Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 190748

Area Forecast Discussion
National Weather Service Sioux Falls SD
248 AM CDT Thu Oct 19 2017

.SHORT TERM...(Today and Tonight)
Issued at 246 AM CDT Thu Oct 19 2017

Warm and windy conditions are expected to finish out this work week.
Generally, temperatures will average nearly 15 to 20 degrees above
normal, but still around 5 to 10 degrees below record highs for this
time of the year!  Here`s a look at the primary modifications to the
forecast through next week.

1. Increased high and low temperatures from today through Saturday.
2. Increased wind speeds Friday through early Saturday.
3. Decreased afternoon dew points today.
4. Increased thunder potential Saturday morning.

Today: Expecting a fairly strong diurnal recovery today from
overnight lows in the upper 30s to lower 40s. 925:850 warm advection
continues this morning and winds are expected to increase through
the day.  Have favored the warmest guidances from MAV/MEX/LAMP/CMC
for today which will push temperatures into the middle and  upper
70s. Models have been a bit generous on boundary layer moisture, so
will mix down slightly drier dew points this afternoon and slow
arrival of higher dew points from the south.

Tonight: We`ll begin to see a bit of an increase in cirrus and mid-
level clouds overnight as flow turns southwesterly. Should see a
fairly mixy overnight timeframe which will keep lows in the 50s
with a few 60s in elevated areas.

.LONG TERM...(Friday through Wednesday)
Issued at 246 AM CDT Thu Oct 19 2017

Friday:  Shortwave energy lifting northeast into the Plains from the
Southwestern US will push into the area on Friday.  For the most
part, it looks like the only impact from this wave will be in an
increase in mid-upper level clouds. With deep upper troughing moving
towards the Northern Rockies and lee side troughing developing over
the Western High Plains, the sfc pressure gradient should steepen
significantly through the day. Models continue to show a strong low
level jet persistent through the day, upwards of 40 to 45 knots at
850 mb.  Depending on the depth of mixing, downward momentum
transfer should result in wind gusts upwards of 40 mph at times
during the day.

Have continued to trend towards the warmest guidance through the
day, despite the threat for increased mid level clouds.  Mixing
upwards of 900-875 mb will result in readings in the upper 70s.
Again favored the warmer guidance numbers, but remain cautious
with potential cloud impacts.

Friday night - Saturday: Stratus looks to arrive a bit later than
earlier thought, more into the overnight time frame.  Broad warm
advection will allow the potential for showers and even a few
thunderstorms to develop after midnight. With sfc troughing well
west of the area, expecting overnight lows to struggle to reach the
50s. Elevated instability does increased across the board as mid-
level lapse rates increase slightly after 4am. Will increase the
probability of thunder slightly.   The aforementioned frontal
boundary begins to move through the CWA early Saturday.  Frontal
forcing may be enough to force a linear area of showers and
thunderstorms along the boundary by mid-morning, quickly moving
eastward through MN/IA by mid-day. Will try to advertise a bit
more thunder than showers. Behind the front, temperatures will
cool back into the 50s and 60s, with a limited diurnal curve.

Sunday - Wednesday: Minimal changes further out into the forecast.
Westerly mid-level flow continues Sunday and Monday, with a
seasonally strong upper jet crossing the Northern Plains by Monday
and Monday night. Models are a bit split, but could see a need for
increased PoPs late Monday and Monday night as a shortwave dips
through the Northern US pushing more favorable jet dynamics
overhead. Temperatures more typical of late October arrive for the
middle of the week, with highs in the 50s and dry conditions.


.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1026 PM CDT Wed Oct 18 2017

VFR conditions through the TAF period. Gusty southerly winds will
arrive by late morning into Thursday evening. Models suggest LLWS
after 20/04Z at all terminals, but opted not to include for now
due to low confidence.




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