Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 251728
AFDFSD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1228 PM CDT Sun Oct 25 2020

.SHORT TERM...(Today and Tonight)
Issued at 302 AM CDT Sun Oct 25 2020

Key Messages:

1. Light snow with occasional bursts of moderate snow will increase
through Sunday morning, with snow shifting south and east
overnight.

2. Additional accumulations of 1 to 4" of snow is expected, with the
highest amounts across southeast South Dakota, northern Nebraska
into northwest Iowa.

3. Record cold continues through Tuesday.

This Morning and Today: Broad isentropic lift persists early this
morning, leading to light snow across much of the forecast area this
morning.  Amounts thus far have ranged from a half inch to as much
as 2.5 inches in portions of the forecast area. As daybreak
approaching we`ll begin to see a minor shortwave lift northeast
along the low-lvl baroclinic zone. This should help sharpen and
intensify the snowfall through mid-day Sunday. More efficient
snowfall rates are expected, with upwards of 0.5" per hour rates
expected across areas along and south of Interstate 90 through 18Z
and shifting towards the Highway 20 corridor after 21Z. Have felt
that NBM SLR have been a bit high with this event so far with most
observed rates around 10:1 as opposed to forecast 14-16:1 ratios.
Lift will be better focused within an elongated portion of the
thermodynamic sounding within the DGZ, so am expecting ratios to
increase slightly. No changed expected with current headlines.

Tonight: Isentropic downglide will commence by mid-late afternoon
shutting snow down from NW to SE.  However, 700:600 baroclinic zone
will remain stretched out from central Nebraska into southeastern
Minnesota this evening, so anticipating light snow lingering in
the far southern portions of the forecast area into the overnight
hours. Further north, we`ll keep an eye on low temperatures. Some
concerns towards dropping into the single digits will be
lingering mid-upr cloud cover and light winds. We`ll again
approach record lows but could fall short.

.LONG TERM...(Monday through Saturday)
Issued at 302 AM CDT Sun Oct 25 2020

Monday: A very cold day is expected on Monday, with additional cold
high temperature records likely. High level clouds combined with
light winds and fresh snow could hold temperatures in the lower to
middle 20s. Yet again, breaking cold high temperature records.

Monday Night: Surface ridging will slide across the area by Tuesday
morning and should allow temperatures to plummet once again. Biggest
concern I have is with persistent mid-upr clouds hanging on into the
night. Soundings indicate this cloud cover could clear the area
prior to daybreak which could allow for a tanking of temperatures
into the single digits approaching records yet again.

Tuesday-Saturday: A very quiet pattern is expected to establish
itself well through the medium range and extended portions of the
forecast. Temperatures will crawl upwards each day, finally reaching
the middle 40s by Friday and perhaps 50s by Saturday.  Winds will
increase with the return of southwest winds, but should avoid any
strong gusts.  The one thing we`ll have to watch for is the
potential of stratus developing with the melting snow cover and
sharpening low-lvl thermal advection.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1227 PM CDT Sun Oct 25 2020

Snow continues to linger across the region, along with low cigs and
vsbys. Should start to see conditions gradually improve at KHON and
KFSD over the next several hours, with VFR levels forecast to return
near sunset. KSUX will be a bit slower to improve though, as snow
slowly drifts southeastward out of the region. Nevertheless, have
conditions improving to VFR levels around 06z. Otherwise, expect
dry conditions, light NW winds, and VFR cigs to prevail at all TAF
sites for the remainder of the period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 1 AM CDT Monday for SDZ061-062-
     066>071.

     Winter Weather Advisory until 7 PM CDT this evening for
     SDZ038>040-052>060-063>065.

     Winter Storm Warning until 7 PM CDT this evening for SDZ050.

MN...Winter Weather Advisory until 1 AM CDT Monday for MNZ072-080-081-
     089-090-097-098.

     Winter Weather Advisory until 7 PM CDT this evening for MNZ071.

IA...Winter Weather Advisory until 1 AM CDT Monday for IAZ001>003-
     012>014-020>022-031-032.

NE...Winter Weather Advisory until 1 AM CDT Monday for NEZ013-014.

&&

$$

SHORT TERM...Dux
LONG TERM...Dux
AVIATION...SSC



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