Now we know that snow is hard to forecast around these parts. There are times - say, after a cold front passes - where the temperature is right for snow, but dry air trailing the front evaporates the necessary moisture. Other times a cold front will meet up with a southerly flow from the Gulf that pulls in the necessary moisture, but also just enough warm Gulf air to split the difference between blizzard and rainy day.
Trickier still: Snow also classifies as "severe weather", so local EMAs and road crews must have time enough to prepare emergency plans and schools must have adequate time to decide whether or not to hold classes. The forecast must be made in time for these folks to do their job in a timely manner. However, due to the complex variables involved in predicting when, where and how much of the white stuff will fall, it is nearly impossible to forecast snow effectively in the state until just a few hours before the event is scheduled to occur.
With that being said, a Stephen Colbert-esqe "wag of the finger" to James Spann at ABC 33/40...who blew this week's snow forecast to hell and back after bucking the National Weather Service's predawn forecast trend. Here's a tragic timeline of the non-snow event, employing archived posts from the ABC 33/40 weather blog (www.alabamawx.com):
Dec. 10 - 3:54 p.m. - The National Weather Service issues a Winter Storm Watch for Marion, Lamar, Fayette, Winston, Walker and Pickens counties. Here's an excerpt from the watch text: "A STRENGTHENING STORM SYSTEM WILL MOVE NORTHEAST ACROSS SOUTH ALABAMA ON THURSDAY...THERE APPEARS TO BE A 6-HOUR WINDOW'85WHEN A BAND OF HEAVY SNOW WILL DEVELOP OVER NORTHWEST ALABAMA."
Dec. 11 - 4:01 a.m. - NWS downgrades the Winter Storm Watch for the aforementioned counties to a Winter Weather Advisory, still expects up to 2 inches of snow...but less than the 3 inches specified in the watch issued the day before.
Dec. 11 - 6:05 a.m. - In his morning weather video, James Spann nails the forecast: "the best chance of accumulating snow will be over Northwest Alabama... the banding effect should set up in the general area from Columbus and Tupelo to Hamilton and to Moulton and Athens. This is where heavy, wet snow could develop, producing possible 3 inch amounts on grassy areas. There is usually a small strip with heavier amounts, and no human knows exactly where that will happen this morning. We will just have to wait and watch. I would say the counties with the best chance of 1 to 3 inches on grassy areas today will be Pickens, Lamar, Fayette, Winston, Marion, Lawrence, Franklin, Colbert, and Limestone."
Dec. 11 - 8:02 a.m. - James Spann completely reverses his forecast: "It sure seems like the heaviest snow band will be father to the south...Based on radar trends and the banding pattern that is setting up over Louisiana and South Mississippi, we are now going to forecast the best chance of 1 to 3 inches of snow on grassy areas southward" The post is accompanied by a snowfall prediction map, which you can see here.
Dec. 11 - 8:09 a.m. - Two comments of note on the new forecast blog posting:
Rory In Atlanta - James has just opened up the floodgates!!!
Paula - As of a few moments ago.. on several stations'85 JASPER (sorry guys, but'85) is in the HIGHER accumulation area, i.e., 2-3 inches, possibly more according to several weather reports. Birmingham/Tuscaloosa appear to be in the dusting area.. but'85 who knows! Everyone have a great day, regardless of how much (or how little) we get!!
Dec. 11 - 11:25 a.m. - James Spann updates the blog, no change in his forecast..."Generally speaking, the best chance of accumulating snow in this situation is under the coldest air aloft, and that path seems to be across Central Alabama. It remains to be seen if the rain can change to snow to the north, over the northwest part of the state, where the dynamic cooling will not be as pronounced. See the map posted this morning a couple of posts below this one."
Dec. 11 - just after noon - ABC 33/40 morning meteorologist Jason Simpson tells viewers that the situation doesn't look like a big deal and will mainly affect the northwestern counties of the state...meanwhile...
Dec. 11 - 1:56 p.m. - Despite a shrinking snow shield in Mississippi and the Simpson's skepticism, the 33/40 forecast remains the same..."Rain will continue over Northwest Alabama this afternoon, but I just don'92t see the dynamic cooling there to change the rain to snow, until maybe the very end of the event. BOTTOM LINE: The best chance of getting some snow accumulation this evening is along and south of I-59, and along and north of U.S. 80, or the basic area between Birmingham and Montgomery. With the heaviest precipitation to the north, I think we can forecast the potential of 1 to 2 inches of snow in grassy areas across Central Alabama"
Dec. 11 - 3 p.m. - Reality begins to set in on the blog:
Snow is decreasing on radar in Mississippi south of I-20. The best moisture is north of the coldest air aloft for now. Seems like there is going to be a sweet spot along the northern part of our forecast accumulation box'85 perhaps over Pickens and Tuscaloosa counties, where cold air aloft will be coincide with decent moisture. Now getting reports of sleet over Pickens County, with snow flakes mixed with rain over Marion County, to the north. If the air aloft is colder than shown on the SPC upper air site, that will be a better setup for snow over Marion/Lamar/Winston/Walker counties.
Dec. 11: 3:15 p.m. - Spann re-draws the optimistic map from the 8-o'clock hour to something more in line with the NWS forecast from the day before. See it here.
The same post reflects what many had expected for hours:
"We continue to see cold air aloft advect up into North Alabama, and considering the lack of echoes south of I-20, the original idea thrown out here last night seems to be the best one; which also agrees with the NWS outlook. Good doing on their part; I hate to be a flip-flopper, but we will have to adjust that box northward again."
Soon after, snow begins falling in northwest Alabama, with counties like Marion and Winston seeing 2-3
inches...as was originally and steadfastly forecast by the National Weather Service.
Now, we don't mean to pick on James; that weather blog is pure genius. But gosh darn it, watching the man forecast these snow events is like watching Geraldo opening Al Capone's vault on a continuous loop.
In the meantime, we're out another snow day, which is a shame since I made a special trip to the supermarket to purchase that corn cob pipe, top hat and lumps of coal for the eyes. Next time that "s-word" starts flying around, I'm getting my forecast from the fine folks at the National Weather Service.
jack
