243 
FXUS63 KFSD 251149
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
649 AM CDT Mon Sep 25 2017

.SHORT TERM...(Today and Tonight)
Issued at 335 AM CDT Mon Sep 25 2017

A cool and wet day in store for much of the area today, persisting 
into tonight, as remain situated between slow-moving upper trough 
over the Rockies, and strong upper ridge east of the Mississippi. 
Entire forecast area should remain on the cool side of the surface 
boundary through tonight, with the nearly stationary 850mb boundary 
near/southeast of KYKN-KFSD-KMML line continuing to focus rain and 
embedded thunderstorms over the southeast 1/2-2/3 of the CWA. See a 
weakening in 300K-310K isentropic lift around 18Z behind the morning 
wave, so could see a decrease in areal coverage of showers around 
midday. However, another decent wave moves in from the southwest in 
the late afternoon/evening, which should expand coverage back to the 
west again. Elevated instability likewise wanes a bit through the 
midday period, but some weak instability returns to the southeast 
CWA through the afternoon/evening, so will keep an isolated thunder 
mention there. Expect we will still see pockets of heavier rain, as 
PWAT values across the southeast half of the CWA remain extremely 
high (1.5+ inches) for this time of year through tonight. The weak 
instability would also support more isolated showers with more 
intense rainfall rates. With the widespread clouds/rain and cool air 
mass, highs today will be 10-15 degrees below normal in most areas, 
with readings only topping out in the mid-upper 50s for all but our 
far southeast.

Although a bit slower than previous runs, still seeing a good punch 
of mid-upper level drying move into the forecast area as the upper 
trough shifts east late tonight. This along with broad downglide on 
the isentropic surfaces and weak cold advection in the lower levels, 
should bring a gradual decrease in precipitation through the late 
night hours. Low clouds and a modest northwest breeze will keep 
temperatures from falling off too much, but still looking at lows in 
the mid 40s-lower 50s.

.LONG TERM...(Tuesday through Sunday)
Issued at 335 AM CDT Mon Sep 25 2017

Could see some light rain linger across our eastern zones into 
Tuesday morning before drying aloft shunts everything east of the 
area. Should see some increasing sunshine by afternoon, though 850mb 
temperatures in the single digits will still yield sub-normal highs 
in the upper 50s-lower 60s.

The broad upper trough slides eastward through the Great Lakes 
through the mid-late week period, while a ridge builds over the 
western CONUS. Anticipate some moderation in temperatures Wednesday 
and Thursday, but models in generally good agreement in dropping a 
wave/associated cool front southward through the Upper Midwest 
Thursday night/Friday. Moisture somewhat lacking as the wave moves 
through, so do not anticipate any precipitation in our area at this 
time. The front will knock temperatures back for Friday, though how 
far back is somewhat in question, as models differ on the strength 
of the cold push. Given this uncertainty, did not alter blended 
guidance, though could see highs a few degrees cooler than current 
forecast if the more aggressive models pan out.

Next weekend sees the upper trough retreat eastward, allowing upper 
ridge to build toward the Northern Plains/Mississippi Valley. This 
should bring warmer temperatures back into the region, along with 
spotty precipitation chances as southerly flow increases Saturday 
night/Sunday ahead of another upper trough. System looks to be more 
progressive, so do not see a repeat of this past weekend as far as 
rainfall amounts. However, GFS does depict PWAT values increasing to 
over 1 inch, so modest amounts are possible.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 641 AM CDT Mon Sep 25 2017

The frontal boundary is still with us and that means another messy
aviation forecast. While some occasional breaks in the clouds may
occur, stratus will be the predominant condition across the 
region over the next 24 hours. This will be combined with showers 
and attendant visibility reductions. Expect MVFR and IFR 
restrictions at all terminals, particularly FSD and SUX. Some 
sporadic thunder is possible as well, but coverage looks to be 
very limited, so have not included it in any of the TAFs.

&&

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

$$

SHORT TERM...JH
LONG TERM...JH
AVIATION...Ferguson