Finally a day without thunderstorms!  However, there is still plenty to discuss this morning, especially with the long range forecast!  Are you a Premium Member?  Get the details on Premium Membership here!

10:06 AM 07/23/10

The brief rest from the high humidity is rapidly coming to an end as a warm front approaches from central Pennsylvania this morning.

The warm front is not only going to bring the return of high heat and even higher humidity to the Philadelphia and New York City metropolitan area, but also a threat for severe weather.

This morning an area of showers and embedded thunderstorms will move through northeastern Pennsylvania, northern New Jersey, the Hudson Valley, and Connecticut.  This rainfall is from the advancing 850 MB warm front, which has already moved north of much of the Northern Mid Atlantic, thus the lack of rain over the Philadelphia metropolitan areas and for much of the southern portions of the New York City metropolitan areas.  However, the real threat is behind the surface warm front.  Note the surface map to the left.  Behind this warm front temperatures and dew points rapidly spike and the atmosphere becomes very unstable.  Helicity, a measure of low level shear, also rapidly increases behind the passage of the warm front, and that is where we need to be concerned!

When the warm front clears, I expect the clouds to rapidly break up and temperatures to climb into the 80′s and 90′s.  As the low levels rapidly warm, the atmosphere will become highly unstable and with that thunderstorms will begin to form.  I expect the thunderstorms to initially develop over central Pennsylvania and march east.  The highest threat for severe weather will be over eastern Pennsylvania and the Delaware River Valley as these locations will be under the influence of the hot, humid, and unstable air mass far longer than areas to the east.

The thunderstorms will move through this evening, weakening after sun set.  By tomorrow morning, the new hot and humid air mass will be firmly in place with low temperatures in the 70′s, likely reaching 80 before 10 AM for many locations.  Temperatures will sky rocket tomorrow into the mid 90′s to lower 100′s along with dew points in the upper 60′s to lower 70′s.  The heat index will easily exceed 100 degrees and possibly approach 110 degrees in some urban locations.

A cold front is expected for Sunday afternoon with another round of strong to severe thunderstorms, fueled by a highly unstable, moisture loaded air mass ahead of the cold front.  The good news is that after the thunderstorms exit, the dew points will crash and the high humidity will come to an end.  High pressure will dominate throughout the Northern Mid Atlantic on Monday and Tuesday with clear skies, highs in the upper 80′s to lower 90′s, and dew points in the 50′s and lower 60′s.

Through the rest of next week, temperatures will remain in the upper 80′s to lower 90′s range for highs, mid 60′s to lower 70′s for lows, and moderate to high humidity.  The influence of the remnants of Tropical Storm Bonnie will begin to be felt towards the end of next week as showers and thunderstorms will increase in coverage ahead of a series of disturbances and cold fronts that will attempt to move through the region.

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

It’s hot and humid this morning and conditions are only going to get worse.  Today, in the Premium Discussions I explain why the weather is only going to get hotter and what influences this will have on the Tropics!  Are you a Premium Member?  Get the details for Premium 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!

The summer pattern continues!  Is there any end in site?  Get the latest information and analysis with the Premium Discussions at NY NJ PA Weather!  Not a Premium Member?  Get the details here!