Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 070930
AFDFSD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
330 AM CST Sat Dec 7 2019

.SHORT TERM...(Today and Tonight)
Issued at 329 AM CST Sat Dec 7 2019

Warm air advection overspreading the region today as a southerly
flow increases across the area with surface ridging moving east.
Current satellite indicating a broad area of cirrus drifting out of
the Northern Rockies, and will see these clouds pass over our area
for at least the early part of the day. Still, we will have the
warmest day of the next several with highs primarily in the 40s -
closing in on 50 along the middle and lower MO River corridor. It
will become breezy in the afternoon in response to a tightening
surface gradient and increasing momentum transfer winds.

Winds will be slow to fall off tonight, and it will be a relatively
mild night with lows mid and upper 20s. Winds will begin to
transition to west/northwesterly overnight as a surface trough
slides through the region.

.LONG TERM...(Sunday through Friday)
Issued at 329 AM CST Sat Dec 7 2019

There will be some cold air advection behind the aforementioned
trough, so temperatures will be cooler on Sunday, with highs in the
lower 30s north of Interstate 90, though still holding in the lower
40s along the lower MO River Valley and our far southern IA zones.
Models continue to offer a slower solution for precipitation onset
on Sunday, so it appears to remain dry through the day. By Sunday
night a northern stream upper level wave begins to pivot out of the
Northern Rockies into the Northern Plains, drawing increasingly
colder air into our area. With increasing frontogenetical forcing
and lift, still looking at light snow developing over the area
overnight. Models continue to portray the better lift and moisture
generally to the north of our area, so the higher snowfall amounts
will remain north of Interstate 90 where 1 to 2 inches could
accumulate. Models are exhibiting some timing differences for the
onset of precipitation, with the ECMWF and NAM offering a slower
solution than the GFS/GEM, thus having snow starting later on Sunday
night and continuing longer into Monday. Kept in the forecast the
potential for a brief period of freezing drizzle at the onset of
precipitation before saturation occurs in the dendritic layer,
though not expecting much in the way of icing with only a small
window of time when this would occur. With the cold air advection,
temperatures will begin to fall on Sunday evening and then continue
to fall into Monday afternoon, when readings will be in the single
digits and teens. Northwesterly winds will pick up late Sunday night
into Monday, so could have periods of blowing snow, mainly through
the Highway 14 corridor.

The bitterly cold air will then settle into the region for Tuesday
and Wednesday as Canadian high pressure builds southward into the
Plains states. Highs both days will be in the single digits and
teens, with lows on Tuesday night from zero to 10 below.

The upper level flow then begins to flatten out a bit for the end of
the week, which will allow for a moderation of temperatures. This
will bring highs back into the 20s and 30s, with lows in the teens
and 20s. There are no major winter weather systems on the horizon,
with primarily dry conditions during the week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1028 PM CST Fri Dec 6 2019

Some limited potential for fog to develop yet tonight, but
probabilities remain too low to include in TAF. Will need to
monitor areas near HON for low stratus development, but elsewhere
VFR conditions are anticipated into Saturday morning.

Winds will increase through the day on Saturday, with 25 mph gusts
likely in the afternoon.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...JM
LONG TERM...JM
AVIATION...Dux


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