 20kts. With the clouds and potential showers, highs will
be below normal and in the 70s.

Behind the front and upper trough, northwesterly flow will settle
over the area for Saturday and bring a cooler than normal start
to the weekend. Could be some weak mid level WAA and moisture
over eastern SD on Sat and will hold on to some clouds in that
area. A shortwave crossing the northern Rockies on Saturday night
will largely dive southeast of the area on Sunday, but the nose of
the best mid level warm air advection along the inverted
trough/cold front will likely influence the south central part of
SD during the day. Models vary on the timing, with the 12Z runs
trending the front a little faster on the southward movement and
keeping much of the precipitation to the south of the area on
Sunday afternoon. Will trend that direction and keep the PoPs
largely confined to the southern CWA border.

Still some uncertainty in the models on how long the disturbance
will linger over the area into early next week, but the large
scale pattern indicates an upper ridge building over the area for
the start of the work week.  This will lead to increasing
temperatures and generally dry conditions for the start of next
week. Current forecast is showing highs rising into the 90s for
the Tuesday/Wednesday time frame and that matches up with the
ensemble guidance from the ECMWF/GEFS (won`t get too fancy
with Wednesday`s temps at this point due to the potential for a
cold front to move through sometime on Wed).


.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 1249 PM CDT Wed Jun 28 2017

VFR conditions are expected for all locations through tonight and
Thursday with some mixing layer cu clouds into the early evening.
Otherwise, the next upper low pressure trough moving in from the
west will spread another round of showers and storms into the
western part of the region later tonight. These could affect both
MBG and PIR at or in the vicinity.




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