FIRST CALL ICE STORM INTERIOR / NORTH
MID ATLANTIC SNOW and ICE NEW ENGLAND
stardate 202202.23 1900 est
One of the reasons WxRisk.com has not issued any sort of statement about this upcoming event for Thursday and Thursday night in the Mid-Atlantic region has to do with the uncertainty regarding temperatures. Earlier, there was a chance that readings might stay mild enough so that the precipitation would not fall as Sleet and/or Freezing rain. However, the new Wednesday short range data has come in and it shows conclusively that surface temperatures will be just cold enough for most of the precipitation on Thursday afternoon and evening to fall as freezing rain, and /or Sleet in the interior portion of the Middle Atlantic region.
Specifically, the threat of freezing rain is quite high for the northern half of the Shenandoah Valley, the far northwest portions of the Virginia, Piedmont, the eastern West Virginia Panhandle, and western and north central Maryland. This would include the areas to the west and north of Highway 15 in the Virginia, Piedmont, north of Interstate 64 in the Virginia, Piedmont, and in the Shenandoah Valley.
Further north the main concern is heavy Sleet and Freezing rain which will impact most of Pennsylvania except for the southwest 20%. Significant Sleet and Freezing rain is possible in the Philadelphia metro area as well as all of the Lehigh Valley, interior central Pennsylvania, and the Pocono Mountains on Thursday afternoon and evening into early Friday morning. This ice storm potential will spread into much of New York state after a few inches of snow and the snow will change to sleet and freezing rain in central and southern New England on Friday, which will help keep accumulations down.
MID ATLANTIC REGION
This will be primarily a rain event for all of North Carolina, southwest Virginia, central Virginia, east of Highway 15, all the way to the Chesapeake Bay on the coast, all of the Delmarva, southern Maryland, and the southern third of New Jersey.
The WORST of the Freezing rain and Sleet impacts will hit the northern half of the Shenandoah Valley — north of Interstate 64, the Eastern panhandle of West Virginia, all of western and central Maryland, and the southern half of Pennsylvania including all of Metro Philadelphia, the Lehigh Valley, and central interior Pennsylvania.
To a lesser degree there will be **some** freezing rain and sleet in the northern interior portions of the Virginia, Piedmont. There is also some concern of sleet and freezing rain into the Washington, DC, Baltimore Metro areas of northern Virginia, and central Maryland.
This is likely to be a significant winter storm with heavy accumulations of snow along the Massachusetts, Vermont, New Hampshire border northward including most of Maine, New Hampshire, Vermont. and the northern half of New York State, north of I-90 (which runs from Albany to Rome / Utica then over to Syracuse and south of Rochester.)
Several days ago this event looked like a potential late-season major snow and ice storm for the northern half of the Mid-Atlantic, and all of New England. However, that sort of assessment was based simply upon what the various weather models were showing and not the actual meteorology. If we take a look at the large-scale weather patterns across the Western Hemisphere, we will notice that the MJO — Madden Julian Oscillation is in Phase 3. Without getting too technical we use the various phases of the MJO in order to figure out the global or large-scale weather patterns. There are eight different phases and each one of them has a specific relationship to temperature, precipitation, and jet stream patterns. In late February when the MJO is in Phase 3 it almost always means LOW pressure area will track well to the west of the East Coast. This is why when the initial Model assessments came out a few days ago about this potential snowstorm for Thursday, February 24 in the northern Mid-Atlantic and New England, we reviewed the model output with a great deal of skepticism.
For example, 36 hours ago the various weather models were producing 12 to 17 inches of snow in central and eastern Massachusetts and southern New Hampshire. But with the precipitation starting around 7 am on Friday, then changing over to sleet by 1 pm on Friday, it is difficult to see how 12 to 17 inches of snow could fall in a 6–7 hour time frame.
