Northeast Storm With Heavy Rainfall and Wintry Mix into Tonight

Happy Friday! The rest of today may not in fact be so “happy,” as a large storm system impacts the Northeast, making the day quite soggy. Periods of rain will continue, becoming heavy at times for the rest of this afternoon and into tonight. Warm-air advection will continue to support very mild temperatures and high dewpoints. This will continue to cause some areas of patchy fog to linger into this afternoon, as the ground may remains colder. In fact, some record high temperatures could be broken by early this evening.

Strong southerly low-level jet and upper-level jet streaks will provide ample lift and also support low pressure to deepen as it moves northeast of the Mid-Atlantic region by tonight. Precipitable water values are between 1.50″ to 2.00”, which is reaching record levels for this time of year. This large amount of lift and moisture will result in much of the region receiving rainfall totals between 1” to 3”. Some weak elevated instability may result in a few isolated thunderstorms, which to could lead to locally higher rainfall totals. This heavy rainfall along with snow melt will also lead to some ice jams that could result in flooding along rivers and streams, especially over the interior. Therefore, the National Weather Service has issued Flood Watches and even some flood warnings already for parts of the Northeast.

3km NAM model showing parts of Northeast underneath right-entrance region of upper-level jet at the 300mb level

3km NAM model showing parts of Northeast underneath right-entrance region of upper-level jet at the 300mb level tonight

Winds are not expected to be a significant hazard with this storm system. A tight pressure gradient will cause a southerly low-level jet to strengthen, with winds 50-70kts at 850mb (around 5000 feet). But a strong low-level inversion will likely prevent much of these winds aloft from mixing down to the surface. Southerly winds may still gust between 30-40mph in some spots, especially with heavy rainfall or any thunderstorms that do develop.

As low-level cold air rushes in, any lingering rainfall will likely change over to sleet and freezing for higher elevations over Northern NJ and the Lower Hudson Valley late tonight and Saturday morning. Subsidence in the mid-levels will not support snow for these areas, but some icy spots could develop. These are where Winter Weather Advisories are currently in effect later tonight and into early Saturday morning. Further over the interior, thermal profiles will support more significant snow and ice to fall. These are where Winter Storm Warning are currently in effect. There is also potential for a flash freeze with any water left on ground, when temperatures crash down below freezing tomorrow morning over the interior.

3km NAM model late tonight showing heavy rain and convection over coastal plains and more snow or wintry mix occurring over the Interior

3km NAM model late tonight and early Saturday morning showing heavy rain and convection over coastal plains and more snow, sleet and/or freezing occurring over the interior

Closer to the I-95 corridor coast, mostly if not all rain is expected until precipitation ends Saturday morning. Drier, downsloping northwest winds will allow for the ground to dry, mitigating a flash freeze threat. Behind the storm, northwest winds will be between 15 to 25 mph with gusts possibly up to 30mph tomorrow. This will lead to windchills in the teens, as surface temperatures drop into the quickly into the lower 30s and 20s later in the day.

Saturday night will feature clearing skies and colder temperatures. Sunday and Monday will again feature some frigid temperature with highs only in mid-upper 20s, but with plenty of sunshine, however. Then the next storm system coming out Midwest/Great Lakes will be arriving for the middle of next week in the Northeast. Model differences continue with the evolution of this storm. Thus, it is too early to detail on how significant the storm will be for the Northeast at this time. But chances for some snowfall are increasing, as the upper-level pattern amplifies again over the Northeast. We’ll will have updates on this next storm throughout the weekend.