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FXUS63 KFSD 022347 AFDFSD

Area Forecast Discussion National Weather Service Sioux Falls SD 547 PM CST Sat Dec 2 2023

KEY MESSAGES

- The light flurry to light snow chances will continue east of I-29 this afternoon and overnight. Accumulation should stay on the lighter side with a trace to dusting expected.

- Above normal temperatures will continue for the foreseeable future with the warmest conditions expected on Wednesday and Thursday.

- Precipitation chances should be fairly limited as we head into the weekend.

DISCUSSION
Issued at 305 PM CST Sat Dec 2 2023

Rest of the Evening/Tonight:

A cool and breezy day continues! Taking a look at satellite imagery, stratus continues to fill in along the Missouri River and northwestern IA in response to the longwave approaching wave from our west. Taking a closer look at things, a few flurries to light snow showers have developed across eastern-central Nebraska in response to some decent 850:700 mb frontogenesis and PVA ahead of the longwave. While this developing precipitation should continue push northeastwards this evening and overnight, model derived soundings show a fairly dry subcloud layer which has kept most of the precipitation from reaching the ground despite the returns on radar.

However, accumulative amounts will range from a trace to a dusting with portions of northwestern IA and far northeastern Nebraska being the the most likely areas to see accumulation. Nonetheless, breezy southerly winds this afternoon will decrease towards sunset and eventually decoupling overnight. Depending on if we get enough moisture in the lower levels tonight, areas along and west of the James River could see some patchy to shallow fog develop. However, confidence is still a bit low on this at this time. Otherwise, overnight lows should drop into the upper teens to low 20s for the night.

The Extended Forecast (Sunday-Friday):

Heading into the extended period a particularly active pattern continues aloft as the base of the aforementioned trough moves overhead by Sunday. At the surface, a closed low will slide southeastwards along the Missouri River Sunday morning possibly bringing some additional flurry along the Missouri River and Hwy-20 corridor. However, with soundings continuing to hint a dry air in the lower levels; not too confident in any flakes reaching the ground. As a result, stripped all mentionable POPs out of the forecast for the day. Otherwise, with mostly cloudy skies and southeasterly surface winds; expect temperatures to slightly cool with highs only expected to reach the upper 30s to low 40s.

Looking into the start of the work week, slightly warmer and quieter conditions return by Monday as a weak upper-level ridge brings a dose of warm air advection to the region aloft. This along with westerly to southwesterly flow should be enough to get temperatures peak in the low 40s to low 50s for the day with the warmest conditions expected along and west of James River. As the ridging departs, a cold front associated with an upper-level clipper will swing through the region by Monday night temporarily bringing cooler conditions back the area along with some smaller precipitation chances. Starting with the precipitation chances, strong PVA and mid- level frontogenesis will trigger a few light flurries along the Hwy- 14 corridor and buffalo ridge Monday afternoon and evening. However, as winds increase behind the cold front, not expect much in terms of accumulation besides a few traces. Shifting gears to Tuesday, cooler air will funnel in behind the previously mentioned surface front.
This along with northwesterly surface flow will lead to slightly cooler temperatures overall with highs expected to peak in the upper 30s to low 40s for the day.

By the midweek, warmer conditions return to the region as amplified upper-level ridging moves in from the northwest bringing a strong dose of WAA aloft. This should work to bring our 850 mb temperatures to the 10-13 degree celsius range which ranks in the 97.5th percentile of climatology. With this in mind, I have continued the trend of increasing our temps for both Wednesday and Thursday by using a blend of the NBM/NBM90th to raise temperatures into the 50s and low 60s for both days. Otherwise, slightly cooler conditions return by Friday as another cold front swing through the region Thursday night. Cooler air will funnel into the region behind the departing surface feature bringing daily highs back into the upper 40s to low 50s to start the weekend.

AVIATION /00Z TAFS THROUGH 00Z SUNDAY/
Issued at 546 PM CST Sat Dec 2 2023

Biggest concern through this TAF period will be potential for low stratus and/or fog developing tonight into Sunday morning, mainly east of the James River Valley. HRRR showing a high probability (80%) of IFR ceilings spreading northward into our forecast area by 04Z-06Z, with moderate probabilities (50-70%)
of IFR visibility (1-2SM) in fog. Already seeing areas of IFR ceilings in central Nebraska, so the potential of spreading northward seems reasonable, and have included sub-1000ft AGL stratus and 1-2SM visibility in this TAF forecast. Highest chances remain east of the James River Valley, so have kept cloud coverage SCT for now at KHON, with IFR ceilings at KFSD and KSUX at times 06Z-16Z.

Prior to this low cloud/fog development, watching an area of light precipitation on radar in eastern Nebraska/western Iowa.
Deep layer of dry air below 7-9kft AGL at KSUX should limit precipitation chances there this evening, but cannot rule out minor visibility restrictions in -SN toward the Hwy 71 corridor KSLB-KSPW later this evening as forecast soundings show deeper saturation in the sub-cloud layer there after 02Z-04Z.

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

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