Area Forecast Discussion
Issued by NWS Sioux Falls, 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

FXUS63 KFSD 291800

Area Forecast Discussion
National Weather Service Sioux Falls SD
1200 PM CST Tue Nov 29 2016

Issued at 1159 AM CST Tue Nov 29 2016

Some fairly minor adjustments to the forecast this morning as
strong stacked low pressure now starting to drift southeast
through west central MN. Precipitation has been largely tied to
the area of wrap-around low-level warm advection extending back
through eastern SD, and has progressed/developed somewhat quicker
and more widespread through mid to late morning. Overall, continue
to lack decent instability, and with lift primarily centered lower
in the thermal profile, efficiency has been somewhat lacking to
precipitation. One larger change has been to focus on primarily
snow as type, with precipitation acting to keep near surface layer
cooler especially as some slightly lower surface dewpoint readings
filtering in with the northwest flow. However, still looking at
core of slightly warmer air surrounding the area of low pressure
in west central MN, and this will wobble across the southwest MN
counties this afternoon where will see a mix of rain/snow until
better band of snow wraps into the area during the later afternoon
per hi-res solutions. As a result of more snow and organization of
band dropping through eastern SD/southwest MN through tonight,
accumulations should a bit higher with 1-2 inches through daybreak
Tue, greatest for elevated locations of east central SD and
southwest MN. Winds will continue strongest through the Missouri
River corridor, especially toward south central SD. However, near
freezing temperatures should keep blowing snow from being an
issue. A bit lesser wind will spread through southwest MN as
bagginess near surface low brushes by, before winds increase again


.SHORT TERM...(Today and Tonight)
Issued at 315 AM CST Tue Nov 29 2016

Ongoing stagnant storm system spinning north of the forecast area
near the lower Red River Valley will be primary focus through the
next 24 hours. Bands of lift and moisture will continue to rotate
around the system, spreading occasional light precipitation into
mainly our southeast South Dakota and southwest Minnesota counties
through tonight. Thermal profile aloft continues to support snow,
although very shallow near surface warm layer could result in some
brief periods of rain or rain/snow mix during the daylight hours
today. Transitions to rain or drizzle could also occur when pockets
of drier air aloft rotate through the region between the bands, and
we lose ice and resulting ability to produce snowflakes within the
column. Thus have introduced some patchy freezing drizzle/drizzle
into the forecast into this evening, however do not anticipate much
additional impact from brief periods of freezing drizzle early this

Widespread cloud cover and scattered precipitation will result in a
small diurnal temperature range, from overnight lows within a couple
degrees of 30, and daytime highs generally 35-40 degrees, though far
southern portions of the forecast area around Sioux City could sneak
a little above 40. Westerly winds will also remain brisk, and could
approach wind advisory levels in south central South Dakota. Appears
to be just shy of criteria, though so will hold off on headlines
for now.

.LONG TERM...(Wednesday through Monday)
Issued at 315 AM CST Tue Nov 29 2016

The cool upper low will be moving slowly east from MN into WI
Wednesday and Wednesday night. Light precipitation coverage
should gradually decrease. It looks like accumulations around an
inch are possible from 12Z Wednesday on, from east of Huron into
southwest MN. Continued weak low level frontogenesis and lift, up
to 850mb, will slowly shift east. Elevation will continue to be a
factor, as will modest diurnal warming. In any event, the best
snow accumulation potential appears to be in the morning

There is some chance of a slight resurgence in light snow Wednesday
evening, as a last short wave moves over the area on the western
side of the retreating low. However, will go with guidance
decreasing chance POPs for Wednesday night, as this wave looks
quite weak.

Dry weather should be the rule Thursday through Monday, with two
possible exceptions. One would be a little light snow early Sunday,
around Interstate 29 and east, north of Sioux Falls. A weak
westerly wave not showing up very well on the GFS, but depicted on
the last couple runs of both the EC and Canadian, could bring that
minor event. The other exception would be a chance of rain and
snow east and south of Sioux Falls by late Monday. This would be a
post frontal band supported by a broad approaching trough. Current
indications are that the coldest air of the season so far will
arrive next week behind this system, and just beyond the current
forecast period. The new EC is slower on this system and would
delay its arrival by a day or so.

Temperatures which are modestly cool will warm to a little above
normal for the weekend into Monday, with highs during that time
frame in the 30s to lower 40s.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1159 AM CST Tue Nov 29 2016

Widespread MVFR to IFR ceilings will prevail through 18z Wed, with
periods more organized snowfall likely to have IFR to LIFR




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