Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 280341

National Weather Service Sioux Falls SD
1041 PM CDT Tue Oct 27 2020

.SHORT TERM...(This Evening through Wednesday Night)
Issued at 337 PM CDT Tue Oct 27 2020

After a record-breaking cold start to the day for most locations,
afternoon maximum temperatures will start trending upwards for the
next couple days. As the upper level trough has pushed through the
area this morning, we remain under northwesterly flow aloft with the
upper level cut-off low slowly meandering eastwards across the
southern states. In the lower levels, winds are largely
southeasterly with some slight veering towards the 850mb layer. This
has resulted in some gusty winds, particularly for areas on the
northeastern slope of the Buffalo Ridge thanks to the downsloping
flow. The same region could experience some patchy blowing snow into
the early evenings hours, but the sun will likely have created a
decent crust on the top layer of snow hindering any widespread
blowing snow issues.

Heading into the overnight hours, winds will begin to calm down a
bit, but should remain strong enough to not worry about any fog from
forming due the recent melting snowpack. Otherwise, looks for
overnight low temperatures to get back down into the mid-20s with
mostly clear skies.

For Wednesday, we remain under northwesterly flow aloft starting the
day with southwesterly winds at the surface. As the day progresses,
a weak cold front will be dragged across the area, bringing a switch
towards north-northwesterly winds that will create some breezy
conditions for the afternoon hours. Cooler air doesn`t arrive
directly behind the front, keeping our maximum temperatures in the
mid-40s. Cloud coverage begins to increase from the north during the
afternoon, with majority of the area under a stratus deck shortly
after sunset. Wouldn`t be impossible to get some very light precip
out of the stratus during the overnight hours, as model sounding
show a tiny layer if instability on top of the mixed layer. For now,
have left mention out of the current forecast as dry air aloft and
lack of any real forcing will likely keep any precip from forming.

.LONG TERM...(Thursday through Tuesday)
Issued at 337 PM CDT Tue Oct 27 2020

Thursday morning will have another chilly start to the day, with
morning temperatures in the 20s. Currently have cloud coverage
decreasing during the later morning hours, but if the boundary layer
becomes stubborn the stratus could be sticking around for most of
the day. This of course will impact temperatures, with NBM box and
whisker plots revealing a 5-10 degree spread between the 25th and
75th percentile showing the uncertainty with surface temperatures.
Snowpack will also have an influence on temperatures, and with the
NAM suggesting an inch of snow on the ground will remain north of I-
90, don`t have a great reason to go above the blended guidance. so
have opted to stay with the less optimistic temperatures around the
40 degree mark.

The aforementioned cut-off upper level low reaches the Ohio River
Valley, allowing a weak ridge to build over the area into Friday.
With the help of a low pressure developing over Alberta, southerly
surface flow returns to the area through Saturday, giving us
consecutive days with highs in the upper 40s and lower 50s.

Both global models show a strong amplified trough with an
accompanied low pressure system skirting past our north, with the
cold front moving through the area Saturday afternoon. With a lack
of any moisture, likely won`t see any precip out of this system, but
winds are looking quite breezy with gusts in the mid to upper 30s. A
surface high slides over the area by Sunday on the back end of the
trough, giving us another cooler day before temperatures look to
warm up into the 50s and 60s to start off the work week.


.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1039 PM CDT Tue Oct 27 2020

VFR conditions expected through the TAF period. Southerly winds
overnight will transition to northwesterly on Wednesday afternoon.




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