Overview A snowstorm is in store for the Mid-Atlantic I-95 corridor region on Monday from the DC metro region-to-Philadelphia-to-New York City. Fresh, moderately cold air will slowly filter into the region late tonight and early tomorrow following the passage of a cold frontal system. Precipitation will begin in most areas well after midnight in the form of rain and then transition briefly to sleet and then ultimately to all snow on Monday with several inches of snow accumulation expected from the northern and western suburbs of DC to New York City. The NAM computer forecast model from NOAA has indeed shifted northward with its precipitation shield for tomorrow’s storm [precipitation totals shown below for the 24-hour period between tomorrow morning and Tuesday morning from last night’s model run versus this morning’s model run].
Specific forecast details by region follow: DC: 1-3 inches in the District; 3-6 inches in the northern and western suburbs; a sharp cutoff to the snow accumulation just south of the District (e.g. southern Maryland gets little if any). Rain begins after midnight and transitions to a brief period of sleet before changing to all snow in the northern and western suburbs during the early-to-mid morning hours. Snow will fall heavily at times in the northern and western suburbs during the latter stages of the morning and into the early afternoon, and for a brief period of time in the District. Snow winds down in all areas by late afternoon.
Philly: 4-8 inches of snow accumulation with the lesser amounts in that range in the city of Philadelphia and the higher amounts in the northern and western suburbs; less overall at the shore in southern New Jersey (1-3 inches). Rain begins well after midnight and transitions briefly to sleet before ultimately changing to all snow during the early-to-mid morning hours. Snow falls heavily at times from mid-morning through the early afternoon hours before winding down by late afternoon.
NYC: An average snow accumulation of 3-6 inches in and around the NYC metro region. There will be a brief period of rain and/or sleet towards morning before a changeover to all snow during the early-to-mid morning hours. Snow falls heavily at times from late morning to mid-afternoon before winding down late in the day.
Other info One difference between this storm and recent snow events is that temperatures will just be marginally cold enough for snow on Monday (ie low-to-mid 30’s). As a result, the snow will be of the “wet” variety and will have some trouble sticking on treated roadways in the initial hours of the storm, but that will likely change rather quickly as soon as the snow begins to fall heavily.
Looking ahead Monday’s snowstorm is just the first storm of what will likely be a very active 10 days or so. Another storm will move into the Mid-Atlantic region on Tuesday night and will continue through Wednesday morning. It appears that storm will bring a period of frozen precipitation to the I-95 corridor before a changeover to plain rain. Most likely scenario in the DC metro region is for ice (ie freezing and/or sleet) on Tuesday night, at least in the northern and western suburbs, before a changeover to plain rain by Wednesday. There can be some ice buildup in the northern and western suburbs of DC before the changeover to rain. In Philly and NYC, there can be ice and/or snow on Tuesday night before a changeover to plain rain on Wednesday. The ice and/or snow can accumulate some in those metro regions on Tuesday night before the changeover to rain. Finally, another storm threatens the entire region next weekend and, while it is too early to say exactly what the precipitation-type will be, it does look like it will be a powerful system loaded with moisture and it could turn out to be an all-out blizzard for parts of the Mid-Atlantic.
Update on the sun On a completely different note, the sun currently has an active and large sunspot region that is directly facing the Earth. For more details on today’s arrival of a coronal mass ejection from a recent solar flare, check the “Climate Info” section of the weather web site.