Snowfall forecast
The first major winter storm of the season will affect the upper-Midwest through the next 24 hrs.
Snowfall totals through Tuesday:
10†– 14†along and 30mi either side of a Bassett, NE to Aberdeen, SD line.
Expect little or no new snowfall west of a Sterling, CO/Rapid City/Minot/Devils Lake, ND line.
Expect 1 inch or less east of an Albert Lea to MPX to Park Falls, WI line.
Discussion:
01Z analysis shows vertically stacked, closing low with a 984mb SFC reflection between CNK and SLN in KS. An impressive area of deformation zone related snowfall has developed to the NW of a HLC to SUX line, and freezing rain is currently reported in ERN NE and SD. Freezing rain will increase across ERN SD and SERN ND over the next few hours. Given copious moisture transport WWRD into the ERN Dakotas as mixing ratios of around 8g/Kg are isentropically lifted over 290K through 296K surfaces at rates of up to –10ub/s, expect ice accumulations in excess of 0.05 inches/hr. The 01Z H85 0C isotherm, which was creeping EWRD at 10 mph, extended along an EAR to 9V9 to HON line.
Further W in SWRN NE, frequent lightning has been associated with the snowfall, probably owing to convection resulting from elevated instability in a region of frontogenesis in the H7 and H85 levels. In the short term, the CF aloft will translate slowly EWRD, resulting in a slow EWRD progression of the snowfall. In addition to the heavy snowfall in progress, very strong winds are resulting in blizzard conditions NW of the low. LBF reports NNW winds 41 mph gusting to 51 mph. Additionally, these winds increase to well over 50 kts just 100mb off the SFC per LBF sounding.
Tonight:
SFC low will slowly deepen and track to the NE, reaching WCNTRL IA by 12Z. Significant moisture will then wrap around stacked low between H85 and H7 levels, which will slow and then reverse what appears to be a dry-slotting trend in NE and KS. With the slow EWRD progression of the CF aloft, expect the snow line to reach an International Falls to Aberdeen to Hastings line through 06Z with a 50 mile-wide band of freezing rain along the ERN edge of the snowfall in the Dakotas and MN. By 12Z, the precipitation changeover will only move 50mi to the E, at which time much of the ERN Dakotas and WRN MN will be in an area of very strong upper-jet (H25) diffluence and associated strong PVA and Divergence. Use 6:1 ratio near the snowfall/freezing rain line, and a 12:1 ratio further to the N and W in CNTRL NE/SD, and all of ND.
Looking ahead – tomorrow through Tuesday:
Cyclone continues slow NEWRD progression as it occludes, reaching MPX by 06Z tomorrow night. Meanwhile, TROWAL (TRough Of Warm Air aLoft), develops along an International Falls to Fargo line tomorrow night through Tuesday morning. The TROWAL axis shows up well on the H85 300K to 304K isentropes on the NAM and GFS charts, and will result in a prolonged period of snowfall as the storm slowly lifts to towards the NE
- bill.
. Im awaiting the 18z models to decide whether I should head to Huron, SD and find a nice motel to setup the webcams. I finished setting up a webpage and feed to broadcast them live but orignally I was just going to keep one here and go out tommorow and travel around locally showing the blowing snow, drifts etc. But since the GFS only accumulates 5 inches at most and the NAM a pathetic 2.50 inches I am thinking about heading out to Huron, SD. Good luck in O'Niel!
