Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 231552 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1052 AM CDT Thu Mar 23 2017

Issued at 1037 AM CDT Thu Mar 23 2017

Continue to watch evolution of system to our south, with dry air
being noted now pushing northeast into southwest SD, which is
allowing for some clearing into the western CWA. Also continue to
see low level stratus clouds streaming northward across eastern
SD. Models continue to suggest these low clouds will continue
streaming northward through the day and eventually cover the
eastern CWA. Warm air advection today is not that strong, and
wonder about the ability for temps to climb under the stratus
clouds. ShortBlend has been trending cooler vs. forecast highs
over the past few hours, and have dropped highs a couple degrees
for some locations. Although, with the clearing out west, left
highs alone for central SD. Models also show potential for some
light shower or drizzle development later today over parts of the
CWA, more so over the eastern CWA. Could see some fog over the
Coteau region by later this afternoon and evening as well, which
many of the models show in aviation VSBY grids.


.SHORT TERM...(Today through Saturday Afternoon)
Issued at 336 AM CDT Thu Mar 23 2017

Showers moving up across western South Dakota this morning
associated with the formation of an inverted trough ahead of a weak
shortwave ejecting out ahead of the main upper low. To our east, a
low level jet is gradually sliding into Minnesota. As the day
progresses, NAM BUFKIT profiles support increasing saturation and
possibly drizzle type soundings across much of the CWA, though with
less thickness as you get closer to central and southwest counties.
Steep lapse rates aloft could also support weak elevated convection
on top of this layer.

As the system evolves, a band of precipitation will set up mainly to
the south and winds will be predominantly out of the northeast. Thus
through the middle of the weekend we will see temperatures with a
limited diurnal range. Any breaks of sunshine should get us into the
40 to 50 degree range with 850mb temperatures around +4C.

.LONG TERM...(Saturday Evening through Wednesday)
Issued at 336 AM CDT Thu Mar 23 2017

The period opens with weak surface high pressure in place across the
region, and plenty of surface/bl moisture. Weak upper level ridging
holds for the first couple of days in the extended and by Sunday
night there is very little in the way of a surface pressure pattern
at all. With light winds and plentiful boundary layer moisture
around, will have to monitor skycover trends over the weekend into
early next week for night-time fog potential. The Fog Tool yielded
some light fog potential each night from Saturday night through
Monday night. Beyond Monday night, the current model progs continue
to produce a gradual flow pattern shift to south-southwesterly flow
aloft by the middle of next week and draw an upper level system into
the region within it. Will have to continue to monitor this trend to
see if it holds, as this scenario would bring some precipitation
(rain) chances back into the forecast.

As the dayshift yesterday indicated, there isn`t much in the way of
low level thermal advection in the out periods. Airmass moderation
almost seems more appropriate. Current 00Z suite of GSM low level
thermal progs and ensemble mean output continues to suggest
temperatures in the out periods will be near to slightly above climo
normal at the end of March.


.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
Issued at 616 AM CDT Thu Mar 23 2017

Current VFR conditions will be dropping into the MVFR/IFR
category due mainly to developing/lowering cigs over the next 6 to
9 hours on continued southerly breezes and falling surface
pressure values. Mid-level warm-air advection showers developed
over western South Dakota earlier and have moved up into north
central South Dakota on their way into North Dakota this morning.
Additional waa-forced mid-level showers are forecast to pick up
by late this morning over eastern South Dakota before lifting up
into North Dakota and MN. Models are forecasting the stratus
clouds to deepen enough (at least at KATY) to support the
development of some light drizzle and lowered visibility by this
afternoon into tonight. Got the ball started with some lower visby
and drizzle mention in the KATY TAF as a result.




SHORT TERM...Connelly
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