Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 212339

Area Forecast Discussion
National Weather Service Sioux Falls SD
539 PM CST Tue Nov 21 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 305 PM CST Tue Nov 21 2017

The short term forecast is relatively quiet once again. High
pressure will build in by late this evening, leading to relatively
light winds and some quite cold temperatures tonight. Light
southerly winds and approaching mid level clouds late tonight should
keep most of our temperatures from falling too far below 10 degrees,

Broad lee troughing east of the northern Rockies will promote a
quasi stationary front stretching roughly from southern Alberta
southeastward through southeast SD. The return of the pressure
gradient will induce some breezy southerly winds through the
afternoon. Wednesday will thus feature quite a bit of contrast in
high temperatures, with a few 60s not out of the question around
Chamberlain and Gregory and a struggle to reach 40 east of the James
River. Forecast soundings suggest +10C readings at 900mb at Gregory.
Have tried to increase highs in our far western zones as a result.
While there is plenty of lift seen on the 280-295K isentropic
surfaces Wednesday, the available moisture appears to be low enough
that no mention of accumulating precipitation is warranted. A
mention of non-accumulating sprinkles and flurries was placed in
parts of southwest Minnesota and northwest Iowa.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 305 PM CST Tue Nov 21 2017

The boundary slides a bit to the east for Thanksgiving, leading to a
similar setup as Wednesday but with warmer overall temperatures.
Once again am seeing a good warm layer aloft in forecast soundings,
but the warmer air is located up around 850mb. Coupled with the
lighter expected winds during the afternoon limiting the ability of
mixing to gobble up some of the warmer temperatures aloft, will
stick closer to consensus for highs.

Friday brings our only real shot at precipitation in the entire 7
day forecast. Decent impulse from the persistent upper low over the
Gulf of Alaska ejects eastward early Friday. This impulse will
induce a surface cyclone that will travel across SK/MB/ON Friday.
Front trailing to the south will impact us Friday afternoon. The
southerly flow of Wednesday, Thursday night, and early Friday will
bring in temperatures well above freezing at the surface and at
925/850mb. Marginal low level moisture will limit precipitation
potential, with most of the rain being forced by frontogenesis along
the 700mb front. Raised winds considerably given the strong pressure
gradient, especially following the frontal passage. Will need to
keep an eye on this day for fire danger, as some of our RH values
will fall into the 30s.

Northwest flow and ridging aloft dominate Saturday through Monday
afternoon. We could see some 60s, especially west of the James, on
Monday with good southerly flow and warm temperatures aloft.

Monday night into Tuesday brings the next wave of note to the
region. CMC/EC/GFS and most available GFS ensemble members swing the
wave through Tuesday afternoon. Once again most of the best forcing
looks to focus to our north. But, with this wave being 7 days out,
something to keep to an eye on for now.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 538 PM CST Tue Nov 21 2017

Northwest winds will continue to decrease this evening, becoming
light and variable by midnight with clear skies. Very dry air near
the surface should prevent any fog formation overnight. Wednesday
morning, winds shift to southerly, with gusts to around 20 kts
beginning after sunrise, as mixing increases. Skies remain mostly
clear through mid-day, at which time some high clouds will move
across the region. No precipitation is expected over the next 24




SHORT TERM...Ferguson
LONG TERM...Ferguson
AVIATION...VandenBoogart is the U.S. government's official web portal to all federal, state and local government web resources and services.