Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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814
FXUS63 KFSD 171747
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1147 AM CST Fri Feb 17 2017

.SHORT TERM...(Today and Tonight)
Issued at 354 AM CST Fri Feb 17 2017

Another spectacular February day is on tap for the region. We`re
going to start the day with temperatures at or near record values
above the ground, evident by sampling from Aberdeen last evening.
Winds will turn southwesterly by mid-day as a weak surface trough
approaches.  This trough should help increase mixing up to or
around 900 mb, and allow highs to push into the 60s for most
locations. With 900 mb temperatures pushing 16 to 19C, have bumped
up temperatures in many areas 3 to 5 degrees. It`s possible areas
near Sioux City could soar towards 70, which would be the 3rd
earliest 70 degree reading on record for Sioux City. Additionally,
elevated terrain areas along the Buffalo Ridge may push the upper
60s.

Another great night expected into Saturday, as surface high pressure
moves into the region. Temperatures will struggle to fall into the
lower 30s with little in the way of high level clouds to worry
about.

.LONG TERM...(Saturday through Thursday)
Issued at 354 AM CST Fri Feb 17 2017

Another splendid day on Saturday as ridging aloft strengthens across
the plains.  While Saturday again has it challenges to warming - a
fair potential for some thicker high-level clouds as well as an
early day full of likely weak flow around the ridge axis - each of
these elements has failed to stop temperatures from reaching a
fuller mixing potential, in this case, a few degrees warmer than the
blend and in fact most guidance.

Amplified pattern with western trough and plains ridge maximizes
Saturday night with southerly flow increasing. Will also be a better
surge of low level moisture which spreads northward during the day
Sunday, and could be accompanied by an increase in low clouds, but
sunshine already will likely dim somewhat from the increase in high
clouds. Highs should still reach the 60s, even close to 70 toward
south central SD. Could actually find some near 50 dewpoints
streaming into the area during Sunday afternoon and evening, and
with the strong southerly low-level jet, this will set the stage for
some ridiculously mild overnight temperatures in the upper 40s to
lower 50s.  As long as temperatures do not fall too quickly toward
midnight Monday night, the likelihood for locations to match or
exceed the all-time warmest minimum temperature would appear to be
quite strong at this point.

Fairly moist neutral profiles spread across the area Sunday night,
with some indication of weak elevated instability. As lift with
deeper jet structure pushes into the area latter Sunday night and
early Monday, would expect an increasing coverage of light showers
to spread north and eastward, and will maintain a small mention of
thunder. Better instability continues to shift east well in advance
of the main upper trough, but could see a few lingering showers east
of I-29 through the afternoon and even early evening along the
eastern border from KMWM to KSLB.

Wave shears by quickly, with westerly flow flushing out moisture and
setting the stage for record or near record warmth again on Tuesday.
Likely to find many spots mixing into the lower 70s for the James
and Missouri valleys. A wave will move along the International
border Tuesday night with a frontal boundary dropping southeast and
confluent flow working to drive a cooler and drier ridge southward
into the northern plains. 10 to 15 degrees cooler, but still a solid
20 to 25 degrees above normal with highs Wednesday mid 50s to around
60. Strengthening of ridge to the north will keep filtering cooler
air southward through Wednesday night and into Thursday.

Inflection to flow begins to take shape on Thursday, with increase
in southwest flow aloft and approach of stronger div Q on Thursday
afternoon, as lower level boundary sharpens south of the area
setting up effective zone of isentropic ascent. Wet bulbing given
the persistent east to northeast trajectory could complicate
precipitation type especially on the northern/leading edge of
precipitation during the morning, but likely to see conditions be a
little slower into the day given leading dry air.

Keeping watch on what has been a very consistent signal of a strong
jet/trough pushing toward the region later Thursday and into Friday.
Enough deviation on track of what would be a significant development
of low pressure to deserve some serious watching at this point, but
several runs also indicating a significant snow scenario for areas
near southeast SD. However it evolves, it will be quite a drastic
change from the taste of spring for much of this upcoming week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1145 AM CST Fri Feb 17 2017

 VFR conditions through the period. Weak cold front will move
through the region this afternoon with surface high pressure
settling into the region tonight. This will result in breezy
westerly winds this afternoon, decreasing with sunset. Light winds
are expected Saturday.

&&

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

$$

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



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