Today's NAM at 850mb valid for tomorrow shows the clashing of airmasses -- summer in the East, early-spring in the Midwest. The chillier air will arrive on Tuesday night.

Weekly Outlook: From summer humidity to early-spring crispness

Unfortunately, it’s Monday again. Fortunately our skies are mostly blue. And fortunately, we’re writing another weekly outlook.

While most of the Spring so far has avoided the warm, steamy days in favor of the very warm and dry days, that has changed somewhat over the past few days, but particularly today. We’ve had a persistent deep southwest flow, each day tapping more and more into the Gulf of Mexico. This southwest flow was aided by the remnants of Tropical Storm Ana, as counterclockwise flow around the storm system in the southern Mid Atlantic leads to a further fetch of southwest winds and tropical air.

As a result, temperatures are generally in the low 80s, with dewpoints in the mid 60s — creating a muggy June-like feel and causing many people to turn on their ACs.

Often times, deep southwest flow with the warm and humid airmass can trigger some showers and thunderstorms. We’ve actually already had a few form in parts of New Jersey.

There is no true trigger or lifting mechanism for thunderstorms, and with the strong ridge in place, most thunderstorm formation will be capped. However, there can sometimes be other sources of lift at a small scale. With the cold ocean temperatures, sea breezes form, and when the winds on the land are light, the sea breeze can penetrate somewhat inland. These sea breezes then collide/converge with the land winds, creating some lift that can sometimes be strong enough to generate precipitation. And in this warm and humid airmass, there can be heavy rain and a few rumbles of thunder.

A few thunderstorms have developed in New Jersey due to the daytime heating, moisture, and some local convergence boundaries. (weather.cod.edu).

A few thunderstorms have developed in New Jersey due to the daytime heating, moisture, and some local convergence boundaries. (weather.cod.edu). This radar is valid at 3:00pm EDT and is not time-sensitive. 

These storms will be possible all through the rest of the afternoon, but the lack of a true large-scale lifting mechanism will prevent a widespread stronger thunderstorm outbreak. Most of the storms will also stay in New Jersey and perhaps make it up to NW suburbs of NYC. Otherwise, most areas will remain dry with some increase in clouds from these storms, but stay quite humid with temperatures in the low 80s. Areas near the coast will hold in the mid 70s. Winds may also increase a bit at times from outflow ahead of the storms as well as in the storms themselves, but they won’t be all that strong.

Moving forward to tonight, the humid conditions will stick around, leading to another warm night. Temperatures will generally hold in the low to mid 60s. Some patchy fog will develop, but the flow generally being southwest instead of southeast should keep the fog from getting dense. Coastal areas in Long Island could still get dense fog, however, and areas along the immediate coast may also fall into the 50s, due to the cold ocean waters.

Moving forward to tomorrow, the remnant low pressure from Ana will pass to our southeast, which could bring a few more clouds, but the rain from it will stay offshore. This is unfortunate, because we could really use the rain.

A cold front and associated trough will finally make its approach tomorrow, which will also help to increase clouds. The cold front itself will provide some more lift, but not enough lift for widespread thunderstorms. Additionally, as Ana passes away from the area, some clouds from it may move out at the same time the clouds from the front move in — which may prevent us from a true overcast day. When this is combined with even more southwest flow ahead of the cold front, some areas in NE NJ could hit 90 degrees tomorrow. Otherwise, upper 80s will be the general rule away from the immediate coast — the immediate coast will probably stay in the upper 70s to low 80s. But if the winds can turn westerly enough, clouds could be even more sparse and the immediate coast could briefly hit the mid 80s.

Today's high-res NAM model valid for tomorrow shows high temperatures in the upper 80s for a lot of our region (weatherbell.com).

Today’s high-res NAM model valid for tomorrow shows high temperatures in the upper 80s for a lot of our region (weatherbell.com).

Any shower or thunderstorm tomorrow could bring some heavy rain and a few gusty winds, but once again, we’re not expecting anything too strong. The best lift from the cold front’s approach won’t be occurring until the drier, westerly flow takes over from behind the front, so we may lose some of the moisture by the time the front gets here anyway. This will preclude widespread thunderstorms and actually lead to lower dewpoints as the afternoon goes on. This may lead any initial increase in clouds from the front to actually decrease, and with more mixing from the westerly flow, this is another reason why some areas could approach or hit 90 degrees tomorrow, and a few wind gusts around 20mph are possible. Unfortunately, since most areas won’t be getting much rain, the drought will continue.

Once the cold front moves through tomorrow evening, temperatures will quickly drop and dewpoints will plummet through the 40s and into the 30s. This will lead to widespread low temperatures in the 50s with a rapid decrease in cloud cover. This will also mean that the persistent foggy nights will come to an end.

Wednesday will feel a lot more dry and crisp — more reminiscent of early Spring. Winds will shift to the Northwest from between 10-15mph with a few higher gusts, as temperatures approach the upper 60s to around 70. With the core of the trough moving in, high-based cumulus clouds could develop, which may make skies mostly cloudy at times and make it feel a tad cooler.

Today's NAM model valid for Wednesday shows a northwest flow and much cooler temperatures -- generally in the 60s. Some downsloping flow could still allow us to touch 70 degrees, however.

Today’s NAM model valid for Wednesday shows a northwest flow and much cooler temperatures — generally in the 60s. Some downsloping flow could still allow us to touch 70 degrees, however.

High Pressure will dominate our weather on Wednesday night through Friday, which may thwart cumulus cloud formation, keeping skies more clear. Temperatures will generally remain in the upper 60s and low 70s, with lows in the 40s and 50s. This will make for a lovely end to the week. The one caveat is that the dry weather could lead to a few fires.

As next weekend comes around, a warm front may approach as another ridge tries to develop. This could lead to some scattered thunderstorms, but a washout is unlikely. We’ll have more details on the weekend’s weather as this week goes on.

 

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