090 
FXUS63 KFSD 122100
AFDFSD

AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
300 PM CST Mon Dec 12 2022

.SHORT TERM...(This Evening through Tuesday)
Issued at 259 PM CST Mon Dec 12 2022

KEY MESSAGES:

1) A complex weather system looks to impact the area this afternoon 
through Thursday. This system will not only bring the potential for 
a mixture of wintry precipitation types but also gusty winds, 
resulting in impacts and travel disruptions across the region.

2) Significant snow accumulations are expected across the central 
and western Dakotas with the greatest icing potential from southwest 
Minnesota into portions of northwest Iowa. Rainfall may result in 
ponding of water in areas of blocked storm drains from recent snow.

3) Notably colder temperatures and wind chills will prevail heading 
into the weekend as breezy northwesterly winds linger across the 
region.

**************************************************************** 

Stratus deck continues to blanket the region as an upper level 
trough edges closer to the Rockies. Have already seen a bit of 
freezing drizzle develop along and east of I-29 late this 
morning/early afternoon and will continue to do so this evening as 
temperatures linger near freezing. Southeasterly winds have also 
remained fairly breezy during this time as the SPG strengthens, with 
gusts ranging from 25 to 35 mph.

Heading into the evening and overnight period, expect a stout 
southerly LLJ to crank up overhead, resulting in increased 
isentropic upglide and omega across the region. As a result, should 
see an uptick in moisture occur. At this time, expect 
drizzle/freezing drizzle to be possible along and east of I-29 
initially, with freezing rain more likely to occur along the Buffalo 
Ridge where cooler temperatures reside. Thus, with ice totals 
approaching a quarter of an inch or greater in areas of higher 
elevation, have gone ahead and issued an Ice Storm Warning for the 
Buffalo Ridge. Confidence wanes as you move further southwest from 
the ridge, given the borderline nature of temperatures. Think it is 
worth noting, that a fairly broad area of rain will gradually lift 
northward west of I-29 while the freezing drizzle/rain is occurring. 
As a result, will likely see temperatures rise a few degrees given 
the moderate rates in place coupled with latent heat release. While 
the warmer model solutions continue to support this theory, have 
also noticed a few of the colder solutions, like the NAM, also 
hinting at this possibility. So, with these factors in mind, believe 
we'll see less in the way of ice accumulations as you move closer to 
I-29. As a result, have decided to only issue a Winter Weather 
Advisory for those areas surrounding the ridge for the time being. 
We encourage you to monitor the forecast in the event that 
additional headlines/expansions are needed. 

Sfc low pressure moves over central Nebraska by Tuesday morning, and 
will continue to deepen throughout the day. SPG will in turn 
strengthen, resulting in stronger winds along and east of I-29. 
Currently have gusts ranging between 35 to 45 mph, though isolated 
gusts up to 50 mph may certainly still be possible. In regard to 
precipitation, expect moderate rain to linger along and south of I-
90, with a transition to snow more likely to occur near Hwy-14. With 
PWATs still in the upper 90th percentile, anticipate liquid 
accumulations will have no trouble reaching/possibly exceeding 0.5-
1.0 inch. Thus, we encourage you to clear any lingering snow away 
from your storm drains, gutters, downspouts, and foundation to help 
mitigate any flooding concerns!

.LONG TERM...(Tuesday Night through Monday)
Issued at 259 PM CST Mon Dec 12 2022

Occlusion process takes place Tuesday night as sfc low pressure 
wobbles overhead. With the dry slot progged to build across the 
region, should see somewhat of a lull in precipitation occur in 
areas east of the James River, though periods of drizzle/freezing 
drizzle may still be possible. For areas west, expect precipitation 
to transition to snow as the TROWAL sets up over central SD. Winds 
during this time will also be notably lighter as the SPG relaxes. 

By Wednesday morning, expect precipitation east of the James to 
gradually transition to snow as thermal profiles cool. Fortunately, 
will not see much in the way of substantial snow/ice accumulations 
as QPF amounts remain fairly low. Rather, will likely only see a 
glaze of ice and around half an inch to an inch of snow accumulate. 
Precipitation intensity and amounts increase Wednesday afternoon 
into Thursday, as the aforementioned TROWAL lifts across our area. 
In regard to snowfall totals, still expect to see the highest 
amounts occur across central SD, with those west of the James River 
standing a decent chance for seeing total accumulations of 6 inches 
or higher. Given that these accumulations will take place over the 
course of a couple days, have opted to lean away from a Winter Storm 
Warning. Instead, have decided to transition the Watch west of the 
James to a Winter Weather Advisory to account for impacts relating 
to persistent light snow, slick conditions, and periods of reduced 
visibility from breezy winds. 

Will likely see snow linger through Friday afternoon as the upper 
level low slowly meanders eastward, with a trend to drier and much 
quieter conditions in store by Friday evening. Otherwise, the main 
story after this event will be focused on the notably colder 
temperatures forecast to build across our area. Currently have highs 
Saturday in the low to mid teens plunging into the the lower single 
digits by Monday. Lows during this time will also take a notable 
dive, as values fall into the negative single digits by Monday. 
Lastly, expect wind chills to feel quite raw, as breezy 
northwesterly winds send values into the negative teens to single 
digits.


&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 1125 AM CST Mon Dec 12 2022

Latest satellite imagery shows widespread stratus across the region, 
resulting in the IFR to LIFR cigs. Expect this to continue 
throughout the TAF cycle as a messy period of weather returns to our 
area. Southeasterly winds during this time will continue to ramp up, 
with gusts between 25 to 35 mph forecast to prevail. Areas of 
drizzle and/or freezing drizzle are expected to form this afternoon, 
with freezing rain more likely in areas east of I-29 this evening 
through the overnight hours. Areas along I-29 are a bit more 
uncertain, as p-type will largely depend on temperatures. If things 
trend warmer, expect to see more in the way of rain, whereas colder 
temperatures would result in a higher potential for freezing rain. 
Otherwise, will generally see rain prevail in areas west of I-29. 


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until noon CST Tuesday for SDZ039-055-
     056-062-067.

     Ice Storm Warning from 6 PM this evening to noon CST Tuesday for 
     SDZ040.

     Winter Weather Advisory from noon Tuesday to 6 AM CST Thursday 
     for SDZ038-050-052-057.

MN...Winter Weather Advisory until noon CST Tuesday for MNZ081-090.

     Ice Storm Warning from 6 PM this evening to noon CST Tuesday for 
     MNZ071-072-080-089-097-098.

IA...Winter Weather Advisory until noon CST Tuesday for IAZ001-003-
     012>014-021-022.

     Ice Storm Warning from 6 PM this evening to noon CST Tuesday for 
     IAZ002.

NE...None.
&&

$$

SHORT TERM...SST
LONG TERM...SST
AVIATION...SST