Severe weather Thursday: Enhanced Risk

Good morning.

Today looks to be an active severe weather day, particularly in the upper Mid-Atlantic and central Appalachians, however it is certainly not a slam dunk forecast. A small area of opportunity exists as a weak cold front tracks across the area. The Storm Prediction Center has upgraded the threat to an enhanced level for today in an area including much of eastern and central Pennsylvania, western New Jersey and northern Maryland. Severe weather is also possible in the area around Baltimore and Washington, D.C. today. The greatest threat appears to be damaging straight-line winds, although a few tornadoes are also possible.

This afternoon, temperatures are expected to soar south of the frontal boundary. Highs could easily reach over 100 as far north as the DC area, and into the 90s into eastern Pennsylvania, according to the RAP model. Meanwhile, highs north of the front will be in the 70s and low 80s for the most part. That will allow for additional fuel, although cloud cover in the main threat area should reduce instability.


RAP model forecast temperatures at 4:00 pm EDT July 9. Notice 100+ reaching near DC.

Low level dynamics look fairly marginal according to the most recent model runs. Cloud cover is a potential limiting factor, which may reduce the threat and dynamics. The wind shear is impressive for July, but overall rather marginal for tornado setups, especially at the time of greatest heating, with models showing the greatest shear arriving this evening. The best tornado potential will likely be if the clearing can hold through the afternoon without additional storm activity. Nonetheless, the strong wind flow and high moisture should allow for wet microbursts and damaging winds.


Satellite image of the Mid-Atlantic at 9:45 am EDT July 9.

Despite the uncertainties, keep an eye on the sky and local conditions if living in that region. All thunderstorms are capable of dangerous lightning and flooding rains, especially in such a moist and humid air mass. There have been more fatalities in the US from lightning so far in 2015 than from tornadoes!

Forecaster Craig Ceecee

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