Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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686
FXUS63 KFSD 251727
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1227 PM CDT Sat Mar 25 2017

.SHORT TERM...(Today and Tonight)
Issued at 251 AM CDT Sat Mar 25 2017

A relatively quiet short term forecast continues, with the main
concerns focused on stratus through the day, and occasional spits of
rain over the eastern zones.

This morning, stratus has pushed all the way west towards the
Missouri river. Continue to see some minor visibility restrictions
over SW Minnesota and NW Iowa and these restrictions will stay in
place through the mid-morning hours.  Models continue to show
erosion of this fairly thin stratus deck, especially west of the
James River valley by mid-afternoon.  Thinning of the stratus will
dictate temperatures later today, with thicker stratus expected to
hold temperatures down a couple degrees from the previous forecast.

With the upper low over SE Kansas sliding eastward today, it`s
possible that slightly deeper moisture just south of the CWA could
rotate north and then back westward later this afternoon and into
the overnight hours.  At most, we`d likely see a few spits of rain,
with a continuation of very low stratus. Models are again bullish in
advecting stratus back westward through the overnight hours.  Have
backed off a bit on the fog mention, as conditions may be very
similar to those of tonight, with the lowest visibility (AOA 2
miles) over the Buffalo Ridge.

.LONG TERM...(Sunday through Friday)
Issued at 251 AM CDT Sat Mar 25 2017

Deep low level saturation is expected across the forecast area on
Sunday morning.  This could lead to some fog across the area, but
stratus will likely prevent it from becoming locally dense.
Therefore, will just keep patchy wording for now.  Not a lot in
terms of forcing for precipitation through the morning hours on
Sunday, but am continuing to carry some slight chance pops mainly
across southwest Minnesota.  Models are producing some very light
precipitation but with lack of strong forcing and dendritic layer
remaining dry aloft, not most efficient atmosphere in place to
produce precip. With light east to northeast flow remaining
throughout the day, may be difficult to scour out the low level
moisture. Will keep high temperatures at or slightly below normal.

Difficult forecast this week in terms of precipitation and
temperatures as models are not in the best agreement.  In general,
expect wave to dig into the southwestern US and become cutoff from
the upper level flow.  Once this occurs, the track of this system
becomes uncertain as it ejects eastward into the plains.  GFS tends
to keep the track of this system far enough to the south that might
be able to remove pops, while the ECMWF is further north.  Both
models have been fairly consistent in their bias, so for now, left
guidance pops as is. ECMWF is substantially cooler than the GFS (by
5-7 degrees C) for Wednesday and beyond.  At this point, guidance
falls in the middle and have left things as is until it becomes
clear which way to trend.

This relatively slow moving system is followed by a northern stream
wave phased with a southern stream kicker wave.  The GFS is fairly
strong with the northern stream, while the ECMWF is weaker.  May
still be brushed by precipitation associated with the kicker wave,
and have left chance pops across the south on Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1224 PM CDT Sat Mar 25 2017

Low clouds will persist through the TAF period. Some improvement
will be see in south central SD this afternoon, but stratus will
build westward once more after 02z. Fog will also be a concern,
with visibilities dropping as low as a half mile at times in
northwest Iowa and southwest MN. Will leave MVFR ceilings at all
three TAF sites.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&

$$

SHORT TERM...Dux
LONG TERM...BT
AVIATION...



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