Scientific Forecaster Discussion
fxus63 kfsd 171148
Area forecast discussion
National Weather Service Sioux Falls South Dakota
548 am CST Fri Nov 17 2017
Short term...(today and tonight)
issued at 323 am CST Fri Nov 17 2017
Clouds will continue to increase across the area this morning, in
the warm air advection regime and low level moisture advection
lifting northward across the Central Plains. The positively tilted
shortwave trough emerging from The Rockies overnight will slowly
swing through the region today and tonight. Meanwhile, surface
boundary noses will nose into south central South Dakota around daybreak today
and track across the forecast area through the afternoon. This will
allow the breezy southerly winds to diminish, then swing around to
the north behind the front. Models suggest that the mid level front
trailing just behind the surface boundary will bring a chance of
light rainfall mainly along and north of I-90, so have added
isolated to scattered pops late morning and this afternoon. High
temperatures this afternoon will reach the mid 40s to mid 50s,
warmest in northwest Iowa.
Trough starts swinging into the forecast area Friday night, bringing
enough weak forcing to produce another shot at light precipitation
Friday evening and overnight. Models focusing the better forcing
across the Missouri Valley into northwest Iowa, with the better
organizing passing to our south. Expect a chance of light rainfall to
move into south central South Dakota and the Missouri Valley in the evening,
spreading into far southeast SD, northwest Iowa and southwest Minnesota in
the early morning hours. The Highway 14 corridor should see very
little if any precipitation. Cooler air will begin advecting into
the region overnight, allowing temperatures to drop into the 20s.
Could certainly see the light rain briefly mix with snow or change
over to snow before the precipitation ends. However, right now it
looks like the bulk of the precipitation will have ended before the
colder temperatures arrive. Not expecting any significant snow
Long term...(saturday through thursday)
issued at 323 am CST Fri Nov 17 2017
Relatively quiet weather with a roller-coaster in temperatures is
the main story on the extended.
Skies will begin to clear out from the northwest to southeast,
resulting in a mostly sunny Saturday for the region. Northwesterly
winds will keep the area dry and cooler than previous days with
highs only reaching the 30s to around 40 along the Missouri River.
With breezy winds increasing in the afternoon, wind chill values
could drop in the lower 20s.
Warmer temperatures return Sunday into Monday night as winds turn to
the south/southwest with the arrival of a dry frontal boundary. This
pattern will keep temperatures 5 to 10 degrees above normal. Highs
will be ranging from the mid 40s to mid 50s.
Models bring series of fast-moving shortwaves, clipper-like systems
across the region for the remainder of the extended. Cold
northwesterly air will push moisture out of the area; therefore not
much in terms of precipitation is anticipated. The first of the
systems brings a boundary across the region Monday night into
Tuesday impacting only temperatures over the area. The roller-
coaster GOES down on Tuesday with strong cold air advection
filtering from the northwest, bringing highs only in the 30s.
The main impact across the area will be in temperatures with the
transition between systems and wind flow pattern. This will result
in warmer than normal temperatures for the end of the period.
Aviation...(for the 12z tafs through 12z Saturday morning)
issued at 539 am CST Fri Nov 17 2017
Low MVFR stratus will continue to impact much of northwest Iowa,
including ksux, spreading further north in far eastern South Dakota and
southwest Minnesota over the next few hours. Once again, stratus edge
will be near kfsd, so confidence is fairly low. However, potential
is strong enough that I have left some MVFR in the forecast for a
few hours around 14z. Otherwise, expect mid level clouds to
blanket the area, with the low stratus very slowly shifting
eastward through the day. Lower visibility will also be a concern
at times this morning with the stratus. Winds will shift to the
northwest, then north behind a front today. Spotty light rain will
follow behind the front, with another round of light rain
possible mainly south of I-90 this evening and tonight.
Precipitation chances too low for mention in the tafs right now.