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By: sullivanweather , 12:00 PM GMT on February 28, 2014
Synopsis and surface features
A powerful ~975mb low pressure system currently over the western Pacific, off the coast of California, will be the focus of attention over the next several days as it will eventually become a long-duration winter storm for a good portion of the region. Elsewhere of note, a very strong (>1040mb) arctic high pressure is sprawling across the Canadian Prairies, building toward the northern Plains. This arctic high will also become a very important factor in the evolution of the upcoming winter storm. Not to be overlooked is a moisture-starved low pressure emerging in the central Plains which will translate northeast to a position north of Lake Ontario by Saturday afternoon. This system will drop an arctic front in its wake, the position of which will be vitally important in determining snowfall amounts and where the transition zone of ice to rain aligns. Closer to the region an arctic front is currently exiting the coast and high pressure is building down from the central Great Lakes as another arctic airmass settles in across the Northeast.
The last of the snow showers and squalls associated with the latest arctic trough passage are now exiting the New England coastal regions of southern Maine and the Cape Cod region. Left behind is a bitterly cold arctic airmass being ushered into the Northeast on 15-25mph winds, with higher gusts. A sheared band of light to moderate lake effect snowfall continues to stream off the still unfrozen Lake Ontario. This will bring two to as much as six inches of snow across the Mohawk Valley/southern Tug Hill region, highest amounts confined in areas closer to the lake. Otherwise expect mostly clear skies and slackening winds overnight, leading to a very cold morning. Temperatures will fall below zero across most of interior New York and Pennsylvania and single digits will extend down to the coast. Perhaps escaping the single numbers will be extreme southern New Jersey, eastern Long Island, southeastern New England and eastern Maine where low teens will suffice; one last cold morning to close the books on this meteorological winter.
Friday will break bright and sunny, despite the cold, for most locations. Lake effect snowfall will end in the morning hours across the Mohawk Valley under subsidence provided for by high pressure. This subsidence inversion will also keep it quite chilly, given the modest sun angle on February 28th. Highs will struggle to climb to ten across far upstate New York and northern New England. Teens will pretty much cover the rest of the interior. Low twenties will do for the coastal/urban centers. These temperatures will challenge daily record low maximums for many locales.
The area of high pressure builds toward Maine during the evening hours Friday and temperatures will begin to warm aloft quite rapidly. At the surface, however, it will be a different story as clear skies, light winds and the very dry airmass still in place will cause a rapid drop in temperatures early in the evening. The normally colder spots across interior Pennsylvania, New Jersey, New York and southern New England; sheltered valleys, pine barrens, places where deeper snow cover still exist, have the potential to drop below zero fairly early on in the evening before leveling off around midnight as clouds and moisture begin to infiltrate from the southwest. Elsewhere across these interior sections temperatures will drop into the single digits once again. Coastal locations will see lows mainly in the teens, as will areas west of the Appalachians and up across the lake plain due to increasing southerly flow. Across northern New England temperatures will have a more typical diurnal pattern through the night will temperatures settling within a few degrees of zero for most locations, although some of the colder sheltered valleys of northern New Hampshire and northwestern Maine will get in the negative ten to negative twenty range.
High pressure moves off to the Canadian Maritime provinces Saturday morning with southerly flow behind the departing high increasing. As mentioned in the synopsis, low pressure will be moving well north of the region, across Ontario and Quebec, aiding in the southerly flow. This will allow for a noticeably milder day, with temperatures just about everywhere across the Northeast some ten to twenty degrees higher than Friday's highs. Breaking the freezing mark will be coastal and valley locations up to southern New England and areas west of the Appalachians. The Pittsburgh area, for example, may even break into the mid-40s. Across the interior, it will be another day in the ice box as temperatures will only climb into the twenties. So although it will be milder and twenties will be a nice climb from the single numbers above and below zero from the morning, highs will still average several degrees below normal. The somewhat brisk wind from the south will, at times, push wind chills into the low teens and single digits.
Some details are starting to present themselves with a bit more clarity in recent model guidance regarding the evolution of the impending winter storm but before the main storm arrives, an arctic front associated with the low pressure over Quebec will sag southward during the overnight hours Saturday. A general light snowfall will develop in the post-frontal airmass and this will deposit a coating to two inches of fine, powdery snow through the morning hours on Sunday across the interior. The higher amounts will be concentrated toward the western half of New York and Pennsylvania. Closer to the coast, any light precipitation from the frontal system may fall in the form of light rain or sleet and won't amount to much. Conversely, for the St.Lawrence/Champlain Valley region northeastward to northern Maine, the overnight Saturday period will start cloudy with some scattered snow showers. Then skies will gradually clear toward daybreak Sunday morning and continue to do so during the day on Sunday as dry air from high pressure to the north filters down.
Event #1 Sunday
Event #2 Monday
Total snowfall from both events
text forecast will follow soon
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