Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 070900

Area Forecast Discussion
National Weather Service Sioux Falls SD
300 AM CST Thu Dec 7 2017

.SHORT TERM...(Today and Tonight)
Issued at 259 AM CST Thu Dec 7 2017

A strong northerly upper level jet max will keep the low levels cold
through the morning. By afternoon a weak ridge of high pressure will
pass to the south and allow surface winds to back a bit more towards
the west. This will aid in advecting warmer air in from the west,
but an abundance of mid and high level cloud cover should limit any
warming potential. Moisture in the lower levels as well as
temperatures warming through the more favorable dendritic levels
suggests that light snowfall and flurries are unlikely today.
Temperatures will be cold to start and slow to warm, so highs will
only reach into the 20s. However winds will be quite a bit less than
yesterday so overall a bit of a better day.

Temperatures will not drop a while lot overnight with mostly cloudy
skies and some wind expected through the night. Anticipate 15 to 25
degrees for lows in most locations.

.LONG TERM...(Friday through Wednesday)
Issued at 259 AM CST Thu Dec 7 2017

As this jet max drifts east the slightly warmer low level air will
allow temperatures to climb towards normal on Friday. However will
still be fighting some cloud cover and both the nam and gfs hint at
some potential for stratus as well. Should pan out to be a fairly
breezy day as well with highs in the 30s.

When the jet max finally shifts east into Saturday colder air will
settle south and high temperatures will drop back a little. But,
while the colder air moves in near the surface, warmer air aloft
will once again keep the better dendritic temperatures high in the
atmosphere so any threat for light snow is very unlikely, especially
given the somewhat dry air. Lows on Saturday morning will again be
in the 15 to 25 degree range with highs ranging from the mid 20s in
southwest MN to near 40 in south central SD. Did increase winds late
Friday night into Saturday morning with what looks like strong cold
air advection.

Sunday and especially Sunday night appears to pose the next threat
for any rain or snowfall. A wave will spill over the crest of the
strong west coast ridge on Sunday and by Sunday night the effects of
this energy will move into the area. With some warm air in place
ahead of this system the type of precipitation is still up for
debate. That and of course how the system actually comes out will
make a difference as well. The latest GFS and ECMWF are pretty
similar so will have a chance in late Sunday night and Monday.

Lowered highs a bit on Monday given a little confidence in timing of
wave by GFS and ECMWF. So looking at upper 20s to upper 30s across
the area.

Tuesday into Wednesday has a modified cold air mass but given no
additional significant snowfall some mixing will be possible so
maybe looking at a period of normal to above normal temperatures.
Chances for precipitation not looking all that good.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1047 PM CST Wed Dec 6 2017

VFR conditions are expected through the TAF period with breezy
west-northwest winds of 10 to 15 knots, gusts to 20 knots.




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