FXUS63 KFSD 261118

Area Forecast Discussion
National Weather Service Sioux Falls SD
618 AM CDT Wed Sep 26 2018

.SHORT TERM...(Today and Tonight)
Issued at 258 AM CDT Wed Sep 26 2018

Building surface high pressure will provide for a fairly nice fall
day across the region. Broad upper level subsidence on the back side
of yesterday's upper level trough will allow for sunny skies and
temperatures largely in the 60s. A tightened pressure gradient
will elevate winds toward the breezy category north of I-90 with a
few gusts around 20-25 mph possible this afternoon.

Tonight, our next jet max and associated surface front slide toward
the area. A lack of any substantial moisture should keep this
frontal pretty uneventful in terms of any precipitation, just some
increasing cloud cover. Overnight low temperatures will largely be
in the mid 40s to lower 50s.

.LONG TERM...(Thursday through Tuesday)
Issued at 258 AM CDT Wed Sep 26 2018

By late Thursday and Thursday night, the previously mentioned jet
max begins to interact with the mid level boundary and may lead to a
bit of frontal shower activity. Latest models continue to trend
toward the most favorable interaction to occur just south of the MO
River and thus will keep lower end chance POPs along our far
southern zones with only slight chances elsewhere. The reinforcing
cold air will keep temperatures Friday well below their seasonal
normals, although with the southern shift of cloud cover associated
with the front, may warm a touch over previous forecasts. Current
thinking is most locations will make it into the mid to upper 50s.

A broad area of surface high pressure builds back in by Friday night
and the big question will revolve around overnight low temperatures
Saturday morning. Wind should become light with dewpoints dropping
into the upper 20s and lower 30s. This would usually spell a very
chilly night, however a southwest to northeast moving cloud deck may
lead to counteract this chilly recipe. At this time, it looks like
our southwest Minnesota counties would stand the best chance of
frost capable temperatures as clouds will likely arrive too late to
prevent sufficient radiational cooling. Overall, confidence in this
portion of the forecast is relatively low and reflected in the
ensemble spreads.

The remainder of the extended forecast will feature periodic rain
chances along with slowly moderating temperatures. Upper level flow
becomes more zonal and eventually southwesterly by the weekend with
a warm front lifting toward the region. The combination of the
presence of this front along with an active jet overhead will
provide for several shower and occasional thunderstorm chances into
early next week. Frontal location is still uncertain and thus so are
potential rainfall amounts. Obviously will need to monitor our flood
sensitive areas but for now, far too much uncertainty to say whether
there is a concern or not.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 614 AM CDT Wed Sep 26 2018

VFR conditions expected through the period. Westerly winds will
become breezy this afternoon, especially north of I-90. A front
will begin to approach the area by late in the TAF period and
could lead to a period of LLWS.




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