Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Sioux Falls South Dakota
512 am CST Sat Feb 13 2016
Short term...(today through Sunday afternoon)
issued at 330 am CST Sat Feb 13 2016
As the wave approaches from the west low to middle level winds are
turning to a bit of a westerly direction and advecting in warmer
and more moist air. This is allowing some light snow to develop in
central parts of South Dakota. Forcing will be fairly minimal
through the morning so will have only chance probability of precipitation west of Interstate
29 through the morning with minor accumulations possible. By this
afternoon the band will try to become more organized but will be
fighting some dry air. Will maintain chance probability of precipitation through the
afternoon and spread them east but this is a spot where a narrow
northwest to southeast band could develop sooner than expected with
the better chances west of Interstate 29.
The chance for snow will increase quickly between 22z and 4z from
west to east as the main wave begins to push onto the plains. The
middle level thermal ridge supports the better chance for snowfall
along and north of Interstate 90 but a bit south of previous
runs.Would not be surprised to see some of the locally higher
amounts from about Delaware smet through Luverne towards Spencer Iowa.
While instability is not overly impressive any lift from about 750-
700mb should have some ability to rise fairly easily. This matches
well with the location of the thermal ridge and better forcing which
seems to come through from about 8 PM this evening through about 5
am Sunday morning. Likely to be lingering snowfall before and after
this lift...this just appears to be the window of best
As for headlines...will go with a Winter Weather Advisory. Snow
amounts should not exceed 6 inches so the main focus will be the
wind interacting with the existing snow pack and the new snow. South
winds will become pretty gusty late afternoon and overnight which
will cause blowing/drifting and reduced visibilities. At times we
overdo the south winds in cases like this as mixing is not as deep
as expected which is one reason for the advisory versus a Blizzard
Warning. But...do suspect some brief whiteout conditions so will
need to pay close attention to conditions this evening as the
potential for widespread whiteout conditions is not that far off.
Long term...(sunday evening through friday)
issued at 330 am CST Sat Feb 13 2016
The main theme for next week will be moderating temperatures with
the next best chance of precipitation coming in on Monday night. In
a warm air advection pattern Monday looks to be milder with highs
into the 30s most areas...though topping out in the 40s through
south central South Dakota. Models in decent agreement...with some
variation in timing...on a shortwave dropping into our area on
Monday night in a northwesterly upper level flow. This system could
bring some light snow to the area...possibly beginning as a little
rain in our southwest on Monday evening with surface temperatures still in
the upper 30s at that point. Quantitative precipitation forecast amounts would suggest around an
inch to near 2 inches of snowfall accumulation for all but the
southwest into early Tuesday morning.
Cooler air will then filter in behind this system...with highs on
Tuesday and Wednesday just a shade lower...in the upper 20s and
30s...to a few 40s far southwest. More significant warming then
looks to move back into the area for the end of next week as a
western Continental U.S. Upper level ridge slides eastward. With that...could
actually see highs into the 50s for the Missouri River valley
corridor for Thursday and Friday.
Aviation...(for the 12z tafs through 12z Sunday morning)
issued at 510 am CST Sat Feb 13 2016
VFR conditions will be fairly prevalent through the morning but
the afternoon into the evening will see MVFR ceilings spread
across the area as snow develops. Strong southerly winds will
develop through this time as well bringing a good chance for IFR
visibilities in snow and blowing snow this evening and overnight.
South Dakota...Winter Weather Advisory from 9 PM this evening to noon CST
Sunday for sdz040-055-056-061-062-066-067.
Winter Weather Advisory from 6 PM this evening to 9 am CST
Sunday for sdz038-039-052>054-057>060.
Minnesota...Winter Weather Advisory from 9 PM this evening to noon CST
Sunday for mnz071-072-080-081-089-090-097-098.
Wind Chill Advisory until 9 am CST this morning for mnz080-081-
Iowa...Winter Weather Advisory from 9 PM this evening to noon CST
Sunday for iaz001>003-012>014-021-022.
Wind Chill Advisory until 9 am CST this morning for iaz002-003-