427 
FXUS63 KFSD 120341
AFDFSD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1041 PM CDT Mon Sep 11 2023

.SHORT TERM...(This Evening through Tuesday Night)
Issued at 242 PM CDT Mon Sep 11 2023

Key Messages:

1. Sprinkles to light showers are are on the table for this 
afternoon. A rogue lightning strike and brief gusty winds are 
possible. 

2. Mostly dry conditions continue through the middle of the week, 
with the next chance for rain arriving late Thursday. Specifics 
regarding rainfall are uncertain at this time. 

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Isolated sprinkles to light showers have developed early this 
afternoon while temperatures have warmed to the 70s. These sprinkles 
and light showers are being driven by nose of an upper level 
vorticity maximum advecting into the area. BUFKIT soundings show 
that there is steep enough mid-level lapse rates to generate a small 
amount of instability on the order of 100 J/kg of CAPE within a 
shallow moist layer. This moist layer is sitting around 600-700 mb 
and is above a dry layer beneath it. Any weak shower that develops 
will be capable of a few rumbles of thunder as well as brief gusty 
winds. Tonight will again be quiet and a bit cooler as lows fall to 
the mid to upper 40s. Although the low levels will be mostly dry, 
can't rule out a small possibility that river/valley fog developed 
in a few spots by tomorrow morning. 

With the forecast area remaining on the backside of an upper low, 
subsidence will prevail and keep sunny skies and mostly dry 
conditions locked over the Northern Plains. However, BUFKIT 
soundings continue to show a shallow moist layer around 700 mb along 
with minor instability on the order of 100 J/kg or less of CAPE 
mainly across northwest Iowa. As such, have introduced slight chance 
PoPs for this area. This could again lead to isolated sprinkles and 
showers that may produce a rogue lightning strike and perhaps brief 
gusty winds due to the dry layer below 700 mb. With 850 mb 
temperatures remaining in the low teens, highs again will warm to 
the upper 60s to 70s. Overnight low temperatures will fall to the 
mid 40s to low 50s from east to west. 

.LONG TERM...(Wednesday through Monday)
Issued at 242 PM CDT Mon Sep 11 2023

Surface high pressure begins to slide eastward into the Midwest 
states on Wednesday. This will tighten the surface pressure gradient 
a bit while also setting up southerly return flow. A warm front will 
move across the area, increasing 850 mb temperatures to the mid 
teens and thus warm high temperatures into the 70s to low 80s. 
Forcing is negligible through so not expecting any rain chances. The 
previously mentioned tighter surface pressure gradient will bring a 
return to breezy winds with the strongest gusts up to around 25 mph 
across locations in central South Dakota. 

Shortwave ridging continues to pass through the Northern Plains, 
keeping conditions dry and quiet for the day on Thursday. Winds will 
further strengthen aloft on Thursday, with boundary layer winds 
increasing to 20+ knots. This will continue breezy conditions across 
the area for the daylight hours. High temperatures will also 
continue to further warm to the mid 70s to low 80s. The next chance 
for rain will come during the late evening and overnight hours as an 
upper level wave begins to move off the Rockies and into the Plains 
states. The Euro, GFS, and Canadian ensembles all show a 50-60% 
chance for exceeding a tenth of an inch of rain during this period 
of time. The wave will slowly push through the Central Plains, 
keeping rain chances going through Friday. Rain at this point looks 
to be driven by a potential deformation zone setting up across the 
area. Ensembles remain rather split on this rain potential as the 
Euro and Canadian ensembles keep similar probabilities for a 
exceeding a tenth of an inch of rain. The GFS shows dwindling 
probabilities, all the way down to a mere 10% chance for exceeding a 
tenth of an inch of rain. Given this uncertainty, have left model 
blended PoPs at this time. 

Broad upper level troughing continues through the weekend and into 
early next week. This will keep seasonable conditions with highs in 
the 70s to low 80s and lows in the 40s and 50s. 

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 1030 PM CDT Mon Sep 11 2023

Isolated very light rain showers or sprinkles will be possible 
overnight through mainly east central SD and southwestern MN, with
little in the way of measurable precipitation. Otherwise, light 
and variable winds tonight. Winds will remain relatively light on 
Tuesday. There will be a small possiblity of isolated 
showers/sprinkles developing over northwest IA Tuesday afternoon 
with little impact.

&&

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

$$

SHORT TERM...Meyers
LONG TERM...Meyers
AVIATION...JM