Scientific Forecaster Discussion
fxus63 kfsd 131124
Area forecast discussion
National Weather Service Sioux Falls South Dakota
524 am CST Wed Nov 13 2019
Short term...(today and tonight)
issued at 259 am CST Wed Nov 13 2019
Continue to monitor precipitation development across southwest
and south central South Dakota early this morning, as a subtle
wave of energy passes through northern Nebraska this morning. Warm
advection ahead of this wave, along with an increase in southwest
surface flow has nudged temperatures upwards slightly in our
southwestern County Warning Area. As this wave moves southeast, anticipating
further development along the MO River Valley into mid-morning.
Max wet bulb temperatures aloft from soundings continue to support
freezing rain/rain, with a bit of sleet at times as you move
northward towards I-90. Even though air temperatures have risen in
areas near Yankton and Vermillion this morning, dew points remain
in the lower 20s, which should prevent any significant warming as
precipitation moves in. Precipitation amounts, given a
pronounced and stubborn dry layer, will be on the lower side and
likely less than a tenth of an inch.
Further north, a secondary area of 850:700 mb forcing tied to a
another subtle embedded shortwave also falling under the right
entrance region of the upper jet, will track across NE South
Dakota, North Dakota, and Minnesota bringing light snow southeast.
The lack of appreciable moisture really limits the overall snow
potential, but will hold a low pop and very light accumulations
into the afternoon.
All that said, icing accumulations near the MO river and along
the Highway 20 corridor may exceed a glaze in spots with snow
accumulations elsewhere of a dusting to a few tenths at most.
Given the timing of arrival of precipitation centered around the
morning commute, will issue a Winter Weather Advisory through late
morning. Will continue to monitor track of precipitation eastward
Temperatures will warm above freezing in most areas by mid-day or
early afternoon, so recovery from any icing should be fairly
Tonight: stratus slowly clears tonight, as temperatures fall into
the teens for lows. Winds remain light from the north.
Long term...(thursday through tuesday)
issued at 259 am CST Wed Nov 13 2019
Thursday: quiet conditions continue on Thursday as surface winds
turn towards the west. Not much for warming on Thursday, but
temperatures will climb above freezing in most locations,
approaching the lower 40s in south central South Dakota.
Friday: models hinting that a backdoor cold front could bring
stratus southwards early on Friday, however the general theme for
the day will be dry and breezy. Broad warm advection will assist in
pushing temperatures into the 40s in most locations.
Saturday-sunday: by the weekend, a progressive upper trough will
swing through the northern plains Saturday night into Sunday.
Favorable mixing on Saturday with a breezy southerly wind will push
temperatures into the 40s once again. A weak frontal boundary moves
through by Sunday morning with low end precipitation chances
given the moisture starved nature of the system. However,
temperatures aloft could support a light wintry mix into daybreak
Sunday. Speaking of Sunday, latest forecast continues to look
favorable. Temperatures will remain near to slightly below normal
in most areas outside of the extreme southwestern County Warning Area.
Monday-wednesday: yet another progressive shortwave drops southward
out of Canada on Monday. Reasonable heating ahead of this wave
should nudge temperatures closer to 50 degrees on Monday, with a low
end chance of precipitation again in the forecast. Despite a low end
pop for Tuesday and Wednesday, favor a dry forecast into the middle
of the week as the pattern begins to evolve.
Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 521 am CST Wed Nov 13 2019
Greatest risk for wintry precipitation will take place in Sioux
City this morning as freezing rain, sleet and snow may be
possible. Further north, feel that dry air will limit snow
potential, but will include some non-restrictive light snow or
flurries in taf through mid-day. Winds this afternoon once a weak
front moves through will gust between 20 and 25 knots at times.
Ceilings will gradually lower later this morning into MVFR levels,
improving this evening as lower ceilings shift further southeast.
South Dakota...Winter Weather Advisory until 10 am CST this morning for
Iowa...Winter Weather Advisory until 10 am CST this morning for
NE...Winter Weather Advisory until 10 am CST this morning for nez013-