Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 232044

Area Forecast Discussion
National Weather Service Sioux Falls SD
344 PM CDT Fri Mar 23 2018

.SHORT TERM...(This evening through Saturday)
Issued at 341 PM CDT Fri Mar 23 2018

Forecast broadly remains on track for the CWA. Open wave currently
ejecting off the Rocky Mountains will translate eastward this
afternoon along the nose of an upper jet, bringing broad lift to the
region. This lift will interact with a frontogenetic layer around
850mb to lead to widespread precipitation by 00z. Main source of
uncertainty with the precipitation remains type, as surface
temperatures will be around 32 degrees as precipitation begins.
Temperatures have remained cool into the early part of the afternoon
so am not worried about rain failing to switch over to snow. Snow to
liquid ratios remain low as -12C heights look to be around 15kft,
which supports a wet snow solution. Main tweak to the forecast was
delaying the onset of precipitation and lowering amounts slightly in
deference to the relatively dry easterly flow that is ongoing today.
Snow amounts will remain robust in southwest Minnesota as a quick
changeover to snow is expected. The wild card is potential
convection in southwest Minnesota. Progged soundings show elevated
CAPE at or less than 50 J/kg that is spotty both spatially and
temporally. While the trend has been away from getting convective
snows, will stick with winter storm warning despite borderline snow
amounts, just in case.

Saturday will be cold as cloud cover lingers across the region.
Expect the fresh snowfall over southwest Minnesota to reinforce
their cold bias from the past several weeks.

.LONG TERM...(Saturday night through Friday)
Issued at 341 PM CDT Fri Mar 23 2018

While most of the focus of this forecast update was the impending
snowfall tonight, there is one highlight in the extended period.
Next chance for precip comes courtesy of advection driven lift and
an inverted trough on Monday. Precipitation type looks to be an
issue with this as well, with a warm nose aloft around 850mb and
the layer isn`t always saturated above -10C. This will bring
chances for freezing rain in addition to snow and rain.

The CWA will be affected for the remainder of the extended periods
by large scale troughing aloft, leading to temperatures at or below
normal. Multiple southern stream impulses far to our south will cut
off most of our access to moisture, leaving only scant chances for
precipitation after Tuesday.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1250 PM CDT Fri Mar 23 2018

A band of light rain/snow across northeast parts of the forecast
area is expected to gradually weaken through 20Z-21Z. Thereafter,
deteriorating conditions are expected through the late afternoon
and evening, as more widespread precipitation develops and expands
across the area in response to a storm system moving across the
central Plains. Precipitation type is a bit of a challenge, but
should begin as rain at our TAF sites. As temperatures cool this
evening, rain should mix with and change to snow at KHON/KFSD. IFR
ceilings/visibility will become more likely with this changeover
between 00Z-06Z, with IFR ceilings persisting into Saturday
morning, even as the precipitation begins to wane.


SD...Winter Weather Advisory from 7 PM this evening to 10 AM CDT
     Saturday for SDZ040-056.

MN...Winter Weather Advisory from 7 PM this evening to 10 AM CDT
     Saturday for MNZ089-097-098.

     Winter Storm Warning from 7 PM this evening to 10 AM CDT
     Saturday for MNZ071-072-080-081-090.

IA...Winter Weather Advisory from 7 PM this evening to 10 AM CDT
     Saturday for IAZ002-014.

     Winter Storm Warning from 7 PM this evening to 10 AM CDT
     Saturday for IAZ003.



SHORT TERM...Ferguson
LONG TERM...Ferguson
AVIATION...JH is the U.S. government's official web portal to all federal, state and local government web resources and services.