Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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562
FXUS63 KFSD 220953
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
453 AM CDT Thu Jun 22 2017

.SHORT TERM...(Today and Tonight)
Issued at 453 AM CDT Thu Jun 22 2017

Abbreviated discussion once again for ongoing severe convection
approaching the highway 14 corridor.  This activity is rooted near
800 mb, and with steep lapse rates from 700-550 mb think some storms
will be capable of producing large hail. In addition, surface
inversion is somewhat weak with temperatures hanging in the lower
70s.  Elevated storms this morning will transition closer to the
surface boundary across northwest Iowa this afternoon.  SPC has a
marginal risk for these storms this afternoon, with hail and
damaging winds the main threats.  Still a fairly strong capping
inversion near 700 mb, but if storms are able to develop good speed
and directional lead to 50-55 knots of 0-6 km bulk shear.

Storms work out of the region this evening leading to a cooler more
tranquil overnight.

.LONG TERM...(Friday through Wednesday)
Issued at 453 AM CDT Thu Jun 22 2017

Abbreviated discussion due to ongoing severe weather.

Dominant feature of the forecast for Friday through the weekend will
be cooler temperatures along with very comfortable dewpoints. Friday
will have brisk northwest winds, which will to some degree repeat
Saturday and Sunday ahead of core of high pressure. Moderated temps
somewhat on Saturday in line with deeper mixing, as sharp trough
digs through Minnesota. Colder air aloft spreads in for later
Saturday into Sunday, but stable layer remains and now looking less
likely for development of diurnal showers for Sunday. Several cool
nights in order with partial decoupling Saturday night and more full
decoupling likely Sunday night, even Monday night toward northwest
IA.  In the meantime, should see a little moderation of temps toward
normal on Monday under the surface ridge.

Next precipitation chance will develop by later Monday night with
wave crossing western ridge and interacting with advancing warm
advection/elevated instability across south central SD areas. With
the wave pushing southeast, support rapidly weakens by early Tue
further east into the CWA.  Better threat with a better moisture
transport and low-level jet developing Tuesday night into Wednesday.

GFS is absurdly hot for most of the CWA on Wednesday, and have
stayed closer to a more modest blended value, with some increase
placed into the west closer to the potential for incursion of
westerly flow.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1233 PM CDT Wed Jun 21 2017

VFR conditions are expected through the TAF period. A few
thunderstorms could develop along the Missouri River Valley, and
move eastward around KSUX after 00Z. A second round of showers
and thunderstorms will also be possible Thursday morning at all
sites. Models are not in good agreement on its timing and coverage;
therefore, have opted to not mention in the TAFs.

&&

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

$$

SHORT TERM...BT
LONG TERM...Chapman
AVIATION...05



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