06/15/10  8:50 AM

Today is likely to be the most comfortable day for the next 15 days if not more as the new summer pattern becomes established over much of the eastern United States.

The water vapor satellite picture this morning really tells the story behind this developing pattern.  There is a saying that a picture tells a thousand words, but I’m going to add a few more.  Note the trough over New England this morning.  This trough is associated with the negative NAO pattern that is shift to the east for the next several days if not weeks.  Right now, that same trough is producing a northwesterly flow at the upper levels and supporting a cool northerly flow at the surface, all of which is keeping relatively dry air over the region.  While clouds will slowly increase through the day, temperatures and dew points will remain very comfortable with highs in the 70′s and 80′s and dew points in the 40′s and 50′s.  A perfect June day!

However, note how mid level moisture (the white and blue colors) have started to move north and northeast from the Ohio and Tennessee Valleys into the northern Mid Atlantic and eastern Great Lakes.  As the trough becomes established over the Canadian Maritimes and another trough sets up over the Mississippi Valley and Plains, an impressive ridge is starting to develop over the Southeast.  This ridge will continue to build over the next several days, and force the stationary front over Virginia this morning to the north through the northern Mid Atlantic.  This newly enforced warm front will bring showers to the region by tomorrow morning through tomorrow evening, but the important detail is that this warm front will move north of much of the northern Mid Atlantic with the exception of portions of northern Connecticut and the Hudson Valley.  Behind this warm front is a building tropical air mass from the Gulf of Mexico that will support high temperatures in the 80′s and 90′s along with dew points in the 60′s and 70′s, in other words hazy, hot, and humid air is on the way!

Let me take a step back here and explain why this evolution is important.  For several weeks I’ve been putting out the call to all Premium Members that a hot, humid, and active pattern is going to become established over much of the East, and that this pattern will evolve in June and become established through much of the summer.  The details of this evolution can be found in the Long Range Thoughts Page, where the major change in the pattern is that the ENSO El Nino pattern has collapsed and the ENSO LA NINA pattern is now quickly becoming established.  This pattern supports a ridge building in the East.  Further, the higher latitude blocking is not expected to weaken due to certain stratospheric influences, which will keep the negative NAO pattern in place over the Atlantic.  All of this points to a western Atlantic ridge becoming established, which has been advertised in the teleconnections, but not the models for several weeks now.  The question was not if, but when the hot and humid weather pattern would set up.

However, with hot and humid weather conditions will also come thunderstorms from Thursday on through next week.  The fact that a trough will be over the Canadian Maritimes and at times over northern New England means that mid level disturbances will drive through the northern Mid Atlantic, which will lead to an out break of strong to severe thunderstorms ahead and along these mid level disturbances.  The forecasting of the track, intensity, and influence of these disturbances will have to be monitored on a day by day to even hour by hour basis.

So basically from Thursday on expect a regime of temperatures in the 80′s and 90′s for highs, mid 60′s to lower 70′s for lows with plenty of humidity in the air.  There will be a risk of thunderstorms, sometimes rather severe, each afternoon especially away from the coast.

For details on the next seven days for your location, visit the NY NJ PA Weather 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!

06/13/10  11:07 AM

For those waiting for those muggy days of summer, well your wait is over!

The key to this forecast for the whole week is the stationary front over the Ohio Valley through the southern Hudson Valley and southern New England.  That stationary boundary is the dividing line between the muggy, humid conditions building over much of northern Mid Atlantic down through the Gulf Coast and the more comfortable weather conditions over the eastern Great Lakes and New England.  Naturally, model guidance is having a fun time handling this feature as each disturbance will alter the exact position of this boundary via various mesoscale influences.  Combined that dubious influence with mid level disturbances, and we have a forecast full of volatility and plenty of thunderstorms!

Okay, so let’s nail down some facts here.  First and foremost, this pattern is not going to be going away any time soon.  In other words, the northern Mid Atlantic is going to be caught in this constant battle of air masses for what I consider the foreseeable future.  The ridge that is being established over the western Atlantic is gaining more and more support from various teleconnections, which I’ve been talking about for weeks in the Premium Members Long Range Thoughts discussion.  So, we know that there will be a constant invasion of warm, sometimes hot, and humid weather conditions over the northern Mid Atlantic for some time.  I think the hottest weather conditions will be over the Gulf Coast where the air mass will have the strongest support, so I do not expect an outbreak of 100′s for the region any time soon.

