December 28, 2000
The idea of a northwestern shortwave phasing with the ejecting energy from the southwest creating a major east coast storm is now history. However, that same northwestern shortwave may very well spin up it's own storm system along the southeast coast sometime Friday evening. Before we get into details about the weekend, lets look at the weather for the next couple of days.
The remainder of the overnight hours will feature clearing skies with a low temperature in the mid 20s. Thursday will be mostly sunny with highs 25-30 across the region. Clouds will increase on Friday as the aforementioned disturbance approaches from the Ohio Valley. Highs will be around freezing.
Model guidance indicates that the disturbance currently digging SEward through North Dakota will intensify and close off as it heads towards Illinois by Thursday night. Meanwhile, the former cutoff low from Texas is fizzing out as it zips off the southeast coast. So, these system will not phase as previously thought. This southern energy will still play an important role in storm development as it leaves behind quite a bit of moisture and weakness in the pressure field directly behind it's exit. Since the energy from the NW is now being progged as stronger, it will spin up it's own area of low pressure somewhere off the coast around the SC/NC border in response to this bagginess.
This new area of low pressure will have ample energy to develop quite rapidly. Questions arise once again as to exact specifics on the exact track of this low and precipitation outputs. Most of the dynamics with this system should be on the eastern side, but that does not mean that we are out of the woods just yet. The majority of guidance tracks this system on a generally northern track, perhaps hints that it even drifts NNW for a while. The trend of the models the past two runs, has been to place the track of the low slightly farther west each run. This is likely in response to the 500mb trough going negative earlier and being deeper than though 24 hours ago.
Heaviest precipitation on most models has been progged at about 50-75 miles to our east, with PHL getting modest, but not substantial amounts of snow. However, since the trend has been a deeper, stronger closed low, would expect the next model suite to shift the system slightly farther west, especially as the sytem goes negative near the DelMarVa peninsula. That doesn't necessarily mean that guidance will still be showing heavy precip on the western side of the low, but if QPF fields remain the same, that would put PHL in the heavy snow band. Too early to pinpoint right now.
There is also the possibility that our theory doesn't hold water and the next guidance suite shifts the track farther east. If the energy is still digging, the tilt would remain positive, thus pushing the system farther off the coast. So, it is all about timing here, something we need to watch over the next 24 hours.
This evening's guidance goes on to say that the system undergoes bombogenesis early Saturday, pushes into the southeastern New England area, and stalls it for a period. That scenario could very well spell that particular region's first (dare we say it) blizzard since the April Fool's Storm of 1997.
So, some questions answered today, many not. At least we now know that the idea of phasing of two pieces of energy is a moot point. We also know that a new low pressure area will develop off the Southeast coast Friday evening. Questions that are still up in the air are: Does the energy continue to dig more than what guidance is showing, thus shifting the system more eastward? Does the tilt go negative early enough that the system actually trends NNWward for a period increasing the likelihood of heavy snow for our area? What will the precipitation shield look like compared to what guidance is showing tonight? How much snow will the Delaware Valley receive? More information tomorrow.
Enjoy the next couple of days is the general idea here. Things look to get stormy over the weekend, especially the farther east you go from here. Will likely post early snowfall amounts late Thursday night/early Friday morning (2AM?). Until then, keep an eye to the sky.
