Severe Thunderstorm Warning 12, NWS Sioux Falls, SD

713 
WWUS53 KFSD 160449
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
1149 PM CDT MON MAY 15 2017

SDC009-160515-
/O.CON.KFSD.SV.W.0012.000000T0000Z-170516T0515Z/
Bon Homme SD-
1149 PM CDT MON MAY 15 2017

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1215 AM CDT
FOR BON HOMME COUNTY...

At 1148 PM CDT, a severe thunderstorm was located over Tyndall,
moving northeast at 55 mph.

HAZARD...Ping pong ball size hail and 60 mph wind gusts. 

SOURCE...Radar indicated. 

IMPACT...People and animals outdoors will be injured. Expect hail 
         damage to roofs, siding, windows, and vehicles. Expect wind 
         damage to roofs, siding, and trees. 

This severe storm will be near...
   Tyndall Now
   Scotland around 1205 AM CDT. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4317 9807 4317 9764 4290 9763 4285 9764
      4284 9770 4285 9777 4287 9783 4287 9785
      4285 9788 4281 9789 4277 9798 4276 9799
TIME...MOT...LOC 0448Z 203DEG 47KT 4298 9785 

HAIL...1.50IN
WIND...60MPH
 
$$

Weisser

895 
WWUS53 KFSD 160512
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
1212 AM CDT TUE MAY 16 2017

SDC009-160522-
/O.EXP.KFSD.SV.W.0012.000000T0000Z-170516T0515Z/
Bon Homme SD-
1212 AM CDT TUE MAY 16 2017

...THE SEVERE THUNDERSTORM WARNING FOR BON HOMME COUNTY WILL EXPIRE
AT 1215 AM CDT...
        
The storm which prompted the warning has weakened below severe
limits, and has exited the warned area. Therefore, the warning will
be allowed to expire.  However small hail is still possible with this
thunderstorm.

A severe thunderstorm watch remains in effect until 500 AM CDT for
southeastern South Dakota.

LAT...LON 4317 9807 4317 9764 4290 9763 4285 9764
      4284 9770 4285 9777 4287 9783 4287 9785
      4285 9788 4281 9789 4277 9798 4276 9799
TIME...MOT...LOC 0512Z 202DEG 36KT 4319 9774 

$$

Weisser

Area Forecast Discussion
National Weather Service Sioux Falls SD
647 PM CDT Mon May 15 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 313 PM CDT Mon May 15 2017

Active forecast period in the short term. Surface boundary sliding
southward across northwest Iowa with much cooler stable air to the
north of the boundary.  Have significantly lowered forecast highs
for the late afternoon and evening hours.  40+ knot low level jet is
expected to develop this evening pushing the boundary back to the
north.  As the boundary works to the north, minimal capping is
expected to develop near 800 mb with 1500-2000 J/kg of elevated
CAPE. With relatively strong speed shear, models suggest 35-40 knots
of 1-6km bulk shear providing ample shear to organize storms to
create wind and hail threat.  Have expanded area of concern back as
far as the James River overnight into the HWO.  Most critical time
for severe weather potential appears to begin around 03z, lingering
through around 09z or so.  May see some lingering convection through
the early morning hours, but expect it to lift off to the northeast
as band of warm air advection lifts to the north.

Expect much of the day to be relatively quiet across the area on
Tuesday as the area is void of any strong forcing moving through and
strong capping inversion in place.  Concentrated pops across south
central SD along the Missouri River Valley late tomorrow after 21Z
as series of short waves approach from the southwest.  Capping
inversion appears to be fairly strong, so pops even at 21Z may be on
the fast side. Cold front moving through the area late in the day
may help to focus storm potential.  If storms are able to develop,
decent potential for strong damaging winds with dry soundings and
surface downdraft CAPE values of 1500-2000 J/Kg.

.LONG TERM...(Tuesday night through Monday)
Issued at 313 PM CDT Mon May 15 2017

Primary concerns in the medium and extended portions of the forecast
are focused on convective trends Tuesday night through Wednesday,
along with cooling temperatures towards the second half of the week.

Convection risks begin to increase Tuesday evening, as synoptic lift
overspreads a stalled frontal boundary across the region. An
initially well capped environment may begin to break down well
southwest of the CWA ahead of the dryline bulge in south central
NEbraska late in the afternoon. Further northeast there is some
uncertainty as to the impacts of downstream instability levels or
contamination from this initial convection early in the evening
to the southwest keeping convection at bay until well into the
evening.

