Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 151720

Area Forecast Discussion
National Weather Service Sioux Falls SD
1120 AM CST Wed Feb 15 2017

.SHORT TERM...(Today and Tonight)
Issued at 246 AM CST Wed Feb 15 2017

A surface ridge axis across the region this morning will drift off
into the Central Plains today, as a surface trough dropping out of
Canada begins to exert influence on the Northern Plains. This will
result in a southerly low level flow returning to our area, and with
ensuing warm air advection will see temperatures begin to climb over
yesterday.  This will play out to highs in the lower/mid 40s east of
the Interstate 29 corridor to upper 50s over south central SD.

For tonight, the aforementioned surface trough slides deeper into
the Plains States with the low level flow becoming more westerly
overnight. Temperatures will be milder tonight, with lows running
upper 20s to lower 30s.

.LONG TERM...(Thursday through Tuesday)
Issued at 246 AM CST Wed Feb 15 2017

A tremendous warmup is anticipated through the medium and extended
portions of the forecast, with a continuation of temperatures in the
50s and 60s for a duration we just haven`t seen in February for some
years. What will likely make this warm spell so unique is the
overall lack of any strong winds, and extreme nature of the low
level thermal ridge. 925 and 850 temperatures will be pushing daily
max readings based on sounding climatology into next week. Forecast
changed revolved around again raising temperatures, utilizing a
blend of the previous forecast along with ECMWF and bias corrected

Temperatures will start their jump on Thursday as mid-level ridging
with 500 heights 1-2 SD from normal sliding into the central US.
Despite light westerly winds, temperatures should have no issues
peaking in the 50s and 60s. By Friday morning, 850mb temperature
average around +16 with 925mb temperature 10-12. A slightly stronger
and deeper mixing ahead of a weak sfc trough should push readings
into the 60s.

Minor shortwave slides through the Northern Plains on Saturday, and
may knock temperature down into the mid 50s, with perhaps a few
sprinkles north of the CWA.

Temperatures again jump for Sunday and Monday as lee side troughing
deepens. Despite a combination of troughs entering into the Pacific
NW and Baja region, mid-level ridging should hold back these waves
until at least Monday. Temperatures will again push 60 on Sunday.

Guidance coming into slightly better agreement with Monday`s system
providing more influence from northern stream troughing, pushing a
weak boundary through in the afternoon. Light rain will be possible
east of I-29, and with MUCAPE 50-100 J/KG an isolated rumble of
thunder is possible. After what looks to be an incredibly warm
overnight period (near 50), Monday`s highs will climb into the lower

With little in the way of colder air behind this trough, much above
normal temperature (50s/60s) may continue through Thursday.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1119 AM CST Wed Feb 15 2017

VFR conditions will prevail through the TAF period. KSUX may see a
brief period of low level wind shear late this evening, as surface
winds decouple and become light southeast beneath a modest
southwesterly low level jet.




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