Friday, December 3, 2004

"It happened before, it will happen again. It's just a question of when."
- Charleton Heston, in opening voiceover of the movie Armaggedon


Indications are that by late next week, an I-95 special may be on the menu, with generous portions to go around for everyone else, including the interior Appalachians from West Virginia to central New York and New England. I am officially making the call that this is going to be the first real accumulating snow of the season for the big cities... from DC to NYC.

We know that the longer warm air lingers, the more severe the next cold outbreak will be. Arctic air that has been building up in eastern and central Canada will begin to spill southward by Wed 12/8 or Thu 12/9.

And not to be outdone by advancing Old Man Winter, Tiffany Tropics has delivered yet another tropical storm on the very last day of the hurricane season… Otto. He is spinning 800 some miles east of Bermuda, with winds of 45 mph. So there you have it… as one season draws to a close, the other is waiting to bust out of the gates.


While the Weather Channel and Accuweather public sites appear to trending away from snow this weekend for PA and MD, the NWS is moving back towards it. The cold front that swept through the northeast Wednesday delivered enough strong wind to knock out power to numerous schools in Baltimore County, giving those in schoolhouseland a 1-hour early closing. A minor upper-level system sweeping in behind the front may have enough moisture and surface instability to trigger some flurries or snow showers on Saturday for central PA.

While it is more likely these areas will only see flurries… this is an unusual system which has the potential to be a little stronger than anticipated. Upper-level short waves, as they are called, have the unique ability to deliver a brief, heavy dose of snow over a concentrated area. Although we currently do not have the cold air of early January… this same kind of thing happened Sunday, January 4, 2003. An upper level short wave arrived that morning, and moved a lot slower than forecast. Snow began that morning, and continued for about 6 hours, leaving 4 inches when all done. It was a total surprise to many forecasters, because there was no surface level system.

So you were warned here first… it may only be flurries, but if it turns out to be a lot more than that, you can say you knew all along.


I am trying to post a map that explains the situation graphically, but for now, here is the steps in the process. A few suggestions first...

- Get your radiator flushed and prepped for winter in the next 7-10 days.
- Stock up on your salt and ice-melter stuff before the rush. The public will be totally unaware of this storm until about Wednesday or Thursday of next week.
- Do whatever other winterizing techniques you do soon, because winter will arrive with a bang.

Steps in the process leading to our first big storm

1. A strong low pressure system will clip across the Great Lakes early next week, merge with another low coming up from the Gulf. These two will deliver a heavy rainstorm for the northeast on Tuesday 12/7, with another cold front that will blast to the coast on Tuesday like the one which just happened. So expect another round of pelting rain and then a blast of wind. I believe this system will end up being stronger than anticipated because of the rapid clash between the surging tropical moisture and the Arctic air moving south.

2. The Great Lakes Low will bring along an Arctic Front. The confluence of the low and the Arctic High will discharge bone shattering cold down the Great Plains and into the northeast. Overnight lows in the Lakes region will be in the single digits by next Wednesday. Highs in PA and MD will step down to the upper 30's and low 40's, with overnight lows in the low 20's. Delivering this cold air in advance of a storm system is key to any accumulating snow.

3. The cold front will trail from the departing low in eastern Canada all the way down to the gulf. This is a classic setup, because a lingering frontal boundary in the gulf creates instability, which eventually leads to development of a secondary low over Texas.

4. The final piece is an active southern subtropical jet. The arrangement of this jet stream is such that it has been consistently delivering warm moist air into developing gulf systems. Hence the strength of the front which just blasted through... it was enhanced by moist Gulf and Pacific air. By next Wednesday, the arctic front will have moved through, and intense cold air will be pouring south and southeast. The southern jet will send the gulf low from Texas/LA to Georgia to North Carolina to the Mid Atlantic coast by Friday morning, 12/10.

While computer models have been waffling back and forth on this for a couple days now, it is becoming clear in their overall trend that a major event is in store for the northeast next Friday and Saturday.

Thus, I believe the right pieces will be in right places to provide you with a rousing powdery kickoff to the winter season by the end of next week. If the clock and the storm communicate accordingly, we might even get enough snow for a day off school.

If this storm delivers accumulating snow, that will change the entire picture for the rest of December. Snowcover means overall cooler temperatures due to reflectivity of the snow, thus the resulting air mass left behind is colder. A second arctic front by the 15th should be the nail in the coffin for our warm trend, and send the eastern third of the country into a 10 day to 2 week cold wave that will last until Christmas.

The stage is set... so let's get ready to ruuummmmbbbbllee.

No comments: