Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 272053

Area Forecast Discussion
National Weather Service Sioux Falls SD
253 PM CST Sun Nov 27 2016

.SHORT TERM...(This evening through Monday)
Issued at 253 PM CST Sun Nov 27 2016

Band of precipitation lifting northeast through the forecast area
associated with leading shortwave with an upper trough moving
through the area.  The upper trough is cut off from the upper
steering flow, so will not be in a hurry to exit the region.  With
the band of precipitation tonight, a small amount of instability may
result in in a few rumbles of thunder east of the James this
afternoon into this evening.

Overnight tonight the TROWAL starts to set up across the western
edge of the forecast area.  Would not be surprised at all if snow
amounts are too low in the forecast, but could not change snow
ratios through collaboration. Forecast is carrying 2-6:1 snow ratios
while it will likely be closer to a 10-12:1 snow ratio west of I-29.
With that said, would not be surprised if places such as Huron to
Brookings along the highway 14 corridor picked up a quick inch of
snow overnight into Monday morning.  Profile right near the surface
warms enough throughout the day to result in rain/snow mix along I-
29, while further to the south may be warm enough to support all
rain.  Model soundings suggest steep enough lapse rates that
instability develops.  If this is strong enough, could see snow
showers develop  mainly along and north of I-90 through the
afternoon hours, as the intensity would be strong enough to keep
precipitation mainly snow.

.LONG TERM...(Monday night through Sunday)
Issued at 253 PM CST Sun Nov 27 2016

Very little change to the forecast from yesterday and last night.
Low pressure will cut off from the stronger upper level flow and
leave a cold pocket of air in place across the northern plains
Monday night into Wednesday night. The thermal structure of the
atmosphere supports mainly snow with just the bottom portion of the
sounding near the surface above freezing. This supports snow in most
cases with some mix possible along and south of interstate 90. While
accumulations will not likely amount to a whole lot due to the
duration of the snow over a few days and near to slightly above
freezing temperatures, 1 to 3 inches of snow will be possible north
of Interstate 90. Went ahead and lowered highs a bit on Tuesday
because of widespread stratus and precip potential and increased
winds Wednesday and Thursday with strong gradient and some CAA.

Friday through Sunday the cool pattern will continue but the chance
for precipitation will not be there. Highs will be in the 30s with
lows in the 20s.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1150 AM CST Sun Nov 27 2016

IFR to LIFR conditions developing as band of rain moves through
the area this afternoon into the early evening. Low ceilings will
remain across the area, especially along and west of I-29 through
the period. Winds will become somewhat gusty late this afternoon
into tonight.




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