Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 201053

Area Forecast Discussion
National Weather Service Sioux Falls SD
553 AM CDT Mon Mar 20 2017

.SHORT TERM...(Today and Tonight)
Issued at 314 AM CDT Mon Mar 20 2017

Surface high pressure will continue to spread across the northern
Plains today. Mid and high clouds will likewise spread east across
much of the area, and will be greatest along and north of I-90.
Clouds will becoming more abundant this afternoon and evening, which
along with minor cold air advection filtering into the region, will
help cap high temperatures much cooler than yesterday`s readings.
Temperatures will be tricky given the increasing cloud cover, but
decided to warm readings a few degrees in the Missouri Valley where
the greatest potential for sunshine exists. Highs will still be
above normal in the 50s to near 60.

Upper level trough digs into the Upper Midwest tonight, with a mid
level shortwave sliding along the South Dakota and Nebraska border
late this evening through the overnight hours. Model consensus has
moved this wave slightly southward, with the best mid level
forcing/frontogenesis setting up near the mid-Missouri Valley late
tonight. Significant low level dry layer will help diminish some of
the precipitation especially initially, with areas east of the
James River likely seeing mainly virga or a very low chance of
precipitation late. Did slow down the onset of precipitation and
nudged chances further south. Still have likely and categorical
pops in the Missouri Valley/South central SD where low level
moisture and forcing is best. Temperatures will be cooling to
near freezing as the precipitation begins, with some wet-bulbing
from rain to snow possible late tonight in south central as the
precipitation rate increases. Still, mainly looking at light rain
or sprinkles and mixing with some snow towards daybreak, but
little to no accumulation for the overnight period.

.LONG TERM...(Tuesday through Sunday)
Issued at 314 AM CDT Mon Mar 20 2017

The short wave will begin to exit the area on Tuesday with the
precipitation ending from northeast to southwest due to the
influence  of the drier air moving in from the northeast. Any
lingering precip should end by early Tuesday afternoon. Less
confident on accumulating snow chances but if any area sees it, it
will be the areas along the Missouri River Valley region. With
the potential mid level squeeze play, I won`t be too surprised to
see an inch or two in those areas.

Then another weak wave is forecast to move across the are on
Wednesday, which is slightly slower than previous runs.  The problem
I see with this system is the limited moisture in the low levels.
The forecast soundings look rather dry so feel we`ll mainly see
clouds with this wave, but still can`t rule out a few sprinkles or
flurries especially in the western counties where the low level
moisture may be a little deeper.

After that, all focus turns to stronger system coming into the area
on Thursday and continuing throughout the day on Friday. GFS and
ECMWF are pretty similar with timing and placement of low and
precip shield. Most definitely looks wet across much of the area
from 18z Thursday to 12 Saturday. Some areas could easily exceed
an inch even though precip may start in the form of drizzle.
Heavier precip/rain is more likely on Friday and could experience
thunder in southern sections of the area, but could get robbed by
convection that will be firing to the south of the area.

Temperatures will still be above normal for the week, but with the
cloud cover and precip it will feel quite a bit cooler.  Don`t
expect much variation with temps through the upcoming weekend.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 549 AM CDT Mon Mar 20 2017

VFR conditions are expected through the TAF period. Mid level
clouds will increase mainly after midnight. Light rain or snow
will become likely across south central SD late tonight and will
likely produced MVFR to IFR ceilings and visibility in snow after
09z. TAF sites will remain VFR.




LONG TERM...Heitkamp
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