Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 231750 AAC

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1250 PM CDT Fri Mar 23 2018

Issued at 1101 AM CDT Fri Mar 23 2018

Warm air advection pcpn continues pushing across the region this
morning. Locations currently under a winter weather headline are
seeing snow, except our far northeastern CWA. Snow should
gradually push into our MN counties within the next few hours.

Based on the latest model trends, convection may develop over
northern Nebraska this afternoon. This pcpn should track
northeastward and transition over to snow tonight. If this
develops as the 3-km NAM suggests, then our current winter storm
warning will need to be expanded further west to Clark County.


.SHORT TERM...(Today through Saturday Afternoon)
Issued at 314 AM CDT Fri Mar 23 2018

Fog has thinned on area webcams with the introduction of a sustained
easterly breeze, high clouds, and eventually the onset of
precipitation. Otherwise, temperatures are just above freezing for
most of the area. Returns have already started to move into central
South Dakota. It is important to note, and this is backed up by
BUFKIT soundings, that it did take a little while to saturate down.

Still not all that certain with how this evolution will go down
today/tonight. Not much of a system as a broad warm advection push,
though it continues to retain a convective look in CAMS with a
little CAPE/steep lapse rates above the saturated layer. We can
better resolve a shortwave that shows up later that will reinvigorate
precipitation, which I`ll explain below.

NAM and GFS BUFKIT profiles remain fairly similar and continue to
put many parts of the CWA on a razors edge rain/snow line. Looking
at Aberdeen/Watertown, once the column saturates we go to snow, with
surface temperatures around/above freezing. During this time,
profiles are right around 0C from near 8 to 3kft, which is quite
deep and thus could go either way between rain/snow, and I`m sure it
will. We then lose saturation within the dendritic growth zone once
the best forcing moves northeast, while surface temperatures hover
at or just slightly above freezing. This should keep ice from being a
major issue though cant seem to completely discount it given how
close the ground/air temp is to 32F. After a few hours of drizzle,
we see the influence of the wave to the south, with the
reintroduction of ice and a return to snow as the P-type.

So, to reiterate all the uncertainties with this system: it will
take a little while to saturate down, ground and air temperatures
are right around freezing if not just a little above which will have
little effect on snow accumulation but will probably keep the ice
issues to a minimum. Lastly, the deep, isothermal layer right
around 0F within soundings is making the P-type forecast a
nightmare. Will keep headlines in place as timing doesn`t seem to
have been shifted too much over latest guidance cycle, and overall
heaviest snow focus area has not shifted away from the Sisseton
hills. Aberdeen to Watertown remain on the transition line and as
such these areas have the least amount of confidence on how the
day will proceed.

.LONG TERM...(Saturday Evening through Thursday)
Issued at 314 AM CDT Fri Mar 23 2018

A fairly active early long term period is anticipated. A
split positive tilt mid level trof is expected to form over the
western CONUS. Several waves of energy will eject out of this trof,
and across the Northern Plains. Most of the energy aloft moves
across the region Sunday through Monday. Critical thickness/sfc
temps and MaxTws aloft indicate a mixed bag of pcpn types,
particularly at night when sfc temps fall below freezing. Daytime
readings should generally get above freezing so not expecting too
much in regards to snowfall. There may be some ice accums at times,
but this is especially tricky to forecast and confidence is low
right now. Temperatures should average out near to slightly below
normal for the period.


.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1245 PM CDT Fri Mar 23 2018

A storm system crossing the region will bring IFR and MVFR
conditions to all terminals. This system will bring rain and snow,
with accumulating snowfall mainly for the terminals of KABR and
KATY. As the precipitation departs the region Saturday morning,
low clouds should continue impacting the area.


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.



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