428 
FXUS63 KABR 192331 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
631 PM CDT Tue Oct 19 2021

.SHORT TERM...(This Evening through Wednesday Night)
Issued at 259 PM CDT Tue Oct 19 2021

The primary forecast challenges are: will the (wet bulb) temperature 
in the column cool enough to support snow late tonight/early 
Wednesday?; and if so, how much snow could accumulate?

As of 2 PM CDT, a cold front is just about completely clear of the 
CWA (far southeast corner). Breezy/windy 15 to 25 mph northeast 
winds with gusts to 35 mph behind the front are now common over just 
about the entire CWA. These winds are ushering in low stratus clouds 
and much cooler low level air (925hpa temps that were in the low to 
mid teens C earlier in the day are now down into the low to mid 
single digits C) throughout the CWA.

There is an upper level closed low pressure system out over 
northwestern Colorado. It's associated surface low is developing out 
over western Kansas. This is about a whole state further south than 
previous model runs had it; placed previously out over 
western/central Nebraska at this time. This is cause for concern 
that perhaps the subtle trends in precipitation foot slipping 
further south in the past three or four model runs is becoming a 
reality. Deformation-zone banded precipitation should begin 
developing/moving into the western/southwestern forecast zones, in 
earnest, by 06Z tonight. Looks like now, the heaviest precipitation 
amounts may end up developing/falling across the southern half of 
South Dakota later tonight and Wednesday (aka the southern half of 
the CWA). BUFKIT soundings/model progs and ensembles output all 
point to portions of central and north central South Dakota (mainly 
the west river counties of Corson down to Jones) seeing p-type 
change from rain to snow or a rain/snow mix between 09Z and 15Z 
Wednesday. Light snow accumulations (<2 inches) still thought 
possible. And, if that materializes in this 15 to 30 mph northerly 
wind where the surface temperature is hovering around the freezing 
mark, the concern is that there could be some slick spots on area 
roadways to contend with heading into the Wednesday morning commute. 
The other tidbit/change in the grids is based off the "appearance" 
of a drizzle sounding at all the points available in BUFKIT (both 
NAM and GFS soundings) over this CWA, at varying times, between 03Z 
tonight and 03Z Thursday. Likely there are times during this event 
when the mid-level saturated layer for precip-production goes away 
(a dry slot), leaving this deep saturated "not-cold enough to 
activate ice" stratus layer around for drizzle to fall out of.

Precipitation should be tapering off Wednesday evening as the system 
moves away from the region, while low cloudiness likely sticks 
around for a good portion of Wednesday night. The cold airmass that 
is advecting into the region today will be sticking around 
throughout the ESTF period.

.LONG TERM...(Thursday through Tuesday)
Issued at 259 PM CDT Tue Oct 19 2021

Surface high pressure will be in place over the region on Thursday, 
with the high eventually moving east of the region Friday into 
Saturday. This looks to bring quiet weather and chilly overnight 
lows both Thursday night and Friday night, with readings dropping 
into the upper 20s for some areas. There are some hints of a weak 
shortwave dropping southeast across the region on Friday, but will 
wait to see how this is handled in future model runs before adding 
any pops for this. Aside from this, the next chance of precip occurs 
towards the latter half of the weekend when models try to bring an 
area of low pressure out into the plains. Quite a bit of uncertainty 
regarding the overall strength and evolution of this system, and 
inherited POPs look OK for now advertising low chances. 

As for temperatures, rather chilly air to start off the period with 
highs in the 40s and 50s Thursday into Saturday. Pretty good 
agreement showing up in another warming trend starting up by early 
next week with upper level ridging moving back in. 60s likely moving 
back into the region, and potentially warmer.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 628 PM CDT Tue Oct 19 2021

Terminals KABR,KATY,KPIR,KMBG

MVFR/IFR cigs are expected regionwide through tonight. Meanwhile,
as rain moves into the area, you can also expect MVFR vsbys late 
tnt and on Wednesday and most terminals.  

&&

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

$$

SHORT TERM...Dorn
LONG TERM...TMT
AVIATION...TDK