Area Forecast Discussion
Issued by NWS Sioux Falls, SD

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KFSD 221742

Area Forecast Discussion
National Weather Service Sioux Falls SD
1242 PM CDT Tue Aug 22 2017

.SHORT TERM...(Today and Tonight)
Issued at 303 AM CDT Tue Aug 22 2017

With eclipse day memorable across the area for so many reasons, it
appears we will settle into a more quiet pattern for the short term.
Bits of lingering fog/low clouds around the highway 20 corridor
through northwest Iowa will flush out as secondary boundary moves
through in the predawn hours.  Overall, will be a nicely mixed day
with conditions actually a bit breezy near and east of I-29.
Temperatures will generally be in the 70s, perhaps near 80 toward
south central SD.  Under high pressure tonight, winds will quickly
diminish, especially through the I-29 stretch from KFSD southward
through northwest Iowa.  Day of mixing should reduce moisture enough
to keep fog from being an issue, but cannot rule out some shallow
fog near waterways.  Likely will see a few temps dip into the upper
40s, but mostly lower to mid 50s.  Some elevated warm advection
spreading into areas west of I-29 late night likely to spawn a few
mid-level clouds, but no precip.

.LONG TERM...(Wednesday through Monday)
Issued at 303 AM CDT Tue Aug 22 2017

Upper level northwest flow continues for Wednesday and Thursday with
no major precipitation chances to speak of. The one exception could
be a small chance for a thunderstorm Wednesday evening, mainly west
of the James River courtesy of some mid level warm air advection. By
Thursday evening, a shortwave and associated vort max sneaks along
the NE/SD border bringing with it additional small precip chances
but shear and instability profiles look pretty meager with either
one of these chances and thus severe weather is not expected at this
time. The main system arrives by Friday and this, in combination
with a warm air/moisture advection regime and increasing low level
jet by Friday evening, will fuel an expanding area for showers and
thunderstorms through this time frame. The unsettled weather will
likely continue into the weekend although the finer scale details
are not yet well agreed upon in the models.

With fairly persistent 850 and 925 mb, high temperatures only vary
by a few degrees from day to day, generally in the 70s and low 80s.
This would put them near or a few degrees below their climatological
normals. Look for increasing southerly surface winds Friday with the
approach of the aforementioned system.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1238 PM CDT Tue Aug 22 2017

VFR conditions expected through the period. Gusty winds will
impact primarily southwest Minnesota and northwest Iowa this
afternoon with gusts likely at SUX and FSD. Winds will decrease to
at or near calm tonight. Reduction in winds brings a conditional
chance for fog tonight at all 3 TAF sites as the amount of
lingering surface moisture from Monday`s thunderstorms will depend
on the amount of mixing this afternoon. Confidence in fog is not
large enough for inclusion at this time.




SHORT TERM...Chapman
AVIATION...Ferguson/ is the U.S. government's official web portal to all federal, state and local government web resources and services.