05/29/10  10:24 AM

The day has started out cloudy with a few showers, however conditions will improve the rest of the day.

The old back door cold front is now rebounding as a very slow moving warm front, however this front is not very strong nor is the frontogenesis organized.  What that means is that the lifting is not very well supported to produce any wide rainfall.  However, as the low clouds break up through the morning hours, the lower and mid levels of the atmosphere will warm leading to some slight destabilization of the atmosphere, and thus the risk of widely scattered to isolated showers.  Many locations today will have dry conditions with scattered to broken cloud cover, and that’s it.  So the day is not completely lost.

The good news is that this front is going to move off the coast this evening and with it all the clouds too.  Note the areas of clear skies over western Pennsylvania and the Ohio Valley this morning, that is tomorrow’s weather.  With the clear skies will come significantly warmer temperatures with highs in the 80′s and even some lower 90′s throughout the region.  Similar conditions can be expected on Monday as high pressure slides over the region.

The next threat for severe weather will come on Tuesday with the approach of a very strong cold front.  There are strong indications that there will be plenty of upper level dynamics or lifting to support a wide spread outbreak of strong to severe thunderstorms along and ahead of the cold front on Tuesday afternoon.  The timing of the cold front is still debatable, but the threat for severe thunderstorms appears to be growing with each model run.  I also expected temperatures to soar into the 80′s and 90′s ahead of this cold front along with dew points in the upper 50′s to upper 60′s, leading to a very humid day on Tuesday afternoon.

High pressure and the return of a less humid yet warm air mass can be expected on Wednesday and Thursday ahead of the next strong cold front for Friday.  Temperatures through the period will average above normal with highs in the 70′s and 80′s.

04/15/10  6:45 AM

Another excellent day is expected as high pressure slips south and east towards the Mid Atlantic coast with clear skies and temperatures warming into the 60′s and lower 70′s throughout the Philadelphia and New York City metropolitan area.

As high pressure gives way, a strong upper low over the northern Plains will drive through the Great Lakes and move towards the northern Mid Atlantic and New England over the next 24 hours.  This upper level low will support a warm front at the surface that will produce scattered showers on Friday afternoon followed by a cold front in the evening and overnight on Friday night.  As the upper low moves towards the New England coastal waters, a new coastal low will develop off the New Jersey coast, which will keep the threat of showers in the region through Saturday afternoon.

So, for today expect clear skies and a light northwesterly wind backing to the southwest.  Temperatures will range from the mid 60′s along the immediate coast to the lower 70′s over the Delaware River Valley and much of the New York City metropolitan area.  The coolest location will be central and eastern Long Island due to the developing southwesterly wind off the Atlantic.  Otherwise, an excellent day is expected.

Clouds will increase tonight, however precipitation will hold off through early tomorrow morning.  As lifting from the approaching warm front increases through the morning, showers will develop, however I do not expect the showers to be wide spread through the afternoon hours.

As the upper low approaches along with a cold front from the west, showers will become more widespread with even a few elevated thunderstorms possible.  The showers will move from northwest to southeast with the heaviest rain expected around mid night through early Saturday morning.  As a new low  pressure system develops along the New Jersey coast, showers will linger into Saturday morning.

The atmosphere will remain unstable through the rest of the day on Saturday into much of Sunday with widely scattered to isolated showers expected.  Otherwise variable cloud cover and cool temperatures will be the theme this weekend with high temperatures struggling in the 50′s.

The weather will improve significantly for next week as high pressure at the surface and aloft takes hold.  A northwesterly flow will remain in place, however skies are expected to be clear with little if any precipitation expected.  Temperatures will moderate through next week into the 60′s and lower 70′s.

A detailed seven day forecast can be found here.

8:00 AM

The coastal low off the Virginia/North Carolina coastal waters this morning continues to slowly exit to the east-northeast this morning.  The coastal low actually has ended up slightly closer to the coast than expected, but is now moving into the Atlantic with diminishing impacts through the rest of the day.  However, much of the northern Mid Atlantic has felt the influences of this low pressure system more than most thought, as the precipitation shield expanded further north and west than what has been suggested on guidance, which was warned by me for several days.

The majority of accumulating snowfall has already occurred for many locations west of the Delaware River with on average 2 to 4 inches of snow has accumulated has the precipitation shield expanded north and west last night.  Through this morning, snow will continue to taper off to scattered snow showers with little significant impact to travel conditions.

Closer to the coast, a mix of rain and snow is moving through the region with temperatures remain above freezing for most locations.  An accumulation of 1 to 4 inches is expected over the Hudson Valley and Connecticut where temperatures will remain at or just below freezing while the immediate New York City metropolitan area through the northern suburbs of Philadelphia will have accumulations of around 1 to 3 inches, mostly on colder surfaces.