Nevertheless, model dew points likely also boosted too high
for this time of the year, but will still result in MLCAPE values
approaching 2000-3000 J/KG in the evening. Initial shear looks
somewhat marginal, but should be enhanced by a 500 mb jetlet pushing
effective shear towards 40 knots.   While initial cells may be
somewhat discrete, unidirectional and somewhat marginal shear
profiles may support the rapid development of clusters as 02z
approaches. Steep mid-level lapse rates would support a large hail
risk (greater than golf ball), with a minor pocket of dry air around
750 mb supporting pockets of damaging winds within localized bowing
segments despite boundary layer stabilization. Greatest severe
weather risks will find themselves focused along and southeast of a
Yankton to Sioux Falls and Marshall line.

Once the LLJ increases after 03z and towards 06z, post-frontal
elevated convection rooted on the 850 mb boundary will begin to
increase substantially further north and west.  Much lower
instability further northwest of the surface boundary, but it may be
supportive of at least a marginal hail risk. However, as the
overnight moves onward and the surface boundary begins to flatten,
we'll likely transition towards an overrunning heavy rain risk.

Rain will continue through Wednesday as the upper low begins to
pivot over the CWA.  As the upper low begins to stack on top or just
northwest of the surface low have some concerns that, if surface
based instability can grow, we could quickly jump towards a very
conditional low end severe weather threat over portions of the Tri-
State area, but especially across NW Iowa and adjacent areas of
MN/SD.  The primary risks would be hail with very low freezing
levels, but any mesoscale surface boundary could even force a minor
tornado risk given the very low LCLs.

High pressure sinks southward Wednesday night into Thursday with
scattered showers lingering overnight.  Seasonally cool conditions
with highs in the 50s and lower 60s return for Thursday and Friday.

While some uncertainty remains, increasing showers with isolated
thunder risks moves northeast into the CWA for Friday and Friday
night.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 643 PM CDT Mon May 15 2017

Strong low level jet is expected to develop by late this evening,
triggering development of thunderstorms through the overnight
hours. Best chances for widespread storms expected to remain
northwest of KSUX, but could impact KFSD and KHON as the storms
lift out of Nebraska. Storms are generally expected to be based
high enough for VFR ceilings, but could see MVFR visibilities in
heavier downpours. Convective cells may produce gusty winds and
large hail. This activity is expected to exit the forecast area by
daybreak Tuesday, with additional development likely holding off
until after the end of this TAF period.

&&

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

SHORT TERM...BT
LONG TERM...Dux
AVIATION...JH

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
832 PM CDT Mon May 15 2017

SDZ050-052-057-058-063-064-170145-
Gregory-Jerauld-Brule-Aurora-Charles Mix-Douglas-
832 PM CDT Mon May 15 2017

This Hazardous Weather Outlook is for portions of central South
Dakota and south central South Dakota.

.DAY ONE...Tonight

Tonight another round of showers and thunderstorms will be
possible. A few of the storms could become strong and capable of
producing hail to the size of nickels and wind gusts to 50 mph.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

Showers and thunderstorms will become likely by Tuesday night into
Wednesday but at this time the strongest storms should be along
and east of Interstate 29. The main threats for any of these
storms will be lightning and heavy downpours.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today and tonight.

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-053>056-059>062-065>071-170145-
Lyon IA-Osceola-Dickinson-Sioux-O'Brien-Clay IA-Plymouth-Cherokee-
Buena Vista-Woodbury-Ida-Lincoln MN-Lyon MN-Murray-Cottonwood-
Nobles-Jackson-Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-
Brookings-Sanborn-Miner-Lake-Moody-Davison-Hanson-McCook-
Minnehaha-Hutchinson-Turner-Lincoln SD-Bon Homme-Yankton-Clay SD-
Union-
832 PM CDT Mon May 15 2017

This Hazardous Weather Outlook is for portions of northwest Iowa,
west central Iowa, southwest Minnesota, northeast Nebraska, east
central South Dakota, and southeast South Dakota.

.DAY ONE...Tonight

Another round of thunderstorms is expected to impact the area
overnight, beginning near the Missouri River Valley after 11 pm,
then lifting northeast across the region through early Tuesday
morning. A few of these storms could become severe, and the
primary threats will be hail to the size of golf balls, and wind
gusts around 60 mph.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

The chance for thunderstorms will return again Tuesday afternoon
and night, and a few of these storms could be severe as well. The
better chance for severe storms should be east of Interstate 29
with tennis ball sized hail and 75 mph wind gusts possible.

Additional showers and thunderstorms will be possible Wednesday,
but at this time, any storms that develop on Wednesday should not
become severe.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed tonight.