A National Weather Service "Critical Weather Day" !! Winter Storm Gemini!

National weather service map for 12/22/2013. Significant colors are: pink in the midwest=winter storm warning. Blue surrounding the pink is winter weather advisory; bright blue up in east Minnesota=severe weather statement. Green to the east of this =flood warnings; rust color east of the green = flash flood warning; yellow = tornado watch. 

The news is full of weather alerts for the central and eastern U.S. and Christmas travel is already a problem in the eastern half of the U.S. The east is basking in spring-like warmth, while the midwest suffers from temperatures below average. We who live in the Pacific Northwest are experiencing mild conditions at the moment, but will get our turn next week when rain/snow return here.  The full National Weather Service report is here.
     Temperatures are in the 20's across Oklahoma (southwest end of the pink/blue area)  while, not all that far away, they are nearly 80 degrees across Mississippi (yellow rain pattern). A big frontal boundary separates these two regions. According to the NWS, the severe icing now occurring in Oklahoma-Missouri will transition to light and moderate snow tonight, and the ice threat shifts to lower Michigan and northern New England.  Flooding is a major concern in some areas where the rainfall is more typical of April and May than December. Melting snow will contribute to the flooding.
     And, as if this isn't enough, tornadoes and straight line winds will continue in the lower Mississippi valley and into the Ohio Valley, much further north than usual for this time of year. Here's a link to a 5:59 p.m. EST warning about the thunderstorms and tornadoes. If the prediction holds, storms will be affecting a broad range of the midwest and even over to Washington DC by Sunday night.
     In researching this, I discovered something new about the NWS. At about 8:30 a.m., the NWS Centers for Environmental Prediction declared a "Critical Weather Day" from their station in Milwaukee/Sullivan. In the affected area their offices are not to make any equipment of software changes that might affect the work flow, i.e., do nothing that will cause the system to fail in this critical time. It is also routinely put into effect during Presidential elections and inaugurations.
     Take care, friends and readers, if you are traveling the next few days!