Severe Thunderstorm Warning 17, NWS Sioux Falls, SD

136 
WWUS53 KFSD 270911
SVSFSD

Severe Weather Statement
National Weather Service Sioux Falls SD
411 AM CDT Thu Jun 27 2019

SDC035-043-061-067-087-270920-
/O.EXP.KFSD.SV.W.0017.000000T0000Z-190627T0915Z/
Davison SD-Douglas SD-McCook SD-Hanson SD-Hutchinson SD-
411 AM CDT Thu Jun 27 2019

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN DAVISON...
NORTHEASTERN DOUGLAS...SOUTHWESTERN MCCOOK...SOUTHERN HANSON AND
NORTHERN HUTCHINSON COUNTIES WILL EXPIRE AT 415 AM CDT...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning will be allowed to expire.

A Severe Thunderstorm Watch remains in effect until 100 PM CDT for
southeastern South Dakota.

LAT...LON 4329 9826 4347 9834 4374 9762 4341 9745
TIME...MOT...LOC 0910Z 249DEG 49KT 4358 9759 

$$

JM

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1135 PM CDT Wed Jun 26 2019

.UPDATE...
Issued at 1002 PM CDT Wed Jun 26 2019

Rapid update hi-res models have been trending slower and farther
north with the primary convective threat overnight into early
Thursday, and incoming 00Z models support this idea as well. Still
signals pointing to a threat of strong/damaging winds impacting
part of our forecast area, but greater threat now appears to be
focused north of I-90 after 3-4 am. Have adjusted our forecast
accordingly, shifting highest storm chances north of I-90 through
12Z, with potential storms then turning southeast across southern
Minnesota through the morning hours Thursday. Lingering cold pool
in the wake of this morning activity may impact temperatures over
the northeast portion of the forecast area. Have slowed the climb
in the hourly grids, but will let next shift interrogate more
closely before making changes to the overall high temperature.

&&

.SHORT TERM...(This Evening through Thursday)
Issued at 240 PM CDT Wed Jun 26 2019

Quiet weather through the daytime hours today, as lingering MCS
across northern Missouri continues to send cirrus across NW Iowa
this afternoon.  Temperatures have been limited thanks to the light
winds and cloud cover. Several areas of concern in the forecast
ahead, including severe storm risks later tonight, hot and humid
conditions this weekend, and returning thunderstorm chances early
next week.

Tonight:  We'll watch two distinct areas for convective development
later today.  ACCAS field slowly drifting eastward across central
South Dakota this afternoon indicative of initial surge of higher
theta-e air aloft and is expected to continue to drift eastward into
the evening.  This ACCAS will likely begin to intersect with a
developing LLJ later this evening, or early in the overnight hours,
across SW Minnesota which could spur some development. It will be
possible to have an isolated hailer in this development later
tonight.

However, the main area of concern will be across the western High
Plains as an elongated shortwave arrives later this afternoon.
Favorable synoptic forcing should force multiple clusters of
supercells later this afternoon or early evening as a highly
unstable atmosphere has developed. Nearly all model guidance in
agreement that cellular merger should take place with cold pool
development allowing one or more small scale MCS beginning to
move east northeast into the night across the Dakotas and northern
Nebraska. The concerning issue for our area is where the primary
development takes place. With a surface/850 front remaining
somewhat pinned southward this afternoon due to MCS activity, and
a stronger EML slightly slower to lift northward, could see
convection take a bit more of a southern track than what the 12Z
NAM/EC/GEM suggested. High elevated instability approaching 3000
J/KG along with strong synoptic forcing suggest that this activity
should be able to sustain some intensity as it crosses the
Dakotas. However a bit concerned that the shear/CAPE profiles are
too unbalanced to support long duration or widespread severe
risks. That said, soundings continue to support a transition from
supercellular strong winds/hail/tornado risk towards primarily a
damaging wind and heavy rain risk as storms cross the Dakotas.
CAMs indicate an increased potential for strong winds at least
towards the James River valley.

Any organized MCS should slide eastward by daybreak, but the
veering LLJ and weaker EML on the eastern half of the CWA (MN/IA)
could lead to persistent redevelopment into the ridge through mid-
morning Thursday. Some of this activity could also be strong to
severe.

Thursday: Temperatures will be very dependent on the evolution of
the overnight MCS and any lingering stratus/cirrus development.
However, temperatures should begin to rise by the afternoon into the
80s, with a distinct increase in dew points.

.LONG TERM...(Thursday Night through Wednesday)
Issued at 240 PM CDT Wed Jun 26 2019

Friday-Sunday: Mid-level heights really begin to rise as we head
into the weekend, allowing hot and humid conditions to enter the
region.  Some concerns moving through the weekend that high
temperatures could be a bit too high, and that boundary layer
moisture could limit heating potential.  Nevertheless, any offset in
heat index values by lowering temperatures would be made up by
higher dewpoints.  Heat headlines are still anticipated, especially
as overnight lows only fall into the lower 70s.

The ECMWF has trended towards the GFS for Sunday night through
Tuesday, bringing a frontal boundary into the area and increasing
the risks for convection to start next week. Shear remains fairly
poor given the synoptic setup, but instability would still allow for
some severe weather risk late Sunday and again Monday.

Tuesday-Wednesday: No real changes made to the extended. A
flattening mid-level ridge could leave the area susceptible to daily
convection, along with near to slightly above normal highs.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1135 PM CDT Wed Jun 26 2019

Convective potential through the first half of this TAF period has
trended north and slower in latest model runs. Confidence is lower
that KFSD will see any thunderstorms, so removed thunder for now,
but will keep a mention of showers mid-late Thursday morning to
indicate favored time frame, should storms develop far enough
south.

Confidence still somewhat higher for KHON, though now looking more
likely toward pre-dawn hours (10Z-12Z) than during the overnight.
Confidence also somewhat higher than KSUX will remain well south
of the convective activity.

After 18Z Thursday, convection expected to push east of the area,
though a few model solutions indicate chance of redevelopment into
southwest Minnesota late in this TAF period.

&&

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

UPDATE...JH
SHORT TERM...Dux
LONG TERM...Dux
AVIATION...JH

Hazardous Weather Outlook
National Weather Service Sioux Falls SD
620 AM CDT Wed Jun 26 2019

IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097-
098-NEZ013-014-SDZ038>040-050-052>071-271000-
Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee-
Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson-
Pipestone-Rock-Dixon-Dakota-Beadle-Kingsbury-Brookings-Gregory-
Jerauld-Sanborn-Miner-Lake-Moody-Brule-Aurora-Davison-Hanson-McCook-
Minnehaha-Charles Mix-Douglas-Hutchinson-Turner-Bon Homme-Yankton-
Union-
620 AM CDT Wed Jun 26 2019

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

.DAY ONE...Today and tonight.

Thunderstorms are possible tonight. These storms will be capable of
producing winds to 65 mph and hail to the size of golfballs.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Temperatures will warm into the 90s on Friday through Sunday. With
dew points near 70, heat indicies of 95 to 105 can be expected.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is possible after 9 PM tonight.