eason. Since it has been a while and since next week is a busy travel week with lots of weather there is lots to talk about so this is quite long and I apologize in advance but do appreciate the time you take to stop and read.
In general, it has been quite tranquil across much of the eastern U.S. this A
utumn but just in time for the busiest week of travel, Mother Nature is about to change things up. I have been watching several factors over the past few weeks that have been hinting at the possibility that the time frame between Thanksgiving and Christmas could be the most active winter weather time period for the eastern half of the U.S. for the entire winter.
The Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO) are both dropping and forecast to drop significantly negative over the next couple of weeks, at least. This will aid in allowing troughiness to build and hold over the eastern U.S. and ridging in the west.
Air from the Canadian Arctic will drop southward providing an early blast of winter chill. This is following similar Decembers that followed active tropical season’s with at least 18 named storms or more; including the years of 2005, 2003, 2000, 1995 and 1969. When I comprised my winter outlook I was considering this as a “Wild Card” possibility but chose to put more emphasis on the moderate to strong La Nina and Negative PDO as the driving factors. This may have been a mistake on my part as it does now appear that December is heading into the “Colder than Normal” category. The image below shows the average temperature anomaly of the above seasons calculated together.
Still feeling confident that the La Nina and negative PDO will take over as driving factors for
January and February as the impact of the strong tropical season should become less apparent. This happened in the previous years mentioned above and the Pacific signatures of those season took over.
So what does this mean now, it appears that BIG changes in the December outlook are likely. Previously, I was forecasting above normal conditions for the Tennessee Valley and for much of the East. Now, I am leaning in the total opposite spectrum. Crunching numbers, yesterday, provided a print out of a possible 9 degree swing from my previous forecast to where I am leaning now for the Valley. Originally, the December forecast called for temperatures to be about 6.3 degrees above normal and the new forecast prints out temperatures being 3.8 degrees below normal (using Huntsville Int’l Airport), OUCH!
This big change is showing its ugly head next week. This weekend, much of the nation from Texas to the Mid-Atlantic will see nice mild temperatures ranging mainly in the 60s and 70s with a few 80s in Texas. These comfy temperatures will linger into the first of next week as a trough digs in the western U.S.
This pattern will set up prime skiing conditions for much of the Rockies as a storm system will spin up and drop snow to much of the Rockies from northern New Mexico into Montana this weekend into early next week.
The trough will be kicking out mid-week and as it does it takes the precipitation to the east. There are differences in the long range in the model forecasts. The international models are leaning closer to each other with the GFS, to an extent, the outlier. The international models are hinting at a first cold front sliding through much of the east, Pennsylvania through the Ohio Valley, Monday/Tuesday and making its way to the Tennessee River while the GFS holds the front much further north, towards the Ohio River. The international model solution would set up a colder scenario for these locations and push the focus of rain further south from east Texas to southern New England versus the GFS which takes most of the initial wetness from Texas into the western OH Valley.
Now this boundary is much weaker compared to the BIG Arctic front the follows a day or two later but still chilly. As the main storm lifts out of the Plains, late Monday, it will help to bring warmer air back to the north. The approaching precipitation will generally fall in the form of rain for much of the OH Valley and Pennsylvania. However, interior valleys of PA may see some of the precipitation begin as a wintry mix as colder air becomes damned but the colder air will be eroded out. Further north, into northern Wisconsin and Michigan much of the precipitation will likely be snow, Wednesday into Thanksgiving. In fact, as the storm system deepens as it moves into the Upper Midwest late Wednesday and through Thanksgiving day, accumulating snow will likely fall across much of Wisconsin and then Michigan and some accumulating snow may fall as far south as I-80 in Illinois.
Snow will also be possible, Thanksgiving across northern New England, initially, but the snow will likely mix with and change over to cold rains before ending briefly, again as some snow showers for all of you heading out to the malls on Black Friday..
For those in the Tennessee Valley, you will see on tonight’s Fox 54 5+4 Day Forecast a day with snow or a wintry mix late in the forecast. This is because I am continuing to follow the international modeling data on the long range forecast, especially the European or ECMWF.
As the storm system mentioned above heads east, a very strong cold front will sweep through the Valley on Thanksgiving. This will likely bring rain/rain showers with it. Depending on the exact timing of the frontal passage, a total guess at this point, we could easily see a mild morning with temperatures in the 60s but temperatures rapidly falling into the 40s through the afternoon and possibly even upper 30s by evening.. The trough will be well in place for those of who looking to head to Bridge Street Town Centre, Parkway Place Mall, Regency Square Mall or any or the hundreds of retailers bolstering their Black Friday deals so be prepared to stand and shop in the cold. Temperatures that morning will likely be in the 20s! Clouds will likely hang on much of the day and that with a breeze will keep it feeling quite chilly; but hopefully put you in the Holiday spirit!
As the first and pattern changing storm exits to the east and north on Black Friday, the ECMWF drops another piece of energy into the four-corners region and sets up an interesting look. This would bring yet another Rocky Mountain snow to much of Colorado to Montana but the question is just want will this wave do as it heads east? As of today’s model run, it takes the wave to the northern Gulf coast, near Lake Charles, by Saturday morning, next week. This path would likely take snow from the Rockies into the Southern Plains. The “Wild Card” becomes the cold arctic air that would be in place as it will be quite dry and that could eat away at much of the snow potential from southern Kansas through Oklahoma and into western Arkansas. But as the wave moves to the Gulf Coast, it would tap into available Gulf moisture and begin transporting it northward and throwing it up and over the cold air at the surface. It is possible, snow or a wintry mix could develop and spread across the Mid-South and Tennessee Valley next Saturday.
Please, please, please, understand this is highly subject to changes. A lot of things have to come together perfectly for the above scenario to occur; however, the ECMWF solution is not unrealistic with the way the pattern wants to set up. The BIG FACTOR will be just where that next secondary piece of energy tracks and the resulting surface low, too.
I have seen many times that where the snow is forecast on Day 9 or Day 10 it actually rains or nothing at all happens because the trend is usually to move the storms further north and west over time so let’s wait and see before getting too excited.
As I will be off the next couple of days, I will still take a look at things and post, at minimum, a brief post on how things are looking for next week and any changes regarding late next week’s weather pattern so make sure you check back during the evening hours.
Thanks for reading!
Dale
www.facebook.com/dopplerdalebader
