Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 232339 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
639 PM CDT Fri Mar 23 2018

Issued at 635 PM CDT Fri Mar 23 2018

Showers are filling back in across eastern SD and west central MN
this evening. A mix of rain and sleet has been observed in the
James Valley. Tried to adjust weather types a bit to reflect the
wintry mix, but ice should have little impact over the next hour
or two as sfc temps remain above freezing. Intensity will increase
and precip will change over to snow over the next few hours.


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

The precipitation associated with the warm air advection has pushed
east and northeast of the CWA. Far northeastern SD and western MN
saw little to no accumulating snow from the initial pcpn. Based on
radar trends, could have delayed the start time of the winter storm
warning until 0Z. Chose to mention a break in pcpn instead.

Currently watching convection develop in north central Nebraska this
afternoon. This precipitation should continue tracking ENE through
tonight, reaching our eastern CWA after 0Z, or closer to 3Z. By
then, profiles suggests the dominate p-type would be all snow,
especially for the I-29 corridor. How far north the pcpn develops is
a little unclear. As of now, Watertown, Milbank, and Ortonville
should have the best potential of seeing moderate to heavy snow
tonight. SPC`s HREF and the 3-KM NAM both suggest snowfall rates of
an inch per hour possible. These kind of rates should overcome
the warm ground and surface temps in the lower 30s. Still
expecting 3 to 6 inches of snow tonight, mainly over the higher
terrain areas of the Prairie Coteau. The next shift will have to
monitor trends for the possible expansion of the winter storm
warning to include Codington and Clark County.

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

Precipitation is tapering off Saturday morning across the far
eastern forecast zones (east of the James River valley). Generally a
trace to up to an inch of snow is possible there, and if p-type is
changed over to light drizzle/freezing drizzle type precipitation,
generally a trace of precipitation is expected at this point.

Late Saturday night through Sunday, the next installment of
precipitation chances shows up with the next low pressure system
moving through southwest flow aloft. Both the NAM and GFS 12Z
solutions in BUFKIT show freezing rain and sleet before a change-
over to snow occurs. Timing and location are non yet in sync,
though. Probably worth a winter weather advisory for a wintry mix of
light ice and snow accums once the models start to line up better on
where/how much Saturday night into Sunday.

Then, later Sunday night through Monday evening, another somewhat
larger system (including potentially double the qpf of the Saturday
night/Sunday system) could be lining up to impact the region,
perhaps moreso with snow p-type versus rain or freezing rain. This
system may need to be watched closely over the next 24 to 36 hours
for winter storm warning criteria potential snow amounts.

Between Saturday and Monday, there is not much opportunity for
substantive impacts to the low/mid-level thermal profile. It`s not
until we get past Tuesday that there is any potential for
significant swings in low level thermal advection pattern. There is
one signal, though, starting to show up in the longer range
solutions; a notable cool down may be on the way for next
weekend/beginning of April, and that`s no April Fool`s joke!


.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 635 PM CDT Fri Mar 23 2018

As precip fills back in across eastern SD this evening, expect
conditions to deteriorate to MVFR/IFR in a wintry mix. After the
precip ends late tonight or early Sat morning, MVFR/IFR cigs will
linger across the region for the remainder of the forecast period.


SD...Winter Storm Warning until 7 AM CDT Saturday for SDZ007-008-021-

     Winter Weather Advisory until 7 AM CDT Saturday for SDZ005-006-

MN...Winter Storm Warning until 7 AM CDT Saturday for MNZ039-046.



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