John Homenuk

Unsettled autumn weather this weekend

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It has been a busy week.Strong thunderstorms which produced damaging winds in New England, a blood red moon and lunar eclipse, and noticeable temperature swings have all made news over the past several days But, finally,some tranquil weather settled into the area on Wednesday and Thursday when highs reached the 70’s and sun was plentiful. The weekend, unfortunately, won’t follow the same path. An approaching disturbance is likely to bring unsettled weather to the area from later tonight through Saturday.

High clouds from the associated system have already filtered into the area this afternoon, in response to the first disturbance moving through the Ohio Valley. This lead disturbance will bring continued cloudiness, as well as a chance of showers to the Mid-Atlantic and southern portions of our area…including Southern New Jersey. This lead disturbance will remain relatively weak and slide offshore, so we aren’t expecting a washout by any means on Friday.

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Doug Simonian

Strong thunderstorms with isolated tornadoes tonight

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A very interesting meteorological setup for severe weather looks to unfold tonight. A large blocking pattern in the Arctic has forced a large trough to dig into the Midwest, and this will eventually swing through to our area, yielding a potent storm system to our northwest. Although it is often much easier to get thunderstorms during the summer when airmasses are warmer, storm systems are usually stronger during the Autumn, as there is often a larger difference in temperature — or a battleground — for a storm to form. Considering this, plus the fact that in early October the Atlantic Ocean is still quite warm, it becomes much easier for severe weather to be supported near the coast. The strong storm system will serve to bring warm, moist air from the Atlantic Ocean, yet also provide colder temperatures aloft, generating plenty of instability. Additionally, instead of the rising air for showers and storms coming from sunshine heating the ground, we are able to generate forcing for lift from that strong storm system. This gives us the basic foundation for severe weather tonight into Wednesday morning. But this situation remains quite unique.

Arguably the most impressive facet of this potential threat is the strong winds just above the ground. When winds change direction (clockwise) from the ground and up, as well as greatly increase in speed, that is when strong wind shear is created, which supports rotating thunderstorms, capable of producing strong wind gusts and isolated tornadoes. Given that surface winds will be out of the southeast, and winds just above the ground will be in excess of 50 knots out of the southwest, plenty of wind shear is generated. When this is combined with instability, those rotating updrafts can be lifted into thunderstorm clouds, and severe weather can be realized. Without the instability to lift rotating updrafts into thunderstorm clouds, thunderstorms greatly diminish in coverage. Lots of recent model data, however, shows a good combination of potentially rotating updrafts and instability, which piques our interest.

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John Homenuk

Gusty winds, isolated tornadoes possible Wednesday AM

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It’s not often that we talk of severe weather potential this late in the season, but the upcoming meteorological setup argues for a bit of anomalous potential. A potent mid level distubrance and associated height falls will approach the area from Tuesday Night into Wednesday morning. More notably, a juxtaposition of instability and shear on most forecast models is likely to create a corridor of severe weather potential. Exactly where, and when, this corridor develops will obviously have major impacts on our forecast. Today, forecast models have come into better agreement on the idea that this corridor could traverse from New Jersey through NYC, Long Island and parts of Southern New England early Wednesday morning.

The main potential for severe weather will come Tuesday Night into Wednesday morning as a surface low passes just to our northwest, over the interior Northeast. As it does so, maximized forcing will pass through the area from southwest to northeast. Forecast models agree that southerly winds ahead of this front will lead to moisture return and developing instability. In addition favorable kinematics including veering/backing low level winds, favorable low level and bulk shear, will juxtapose with the developing instability to support the potential for severe weather.

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Doug Simonian

Strong cold front to bring rain, thunderstorms, late tonight and Saturday

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The persistent cloud-cover over much of the region during the past several days finally broke today, leading to a beautiful fall day. However, as the evening progresses, clouds will be on the increase due to a strong low pressure system in Ontario, Canada, and its associated strong cold frontal boundary dragging to its south. These features will be moving eastward throughout the night and approach our area during the day tomorrow.

Today's NAM Model valid for 2:00pm tomorrow afternoon shows the strong cold front crossing our area, with much colder 850mb temperatures about to move in.

Today’s NAM Model valid for 2:00pm tomorrow afternoon shows the strong cold front crossing our area, with much colder 850mb temperatures about to move in.

Fortunately, for people going out tonight, any rain should hold off until midnight or slightly later for western sections, and after 2:00am for NYC and east. Plus, given that we are still on the warm side of the cold front, temperatures will not be all that chilly tonight, with lows around 60.

7:00pm: Mostly cloudy skies, temperatures in the low to mid 60s.

10:00pm: Cloudy skies, temperatures in the low 60s.

Midnight: Cloudy skies, temperatures in the low 60s. A 30% chance of showers for western zones, with only about a 10% chance of showers for NYC and east.

2:00am: A 60% chance of rain for western zones, with a 30% chance of rain for NYC and east, and temperatures around 60.

4:00am: An 80% chance of rain for western zones with a rumble of thunder possible, and a 60% chance of rain for NYC and east, with temperatures around 60.

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