Instead, what we have at the surface is a reflection of a battle going on at 500 MB.  That persistent negative NAO pattern that gave the northern Mid Atlantic plenty of winter storms a few months ago, has not gone away.  Instead, the upper level pattern has simple shifted to a higher latitude, which will keep a trough over eastern Canada and the Canadian Maritimes through much of the summer.  That means that cold front will continue to attempt to drive through the northern Mid Atlantic only to stall or weaken to the point where only a slightly drier air mass follows only to be quickly replaced by higher humidity once again.  As a result, through this weekend and into next weekend, you can bet on the same story again and again.  Variable cloud cover, risk of fog in the morning due to all the low level moisture in the air, and a risk of widely scattered to isolated thunderstorms each day.

The cold fronts in this pattern will end up being more wind shift lines rather than true air mass changes.  For example, the HPC has a cold front drive south into the southern Mid Atlantic, however high temperatures are just as warm today as in Tuesday.  The only real change, if any, is that the winds from the northwest and west as another high pressure system slides east.  Dew points drop for one day below 60 degrees before rebound the very next day into the lower to mid 60′s once again.  The influence of the new air mass is temporary, if anything.  In fact, I would not be surprised if the humidity returns much faster by Tuesday evening or Wednesday morning.

The point I’m trying to make is that I believe we have our established summer pattern in place now.  Sure, there will be some tweaks here and there, but you’ll find that I will be less inclined to change the overall thinking of my forecast regardless of model changes.  The reason is that the pattern drivers and their characteristics have been established and what they are going to produce is a pattern that is humid and warm to hot with a constant threat of thunderstorms.

For details on the next seven days for your location, visit NY NJ PA Weather Seven Day Forecast!

05/11/10  7:54 AM

After a cold start with temperatures in many locations bottomed out into the lower to mid 30′s for lows, a developing southerly wind will warm temperatures back into the 50′s and lower 60′s by this afternoon.

High pressure is slowly moving north and east of the Philadelphia and New York City metropolitan area this morning as a warm front over the Tennessee River Valley approaches the region.  Clouds will increase through the day as winds veer to the southeast and south through the day.  Overcast skies can be expected by the late afternoon hours with showers approaching the Philadelphia metropolitan area by late tonight.

The warm front is expected to stall just to the south of New Jersey as the high pressure system over New England will prevent the warm front from moving much further.  As a result, an east to northeasterly wind will develop and mature over the northern Mid Atlantic late tonight through Friday morning, which will draw low level marine air from the Atlantic into the region.  Waves of low pressure will travel along the stationary front through the period with areas of steady rainfall followed by variable clouds and drizzle.  With the easterly fetch and overcast skies, temperatures will struggle in the 50′s both tomorrow and on Thursday.

The upper level disturbance and main surface low associated with this warm front will exit off the Delaware coast on Friday morning with showers lingering until the early afternoon hours followed by clearing skies.  As skies clear, temperatures will be able to jump rapidly into the 60′s and 70′s by Friday afternoon.

High pressure will build in from the Ohio Valley on Friday evening and will remain in control through the weekend with clear skies and temperatures in the 60′s, 70′s, and potentially lower 80′s throughout the region.

For details for your location, check out the seven day forecast!

04/21/10  4:50 PM

An upper level disturbance moving through southern Pennsylvania, southern New Jersey, and the DELMARVA Peninsula this afternoon.  The upper disturbance has destabilized the atmosphere leading to showers and strong thunderstorms to develop over much of central and eastern New Jersey.  Through this evening, the showers and thunderstorms will move east-northeast through the entire Philadelphia and New York City metropolitan area.  These thunderstorms will be capable of heavy downpours, occasional lightning, small hail, and wind gusts up to 40 mph.

The showers will linger through tomorrow morning as the disturbance exits followed by clearing skies as high pressure takes hold.  High pressure will remain in control tomorrow afternoon through Saturday with clear skies, light winds, and near normal high temperatures in the 60′s and even a few lower 70′s.  However, conditions go downhill after Saturday evening.

The combination of a back door cold front dropping south and west through New England and a strong upper level low over the Mid West will lead to a stationary front forming just to the south of the Philadelphia metropolitan area.  The upper low to the west will open up on Sunday, sending a series of disturbances along the stationary front, leading to waves of moderate to heavy rainfall on both Sunday and Monday.  Between waves of steady rain, the cool marine layer in place will support overcast skies and drizzle through both days.

On Tuesday, the upper disturbance will exit off the Mid Atlantic coast and interact with a strong upper level disturbance over Quebec.  The combination of the two disturbances will lead to a coastal low forming well to the east of New Jersey.  While I don’t expect steady rain with this low pressure system at this time, I will keep the threat of showers in the forecast.

High pressure will finally take hold on Wednesday with clearing skies and temperatures rebounding to near normal levels.

For a detailed seven day forecast, go here!