Indeed, during the past 72 hours, the various weather models have consistently tracked the main LOW pressure area further to the north with each new model cycle. This means that with the main LOW pressure area coming up the Appalachian Mountains and tracking further to the north and west of I-95, the model output for snow would have to decrease, especially, in Pennsylvania, New York State, northern New Jersey, and New England .That is exactly what we have seen with all of the snow data trends for New England.
In the short term, the main trend has been for the event to come a little faster and that makes a significant difference because it means that the amount of cold air coming down from the north will not be as deep. Additionally, ground temperatures have warmed significantly over the past several days due to the mild temperatures and strong sunshine.
This image shows the forecast temperatures as of 9 pm Thursday evening. Notice that readings are still relatively mild in the Shenandoah Valley, northern Virginia, as well as into southeast Pennsylvania and New Jersey. Readings generally are between 40 to 45 degrees. Further inland, we have some temperature readings in the mid and upper 30s in the eastern portions of West Virginia, central Maryland, interior southeastern New York, and central New Jersey.
By 7 am Thursday morning temperatures have dropped around 30 or 32 degrees in the northern half of the Shenandoah Valley, the eastern panhandle of West Virginia, and in northern Virginia, and in the DC and Baltimore Metro areas. Readings are closer to 30 degrees in western Maryland and in the upper 20s in the southern half of Pennsylvania, and interior southern New Jersey.
By 1pm, there will be light to moderate freezing rain in much of the Shenandoah Valley, but temperatures are around 30 or 32 degrees. And with the relatively mild road conditions it is quite possible that even though we may be experiencing freezing rain in the Shenandoah Valley, the ice buildup may be rather mild.
This image shows what the surface map and precipitation will look like by 5 pm on Thursday. Notice there is moderate freezing rain across all the Virginia Piedmont, the northern half of the Shenandoah Valley, southern Maryland, DC -Baltimore and central and northern Delaware. But again, the temperatures are marginal with readings around 30 or 32 degrees and ground temperatures are warm.
By 10–11 pm, much of the freezing rain is coming to an end in Virginia except for the far northwest areas around Winchester and Leesburg. There is still moderate freezing rain in the eastern panhandle of West Virginia and central Maryland, but it has ended in DC and Baltimore.
Meanwhile, extremely heavy sleet is falling in much of central and eastern Pennsylvania.
By 6 am the snow will move into Boston and moderate sleet will be falling in much of southern Connecticut, and southern central and interior southeast New York State, north and northeast Pennsylvania .
This image shows a total possible freezing rain from this event and at first glance, it looks quite severe. The models are producing freezing rain accumulations of up to 0.50” in most of the Shenandoah Valley from Lexington northward, as well as the eastern panhandle of West Virginia, western and central Maryland. This is where the mild recent weather conditions and warm ground temperatures come into play and reduce the amount of icing on the actual roads. One can hypothesize how bad the ice storm potential could be in an event like this if we had experienced near normal temperatures and normal surface ground conditions during the past 10 days.
This image shows a total Sleet anticipated by some of the short-range models in central and northeast Pennsylvania, the southern interior portions of New York State, northwest Connecticut, and western and central Massachusetts. These areas will have somewhat colder temperatures in the mid and upper 20s, so the sleet and icing problem could be much more significant than the marginal conditions in and around DC, Baltimore Philadelphia, central Maryland, northern Virginia, and the northern half of the Shenandoah Valley.
Finally, here is the snowfall map from the 3km NAM model with the enhanced or maximum snowfall algorithm being used. Notice that output is no longer showing 12 to 17 inches of snow in Massachusetts, southern Vermont and southern New Hampshire or in Boston. There are areas of 10 inch snow amounts in much of New York State, central and interior portions of Vermont, New Hampshire and southwest Maine.
18z op GFS and EURO keeps the sleet out of Massachusetts and confined to CT and RI. If so Boston Worcester, Springfield as awell as Albany and the central Hudson Valley will see 12 inches plus ,