08/23/10  5:20 PM

A warm front has been slowly moving through the Philadelphia and New York City metropolitan area today with clouds and areas of showers, especially over the northern tier.  Behind this warm front is a hot, humid, unstable, and very dynamics air mass.

As the warm front moves northeast this evening, the first observation you’ll notice is a big jump in humidity and temperatures, even this evening.  The normal decrease in evening temperatures will be overwhelmed by the strong warm air advection impacting the region.

Meanwhile, a strong disturbance over western and north-central Pennsylvania is going to move through the Northern Mid Atlantic tonight.  In normal circumstances, most of the strong to severe thunderstorms would weaken as the atmosphere stabilizes.  However, in this case the atmosphere will remain unstable.  Additionally, low level shear will help to enhance thunderstorms, cause these thunderstorms to rotate.

While I do not expect widespread severe thunderstorms at this time, there is a slight risk for isolated severe thunderstorms this evening.  These thunderstorms will be capable of very heavy downpours, frequent lightning, wind gusts exceeding 50 mph, small hail, and even an isolated tornado.

I will be keeping track of these thunderstorms and should any thunderstorms reach severe levels or produce a potential tornado, I will update immediately!

Aside from the thunderstorms, there is also the return of oppressive heat to the Northern Mid Atlantic.  Temperatures tomorrow morning will only fall into the lower to mid 70′s and will likely pass 80 degrees in many locations by 10 AM.  High temperatures tomorrow will rocket into the mid 90′s to lower 100′s throughout the New York City and Philadelphia metropolitan area.  These high temperatures combined with dew points in the 60′s and 70′s will lead to a heat index ranging from 100 to 110 degrees.  The hottest locations are likely to be located in urban locations and the Delaware River Valley.  In addition to the heat will be the threat of isolated strong to severe thunderstorms in the afternoon and evening.

A cold front will follow on Sunday afternoon with another round of strong to severe thunderstorms.  This cold front will bring some relief in dropping the high humidity to a more comfortable level by Monday morning.  Tranquil conditions are expected on Monday and Tuesday before the return of hot and humid conditions once again with highs in the mid 80′s to lower 90′s, lows in the 60′s and lower 70′s, and a risk of thunderstorms each day.

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9:13 AM  07/21/10

Those looking for a break in the heat and humidity will continue to remain disappointed.  Of course, I also know plenty of people calling this the best summer in years as they flock to the beach.  You know who you are!

However, with the hot and humid conditions also comes the continued threat of strong to severe thunderstorms throughout the New York City and Philadelphia metropolitan area.  The best dynamics for severe weather will be to the north of the Northern Mid Atlantic as an upper level disturbance enhances lifting over the eastern Great Lakes, the Mohawk River Valley, and much of New England.  However, with the air mass in place already unstable, moisture loaded, and showing signs of developing low level shear; even a weak disturbance or mesoscale boundary will ignite strong to severe thunderstorms throughout the region.

The strongest thunderstorms this afternoon will feature very heavy downpours, frequent lightning, large hail, and wind gusts over 50 mph.  There is an isolated threat for a tornado, but I think that threat will be focused more to the north with the strong upper level disturbance.  Still because of the nature of these thunderstorms, super cell and isolated, the threat for an isolated tornado can not be ruled out.

The thunderstorms will reach peak intensity over the Northern Mid Atlantic after 2 PM and continue to impact the region through 8 PM when I expect most of the thunderstorms to rapidly weaken.  Meanwhile, temperatures will soar into the upper 80′s to mid 90′s with high humidity creating a heat index in the mid to upper 90′s.

The thunderstorms will exit this evening followed by a return to more tranquil weather conditions into tomorrow morning.  Once again, hot and humid weather conditions will continue for tomorrow afternoon, however a lack of mid and upper level disturbances will mean thunderstorms will be isolated at worst.