Along the coast, a mix of rain and snow will continue, but given that none of the snow is accumulating, the precipitation might as well be rain.  Precipitation totals through this afternoon will range from a half an inch to as much as an inch along the immediate coastline.  Winds will be sustained at 15 to 30 mph with higher gusts through this afternoon.

The most impressive impact from this storm will be the coastal flooding and strong winds along the coast and over the coastal waters.  A coastal flood warning has been issued for all of the New Jersey coast and a coastal flood advisory has been issued for Long Island through tonight.  As the low pressure system continues to intensify, gale warnings for sustained wind of 20 to 35 mph and gusts over 40 mph has been issued for all of the New Jersey coastal waters through tonight.

Once this low pressure system exits tonight, the weather pattern will become much more tranquil with a steady moderation in temperatures expected.  High pressure will become established over the Tennessee Valley tomorrow through Sunday with dry conditions, scattered clouds, and temperatures averaging near normal with afternoon highs in the upper 30′s to mid 40′s through the period and lows in the upper 20′s to mid 30′s.  Temperatures will moderate into the 40′s and lower 50′s by this weekend.

A cold front will move through the northern Mid Atlantic from the Great Lakes on Monday night and Tuesday morning with scattered showers, mostly rain, and slightly cooler temperatures.  However, no significant turn to colder weather is expected over the next seven days.

7:49 AM

A strong upper low over northern Virginia this morning will move through New Jersey this afternoon with bands of light to moderate snow throughout the Philadelphia and New York City metropolitan areas.  This upper low will support the intensification of an area of low pressure to the east of Monmouth County, New Jersey which will move towards the southern New England coastal waters by this evening.

A band of moderate snowfall is developing over Maryland and southeastern Pennsylvania this morning that is expected to move through southern and central New Jersey through late this morning and continue through Long Island this afternoon.  Another band of snow is developing over central Pennsylvania that is expected to move through the entire northern Mid Atlantic through this evening.  Finally, snow is also developing with the coastal low over portions of the Hudson Valley, Connecticut, and southern New England.  This storm is rather disorganized right now with several parts of the storm coming together over the region, but will become a well organized storm to the east of northern New England by late tonight.

Snowfall totals through the rest of the day will depend on the development of the various features discussed above.  As such, lesser amounts are expected to the southwest with higher snowfall totals of over 4 inches can be expected over Connecticut.  Overall however, most locations through the Philadelphia and New York City metropolitan areas will range from 1 to 4 inches of snow as these bands move through.

Persistent cold air advection will hold temperatures in the lower 30′s this morning and then fall into the mid to upper 20′s throughout the region this afternoon.  Wet surfaces this morning will freeze over, making the threat for black ice and thus slippery conditions a significant concern for this evening’s rush hour.

After this low pressure system exits by this evening, high pressure will remain in control late tonight through Saturday with scattered clouds and temperatures ranging from the upper 20′s to mid 30′s for highs and upper 10′s to upper 20′s for lows.  Overall, temperatures will average slightly below normal.  A few scattered snow showers will be possible each day due to weak disturbances passing through the northern Mid Atlantic, however accumulations from these disturbances will remain below 2 inches throughout the region.

Another major winter storm appears to be developing by the start of next week.  There are strong hints of a major Nor’ easter impacting the northern Mid Atlantic Monday afternoon through Tuesday evening with strong winds, heavy precipitation, and cold conditions.  At this time precipitation type is in question due to the uncertainty of the exact track and the state of boundary level conditions.  However, the potential for significant snowfall throughout the region does exist and this storm will have to be monitored for impacts ranging from coastal flooding to high snowfall totals.

5:35 AM

The coastal low this morning has moved further south than forecasted and as a result the brunt of the light precipitation expected to impact the Philadelphia metropolitan area and southern New Jersey will remain off the coast.  While temperatures are cold enough to support a frozen mix of precipitation, the steady precipitation has tracked just off the southern New Jersey coast and is expected to remain off the coast through the morning.  Scattered rain and snow showers will move through the Philadelphia metropolitan area and central/southern New Jersey through the early afternoon hours, however no accumulation is expected from these showers.  The New York City metropolitan area will remain dry yet with broken cloud cover.

One thing that is not lacking is the ability for the upper level disturbance driving towards the Mid Atlantic coast to produce strong lifting.  Cloud tops continue to rapidly cool off the North Carolina and Virginia coast suggesting strong lifting is occurring.  The coastal low is rapidly deepening with surface pressures down to 998 MB at the center of this low pressure system.

The low will exit to the east with some breezy conditions through the early afternoon hours.  The rest of the day will have clearing skies and temperatures in the 40′s with no significant impacts expected.

Additional updates for the weekend and early next week on the way!