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
FXUS63 KFSD 291047

Area Forecast Discussion
National Weather Service Sioux Falls SD
547 AM CDT Sat Jul 29 2017

.SHORT TERM...(Today and Tonight)
Issued at 238 AM CDT Sat Jul 29 2017

An upper level ridge and surface high pressure will continue to
influence the weather for today and tonight. With the surface ridge
axis located through the Upper Mississippi Valley and western Great
Lakes region, our winds will continue to be relatively light out of
the south/southeast through the period. With rising upper level
heights, may see temperatures warm slightly today, though readings
will be tempered somewhat by developing cumulus in the afternoon.
Looking at highs around 80 east of I-29 to upper 80s over south
central SD. Models have backed off on convection potential over our
area in the afternoon, so removed pops with the exception of extreme
western Brule and Gregory counties.

For tonight. a weak shortwave drops through western SD during the
night as a fairly meager low level jet develops through the south
central portions of the state. This may be enough to result in the
development of isolated convection through south central SD/James
River Valley later in the night, though models continue to be in
disagreement with this scenario. Low temperatures will be similar to
recent nights - in the lower to mid 60s.

.LONG TERM...(Sunday through Friday)
Issued at 238 AM CDT Sat Jul 29 2017

A light northwest flow aloft exits across the northern plains Sunday
and Monday, with an upper ridge of high pressure extending from the
intermountain west to Texas. At the surface, high pressure is rather
stationary across Iowa and points eastward greatly influencing our
weather into early next week. There is just not a lot to latch onto
in terms of dynamics, with the moisture supply largely cutoff due to
the high east of our area disturbing moisture flow northward.
Only skittish low pops are warranted in our far western zones on
Sunday along some weak thetae advection. Otherwise, temperatures
look seasonal, with highs in the 80s both on Sunday and Monday.

Low pops are still warranted Tuesday afternoon and night as a cold
front moves through this area. This is courtesy of an upper trough
moving toward the western Great Lakes through southern Canada and
Minnesota. Highs on Wednesday will be about 4 to 7 degrees cooler
when compared to Tuesday`s highs, and it looks as though Tuesday
will be the warmest day next week, albeit still seasonal.

With variations in each of their solutions, the deterministic GFS,
ECMWF and GEM Global are all pointing at cooler conditions with
below normal temperatures by late next week. The ECMWF is the most
aggressive with the Canadian air mass moving southward, as it dives
a very strong upper trough southward into the northern and central
plains Wednesday night. Therefore the ECMWF would be almost rather
chilly for this time of year, with the raw model values only about
70 to 75 for highs on Thursday and Friday, and slightly warmer on
Saturday. The GEM Global and GFS are more subtle with that wave. But
still, all models carve a long wave trough across the eastern half
of the United States by Friday and Saturday. At this time, using
bias corrected temperatures looks the way to go after blending which
gives upper 70s to mid 80s for highs Thursday through Saturday.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 547 AM CDT Sat Jul 29 2017

VFR conditions expected through the TAF period.




AVIATION...JM is the U.S. government's official web portal to all federal, state and local government web resources and services.