Winter Weather in Nebraska, November 18, 2016

Area Forecast Discussion
National Weather Service Sioux Falls SD
322 AM CST Fri Nov 18 2016

.SHORT TERM...(Today and Tonight)
Issued at 322 AM CST Fri Nov 18 2016

Latest water vapor loop shows a deepening low pressure moving east
northeast through Nebraska. Strong lift was allowing a band of
precipitation to develop from northeast Nebraska into eastern SD at
9z. Over parts of northwest Iowa a few thunderstorms occurred and a
few pockets of brief sleet was also occurring along the leading edge
of the lift, and was rapidly lifting north. A broad area of moderate
snow was falling to the west of Interstate 29 with some heavier snow
beginning to fill in from about Tyndall to Yankton north towards
Madison. Suspect that this will be the focus the next couple of
hours and will transition gradually north northeast through the
morning. Areas to the west of this line will gradually diminish in
intensity over the next few hours with another couple of inches of
accumulation possible. Did decrease amounts there a bit but still
expecting 3 to 5 inches. From about Ivanhoe to Madison to Olivet
there could be amounts approaching 6-8 inches. Interstate 29 from
Flandreau south should see about 3 to 6 inches. Amounts drop off
fairly quick into northwest Iowa where the cold air lags a little
too long behind the strongest forcing. North winds will continue to
increase through the morning and gusts around 50 mph still look very
likely.

The main challenge, as has been the case the entire time, is will
wet snow blow around enough to cause decreased visibility in blowing
snow. Will not change headlines but still suspect that true blizzard
conditions will be hard to come by. But, with some locations
expected to get about 5-9 inches and wind gusts to 50 mph will not
take any chances on changing headlines.

Temperatures will remain fairly chilly through the night. Decreased
low temperatures a bit with snow cover and surface ridge building
into central SD late tonight.

.LONG TERM...(Saturday through Thursday)
Issued at 322 AM CST Fri Nov 18 2016

On Saturday surface ridging spreads across the region. This will
lead to dry conditions with relatively light winds in a weakening
gradient. Snow cover will obviously have an impact on temperatures,
and stayed on the low side of guidance with respect to highs, with
afternoon readings in the upper 20s to mid 30s. On Saturday night
the surface ridge axis slides to the east as a southerly low level
flow returns to the area. In spite of that, it will be another very
cold night with expected snow cover and lows in the mid teens to
lower 20s.

An upper level ridge builds across the central CONUS on Sunday and
Monday. This will lead to some warming, though with the expectation
that this will be tempered some by snow cover, will stay with highs
in the 30s north to 40s over northwestern Iowa on Sunday. By Monday
it appears that most locales will be able to climb into the 40s as
the snow cover slowly gets whittled away.

By Monday and Tuesday the upper level ridge shifts off to the east
and an upper level low ejects northward out of the Four Corners
region. This features tracks into the central Mississippi Valley by
Tuesday night, as a surface low slides from Kansas into central Iowa
during the Monday night to Tuesday time frame. As warm air
advection/isentropic lift spread out ahead of the aforementioned
shortwave, precipitation chances will increase across the area late
Monday night, becoming likely by Tuesday. Initially, with a warm
layer aloft, it appears that there could be some mixed precipitation
on Monday night, then transitioning to a more rain or snow scenario
on Tuesday as thermal profiles cool. Still too far out to hammer out
the precipitation type details. In coordination with surrounding
offices, knocked temperatures back a bit from given guidance on
Tuesday with clouds and precipitation.

For the end of the extended period, upper level ridging builds back
into the region with a warming trend for Wednesday and Thursday of
next week.  Even so, temperatures will still be close to normal for
this time of year.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1035 PM CST Thu Nov 17 2016

Light snow is now beginning to fall in KHON and will continue to
build through the overnight hours. Visibility may fall below 1
mile at times, with IFR ceilings into mid-morning.

Further east, convection building over eastern Nebraska will begin
to arrive after midnight. Large concerns continue over a lingering
warm nose nestled in from Sioux Falls to Sioux City, which could
allow rain to mix with snow longer into the night. Nevertheless,
once the transition occurs, visibility may drop below 1/2 mile at
times, with ceilings holding between 500-1000 ft.

Snow will linger into the late morning hours, before rapid
improvement in the afternoon. With temperatures holding into the
lower to middle 30s, blowing snow may be difficult to achieve
given the slushy nature of the fallen snow. Most visibility
restrictions will be felt by falling snow only.

VFR conditions will return late in the TAF period, but winds with
gusts greater than 30 knots also continue into the evening hours.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 6 PM CST this evening for SDZ070-
     071.

     Winter Storm Warning until 6 PM CST this evening for SDZ054>056-
     060>062-065>069.

     Winter Storm Warning until noon CST today for SDZ038-050-052-053-
     057>059-063-064.

     Blizzard Warning until 7 PM CST this evening for SDZ039-040.

MN...Winter Weather Advisory until 6 PM CST this evening for MNZ081-
     090.

     Winter Storm Warning until 6 PM CST this evening for MNZ089-098.

     Blizzard Warning until 7 PM CST this evening for MNZ071-072-080-
     097.

IA...Winter Weather Advisory until 6 PM CST this evening for IAZ001-
     012.

     Wind Advisory from 9 AM this morning to midnight CST tonight for
     IAZ002-003-013-014-020>022-031-032.

NE...Winter Weather Advisory until 6 PM CST this evening for NEZ013.

     Wind Advisory from 9 AM this morning to midnight CST tonight for
     NEZ014.

&&

SHORT TERM...08
LONG TERM...JM
AVIATION...Dux

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