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James Spann @spann - WEEKEND WINTER STORM POTENTIAL: New global model runs continue to show a strong signal for winter storm conditions across parts of the Deep South over the weekend. New 12Z model output is attached to this post. Here are the key messages this evening... *The cold air moving into Alabama will be shallow, meaning there is potential for freezing rain (liquid precipitation that falls when surface temperatures are at or below freezing). *A long duration of freezing rain can lead to an ice storm. Thankfully temperatures will be in the 50s over the latter half of the week, so the infrastructure won't be especially cold as the event begins. That is a positive. *The main window for wintry precipitation is over the northern half of Alabama from around 6:00 a.m. Saturday to 6:00 a.m. Sunday. *If low level thermal values are warmer than models suggest, it will simply be a cold, rainy day Saturday. That is a very real possibility. *The cold air will be a bit deeper across the Tennessee Valley of North Alabama, where some snow could be involved. *It is too early to answer questions about specific impact in any given location (like road conditions). *We will be more specific about the event by Wednesday, and a good impact forecast can be made Thursday. But with winter weather situations like this, there will always be uncertainty even one day in advance.
https://x.com/spann/status/2013368506260054358

James Spann @spann - TUESDAY NIGHT NOTES: Here are some key messages on the potential winter storm for North Alabama this weekend...
*It is still too early for an impact forecast for any specific point. We will feel comfortable doing that Thursday as we get within 60 hours of the event and we get a peek at high resolution models.
*I have many questions about travel this weekend. Understand I possess no knowledge or skill about future road conditions, and can't give specific advice. It depends on your risk tolerance, and your ability to drive on wet/icy roads. I do my best to give you the information you need to make a good decision.
*Attached graphics are from the National Blend of Models, the NBM. Basically an ensemble approach, which is the best way of looking at snow and ice potential this weekend.
*Freezing rain and snow will likely move into North Alabama early Saturday morning, and continue through the day into Saturday night.
*Best chance of getting really good snow accumulation (3" or more) is over the Tennessee Valley of North Alabama, especially north of the Tennessee River. Much of Tennessee will likely see 4-8 inches of snow this weekend.
*Freezing rain is likely south of the Tennessee River. This is precipitation in liquid form that falls when surface temperatures are 32 degrees or lower. A long duration period of freezing rain can coat exposed objects and surfaces (like roads and trees) with ice.
*Defining the southern border of the freezing rain is the most difficult part of any winter weather forecast. And, it will move back and forth during the event. Generally speaking, the highest chance of meaningful ice accumulation will be along and north of I-20, but some icing is possible in spots south of I-20 as well.
*If low level thermal values are warmer than forecast, Tuscaloosa, Birmingham, and Anniston could get away with just a cold rain for much of the event. That is just a possibility at this time; these cities sit on the I-20 boundary that separates rain from freezing rain and icing.
*Confidence is very high in ice/snow issues along and north of U.S. 278 (Hamilton to Cullman to Gadsden).
*South Alabama will see just a cold rain this weekend.
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