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Bouts of heavy rain expected through Thursday

Although it has been quite the grey, dreary, chilly day, rainfall throughout the area has not been all that heavy yet. The main reason for this is because the surface pressures are still quite high, thanks to a large high pressure system north of Maine, which is wedging in very high pressures into the area. Higher surface pressure is an indicator of downward motion in the atmosphere, which is not conducive to precipitation.

This afternoon's NAM valid for 5:00pm shows a large high pressure system to the north, with high pressures still wedged into our area. This is why a lot of the rain has broken up as it has headed east (weather.cod.edu).

This afternoon’s NAM valid for 5:00pm shows a large high pressure system to the north, with high pressures still wedged into our area. This is why a lot of the rain has broken up as it has headed east (weather.cod.edu).

The image above explains it well — note the blue isobars of higher pressures that are being “pushed” into our area. The lower pressures are relegated to the west, southwest, and northwest, while the higher surface pressures are to the north and northeast. The station pressure at Rutgers Gardens is 1027mb. That is certainly not conducive for heavy precipitation. This is further augmented by the fact that an associated warm front is still well to the south of the area. If the atmosphere is going to generate lift for precipitation with high surface pressures, we need forced ascent from a frontal boundary, which will finally be approaching the area on Wednesday.

Moving forward through 11:00pm tonight, the surface pressures remain high, and the warm frontal boundary is still well to the south. This most likely means the Yankees will play baseball tonight (weather.cod.edu).

Moving forward through 11:00pm tonight, the surface pressures remain high, and the warm frontal boundary is still well to the south. This most likely means the Yankees will play baseball tonight (weather.cod.edu).

However, over the next several hours, notice how the strongest temperature gradient associated with the warm front is still well to the south, and the high surface pressures are still being wedged in. This combination leads us to believe that any rain that falls this evening and tonight will be very light, and not enough to cancel the Yankee game. As time goes on, the warm front will slowly be approaching the area, and the easterly winds from the cold, yet moist ocean will finally be enough to moisten the atmosphere and generate the necessary lift for precipitation.

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Pleasant start, but heavy rain likely Friday Night

It is not often, this time of year, that a relatively progressive passing disturbance will force the development of a low pressure system around 995mb off the Northeast US Coast. Exactly that will occur late Friday Night into early Saturday, as a mid and upper level disturbance passing through the Northeast US with some vigor moves toward New England. Forecast models indicate a high likelihood of increasing moisture as well as strengthening lift for precipitation by Friday Night — even some weak instability which could force thunderstorms — along an axis which will shift from west to east. This raises confidence in a period of heavy rain Friday Night into Saturday morning, as the low pressure system passes nearby and eventually into the Gulf of Maine.

Not all will be lost, however. Much of Friday will turn out pleasant. This morning, visible satellite imagery showed only some filtered high clouds moving into the area. High temperatures on most forecast models are expected to reach into the lower 60’s. Most notably, however, the winds which were blustery over the past few days have settled down. As a result, the 60 degree temperatures will feel much more comfortable in the warm sun as opposed to the brisk and blustery winds. Rain is forecast to move into the area after the PM Rush, and will be out of the area by Saturday’s sunrise.

Simulated radar for tonight shows an area of moderate to heavy rain with embedded thunderstorms.

Simulated radar for tonight shows an area of moderate to heavy rain with embedded thunderstorms.

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Pleasant, but fire danger through Friday

Calm weather has settled into the area during the middle part of this week in the wake of a cold front, but gusty winds have ramped up over the last 12 to 24 hours with a tightening pressure gradient over the area. Blustery northwest winds led in a surface high pressure on Wednesday Night, as a low pressure system deepened well off to our north and east. The northwest winds and very low humidity are leading to concern for brush fire spread throughout the area. Subsequently, the National Weather Service has issued a Red Flag Warning for much of the area — save for Long Island, where higher humidity values are present near the coasts.

A Red Flag Warning is issued by the National Weather Service when high winds and low humidity are expected to make conditions favorable for dangerous and rapid spread of brush fires if ignition occurs. Despite the concern for fire spread, pleasant weather will continue — albeit a bit cool of this time of year. Highs in the lower 60’s will be common on Thursday and Friday before a disturbance approaches with a period of rain expected Friday Night.

Very low dew points and gusty winds could cause rapid fire spread today.

Very low dew points and gusty winds could cause rapid fire spread today.

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Onshore flow, cooler through Friday

Cooler than normal weather has been settled into the region for the past few days, after snow and ice on Wednesday morning made for a dramatic entrance. An onshore flow, rooted by east/southeasterly winds off of cooler ocean waters, will continue on Friday bringing temperatures in the 40’s and 50’s throughout the area and the presence of some clouds. Farther inland, over Pennsylvania and much of the Ohio Valley, a warmup is underway as the ocean effects are much more muted. This warmup will head our way by later this weekend into the early next week, but before the cooler/unsettled weather puts up a fight.

To our south this weekend, an upper level low with a tremendous amount of moisture will shift from the Gulf Coast to the Southeast States. Several inches of rain are expected along the Southeast Coast as the low pressure system shifts east. Luckily for our area, the incredible moisture return will remain south of our area and the storm system will skirt out to sea — leaving us without any significant rainfall amounts. But temperatures will remain generally in the 50’s and possibly approach the 60’s as the system begins to pull away.

Onshore flow keeping temperatures cooler than normal this weekend.

Onshore flow keeping temperatures cooler than normal this weekend.

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