Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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396
FXUS63 KFSD 102011
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
211 PM CST Sun Dec 10 2017

.SHORT TERM...(This evening through Monday)
Issued at 157 PM CST Sun Dec 10 2017

A fast moving Alberta clipper diving southeast into the Northern
Plains later tonight will be the primary focus in the short term
portions of the forecast. Temperatures this afternoon have warmed
into the upper 30s and 40s to even scattered 50s in the
southwestern corner of the CWA in the Missouri River valley.

Tonight: As surface low pressure moves into northwest Minnesota
late this evening, a narrow warm advection wing will form across
western Minnesota, likely grazing or staying just northeast of the
CWA this evening. It`s not impossible to see a bit of light
rain/snow from Marshall to Windom, but more likely areas would be
northeast in the Minnesota River valley. The evening shift will
need to monitor trends. Otherwise, surface winds will turn
westerly this evening, and will prevent any extreme temperature
drop. Areas west of the James River may fail to fall below 30,
with temperatures warming in areas east of the James River
overnight. Used a non-standard diurnal trend.

Monday: As the clipper swings through the Great Lakes, an initial
cold front will approach the area by daybreak. Behind this front
we`ll see a quick turn to more typical northwesterly winds, along
with the development of very gusty conditions.  Soundings suggest
near advisory level winds for a couple hours from mid-morning to
mid- day, especially along and southwest of a line from Huron to
Sioux Falls and Sioux City. Populated with higher MOSGuidance and
ARW, but even HRRRx guidance suggests peak gusts approaching 40
knots. Could see the need for a short term wind advisory.

The other concern for Monday will be with a quick burst of light
convective precipitation as colder air aloft, and a secondary cold
front, rushes southward.  Temperatures should plateau quickly in the
morning, falling as stratus and secondary cold front arrive mid-day.
 A narrow and fast moving precipitation axis may be just strong
enough to produce a few tenths of snow accumulations through mid-
day, with any precipitation moving south of the CWA by sunset.

.LONG TERM...(Monday night through Sunday)
Issued at 157 PM CST Sun Dec 10 2017

Tuesday will be very similar to Sunday, falling ahead of yet another
clipper dropping southward on Wednesday.  Temperatures will climb
back above normal thanks to a west southwest wind.

Models are considerably less certain with details in the
Wednesday/Thursday timeframe regarding the intensity and location of
individual waves within the longwave trough. The more certain
details of the forecast seem to point to increased northwesterly
winds through the day, and potential for another round of very light
QPF into Wednesday night/Thursday.

As we move into the late week timeframe and into next weekend, the
overall pattern begins to take on a more active alignment featuring
fast progressive shortwaves, and generally an above normal
temperature pattern.

Given the absence of any substancial snowfall in the area, would
favor guidance that is warmer than populated blends for
temperatures.  Precipitation chances continue to appear minimal, at
least in regards to any major winter precipitation through next
weekend.


&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1128 AM CST Sun Dec 10 2017

VFR conditions will dominate through much of tonight. MVFR
ceilings begin to slide southward into the area late in this TAF
period, behind a cool front which will also bring increasing
northwest winds to the region late tonight and Monday. Winds
behind the front will average 20-25kt, with gusts nearing 35kt in
most areas after 10Z-12Z Monday.


&&

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

$$

SHORT TERM...Dux
LONG TERM...Dux
AVIATION...JH



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