Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 101214 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
614 AM CST Wed Jan 10 2018

.UPDATE...
Issued at 614 AM CST Wed Jan 10 2018

12z aviation discussion updated below.

&&

.SHORT TERM...(Today through Thursday Afternoon)
Issued at 316 AM CST Wed Jan 10 2018

Taking a look at current conditions, patchy fog remains mainly over
our western counties with MBG vis fluctuating between 1 and 4SM
since around 1Z. The nearest precipitation was in the form or rain
and snow over eastern MT. Behind this area of rain, temperatures
quickly fell from the 20s and 30s to the single digits. This is what
we have to look forward to. At the sfc, low pressure was stretching
from southern Manitoba through ND and the northwest half of SD into
eastern WY, with an additional low over eastern CO. This elongated
trough will slide east of our forecast area shortly after 21Z this
afternoon. The CO low will move into the western OK panhandle by
late evening. Our area will be stuck in between the exiting trough,
and strong high pressure diving in from Saskatchewan. Strong
northerly winds in the cold air advection will be the theme tonight.
Gusts of 28-35kts are expected to slide into our northwestern
counties shortly after 18Z, and overspread the west half of the
forecast area by 00Z, before expanding across the entire area, and
slowly diminishing west to east after 06Z. Timing is a concern, with
much of the precipitation starting later for our southwest counties.
 This slower onset may be a positive, in that cooler temperatures
may help much of the precipitation fall in the form of snow. The
potential still exists for freezing drizzle/drizzle at the onset.
However, storm total ice was reduced significantly over our
southeastern counties from 0.03 over Hamlin/Deuel to mainly 0.01 or
less.

While the 00Z NAM and GFS (as well as the Canadian) are pretty
consistent with the band of higher precipitation over IA and
southeastern MN, they are less in line on the lighter precipitation
across our area. In fact, they are nearly complete opposites when it
comes to the southeastern corners of our forecast area, especially
near ATY where precipitation may vary from 0.05 to 0.26. To limit
the need to jump on the NAM, many of the other 00Z solutions are
closer to the GFS near ATY. Also, the operational GFS is very close
to the mean in its GEFS plumes, giving confidence in its output.

Main concern will be our far northwest counties, where they have the
best chance of receiving snow near 3 inches, and around I-29 and
east where blowing snow will be the biggest concern for the morning
commute Thursday. Still, with mainly crusted over snow or no snow to
begin with, the 2 inches of new snow may not be more then a
temporary concern. Will highlight the threat of periodic near
blizzard conditions in open areas with nighttime driving in WSW/HWO.
Otherwise, dropping the Winter Storm Watch to an Advisory for
headlines seems reasonable.

While storm total snow may be 1 to 3 inches, exact measurements may
be tricky with the significant blowing and drifting. During the day
Thursday the sfc high will continue its southeastward progression,
making it to ND and much of central SD by 00Z Friday. Single digit
highs still look reasonable for Thursday afternoon. Wind chill
values to flirt with -25F around daybreak Thursday through around
18Z. Will mention this in the HWO/WSW.

.LONG TERM...(Thursday Evening through Tuesday)
Issued at 316 AM CST Wed Jan 10 2018

Not much has changed with the models with the long term forecast
period with Arctic air in control bringing much below normal
temperatures along with several periods of bitter cold wind chills.
The first Arctic high pressure area will build in Thursday night.
With the new snow cover along light winds and clouds increasing from
the west with the next short wave trough, expect temperatures to
fall off quickly Thursday evening. At this time, have single digits
and teens below zero for Thursday night. Will probably have to lower
these even more in following forecasts as conditions will be right
for quick cooling Thursday evening. The short wave trough sliding
southeast across the region will bring fluffy light snow back to the
region from late Thursday night into Friday evening. Could see an
inch or two with this system. Another Arctic high pressure area
builds into the region Friday night into Saturday. Surface pressures
get to almost 1050mb within the center of this high pressure area.
Friday night will be mostly in the teens to the lower 20s below zero
and could be even colder in the east. With clear skies and light
winds on Saturday, most highs east river will be below zero.

The models then show a clipper system coming into the region late
Saturday night and Sunday. Again, will the clouds come in early
enough with this system to hold off another big fall in temperatures
Saturday night. Sunday will be relatively warmer with highs mainly
in the single digits and teens as another Arctic boundary makes it
way across the region. Sunday night and Monday will be bitter cold
as another almost 1050mb surface high pressure area makes it into
the region. Highs on Monday are expected to again be mainly below
zero across the region. Monday night could be the coldest night of
all as the surface high pressure area will be right over the cwa
with light winds and clear skies. Suspect we will have several
readings in the 20s below zero across the eastern cwa. Temperatures
will not rebound much on Tuesday as the high builds east of the
region with only single digits and teens expected at this time for
highs.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 614 AM CST Wed Jan 10 2018

As an upper level low pressure trough and surface Arctic front
affect the region today, widespread snow and blowing snow will
develop. VFR conditions this morning will become IFR/MVFR as the
mean column rh increases through the day and large scale lift
increases. Expect low stratus ceilings to form along with light
drizzle/freezing drizzle into the afternoon along with fog.
Otherwise, expect snow to develop from northwest to southeast across
the region into the early evening. Along with the snow, north winds
will increase to 20 to 35 knots into the early evening causing
blowing snow at all locations with vsbys down to a half mile at
times. The snow will end from west to east through the evening and
overnight with continued blowing snow.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from noon CST /11 AM MST/ today to 6 AM
     CST /5 AM MST/ Thursday for SDZ004-009-015-016.

     Winter Weather Advisory from 3 PM this afternoon to 9 AM CST
     Thursday for SDZ005>008-010-011-017>019-036-037-051.

     Winter Weather Advisory until 5 AM MST Thursday for SDZ003.

     Winter Weather Advisory from 3 PM CST /2 PM MST/ this afternoon
     to 6 AM CST /5 AM MST/ Thursday for SDZ033>035-045-048.

     Winter Weather Advisory from 6 PM this evening to 9 AM CST
     Thursday for SDZ020>023.

MN...Winter Weather Advisory from 3 PM this afternoon to 9 AM CST
     Thursday for MNZ039-046.

&&

$$

UPDATE...Mohr
SHORT TERM...KF
LONG TERM...Mohr
AVIATION...Mohr



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