Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 011742

Area Forecast Discussion
National Weather Service Sioux Falls SD
1142 AM CST Wed Mar 1 2017

.SHORT TERM...(Today and Tonight)
Issued at 339 AM CST Wed Mar 1 2017

Main issues over the next 24 hours will continue to be
precipitation. Isentropic lift developing ahead of an upper trough
moving through the area this morning will result in light snowfall
along and east of the James River Valley this morning. Lift really
decreases by mid to late morning, so expect most of the
accumulations with this disturbance to be done by then.
Accumulations will be relatively light, but may total up to around
an inch.

This afternoon, could see some scattered snow showers develop as
some weak CAPE develops at the top of the mixed layer.  NAM is
slightly more unstable than the GFS as is super adiabatic near the
surface.  Still some question as to whether the dendritic layer will
saturate or not, so only have some 20 pops for this at this point
across southwest Minnesota.

Another disturbance is expected to drop down in northwest flow
tonight. Have raised pops across southwest Minnesota after 09Z.
Questions still remain in terms of where the back edge of
precipitation shield will develop.

.LONG TERM...(Thursday through Tuesday)
Issued at 339 AM CST Wed Mar 1 2017

Thursday will see a threat for some light snow along and northeast
of a Huron to Storm Lake line. The EC/Canadian and GFS all fairly
agreeable on the path of the surface low, with the snowfall expected
to be northeast of the path, while the nam is a north outlier. So
will lean towards the EC/Canadian and GFS output which means that
some light snow will be possible. The precipitation and cloud cover
will keep temperatures in check with highs in the 30s.

Thursday night into Friday morning will see high pressure build
southeast and bring some chilly morning lows. Expecting these lows
to range from the mid teens to lower 20s. The surface high pressure
shifts quickly east and should allow for a fairly gusty south wind
to develop. Raised winds a bit and will shoot for about 15 to 30 mph
most locations.

An upper level trough will dig into the west coast which will allow
an upper level ridge to build across the Plains. This will bring a
warm and dry weekend to the area. South winds will be a bit gusty
again on Saturday but should not be quite as bad on Sunday. Highs
both days at least in the 50s with some 60s likely in central SD
down the Missouri River into northwest Iowa.

A fairly strong system will move through Sunday night into Monday
and will bring a chance for rain or snow to the area. While this
system will zip through the area another wave will dig onto the west
coast which will bring another period of upper level ridging to the
area. This will support above normal temperatures Monday and
Tuesday with very little chance for precipitation.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1139 AM CST Wed Mar 1 2017

There are two items to watch for the 18Z TAF period. First is a
narrow band of snow continuing to move eastward at this time. This
area of snow will affect the KFSD TAF site with short term IFR
conditions early this afternoon, and could even build southward
and affect KSUX also early this afternoon. The snow will be very
brief, but will then be followed by what will likely by MVFR
ceilings until late this afternoon. This evening a period of VFR
will set in, followed by yet another disturbance moving through
late tonight and very early Thursday giving another round of IFR
snow for KHON and KFSD. At this time, this second round of snow is
predicted to remain north of KSUX.




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