Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 221849 AAC

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1249 PM CST Mon Jan 22 2018

Issued at 1240 PM CST Mon Jan 22 2018

See below for an aviation forecast discussion for the 18Z TAFs.

UPDATE Issued at 1059 AM CST Mon Jan 22 2018

Made minor modifications to the sky, wx, wind and temperature
grids for the rest of today. Also, visibility on area webcams
still looked pretty low a short while ago, so have extended the
Dense Fog Advisory over north central South Dakota and the Prairie
Coteau of far northeast South Dakota to 3 PM CST this afternoong.
Updates are out.

UPDATE Issued at 515 AM CST Mon Jan 22 2018

12z aviation discussion updated below.


.SHORT TERM...(Today through Tuesday Afternoon)
Issued at 317 AM CST Mon Jan 22 2018

Fog and low stratus today will be the main issue in the short term.

A strong area of low pressure currently over northeastern Kansas
will slowly track northeastward toward Chicago today through
tonight. While this system will bring breezy northerly winds to
eastern SD and western MN today, with no significant snow in our
southeast CWA, will remove the mention of blowing snow.

With an abundance of low level moisture and light winds along the
Missouri Valley, dense fog has developed, especially in north
central SD. NAM buffer soundings keep the dense fog and low stratus
through a better portion of the day before lifting later this
afternoon. Based on short blend of models, will issue a dense fog
advisory until 17Z in our northeast. In our eastern CWA, upslope
winds along the eastern side of the Sisseton Hills is producing
dense fog. A consensus among short term models suggest the fog in
our east will continue through the morning hours with gradual
improvement by early afternoon.

Fog may reform again this evening before drier, northwesterly winds
move into the region. An upper level trough will cross the Northern
Plains on Tuesday with light pcpn possible along the ND/SD border.
The NAM, along with the ARW and NMM support the possibility of light
pcpn with this trough. Other models suggest dry conditions. After
looking at the NAM`s moisture profile, will maintain a dry forecast
on Tuesday.

.LONG TERM...(Tuesday Evening through Sunday)
Issued at 317 AM CST Mon Jan 22 2018

Overall, pretty quiet long term period with limited precipitation
chances and above normal temperatures.

Upper ridge will slide over the area for the second half of the
week behind a weak shortwave and surface trough Tuesday
afternoon/evening. 850mb temps will warm into the single digits
above zero C by Thursday, so amount of warming will depend on the
appearance of low stratus and the amount of mixing that occurs
during the day. Both GFS/NAM are indicating the potential for low
stratus Wed/Thurs (below inversion around 900mb), but as usual the
NAM is the most aggressive. CMC/ECMWF are not as enthused, so
will continue to show partly cloudy skies for Wed/Thurs and more
for the high clouds streaming in ahead of the next low pressure
system and along the favorable right rear region of the departing
upper jet. Thursday will likely be the warmest day with the
increasing south-southeasterly flow aiding mixing and latest
blends have highs in the upper 30s to upper 40s. That aligns
fairly well with the ECMWF ensemble members, so no adjustments
were made.

Those stronger south-southeasterly winds on Thursday (gusts up to
20kts at this point) are ahead of a surface low that will move
east across the Dakotas and southern Canada Thursday night. At
this point, with the low interacting with abundant dry air still
in place on the back side of the departing upper ridge, not
really expecting much precipitation potential (just mid-high
clouds), at least until trailing shortwave and colder air slide
in on Saturday. Even then, best cold air pocket and steeper low
level lapse rates end up being to the northeast of the area. Will
also see gusty northwest winds Friday/Saturday afternoons behind
the cold front (gusts to 25-30kts over north central SD).

Behind that low and brief cold air push (850mb temps in the teens
below zero C), upper ridging develops again over the western
CONUS and moves east over the Northern Plains for early next
week. That will push temps well above normal for the start of
next week.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 1240 PM CST Mon Jan 22 2018

With the exception of KPIR (and maybe KMBG for a couple hours
early this evening), sub-vfr conditions (cigs and occasionally
visbies in fog or fog/freezing drizzle) are expected to persist
over the next 24 hours.


SD...Dense Fog Advisory until 3 PM CST /2 PM MST/ this afternoon for



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