December 29, 2000
The National Weather Service in Mount Holly has issued a Winter Storm Watch for the entire Delaware Valley on Saturday. As it stands now, the area is a little more than 24 hours away (2:15AM at time of update) from the start of it's most significant snowstorm since January 25th where we picked up close to 9 inches. This is not necessarily a very *complex* forecast in terms of rain/snow line, but the exact details are still a bit sketchy and will likely remain through the duration of the storm. Lots of information to discuss, so let's get right to it.
The remainder of the overnight hours will feature clear skies with light winds from the North. Low around 15. Friday will start off partly sunny, but clouds will be on the increase throughout the day. High around freezing. Friday night will be mostly cloudy with the low in the mid 20s.
Snow is expected to break out after midnight on Friday, likely around 3AM as we see it right now for most of the Delaware Valley. The farther south you are, the sooner the snow begins and vice versa for points farther north.
So what is causing the snow? An area of upper level energy is currently digging SEward through Iowa. It will continue to dig farher south and east through the day on Friday and should finally cease it's SEward digging by the time it reaches Kentucky later Friday night. In response to digging area of upper level energy, an area of low pressure will develop just east of the South Carolina/North Carolina border sometime Friday evening. This area is favorable for development in part by the exiting shortwave currently zipping off the SE coast. That area of low pressure leaves behind some general weakness in the atmosphere conducive to development by the digging vortmax in the Plains.
Snow will be generally light through the morning hours on Saturday as the system begins to organize and head Northward. As the system approaches the North Carolina/Virgina border (about 50-75 miles east) by around 7AM Saturday, it really starts to develop nicely. Pressure, as indicated by guidance, would be just under 1000 mbs. At this time or shortly after, more moderate snows will have begun to advance into the Delaware Valley. As this sytem continues to move Northward, it continues to intensify rapidy. By around noon on Saturday, our area will be starting to see heavy snowfall and northeast winds will have increased noticeably. The system is progged to be near 992 mbs about 50 miles east of Wildwood, New Jersey. Heavy snow and strong northeast winds will continue through the afternoon hours on Saturday. Blizzard conditions will likely be seen due to the combination of high winds, low visibilties, and blowing and drifing snow. By Saturday evening, the area of low pressure will not have moved much and will be about 25 miles east of Atlantic City. Meanwhile, the pressure will have dropped to roughly 986 mbs. By early Saturday night, snow begins to taper to flurries as the system shifts Northeastward into the Cape Cod vicinity. The high temperature Saturday will be around freezing, so no concerns here about a changeover to rain, although during the afternoon, it *may* mix with sleet at times.
Obviously, we are not the only area that will be affected by this storm. Some areas in New England will see heavy snowfall as well. However, the track and positioning of the low gets a bit fuzzy by the time it reaches that far north. Areas to our south and east will also get in on some very heavy snows. But, areas farther to our west will be spared by a sharp dropoff in precipitation. As it stands now, areas such as Eastern Maryland, Delaware, Southeastern PA, and parts of New Jersey will see the heaviest snowfall amounts out of this storm.
How much snow? Early indications are the the Phildelphia area and close suburbs will see anywhere from 8-14 inches. The farther west you go, say towards Harrisburg, the amounts decrease to 3-7 inches. The farther east you go, the amounts should be slightly higher, especially inland sections of New Jersey where as much as 16 inches of snow may fall. Points closer to the coast should be on the order of 6-10 inches as mixing should keep totals somewhat lower (although am not certain that mixing will occur as this system intensifies quite rapidly). These are a bit early still to pinpoint any more specifically, just an idea of what we are looking at. By tomorrow afternoon, these ranges will be narrowed to give a better idea of what to expect.
As is generally the case with any noreaster, a slight deviation east or west from the current progged storm track would mean differences in snowfall amounts. A shift to the east, we are in the 4-8 inch range. A shift to the west, we are in the 8-16 inch range. If the system follows the track but stalls or slows down, totals go substantially higher. This scenario is actually hinted at by a handful of models. Again, by tomorrow, we will more accurately know what the storm intends to do as far as track, timing, and totals.
So, just to reiterate here, as it stands now, PHL and Delaware Counties respectively are looking at snowfall beginning early Saturday morning and continuing through the day Saturday. Near blizzard conditions are likely at times. Snow will taper to flurries by early Saturday night. Snowfall totals for our area right now fall in the 8-14 inch range. More tomorrow. Update between 2-3AM.
