Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 251130
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
630 AM CDT Sun Aug 25 2019

.SHORT TERM...(Today through Monday Afternoon)
Issued at 313 AM CDT Sun Aug 25 2019

Light shower activity associated with a weak wave continues to lift
north out of southeast South Dakota, mainly east of the James
valley. To the west, The left exit region of a 110kt jet is slowly
moving towards the western Dakotas, in conjunction with a deepening
upper trough. There is already elevated convection associated with
these features in central North Dakota through eastern Montana. As
the general pattern shifts east, overtop a moist and unstable
atmosphere, and a front descends into the region, convection
looks like a certainty. The environment features 0-6kt shear of
30-40kts and freezing levels around 11-13kft (the gradient is from
west to east respectively). Westerly flow aloft suggests that
storms will be at least somewhat progressive, and the northeast to
southwest orientation of the front will limit training. We
currently have quite low LCLs albeit mixing will generate somewhat
higher LCLs. MLCAPE is generally around 2-3k j/kg. Speed shear in
the mid levels is good enough to support structure for
supercells, although winds below 600mb are a little on the weak
side until we get into the boundary layer which will continue to
feature breezy southeast winds. Its uncertain, but I think this
will limit the tornado threat, but generally have little impact on
the wind/hail threat. Overnight, storms continue east, however
the low level jet will be deflected east of the CWA.

For Monday, flow aloft features a secondary shortwave crossing the
area mid-day. Profiles remain unstable thanks to cooling despite
being on the cold side of the front. Profiles feature shear and
skinny CAPE so while severe weather is probably unlikely, there will
be additional thunderstorm development during peak heating.

.LONG TERM...(Monday Evening through Saturday)
Issued at 313 AM CDT Sun Aug 25 2019

Precipitation may brush our northern border Monday night through
Tuesday, as a surface trough still extends across ND/northeastern
SD/northern MN from the low across Ontario, and the 500mb low over
Manitoba keeps a large through across much of the northern half of
the U.S. The upper low will shift into Ontario Tuesday/Tuesday night
as a large ridge builds from the southern U.S. into the west coast.

With the elongated surface ridge still lingering to our west and
southwest, the main theme will be breezy winds out of the northwest
Tuesday afternoon, on the order of 20 to 25kts with higher gusts.
Wouldn`t be surprised if we end up with more cloudy conditions
Tuesday night, as disturbances rotate around the 500mb low. The west
coast ridge will not move too far east through next Sunday, so
expect northwesterly flow to linger across the Norther Plains.

Southerly flow/warm air advection will return Thursday morning. Just
how quickly it goes away is uncertain. The operational GFS maxes out
850mb temperatures of 17 to 23F through the afternoon hours. While
the ECMWF nears those temperatures too, but it`s about 6 hours
earlier with the cold front sinking in from the north. At this
point, highs in the upper 60s to mid 70s look reasonable each day
but Wednesday and Thursday afternoon, when temperatures rise into the
70s to near 80 degrees. The cool surface high across Alberta
Thursday morning should sink across the Dakotas Friday, and
Minnesota/eastern SD Saturday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
Issued at 626 AM CDT Sun Aug 25 2019

A mix of MVFR/IFR CIGS this morning. These are expected to mix
out, although that is not guaranteed. Storms are expected to pass
through the area late this afternoon through the early overnight
hours.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

SHORT TERM...Connelly
LONG TERM...KF
AVIATION...Connelly


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