at the Bottom of this there is an added section regarding the 12z WED Model data
The event will begin late on the 15th in northern Tennessee, Georgia, and the western Carolinas. There continues to be a significant difference between the regular or operational “Global” weather modes, such as the European, the GFS, and the Canadian and their associated ensembles. The difference between these groups of models is quite profound because they show significantly different kinds of weather with respect to how much snow, where the heaviest snow will fall, when/ where there is going to be a changeover to sleet and rain, any change back to snow, and the overall timing of the whole system.
WHAT EARLY WED MORNING WEATHER MODELS ARE SAYING.
In this discussion, the term GLOBAL MODELS — refers to the operational or regular GFS European and Canadian models.
The term “big cities of Interstate 95” refers to the area from Richmond to Boston.
All of the early morning Wednesday models that came in between midnight and 3 a.m. show the main LOW pressure area coming out of the Deep South on Saturday night, will spread heavy snow into Tennessee, the northwest half of South Carolina, western and central North Carolina, and Southwest Virginia late Saturday night into early Sunday morning. By 7 am Sunday, there will be several inches of snow on the ground in Tennessee, northern Georgia including just north of Atlanta, the northwest half of South Carolina and the western third of North Carolina. This snow will be from the initial LOW pressure area coming out of the Gulf coast states spreading moisture into the cold air.
At that point, the main LOW pressure area will die or begin to weaken and a new LOW pressure area will form in eastern North Carolina. This new LOW pressure area in eastern North Carolina will move along the coast will continue to spread heavy snow in the western half of North Carolina, all of southwest Virginia, into the Shenandoah Valley, and into western and central Maryland during Sunday. Moderate snow spread into central Virginia including Richmond and the Virginia Piedmont, Fredericksburg Washington DC and Baltimore during the day on Sunday.
By 6 or 7 p.m. on Sunday the front of the snow line will be north of Philadelphia, across much of southern Pennsylvania and New Jersey and headed for New York City. Up to that point, all of the weather models are in very good agreement.
Now here is the tricky part. Let call this Scenario #1
If the regular or operational Global weather models are correct, the new coastal LOW area tracks will track just inland from the coast in a due south to North direction. This will pull in milder air from the ocean well inland so the snow will change to sleet then rain in central North Carolina, central and interior eastern Virginia, central Maryland, Washington DC and Baltimore, all of the Delmarva, all of New Jersey, into southeastern Pennsylvania, New York City and all of central and southern New England. This would, of course, reduce the snow accumulations.
On the other hand, this inland track of the coastal LOW places the heaviest snow area in western North Carolina, all of southwest Virginia, the Shenandoah Valley, the Virginia Piedmont, the western half of Maryland, central and northeast Pennsylvania, interior eastern New York State and northern New England. Those areas in this scenario would see 1 to 2 feet of snow.
If we take the operational Global models verbatim, then we get some interesting snow looking Maps. The various weather models show anywhere from 8 to 12 inches of snow in northwest portions of South Carolina while Philadelphia and New York City and Boston would see less than 3 inches of snow!
If the track of the coastal LOW is inland then we are looking at a shorter duration event for the Mid-Atlantic and New England because the storm would develop a ‘DRY SLOT‘. The term DRY SLOT in the weather business refers to an area of weakness in large LOW pressure systems which has no precipitation and sky conditions sometimes become partly cloudy. The dry slot area in large LOW pressure system occurs because the circulation is very large and pulls in drier air from the interior of a continent which gets wrapped into the SW quadrant of the system.
If the global models are correct the Inland track of the coastal LOW is going to pull the dry slot across central and eastern North Carolina, central and eastern Virginia, all of Maryland, Delaware, central and eastern Pennsylvania, New Jersey southern New England, and southeastern New York. This results in a shorter duration event with less snowfall and it does not al LOW the rain or mix precipitation to turn back the snow before it ends.
