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3.1 Zones 4/5/6 (SE PA, S/C NJ) Severe Weather Update

A low pressure system will drive into the Great Lakes today, with warm air surging into the region from the southwest. This warm air has already arrived, with temperatures much above normal for this time of year. As a cold front moves towards the region later today and tonight, the combination of this warm air and plenty of wind shear in the atmosphere will lead to the potential for strong and severe thunderstorms. The wind shear in particular is impressive and could lead to the potential for strong, damaging winds in thunderstorms.

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Technical Analysis: Northeast US Severe Weather Wednesday

Yet again, the weather is completely divergent from the calendar, as we are tracking a severe weather event in the Northeast on Wednesday. This is following a moderate risk of severe weather in the Ohio and Tennessee Valleys today. It all starts with a warm front moving through the region tonight and early Wednesday morning, which will help make the already warm airmass even warmer, and also more moist. This will trigger some showers and possibly a rumble of thunder during the overnight and on Wednesday morning. Afterward, mid-level winds look to dramatically increase in strength as dynamics become extremely impressive ahead of a strong cold frontal boundary.

There will also be an elevated mixed layer (EML) moving into the region, which further helps promote high amounts of mid-level instability — perhaps more than we had on Saturday. We also have more deep-layered wind shear thanks to extremely fast westerly winds aloft, which could lead to multicellular clusters and even some supercells forming on Wednesday afternoon. The EML and westerly mid-level winds also lead to more dry air aloft, which is favorable for hail formation as well as being able to efficiently transfer strong winds down to the surface via density momentum. Saturday’s soundings were more moist aloft, and also had a marine layer closer to the coast — so in a lot of ways, this setup has a higher potential than Saturday’s storms, which is saying a lot.

But the devil lies in the details, and there are a few factors that make this setup have a much higher bust potential than there was for Saturday’s storms. Saturday was pretty much a guaranteed setup to get a solid line of thunderstorms, but not truly good severe potential from I-95 and east. Wednesday will have much higher potential but also have a few more things that could go wrong and prevent widespread severe convection.

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2.23 PM All Zones: Very warm weather has arrived

A well discussed period of above normal temperatures has arrived throughout the Eastern United States today, and is gradually making its way northwards from the Mid Atlantic States into the Northeast States as well. A warm front, situated over the Delaware River Valley this morning, has shifted northwards passing through much of New Jersey. The front will gradually continue its trek northwards as the afternoon goes on today and will continue into New England.

This morning, low clouds and fog were widespread throughout the Mid Atlantic and New England as a cool flow on the north side of a warm front allowed for moisture to remain trapped in the atmosphere’s lower levels. The fog eventually lifted this afternoon and a change in wind direction will continue to aid in warmer air surging northwards. The fog may return tonight for some locations, particularly near the coast, as warm air continues to advect towards the area.

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2.22 PM Zone Update: Record-breaking warmth on the way

As a trough digs into the West Coast of the United States over the next 24 to 48 hours, a ridge is forecast to develop throughout the Central and Eastern United States. Southerly winds in the mid and low levels of the atmosphere will aid in the ridge moving northward and expanding, with anomalously warm air surging northwards from the Southern and Central US into the Eastern United States by the latter half of this upcoming week.

While the ridge is impressive in the mid levels of the atmosphere, the surface temperature response will be even more impressive. Temperatures on Thursday and Friday afternoon, throughout the Northeast (and especially in the interior) will average 20-30 degrees above normal averages for this time of year. In many areas, this will mean afternoon high temperatures in the 60’s and possibly even lower 70’s!

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