Hot and humid conditions can be expected through this weekend with the threat of temperatures hitting the upper 90′s to lower 100′s in a few isolated locations in the Delaware River Valley and urban locations.  There will continue to be a threat for strong to severe thunderstorms as well each day through next week as cold front fronts attempt and fail to move through the region.

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The Philadelphia and New York City metropolitan areas have had a very active afternoon with heavy rain, flash flooding, and strong winds.  What else can the region expect going into the evening?  Get the details with the Premium Discussions!  Are you a Premium Member?  Get the details for membership here!

4:30 PM 07/12/10

A strong disturbance exiting from the Ohio Valley this afternoon will drive towards the northern Mid Atlantic this evening and overnight.  As the disturbance moves towards the Philadelphia and New York City metropolitan areas, a line of strong to severe thunderstorms will march east towards the coast.

These thunderstorms will be capable of very heavy downpours, frequent lightning, large hail, and wind gusts over 50 mph.  These thunderstorms over central Pennsylvania have already produced hail over an inch in diameter and wind gusts over 60 mph.  Now, I do expect some weakening of these thunderstorms, however the strengthening low level jet stream at 850 MB will keep the threat for these thunderstorms to produce very heavy downpours and strong wind gusts, potentially up to severe levels through the overnight hours, so use caution when driving this evening.

Tomorrow another round of strong to severe thunderstorms will impact the northern Mid Atlantic as a warm front moves through that will mark a drastic increase in dew points throughout the region.  Thereafter, a hot and humid air mass will take hold through this weekend and into next week.  A series of cold front will attempt to move through the region, only to fail, but still will keep a threat for strong to severe thunderstorms each afternoon through the period.

For more details on your location, visit the NY NJ PA Weather Local Seven Day Forecast!

06/26/10  11:04 AM

Unlike last summer, this summer is full of plenty of hot and humid days.  Today is yet another one as high temperatures are rapidly rising into the 80′s and 90′s already!

High pressure over the southern Mid Atlantic will continue to slide east towards the coast by this afternoon.  As a result, winds are shifting to the southwest throughout the region, which is transporting an increase in low level moisture.  In other words, higher humidity!

A weak disturbance over the Great Lakes will continue to weaken under the influence of high pressure over the region.  While an isolated thunderstorm is possible over portions of the Hudson Valley, and interior Connecticut, the majority of the New York City and Philadelphia metropolitan area will remain dry.

I expect the hazy, hot, and humid conditions to continue through tonight on through tomorrow with little sign in the pattern breaking over the region.  There will be a better chance of strong to severe thunderstorms tomorrow afternoon as the center of high pressure will be in the Atlantic and disturbances will have a high potential of reach the northern Mid Atlantic.  These thunderstorms, though isolated, will have the potential to be rather severe.  Don’t be surprised if a few severe thunderstorms produce wind gusts over 60 mph along with large hail as the atmosphere will be rather unstable!

A strong cold front is expected on Monday with widespread showers and strong to severe thunderstorms.  This set up strongly reminds me of Thursday afternoon.  However, I do think the models are over playing the strength of the cold front, much like Thursday’s event.  I think a major player for the event on Monday afternoon will be the influence of convection the day before.

The humidity should drop on Tuesday behind the cold front, but not the heat as temperatures will remain in the 80′s with a few lower 90′s possible in portions of the Philadelphia metropolitan area, especially the Delaware River Valley.  The humidity will not be gone for long though as the southwesterly flow return for Wednesday and continue right on through Thursday afternoon ahead of another cold front.

Now, this set up for the end of the week sure looks familiar.  Once again models are advertising a deep trough, a big drop in 850 MB temperatures, and a rapid decrease in dew points.  I am not buying it.  The seasonal trends are an important signal, and those trends are to stay warm, which I am doing in the forecast.  While Thursday evening and Friday will see a nice drop in dew points and a slight decrease in temperatures, I’m thinking the heat and humidity will be right back by Saturday.

For details on your location, check out the NY NJ PA Weather Seven Day Forecast!