Area Forecast Discussion
Issued by NWS Aberdeen, SD

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KABR 281130 AAA
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
530 AM CST Mon Nov 28 2016

.UPDATE...
Issued at 525 AM CST Mon Nov 28 2016

See updated aviation discussion below.


&&

.SHORT TERM...(Today through Wednesday Afternoon)
Issued at 351 AM CST Mon Nov 28 2016

A sub 980mb low is currently lifting to the north-northeast
across eastern SD at this time (located near watertown at 3am).
Have seen rainfall amounts between a tenth of an inch over south
central SD to nearly two thirds of an inch over some northeast SD
locations. Over northeast SD, the rain has become scattered as
the dry slot noted on WV imagery has moved through that area.
Therefore, that area is primarily seeing low clouds and drizzle
with an occasional period of light to moderate rain. Temperatures
at 3am have risen into the lower 40s for areas east of the James
River valley. Farther west, the transition to snow has already
occurred over north central SD and is slowly pushing to the east.
Webcams in the mobridge area (especially west into Corson/Dewey
counties) indicate snow accumulation on the roadways late
yesterday evening as the TROWAL precipitation on the
west-northwest side of the mid level low continues to pivot through
that area. In addition, reports from the Trail City to Selby areas
indicate 1-3 inches of snow has fallen and roads are
slushy/slippery. That area will be the primary focus for the
forecast for today.

Since temperatures aloft have cooled enough for snow in NC SD,
expect that to continue through the day in that area (and even the
first half of the work week). Expect the heaviest precipitation
to occur through the first part of the morning before the
occlusion cuts off the feed of warm/moist air on the nw side of
the low and diminishes precip rates into the afternoon. As shown in
the model wetbulb0 values 24hrs ago, don`t expect there to be much
if any change over to rain in this area as the model near surface
fields have finally caught on to the cooler scenario.
Thus, have trended areas around Mobridge more towards snow and
thus increased amounts some. The question will be the impacts of
the snow on roadways with surface temperatures still around
freezing. As roadways are treated, do expect a transition to more
wet or just slushy snow on the roads today although the stronger
rates this morning maybe enough to overcome that at times. Expect
the greatest accumulations on grassy surfaces (up to 3-5 inches
by sunset tonight, greatest near ND border). Due to slushy roads
already occurring and another couple inches expected through the
morning, opted to issue a winter weather advisory for part of NC
SD through 18Z. While winds pick up after that, felt the wet
nature of the snow will keep blowing snow potential too low to
keep advisory going past 18z.

For the rest of the area, expect a continued transition to snow
this morning as the colder air moves into the area behind the
upper 970s low moving into southeast ND. The question is how far
east it will go. Wetbubl0 values are indicating that it will try
to make it east of the James River valley this morning and then
likely bounce between rain and snow through the rest of the day
as temperatures try to warm into the mid and potentially upper 30s.
All of this depends on the track of the surface low, as there will
likely be some warmer temps (higher wetbulb0 values) associated with
it through the afternoon. Thus, while the WBZ values push for mainly
snow much of the CWA, will show some rain/snow mix over the eastern
half to third and on the edges of the heavier snow over south
central SD. All told though for today, expect limited impact of the
rain/snow mix for the southern and eastern portions of the CWA.

For the rest of the period, the surface low will gradually weaken
tonight into Tuesday before moving southeast across Minnesota
Tuesday night into Wednesday. Have trended PoPs up through
Wednesday and above model consensus (low QPF, high PoP scenario),
especially over the northwest half of the CWA as waves of
precipitation continue to move around the low. Expect a secondary
increase in snow Tuesday (especially afternoon) as a shortwave and
850-700mb trough rotate around the upper low. Models varying on
amount of low level warm air (GFS is the warmest over the eastern
CWA on Tuesday), so may see rain mix in again on Tuesday
afternoon over the east. Snowfall amounts should be anything too
significant, with most locations experiencing 1-2 inches every 12
hours or so.

Finally, it will get breezy over the CWA later today and
especially Tuesday into Tuesday night. Expect the strongest winds
to occur over the western cwa (along and west of the Missouri
River). With the wet nature of the snow and surface temperatures
likely in the lower 30s during the day, have concerns of there
being much for blowing snow. It will likely be tied to periods of
moderate snow occurring, which was similar to our blizzard a
little over a week ago. Thus, will only mention some periods of
patchy blowing snow for now.


.LONG TERM...(Wednesday Evening through Sunday)
Issued at 351 AM CST Mon Nov 28 2016

The strong upper level low that was associated with this week`s
storm system will be centered over the western Great Lakes when the
extended period begins, then quickly slides off to the east
Wednesday night. Weak ridging builds over the Northern Plains
Thursday through early Saturday, then another shortwave trough looks
to settle over the region through the remainder of the period.

At the surface, the main low pressure system will be well to the
east Wednesday evening, but lingering light snow will continue to
affect the CWA Wednesday night and Thursday. Additional snow
accumulations during that 24 hour time period should be one half
inch or less, and confined to the eastern half of the CWA. The
remainder of the period looks to be dry as weak high pressure
dominates through the majority of the period.

Daytime highs will generally be in the upper 20s to mid 30s through
the period, with overnight lows in the upper teens to mid 20s.


&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
Issued at 525 AM CST Mon Nov 28 2016

A low pressure system will remain over the region through the TAF
period, keeping IFR cigs and IFR/MVFR vsbys in place. Rain and
snow will occur with this system today, with the precipitation
becoming all snow tonight. Also look for west to northwest winds
to increase into the 15 to 30 knot range across the west this
afternoon, and across the east this evening, which will further
aid in reduced vsbys due to the falling and blowing snow.

&&


.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until noon CST /11 AM MST/ today for
     SDZ003-004-009-015.

MN...None.
&&

$$

SHORT TERM...SRF
LONG TERM...Parkin
AVIATION...Parkin



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.