Wednesday, December 23, 2009

Winter storm to blast the Plains - effects on the Mid-South

A significant winter storm is now upon us as we head into the holiday home stretch. Is it fortunate or unfortunate that warm air is over us as precipitation falls? If you'll remember back about a week and a half ago, I started talking about the possibility of a "White Christmas" and have updated that prediction a couple of times (here and here) . My main points were that the early December pattern would continue through the end of the month (check), it would produce a significant storm within a couple of days of Christmas (check), and that we would get precipitation, which would have a low chance (10-20%) of being "white" (check).

The devil is always in the details though. This particular storm, which will bring nasty winter weather to the Plains and Midwest over the next couple of days, is not taking the "El Nino" track along the Gulf Coast. Instead, it has emerged from the southern Rockies, will hit the southern Plains, then pull north and wrap up over the central Plains before ejecting east late in the weekend.

This will be one doozy of a storm, as locations from the Dakotas south to eastern Kansas and then east into western Wisconsin and Missouri will get anywhere from 6-12" of snow with more than a foot likely over parts of South Dakota, Nebraska, Minnesota, and Iowa. In the warm sector of the storm, rain and thunderstorms, some of which could be severe in the south, could produce areas of flooding for a large part of the Mississippi River Valley and eastern portions of the Midwestern states. In addition, this storm will be a wind machine for most of the central portion of the country. This will create blizzard conditions for the Plains and possibly damaging straight-line wind and isolated tornadoes along a squall-line that moves across the Gulf Coast states.

As for effects in the Memphis area, rain showers with embedded thunderstorms will continue through the night tonight with wind increasing and becoming gusty. Wind gusts to 30 mph will be likely overnight and into the morning. During the day, we will see scattered showers in the morning followed by a potential squall line during the afternoon. High wind is likely in the afternoon and evening hours with gusts to 40 mph not out of the question, perhaps a little higher as the squall line moves through. The NWS will be issuing a Wind Advisory from midnight tonight until noon Thursday, then a High Wind Watch will be in effect from noon until midnight Christmas night, due to the potential for damaging straight-line gusts that could cause fallen trees and perhaps power outages. Total rainfall from this system will probably end up in the 2" range by midnight on the 25th, with much of that falling during the day on Thursday.

Wind will decrease somewhat on Christmas Day, but will still be gusting and, combined with temperatures that are nearly steady in the upper 30s, will make for a very cold holiday! As to the possibility of winter weather, there is a very small chance of some flurries around the backside of tomorrow's system, which would occur late Thursday night/Christmas morning. Don't get your hopes up - the chance is about 10% as it stands now (amazingly enough, exactly what I predicted 10 days ago!).

The MWN Forecast will be updated with the latest expected conditions throughout the day Thursday. In addition, updates will be sent via MWN's Twitter feed and on our Facebook page.

Finally, I want to thank all of you who read The MWN blog and visit on a periodic or regular basis! I hope you all have a great holiday season and safe travels if you will be visiting family or friends elsewhere in the country.

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