Area Forecast Discussion
Issued by NWS Aberdeen, SD

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726
FXUS63 KABR 230549 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1249 AM CDT Sat Sep 23 2017

.UPDATE...
Issued at 1249 AM CDT Sat Sep 23 2017

06z aviation discussion updated below.

UPDATE Issued at 927 PM CDT Fri Sep 22 2017

Forecast is on track. No updates/changes planned at this time.

UPDATE Issued at 706 PM CDT Fri Sep 22 2017

See below for an aviation forecast discussion for the 00Z TAFs.

&&

.SHORT TERM...(This Evening through Saturday Afternoon)
Issued at 341 PM CDT Fri Sep 22 2017

A nearly stationary frontal boundary currently extends from around
Leola to Presho as of 19z, with a more solid deck of lower clouds to
the west of it, and cumulus clouds to the east. A sizable
temperature gradient is also in place, with current temperatures in
the 50s over Corson county, and into the mid to upper 90s along and
east of the James River Valley. Main question now is if and when
convection may be able to get going in association with the frontal
boundary. The warm layer is currently well capped with H7 temps in
the +10 to +13 degree range. This cap really doesn`t look to break
down until into the late evening or overnight hours. CAMS solutions
seem to have picked up on this with no indications of convective
development until 03z or later. This timing also seems to fit in
line with a redeveloping low level jet and slightly increasing shear
values. If anything strong enough is able to get going, large hail
will be the main threat. The front looks to be over the far eastern
CWA by Saturday morning, with precipitation chance turning to mainly
rain as instability and dynamics remain weak behind the front. Best
chance look to be across the southern CWA through the day.

Low temperatures will range from the lower 40s northwest to around
60 southeast. High temperatures on Saturday will range from the
upper 50s west to the mid 60s east.

.LONG TERM...(Saturday Evening through Friday)
Issued at 341 PM CDT Fri Sep 22 2017

Main story in the extended period continues to be the prolonged
rainfall this weekend into Monday. It still appears the main slug of
moisture moves in Saturday night and lasts through the day Sunday,
but models disagree slightly on the axis of heaviest precipitation.
Although, models agree fairly well that it sets up somewhere near
the James River valley east towards the Watertown region. PWATS are
rather impressive for this time of year which indicates potential
for hefty totals. Current storm total precip grid does have about 2
to 3+ inches from the James valley east. The mean totals from the
EMC GEFS plumes are a bit lower than this though. Models continue to
show the surface boundary sliding far enough east into MN by Monday,
thus allowing for precipitation to eventually end. May need to take
another look at the small POPs that are in the forecast for Monday
night and Tuesday for possible removal.

Surface high pressure follows and will be centered over the area by
12Z Tuesday. Although, models suggest there will be some clouds to
contend with, so left inherited SuperBlend lows alone for the time
being. With another high pressure system moving in for the end of
next week, could be looking at chilly overnight lows once again.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 1249 AM CDT Sat Sep 23 2017

There are currently MVFR/IFR cigs over KMBG/KPIR and KABR, while
KATY remains VFR for the moment. Expect these sub-vfr cigs to spread
south and east over the KATY terminal by 12Z Saturday, and then
persist at all four terminals through at least, the next 24 hours,
if not longer. While this is going on, showers and thunderstorms
will continue to periodically overspread the region, bringing rain
chances to all four terminals off and on for the rest of tonight
through Saturday night. Expect liberal application of TAF amendments
while this event is unfolding.

&&

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

$$

UPDATE...Mohr
SHORT TERM...Parkin
LONG TERM...TMT
AVIATION...Mohr



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