Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 231121

Area Forecast Discussion
National Weather Service Sioux Falls SD
621 AM CDT Thu Mar 23 2017

.SHORT TERM...(Today and Tonight)
Issued at 338 AM CDT Thu Mar 23 2017

Unsettled weather arrives into the area today. Early this morning,
persistent southerly flow continues to pull low level moisture into
the region, albeit slowly.  Models generally too aggressive in
current dew points this morning within their initializations, but
suggest that reservoir of 50 dewpoints over Oklahoma will surge
northward into the mid- Missouri River valley late this afternoon.
Satellite imagery this morning is beginning to showing deeper low
level moisture across Kansas and Oklahoma beginning to accelerate
northward, with lower ceilings (at or below 1k FT AGL) arriving
shortly after daybreak.

Today: Arriving stratus will overtake the area through the morning.
Broad low level warm advection working with this deepening moisture
layer should be sufficient to produce some drizzle potential by late
morning. Will also watch an area of strong theta-e advection aloft
(AOA 700 mb) that will pivot northeast through the area by mid-day.
Steepening mid-lvl lapse rates above this layer may owe to the
development of scattered showers or even a few thunderstorms as
the lift axis pivots through the CWA. A more concentrated focus
in the afternoon develops over west central and central MN. The
afternoon hours may feature occasional spits of light rain and/or
patchy drizzle. Temperatures will climb into the 50s in many
areas, with the warmest readings closer to the 60s focused in
South Central SD along axis of a developing inverted trough and
northward lifting warm front.

This Evening/Overnight: Several areas for convective focus
tonight. Along an advancing dry-line over western Kansas,
developing surface low over NE Colorado, and then further north
late in the evening along the stalled warm front in the mid-
Missouri River valley. Models continue to have some discrepancies
as far as the northern extent of warm front. 00Z/06Z NAM continues
to be the southern outlier, with other models beginning to focus
the increasing 50-55 knot LLJ in the evening along a convergence
boundary over north central Nebraska by 03z. Lapse rates with the
850:700 mb layer to sharpen over the CWA deeper moisture arrives,
and freezing levels hold near 8k ft AGL, so while not a large
threat, couldn`t discount a few stronger hail producing storms
between 03-07Z as they lift northeast along the elevated boundary.
High resolution CAMs seems to be shifting towards this soln. The
other concern overnight would be with potential for locally heavy
rains. PWAT values do spike near 1.15" during the evening, at or
above the daily max climatology values for the day. While storms
should be fairly progressive along the SW-NE oriented boundary, a
few spots could pick up a quick 1-1.5" of rainfall.

.LONG TERM...(Friday through Wednesday)
Issued at 338 AM CDT Thu Mar 23 2017

Friday: The large upper trough will continue to slide eastward into
the lower Missouri River valley on Friday. A rather soggy day is
anticipated as lift continues across the 850:700 mb boundary.
Thunder chances won`t be that high on Friday, with renewed
instability flowing over the boundary in the afternoon, could see an
isolated rumble south of I-90. Rain slowly pivots away from the area
on Friday night, albeit slowly.

Saturday-Sunday: Drier air will filter into the Tri-State area for
Saturday and Sunday. Temperatures will average  near their seasonal
normals. Stratus may linger over the eastern half of the day through

Monday-Thursday: An active pattern continues through next week, but
model differences are starting to develop as a greater amount of
uncertainty with upper troughing digging into the Western CONUS
develops. With most of the focus on the short term, made only minor
changes in the extended. Only focused changes were to slightly lower
PoPs from Wednesday to Friday given the very high uncertainty with
upper troughing.  Did not feel categorical PoPs provided by the
blends were warranted yet with such high variance in individual


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

Messy aviation forecast for today. We`re continuing to watch MVFR
and IFR stratus race northward this morning. This stratus will
overtake the terminals through the morning. Potential for
development of light fog and drizzle by mid-day and this may
linger into the early evening. After 00Z convective signals start
to increase over northern Nebraska, with convection gradually
lifting northeast through the late evening and overnight hours.
The prime time for any thunder will be focused from 03-07Z for
Sioux Falls, with the window more limited for Sioux City.

Low confidence after 06Z, but trends support ceiling and
visibility restrictions through daybreak.




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