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Area forecast discussion
National Weather Service Sioux Falls South Dakota
503 am CST sun Dec 8 2019

Short term...(today through monday)
issued at 336 am CST sun Dec 8 2019

Main change to this forecast package has been to increase snow
amounts a bit from the Interstate 90 corridor and northward for
tonight into early Monday with model consensus shifting
forcing/higher quantitative precipitation forecast slightly farther south. Even so, not a
significant shift with total snowfall amounts topping out just
either side of 2 inches through the Highway 14 corridor, tapering
downward to around 1 inch or less to the south of I-90.

For today, a rather quiet day with models continuing to slow onset of
any precipitation until after 00z-03z tonight. A weak frontal
boundary will drop southward through the morning, with the main
result being to bring slightly cooler temperatures to the area
today, along with increasing low clouds by afternoon. The truly cold
air will lag the front, not appearing until later tonight as the
upper level shortwave pushes into the region. Coolest readings today
will reside north of Interstate 90, with highs in the lower 30s,
while to the south we are looking at highs in the lower 40s through
the lower MO River Valley.

By later tonight, will see precipitation begin to develop across the
area with the approach of the upper level wave and increasing
frontogenetical forcing. Still looking at the potential for freezing
drizzle initially with soundings showing a warm layer from roughly
around 900-750 mb with shallow moisture trapped under the inversion.
Initially, there will be enough lift above the shallow moisture to
induce drizzle, before the atmosphere cools and moisture deepens
producing Bona fide snow. Do not expect a prolonged period of
freezing drizzle, so do not anticipate significant icing across the
area. As mentioned previously have, have increased snowfall amounts
a bit, and ignored the NAM for now as it is an outlier with respect
to bringing more significant quantitative precipitation forecast farther to the south. Once the
strong cold air advection initiates later tonight, temperatures will
continue to drop through late morning into early afternoon on
Monday, when readings will be in the single digits and teens. The
winds will also begin to ramp up on Monday, though fortunately it
looks like the strongest winds will lag the precipitation, which
will come to and end by Monday morning. However, any snowfall that
accumulates will have the potential to blow around from late tonight
into Monday. Winds will diminish by Monday evening, leading to a
bitterly cold night with lows in the single digits to just below
zero.

Long term...(tuesday through saturday)
issued at 336 am CST sun Dec 8 2019

Cold temperatures will remain entrenched across the region for
Tuesday and Wednesday in a northwesterly upper level flow as a
trough deepens over the eastern Continental U.S.. highs both days will be in
the single digits and teens, perhaps touching on the lower 20s far
south on Wednesday afternoon. The coldest air will culminate on
Tuesday night with lows ranging from 10 above to 10 below. Cannot
rule out some light snow/flurries on Tuesday night and Wednesday
night as a couple of weak waves slide through the region.

Temperatures look to moderate on Thursday and Friday as the upper
level flow flattens out a bit, and highs could be well into the 30s
on Friday. Models then indicate a piece of upper level energy
drifting into the northern plains for the upcoming weekend, though
there are differences in timing with this feature. This would bring
slightly cooler temperatures and the potential for light snow to the
area.

&&

Aviation...(for the 12z tafs through 12z Monday morning)
issued at 456 am CST sun Dec 8 2019

Light and variable winds will become northerly and pick up a bit
through the afternoon. MVFR/IFR stratus will work southward across
the area through the day, with a brief period of freezing drizzle
this evening, becoming light snow overnight. Northwesterly winds
will begin to increase after 06z, gusting 20 to 25 kts. This may
result in some blowing snow north of Interstate 90 by late
tonight.

&&

Fsd watches/warnings/advisories...
South Dakota...none.
Minnesota...none.
Iowa...none.
NE...none.
&&

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