Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 211749

Area Forecast Discussion
National Weather Service Sioux Falls SD
1249 PM CDT Sun May 21 2017

.SHORT TERM...(Today and Tonight)
Issued at 356 AM CDT Sun May 21 2017

Showers will be slow to end across our northern zones this morning
as low pressure lifts slowly to the northeast due to trowaling.
However eventually drier air in the low levels finally moves into
the area by midday and afternoon. The one exception is in southwest
MN where high moisture levels still exists all afternoon in the 1.0
to 1.5km layer. Coupled with unstable dry adiabatic soundings for
the lapse rates in the low layers and a vort filament, a few
instability showers could linger in these zones through the
afternoon. It will also be pretty breezy today throughout the
forecast area. 25 to 30 knots exists in the mixed layer and as
mentioned, it is unstable in the lowest kilometer. Therefore we are
looking at 20 to 30 mph winds for most locations by late morning and
afternoon. Highs today will certainly modify from what they have
been. Mixing suggests 50 to 55 in southwest MN, to the upper 60s
toward central SD.

Tonight, not a lot going on for a change. Sprinkles are possible
along a band of mid level moisture moving quickly eastward near the
I 90 corridor. But otherwise shaved a couple of degrees off of
consensus lows due to winds becoming very light. And despite the
band of mid clouds moving eastward, the CWA looks fairly clear by
late in the night allowing temperatures to drop after a cool Sunday.

.LONG TERM...(Monday through Saturday)
Issued at 356 AM CDT Sun May 21 2017

Clouds will increase fairly quickly on Monday as a shortwave
approaches from the north and west.  The timing of the disturbance
is slightly quicker than previously expected, but the net result is
the same with showers and thunderstorms developing across the area.
CAPE profiles continue to be very tall and thin, and with weak wind
shear, am not expecting storms to approach severe limits.

On Tuesday, could see some diurnal showers develop during the
daylight hours.  Best chances for measurable precipitation will be
east of I-29 where lapse rates in the 800-700 mb layer are slightly
steeper.  With a fair amount of self destructive sunshine, could be
a struggle to warm beyond the 50s.

Expect dry and warming conditions as weak ridge moves through the
area and southerly flow develops in earnest on Thursday.

More active pattern is expected Friday lasting through at least the
first half of the weekend as a series of disturbances work through
the region. Timing of the various disturbances are uncertain at this
point, so left the blended pops for now.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1235 PM CDT Sun May 21 2017

MVFR ceilings slowly improving this afternoon as cloud gradually
erode from west to east. MVFR/VFR ceiling will persist through
late this evening; but scattered low to mid clouds could stick
around a bit longer across southwest Minnesota. Gusty surface
winds to 25 to 30 mph expected through sunset at all sites. LLJ of
40 knots at around 1400 ft possible in the nighttime at KSUX.




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