ZCZC SPCSWOMCD ALL ACUS11 KWNS 150244 SPC MCD 150244 MNZ000-IAZ000-NEZ000-SDZ000-150745- Mesoscale Discussion 0019 NWS Storm Prediction Center Norman OK 0844 PM CST Thu Jan 14 2021 Areas affected...Southeastern South Dakota...southwest Minnesota...northeastern Nebraska...and northwestern Iowa Concerning...Blizzard Valid 150244Z - 150745Z SUMMARY...Increasing winds with concurrent snowfall should lead to scattered to widespread blizzard conditions along the I-29 corridor through portions of South Dakota, Nebraska, and Iowa heading into early Friday morning. DISCUSSION...Surface observations from along the I-29 corridor in the SD/MN/NE/IA region show sustained winds between 20-30 mph with temperatures in the upper 20s and low 30s. Blowing snow model output suggests that isolated blizzard conditions may be ongoing. This idea is supported by recent visibility observations and regional web cams, which mostly show visibilities above a mile (with the exception of a few localized areas where stronger winds and moderate snowfall are concurrent). While widespread blizzard conditions are not yet ongoing, conditions should begin to deteriorate heading into the early morning hours. A stalled, but slowly deepening surface low across east/northeastern IA will help strengthen the pressure gradient along the I-29 corridor. Snowfall amounts through 08 UTC are forecast to generally be less than a couple of inches for this area, but increasing winds coupled with this falling snow will increase the probability of visibility falling to one-quarter mile or less. Blowing snow model probabilities suggest that persistent/widespread blizzard conditions will be most likely for locations that see a combination of temperatures in the 20s, sustained wind speeds above 35 mph, and concurrent snowfall. For locations that do not see sustained winds at this magnitude, frequent gusts up to 50-60 mph with concurrent light to moderate snowfall will likely result in at least transient visibility reductions to one-quarter mile or less. Blizzard conditions should gradually begin across the SD/MN/NE/IA region between 03-08 UTC (where temperatures have already fallen below freezing, snow is ongoing, and recent guidance suggests winds are most likely to begin increasing through 08 UTC). Blizzard conditions should gradually spread south and east through 12 UTC Friday morning as temperatures continue to fall and sustained 35+ mph winds increase in coverage. ..Moore.. 01/15/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MPX...DMX...FSD...OAX...ABR... LAT...LON 43239736 43879757 44689762 45109711 45109659 44739587 43969560 43789553 42939514 42369525 42109553 41999586 42059644 42279681 42799720 43239736 NNNN