Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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879
FXUS63 KFSD 272251
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
551 PM CDT Sun May 27 2018

.SHORT TERM...(This evening through Monday)
Issued at 305 PM CDT Sun May 27 2018

Record-breaking heat will continue through sunset this evening.
Everything remains on track with the current Heat Advisory, with
heat index values forecast to remain in the 95 to 100 range,
largely due purely to temperatures given dew points are in the 50s
to low 60s across the region. Cloud cover looks to remain minimal
through the daylight hours, with the region sitting squarely
under the ridge axis. Nevertheless, a few isolated thunderstorms
with gusty winds are possible in the Worthington, MN to Spencer,
IA area as a weak boundary focuses convergence there this
afternoon.

This evening into the overnight hours, models are consistent in
depicting thunderstorm development to the west and north of the
tri-state area, but storms look to remain along and west of a
Pierre to Aberdeen, SD line. Monday shower and thunderstorm
activity will be in response to the slow eastward progression of
the large cut- off low pressure currently over the Rockies.
Multiple shortwave impulses will provide isolated breaks in the
capping inversion throughout the day Monday, with short range
models showing scattered thunderstorms possible area-wide during
the afternoon hours. Only west of the James River is there modest
shear, and this would be the location most favorable for isolated
strong storms capable primarily of damaging wind gusts. Although
brief heavy rain is possible under thunderstorm cores, many
locations will remain dry.

Temperature-wise, Monday will remain hot, but temperatures
themselves may not get to the readings experienced Sunday. Low to
mid-90s are likely, with some cloud cover helping keep the heat
less oppressive. Dew points will be higher, so the heat index
could again reach 95 plus, so another round of Heat Advisories is
not out of the question. Leaned toward consensus guidance at this
point through, and held off on any highlights, deferring the
decision to later shifts when more high resolution guidance comes
in. Regardless, the takeaway message remains clear: Hot, mid-
summer like heat persists for another day.

.LONG TERM...(Monday night through Sunday)
Issued at 305 PM CDT Sun May 27 2018

Tuesday will bring the arrival of the upper level trough, as it
slowly is re-absorbed into the northern stream of the jet. Rain is
likely for many areas, as a broad band of showers and thunderstorms
moves west to east throughout the day. Decreased instability will
keep the chances for strong thunderstorms marginal at best,
despite better shear. Temperatures show a slight cooling trend,
with highs in the 80s.

The upper low is slow to clear the region, so areas along and east
of I-29 will see continued chances for rain through Wednesday
evening. Temperatures rebound Thursday as the amplified flow over
the U.S. leads to another small-scale ridge building, with a return
to 90s with mostly dry conditions. Next weekend does look to
feature another slight cool-down into the 80s, but given seasonal
average temperatures in the mid-70s, the trend of above normal
warmth continues.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 550 PM CDT Sun May 27 2018

VFR conditions expected through the TAF period.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory until 7 PM CDT this evening for SDZ062-066>071.

MN...Heat Advisory until 7 PM CDT this evening for MNZ071-072-080-081-
     089-090-097-098.

IA...Heat Advisory until 7 PM CDT this evening for IAZ001>003-012>014-
     020>022-031-032.

NE...Heat Advisory until 7 PM CDT this evening for NEZ013-014.

&&

$$

SHORT TERM...VandenBoogart
LONG TERM...VandenBoogart
AVIATION...JM



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