The storm system passing over New England today will continue to organize and strengthen as it passes over Maine this afternoon. While a dry slot will work into southern New England this afternoon and spread north and east, this strengthening storm will continue to bring steadier precipitation to much of Maine through the afternoon and into the evening. An onshore with the system will bring Maine's coastal plain a wintry mix and even plain rainfall while northern areas remain all snow.
Below: HRRR showing potential weather early this afternoon:
An area of warm frontogenesis (the formation and intensification of fronts) continues to look likely across northernmost Maine. This will support snow banding and the potential for several hours of intense snowfall rates. These rates continue to look like they could approach 1.5 inches an hour for a time. These bands will most likely be rotating through northern Maine from around 10am-4pm. This will support total snowfall in the 6-10 inch range for many across the northern half of Aroostook County.
For the rest of New England (outside of Maine) this afternoon, precipitation will gradually lighten up and eventually shut off from south to north through the afternoon. The snow/mix line will also continue to push northward prior to the precipitation shutting off. Across southern and central New England, the surface cold air should get scoured out as the system lifts away, allowing for a transition to plain rain showers/drizzle. Overall, precipitation types through this storm could be decided and changed by just a degree or two.
Several hours of mixed precipitation (sleet, freezing rain) will remain possible before this changeover. A light glaze to up to a tenth of an inch of ice will be possible by early this afternoon The greatest likelihood of noticeable icing will be across southern and central New England away from the coastal plain. Icing will remain below impactful levels in regards to trees and infrastructure,but will create very slippery surfaces.
Below: Potential for at least a glaze of ice through early this afternoon:
This afternoon and heading into the overnight, a moderately strong low-level jet of 55-65mph will move over New England. This will coincide with a well-mixed boundary layer, allowing gusts of 40-50mph to reach the surface this evening and into the overnight hours. It will remain windy through Friday with gusts of 30-50mph. The higher end of the range will be across Maine on Friday.
New England's next storm coming this weekend will involve an area of low pressure that will initially dive into the deep south. There, it will pick up plenty of Gulf moisture as it begins to lift northeast toward the Ohio Valley later this week and phase with northern stream energy. By late Saturday into Sunday morning, the system's primary low will likely be over the Ohio Valley while a secondary low forms near New England/Long Island. Exactly how the system plays out from there will determine impacts in New England.
Conditions are favorable for cyclogenesis of the system Saturday night over the Ohio Valley. An area of strong upper-level divergence will likely occur, which will increase convergence at the surface. Without going into great detail, this is a sign of an intensifying storm system (versus the opposite effect, which would be weak upper-level divergence and a signal for a weakening storm).
At this point, the system's secondary low looks to deepen and track well inside the benchmark. There is overall better agreement this morning among guidance in regards to the storm's track. This continues to point toward another situation with a snow/mix/rain line across southern and coastal New England. Inland areas across northern New England will likely see mainly snow. The exact track of the system will determine how far inland the mixing line is pushed.
The general timing on the storm continues to look like it will be a burst of snow for all of New England at the start. This will likely be followed by a changeover to a wintry mix and possibly even rain from south to north through the day on Sunday. The snow line will then likely begin to collapse back southward later Sunday.
The exact northern extent of where the mixing will reach on Sunday remains a point of contention (which is why that box was included on the graphic above). Generally, operational models have begun trending colder with the storm, which isn't a surprise given how much colder ensembles have been running compared to the deterministic guidance. The Euro remains the most aggressive with pushing warmer air farther north while the CMC is generally displaying the coldest scenario among major models.
Below: Euro vs CMC for early Sunday afternoon:
As for amounts, this storm will likely be strengthening as it passes New England. It is also poised to be moisture-rich, so moderate to heavy precipitation rates will be possible. Areas that remain all or mostly snow (likely interior northern New England) will have the chance to see a significant snowfall (6-12+ inches). Snowfall amounts will generally drop moving southward in the region due to an earlier onset of mixing.
Below: Probability of impactful winter weather Sunday during the daylight hours:
Just about everyone in New England will have a chance to pick at least a few inches of snow on the initial burst at the onset Saturday afternoon through the start of the overnight hours. This burst of snow for southern New England may involve a period of steady snow, with snowfall rates of 1 inch an hour before the changeover. In the end, it will be the timing of the warm air intrusion that will determine snow totals for southern and central New England.
Below: Current probability of at least 2 inches of snow through sunrise Sunday:
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