Now lets look at Scenario #2
All that being said it needs to be pointed out that there continues to be a significant difference between the regular/ operational Global models and their respective ensembles. All of the ensembles are significantly further to the east when compared to the operational global models. A track further to the east even by 50 or 75 miles would have a huge difference in the big cities of I-95 with respect to:
the duration of the storm
the changeover from snow to rain
which areas well change over
snow accumulations,
whether or not the precipitation might turn back to snow before it ends for several hours.
The black line on these maps = the r/s line
Moreover, If the coastal Low tracks more to the to the east, this would mean that there would be no dry slot in central and eastern Virginia, all of Maryland, Delaware, central and eastern Pennsylvania, New Jersey southern New England, and southeastern New York.
Indeed, the Canadian and European ensembles show the rain- snow line only pushing in just west of I- 95 so that areas such as Charlottesville, Danville, Culpeper Dulles- Sterling Hagerstown, Reading, Allentown, Interior northern New Jersey, the NYC northern suburbs, and most of southern and eastern New England would stay all snow.
In addition, this more east track would also allow for the precipitation to change back to snow for 3 to 6 hours in the morning hours of Monday January 17 and a couple of more inches of snow could fall in the big cities of I-95.
in BOTH scenarios western half of North Carolina and southwest Virginia and the Shenandoah valley are going to ger crushed. 1–2 feet of snow
WHAT IS WxRisk THINKS IS GOING TO HAPPEN
Our prediction of a major snowstorm on the East Coast for January 15–16 which we first made back on January 3rd, continues to look increasingly likely.
· Based on the latest data the heaviest snows are clearly going to fall west and northwest of Interstate 95. The North Carolina Piedmont area — which is from west and northwest of Interstate 85, as the Virginia Piedmont, into central Maryland, up into Harrisburg and the Lehigh Valley and the Poconos region of northeast Pennsylvania, have a high probability of seeing 1 to 2 feet of snow.
· In Virginia and Maryland, the tricky portion of the forecast is the area from Baltimore to Washington, Fredericksburg, to Richmond. The snow amounts in these areas could range anywhere from 2 to as much as 8 inches depending on the actual track of the LOW. The further west you are from Interstate 95, the more snow will fall and less rain.
· If scenario #1 which is based upon the operational Global models being correct, actually verifies this is not going to be a big snow for New York City or the southern half of New England.
· There is still some chance of an eastward shift on all of the global models because the main pieces of energy that will cause this big east Coast LOW pressure area to form, is still in the northern Pacific. Once it reaches North America, the information about the strength of this jet stream energy will become more reliable and detailed which al LOWs the various weather models will do a better job handling it.
· If there is going to be a change in the track of the coastal LOW pressure area to the east, it will probably show up on the Thursday 12z / midday or early Friday morning/ 0z weather models.
And yes there is plenty more activity coming up after this event
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12z WED MODEL UPDATE
I continue to see a lot of comments from people claiming this to be an all rain event simply because NYC/ Philadelphia/ southern New England gets screwed out of the big snow -as if the only people that matter are the ones in the big cities of the Northeast. Well let me just say — blow it out your ass.
In this case, because NYC/ NJ / New England stick further out to the east, the track that THIS particular LOW takes on the coast or just Inland really does hurt them so the early snow quickly changes over to rain on E or SE winds with the more Inland track. However, in central Maryland and central Virginia, those areas do get some of the early snow from the initial first LOW pressure coming out of the Deep South on Saturday night and Sunday morning.
For this reason, the midday GFS and European models have a nice band of 3 to 8 in snows along Interstate 95 corridor…. with the 7–8 inch snow being 25 miles WEST of Interstate 95 and the 3 inch snow being 25 miles EAST of Interstate 95. And yes all of Interstate 95 in central North Carolina, central Virginia and central Maryland will go over to some form of mix or rain as the majority of the data — even the 12z ENSEMBLES now shows this.
But I continue to be extremely concerned about the heavy snowfall in the western half of Virginia from Route 15 all the way into the eastern portions of West Virginia and southwest Virginia as well as the entire Western half of the state of North Carolina and Northwest portions of South Carolina. I don’t know what the records are for snowfall in Greenville-spartanburg or Charlotte but some of these places are going to get 10 to 20-in of snow easily from this event.
DT