07/20/10  9:12 AM

After a very active severe weather day yesterday, another risk of thunderstorms is developing to the west of the Philadelphia metropolitan area.  However, unlike yesterday, severe thunderstorms will be isolated in nature rather than the wide spread event from yesterday.

A strong upper level disturbance is moving east towards the Philadelphia and New York City metropolitan area.  This area of showers and thunderstorms is expected to impact the Northern Mid Atlantic this afternoon with period of heavy rain along with embedded strong to severe thunderstorms.

The majority of the thunderstorms will remain below severe levels, however a few isolated thunderstorms capable of wind gusts over 50 mph will be possible as the air mass ahead of this disturbance rapidly destabilizes.  The air mass will become unstable due to clear skies over the region now allowing temperatures to rapidly warm into the 80′s and eventually lower 90′s ahead of the thunderstorms.

This disturbance will exit into the Atlantic by later this afternoon with clearing skies by the evening hours.  The rest of the week will continue to feature the same air mass regime with temperatures in the 80′s and 90′s for highs, lows in the 60′s and 70′s, morning fog, and afternoon thunderstorms.  Each upper level disturbance that moves through the northern Mid Atlantic will have the potential to produce strong to severe thunderstorms as the lower levels of the atmosphere will have plenty of low level moisture to feed the developing thunderstorms.

Towards the end of this weekend, a stronger cold front is expected to move through the Northern Mid Atlantic.  I suspect the model guidance is playing up the strength of the cold front too much, however a more wide spread threat of strong to severe thunderstorms can be expected on Sunday afternoon into Monday morning.  Otherwise, I see no change in the overall characteristics of this pattern.

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

9:42 AM 07/19/2010

Strong to severe thunderstorms have already developed throughout the New York City and Philadelphia metropolitan area this morning and more are on the way!

The important feature to keep an eye on once the first batch of thunderstorms exits to the east is the clearing skies over central Pennsylvania.  This area of clearing skies is key.

When thunderstorms develop and move through an area in the morning hours, the air mass tends to stabilize due to the rainfall cooling the mid and lower levels of the atmosphere.  In order to destabilize the atmosphere, the atmosphere must warm.  Well, here comes our heat lamp!

The clearing skies to the west will allow temperatures to spike quickly through the 70′s and into the 80′s and 90′s by this afternoon.  Meanwhile, a disturbance over the Ohio Valley will approach from the west.  This disturbance will enhance lifting throughout the Northern Mid Atlantic and produce a line of strong to severe thunderstorms this afternoon.  These thunderstorms will redevelop after 2 PM and will impact the Philadelphia and New York City metropolitan area through this evening.

Even with the passage of these thunderstorms, there will be no relief to the heat and humidity plaguing the Northern Mid Atlantic this month.  The disturbance will bring little in the way of relief with high temperatures through this week in the upper 80′s to mid 90′s throughout the region along with high levels of humidity.  Each afternoon will carry a threat for strong to severe thunderstorms as several disturbances attempt to move through the region.

By this weekend I expect temperatures to become even hotter with a higher threat for highs in the mid to upper 90′s as July comes to an end.

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

06/14/10  9:22 AM

The stationary front that was to the north of the northern Mid Atlantic yesterday has sank to the south of the region this morning, which has a slightly cooler but just as humid air mass in place over the region.

The stationary front will remain south of the Philadelphia and New York City metropolitan area through tomorrow morning, which will keep variable cloud cover over the region through tomorrow morning.  The best lifting will remain to the south of the region, which will lead to only widely scattered to isolated showers through tomorrow morning.  Most locations will remain dry.

The stationary front will rebound to the north tomorrow afternoon with increasing clouds and showers tomorrow night through Wednesday.  The rain will become steady at times, especially along the coast on Wednesday afternoon.  However, as the warm front lifts north, winds will veer to the southwest and skies will begin to clear towards Thursday morning.

High pressure will take hold from the Tennessee Valley by Thursday evening with clearing skies and dry conditions.  High pressure will remain in control Friday through the weekend and into Tuesday.  However, with high pressure will come an established southwesterly flow which will bring hot and humid weather conditions to much of the northern Mid Atlantic.  Mid level disturbances will move through the region each day, leading to isolated showers and thunderstorms in the afternoon.  Otherwise, dry conditions can be expected with at times uncomfortable conditions.  Father’s Day is looking like a very good day to take your father to the beach!

