Coastal storm to bring periods of heavy rain Sunday

A developing coastal storm system is expected to bring periods of heavy rain to the area later on Sunday, with a low pressure system tracking from the Mid Atlantic states to a position just off the coasts of New Jersey and eventually Long Island. Despite the historically good track for wintry precipitation, a lack of cold air in the antecedent airmass will lead to mostly if not all rain throughout the forecast area — with no wintry precipitation concerns.

Instead, high clouds will begin filtering into the area on Sunday and rain will stream into New Jersey from southwest to northeast. Increasing moisture and warming temperatures both in the mid and low levels of the atmosphere will mark an environment which will become favorable for heavy rain by later Sunday evening. As the surface low passes off the coast of New Jersey early on Sunday evening, enhanced lift and dynamics will create a period of very heavy rain — which will shift through New Jersey and New York City , eventually moving northeast into New England. Rainfall totals are likely to exceed 1″ throughout a vast majority of the area.

NAM model showing Sunday's forester at many different levels of the atmosphere, producing heavy rain in our area Sunday evening.

NAM model showing Sunday’s forester at many different levels of the atmosphere, producing heavy rain in our area Sunday evening.

With the peak of the rainfall Sunday night will also come a brief window of potential for strong winds along the area coasts, but forecast models have wavered slightly east with the track of the low pressure system. This increases the likelihood of calmer winds, especially inland. Near the coasts of New Jersey and Eastern Long Island, however, a few hours of gusty winds are still expected — with some gusts over 40 mph possible. Rainfall totals, as a whole, should exceed 1″ throughout the area by late Sunday evening.

Behind the storm system, westerly winds will pick up in earnest and arctic air will return. In fact, the Polar Vortex will be establishing itself over Central and Eastern Canada by the early part of next week. Warmer air brought northward with the weekend storm system will quickly be scoured out of the area, and temperatures will return to slightly below average.

Eyes peeled to potential late week snowstorm: Forecast models have come into better agreement on the eventual evolution of the large scale upper air pattern during the greater part of next week. The breakdown of the pattern evolution includes the transition of the Polar Vortex from Central to Eastern Canada, acting as a mechanism to keep cold air locked in to the north of the area as a ridge builds over the top of this vortex near Greenland and the Davis Straight.

GFS model forecasting a significant disturbance to amplify over the Tennessee valley during the middle to latter part of next week.

GFS model forecasting a significant disturbance to amplify over the Tennessee valley during the middle to latter part of next week.

As a disturbance drops southward from the Pacific into the Central United States, forecast models are hinting that it will interact with a southern stream disturbance, and rapidly deepen and amplify near the Tennessee Valley. As a low pressure system moves northward, it will be forced to deepen and redevelop off the East Coast due to the positioning of the Polar Vortex and blocking high pressure system over New England. Such a development would increase chances of a moderate to significant snowstorm for much of the forecast area by late next week.

However, uncertainty remains quite low. Forecast models at this range are prone to wild swings and variations in forecasts, and individual nuances and perturbations in the pattern can cause big changes in the eventual forecast. That said, medium range ensemble support seems to be strengthening for this potential event. Stay tuned over the next few days for updates..

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