Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 192345

Area Forecast Discussion
National Weather Service Sioux Falls SD
545 PM CST Sun Feb 19 2017

.SHORT TERM...(This evening through Monday)
Issued at 334 PM CST Sun Feb 19 2017

Stout southerly flow expected across the area tonight in advance of
a cold front approaching fro the west.  Low level jet increases
shortly after sunset leading to low level wind shear.  Stratus
across east central Kansas late this afternoon will also advect
north and expand throughout the night.  With relatively strong low
level flow, am not expecting fog to develop, but could see showers
and maybe a thunderstorm or two as a series of weak wave lift
northward in the southerly flow. Have kept lows near record levels
for the month of February in the low and mid 50s.

Cold front will work its way across the forecast area on Monday.
Once the cold front moves through, atmosphere becomes more stable
and quickly dries out in the low levels.  Despite this, cold air
advection behind the front is strong enough to limit the amount of
recovery temperature-wise.  With clouds hanging tough east of I-29
ahead of the front for a better part of the day, kept temperatures
towards cooler guidance values.

.LONG TERM...(Monday night through Sunday)
Issued at 334 PM CST Sun Feb 19 2017

Unseasonable warmth will continue into the first half of the week,
however a potent storm system will bring a return to winter weather
for late week.

Drier weather quickly returns to the region Monday evening, with
upper flow quickly turning more zonal into Tuesday. Breezy northwest
winds behind the front quickly diminish and shift back to the west
or southwest overnight. With skies clearing out, overnight
temperatures will cool into the mid to upper 30s. This will lead
into another extremely warm February day on Tuesday. Again, nudged
temperatures slightly warmer than the Superblend, with highs in the
60s to mid 70s. Many locations will likely see record highs across
the region.

A northern stream wave tracking along the Canadian border quickly
races through the area Tuesday night into Wednesday. A cold front
will track through the area, however dry weather will prevail.
Breezy northwest winds and some scattered high clouds will keep
temperatures cooler than the previous day, however it will still
remain well above normal in the upper 50s to upper 60s.

Broad southern stream trough digs into the western Plains on
Thursday and will likely provide a significant impact to the region
into at least Friday. Models continue to show some fairly
significant differences in the track and timing of this system,
however the most recent 12Z GFS and ECMWF are coming into much
better alignment. The GEM is much more of an outlier, following a
slower, deeper, and slightly more northern solution.

Precipitation will likely start out as light rain spreading eastward
across the region late Wednesday night into Thursday morning. The
best potential for precipitation will be along and south of I-90 on
Thursday afternoon and evening. As the system winds up, gusty
northerly winds and colder air filters southward through the region
Thursday evening and overnight, allowing rain to mix with snow, then
become primarily snow overnight. The GFS and ECMWF paints the
highest QPF and best precipitation chances across far southeast SD
into northwest Iowa and southwest Minnesota Thursday night and
Friday morning. The low lifts away from the region on Friday,
allowing the snow to taper off from west to east, however the much
slower GEM solution holds onto the low into Friday night and
Saturday morning. Snowfall amounts/location still remain quite
uncertain given the model differences and run to run
inconsistencies, but still feeling pretty confident that both rain
and snow will impact much of the forecast area late week.

Headed into the upcoming weekend, temperatures remain closer to
seasonal normals, with highs near freezing and lows in the teens.
The GFS brings a weak shortwave through the region around the
Saturday afternoon/night time frame, while the ECMWF is dry, and the
GEM is still slowly exiting the Thursday/Friday system. Not much
confidence, so did not stray from the low end pops in the SuperBlend.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 545 PM CST Sun Feb 19 2017

VFR conditions will deteriorate after 06Z as low stratus develops
and streams northward into the area ahead of an approaching cool
front. IFR ceilings appear most likely east of the James River
Valley, and especially along and east of Interstate 29 including
KSUX and KFSD. Spotty high-based showers or possibly an isolated
thunderstorm may develop, but timing/location too uncertain to
include any mention of thunder in the TAFs at this time.

Low level jet also develops early this evening, creating a period
of low level wind shear into the early morning hours Monday.




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