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

06/07/10  7:55 AM

After a rather active period of weather the past several days, high pressure is building in and providing more tranquil weather conditions with considerably less humidity.

A weak disturbance at 700 MB will move through the Philadelphia and New York City metropolitan areas today with a few clouds, but no precipitation.  I expect clouds to increase around 11 AM from west to east, however as the disturbance progresses to the east, subsidence will cause the clouds to break up leading to more fair weather clouds than anything else.  Otherwise, high temperatures will rise to normal levels in the 70′s and dew points will remain low in the 40′s and 50′s.  Today will be on of those days where you walk outside and just feel refreshed!

Similar conditions are expected tomorrow with only a few scattered clouds and dry conditions.  Temperatures will remain near normal with lows in the 40′s and 50′s and highs in the upper 60′s to upper 70′s for the region.  However, the excellent weather will not last for long.

A disturbance over the Plains this morning will move east over the next two days.  The disturbance will weaken by the time the upper trough reaches the northern Mid Atlantic, however enough moisture advection ahead of the surface low will support the development of scattered showers throughout the region on Wednesday afternoon through Thursday morning.  I don’t expect a wash out, but still the shift in winds from the northwest to east will prompt a cooler regime with overcast clouds.  Temperatures will struggle in the 60′s and lower 70′s as a result, especially along the immediate coast.

High pressure will return on Thursday night with clearing skies and will remain in place through Saturday with clear skies and moderating high temperatures back into the 70′s and 80′s.  Now, that disturbance that exits on Thursday morning is going to have a significant impact on the end of next weekend and into next week.  If the disturbance amplifies off the New England coast, a deeper upper low develops over the Canadian Maritimes and as a result temperatures remain near normal.  However, if the disturbance remains weak and sheared, than the ridge over the Southeast can build north and with it higher humidity and high temperatures in the 80′s and 90′s.  There is some uncertainty in the forecast.

For details on the next seven days for your location, check out the NY NJ PA Weather seven day forecast!

06/01/10  7:52 AM

When you walk outside this morning, you might feel like the world is weighing on your shoulders.  Don’t worry, this is more than just the fact you are coming back to work after a great holiday weekend.  That’s the water vapor in the air mass this morning with dew points already in the lower to upper 60′s throughout the northern Mid Atlantic, and that is an important clue to the potential development of thunderstorms this afternoon.

A weak cold front is to the west of the Philadelphia and New York City metropolitan areas this morning.  This cold front is not an impressive feature, but is strong enough to create some lifting that will help ignite the thunderstorms.

The lower levels of the atmosphere are becoming unstable and instability will increase as the low level clouds continue to clear and the sun is able to continue to warm an already humid air mass.

The thunderstorms will develop after 1 PM over eastern Pennsylvania and march east through the northern Mid Atlantic this afternoon and evening.  With plenty of low level moisture in place, these thunderstorms will be capable of very heavy downpours with rainfall rates of an inch to two inches per hour not out of the question.  As a result, I think there is a threat for flash flooding with these thunderstorms.  Further, given the fall in temperatures at 500 MB, the environment will be capable of supporting thunderstorms that produce small to large hail, down burst wind gusts over 50 mph due to rapidly sinking rain cooled air, and frequent lightning.  The thunderstorms will exit into the coastal water by this evening with clearing skies expected by mid night.

After the cold front exits, there will not be much change in the overall air mass. With a lack of rainfall expected, high temperatures on Wednesday and Thursday are expected to be higher with temperatures expected to reach the lower 80′s to lower 90′s over many locations along with dew points in the 60′s.  So the hot and humid conditions are not expected to abate for much of this week, but of course we are in June so this isn’t out of the ordinary.

Another cold front will attempt to put an end to the hot and humid conditions with another round of showers and strong to severe thunderstorms once again.  Like the previous cold front, this one will not have a strong upper level support to change the air mass, so I don’t expect much change in the overall air mass once the cold front leaves, just another threat for severe weather.

Next weekend will feature more high temperatures in the 80′s and 90′s with high humidity, especially on Sunday afternoon.  I can’t rule out an isolated thunderstorm, but overall the region will remain dry.  Another cold front will approach by Sunday evening, and the latest guidance suggest that this cold front will have the backing of a strong Polar air mass.  However, I should stress that previous guidance seven days out also had today’s cold front with similar support, so I would not be surprised if model guidance is over enhancing the Polar air mass by next week.

For details on your locations forecast, check out the NY NJ PA Weather seven day forecast!