Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 200912

Area Forecast Discussion
National Weather Service Sioux Falls SD
312 AM CST Mon Nov 20 2017

.SHORT TERM...(Today and Tonight)
Issued at 311 AM CST Mon Nov 20 2017

Another pleasant day is expected across the region with unseasonably
warm temperatures and relatively light winds. Highs today will reach
the 50s to lower 60s, as much as 15 to 20 degrees above normal.
Skies will start mostly clear, however cirrus clouds will be on the
increase by midday, leading to partly to mostly cloudy conditions.

A trough located in southern Alberta will dig southeast to near the
ND and MN border with Canada by late afternoon. The main forcing
will pass well to the north of the forecast area, however a cold
front is expected to sag southward across the forecast area this
afternoon and evening. The frontal passage will remain dry, however
southwest winds today will turn westerly then northwest behind the
front. Winds overnight will also increase, becoming breezy at around
15 to 25 mph by daybreak Tuesday. With mixing occurring overnight,
the cold air advection will be a little delayed, which will likely
lead to low temperatures after sunrise.

.LONG TERM...(Tuesday through Sunday)
Issued at 311 AM CST Mon Nov 20 2017

Tuesday brings a big change in temperatures in the wake of the cold
front exiting the area early in the morning. As a surface high
settles in, skies will clear out giving way to a mostly sunny day.
Even with the sun, temperatures will struggle to warm up. Drier
northwesterly flow brings cooler than normal temperatures with highs
only reaching the upper 30s. The main impact looks to be winds as
pressure gradient tightens behind the front. Soundings suggest a
strong mixed layer mainly east of I-29 in the mornings hours into
mid afternoon. Have increased winds by using a blend between
Superblend and ADJMET to produce winds from 20 to around 30 knots.
Winds will be diminishing and temperatures will drop into the teens
over the entire forecast area.

By Wednesday clouds will be increasing from west to east as an upper
wave and associated frontal boundary dives southeast from the
Northern Plains. Temperatures will bounce back to near normal as
southerly warm air filters in. This flow may also support a little
precipitation north of I-90 where soundings indicate a saturated mid-
layer, but due to limited low-level moisture, have only left small
chances north of Highway 14.

Thanksgiving Day promises to be pleasant and dry. Highs will
generally range from the 40s across southwest Minnesota to lower 50s
along the Missouri River Valley. The next wave arrives Friday
impacting the area with well above normal temperatures. The 925mb
continues indicating a very warm layer. The GFS and ECMWF show a
warm layer of 10 to 15 C, and the Canadian brings even warmer
temperatures of 10 to 20 C. Have blended between
Superblend/GFS/ECMWF to increase temperatures into the mid 50s to
lower 60s. Cooler but slightly above normal temperatures returns
into the weekend, with little to none precipitation.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1033 PM CST Sun Nov 19 2017

Light south to southwest surface winds are expected to
continue through Monday afternoon, with periods of passing high
clouds, and very little weather-related impact to aviation




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