7:04 AM

I have to wonder after looking at the guidance over the past three days if this is going to be a theme for the winter to follow?  Model guidance took a big jump back away from the upper low, heavy rain event for Sunday.  I was originally skeptical of this solution in the first place, however when all the guidance jumps in one direction, usually that indicates that additional data was introduced to support the GFS solution.  Now I feel like Charlie Brown after Lucy pulls the football away.

6 AM Surface- Penn State E-wall

This morning, surface high pressure is building in as 3 hour pressure rises are being observed throughout the Northeast and Mid Atlantic.  The coastal low that developed off the New Jersey coast yesterday morning is now well to the east of the Mid Atlantic.  High pressure from southeastern Quebec is taking hold and will support a persistent easterly wind over much of the northern Mid Atlantic through tonight.

The water vapor satellite picture this morning shows a strong upper level ridge is building over much of the Mid Atlantic through the Southeast.  A few features I want to point out before going forward.  First, the Sub Tropical Jet

Water Vapor This Morning-NWS/NOAA

Stream appears alive and well with mid and high level moisture streaming north from the south Pacific into the Gulf Coast and Southeast.  This moisture advection is producing widespread showers and weak thunderstorms over the Mississippi Valley where lifting from the developing upper trough over the Rockies and southern Plains is developing.

Also if you examine the water vapor signatures closely, you can examine a clear divide between the air mass racing northwestward from Mexico and the air mass currently over the Mississippi Valley.  The upper trough and developing upper low over the Southwest is clearly starting to draw upon several different air masses over the next several days.

Upper Level Pattern Tomorrow- Penn State E-Wall

High pressure will remain in control over New England through Saturday morning.  I want to take a moment here ti make a point.  Many individuals were speculating a major warm up was on the way due to this ridge, but we can clearly see over the past several days that the duration of the warm conditions and above normal temperatures will last roughly one day.  The reason for the limited period of above normal temperatures is the position of the surface high pressure system.  The fact a ridge builds does not always mean that warm temperatures can be expected.  To make an accurate forecast, you have to look at the area of best convergence and confluence and in this case, that area is New England, which leads to a significantly cooler forecast than a high pressure position over the Mid Atlantic or Southeast.

Upper Level Pattern for Saturday-Penn State E-Wall

The high pressure system over New England will not keep the warm air at bay for much longer as the high pressure system shifts into the Atlantic on Friday night.  As a result, the easterly winds will veer to the south and allow for milder conditions to return.  A strong cold front will be approaching the New York City and Philadelphia metropolitan areas by Saturday afternoon, which will significantly enhance the southwesterly flow over the northern Mid Atlantic.  As a result, temperatures in the afternoon will be allowed to soar into the 60′s and 70′s under strong warm air advection.

As discussed in the opening, the change in the model guidance the past three days is rather striking.  What we have here is the model guidance, of all variety, having a difficult time handing the additional energy at the bas of the trough.  This morning, the GFS and other guidance now focuses this energy into a positively tilted line of PVA that looks to be very intense.  What I see out of this change is that the model guidance is trying to tell us that the base of this trough is going to be very energetic, but no clue how to handle that energy.  As a result, we get this change in the model guidance from strong troughs and slow moving cold fronts to deep upper lows and secondary lows.  Heavy rain events that impact the entire Northeast to just a simple cold front passage.

My thoughts is that the potential for cyclone genesis along this cold front over the Southeast is too high to ignore.  However, I never really bought into the whole major deep low idea over the eastern Great Lakes because the pattern is just too progressive.  So my forecast is that this cold front will slowly approach the Philadelphia and New York City metropolitan area late on Saturday night with waves of showers producing moderate to at times heavy rainfall.  A weak wave of low pressure will develop along the cold front on early Sunday morning around eastern Virginia and race northeastward under the influence of that additional energy over the Southeast.  Remember I pointed out the Sub Tropical Jet Stream this morning?  Well, that additional moisture source will be alive and well, which means that a period of steady rain is going to impact much of the forecast area, especially towards the coast, on Sunday morning followed by clearing conditions in the afternoon as the low pressure exits.

Now, I want to make a point that model guidance clearly does not show a coastal low of any kind at this time, however when you consider the air masses at play, the significant amount of energy available, and the moisture advection being supplied; the threat is there and the hints of a slowing cold front in a progressive pattern can only mean some sort of low pressure development off the Mid Atlantic coast is developing.  Not a major storm, but a pain in the neck for Sunday morning.  Then again, clocks go back so you might just sleep right through it!  Unless you have kids with a serious sugar rush that is.

Cool Canadian high pressure will dominate the weather pattern for the start of next week with scattered clouds, dry conditions, and cool temperatures.  High temperatures will average in the mid 40′s to mid 50′s (warmer towards the coast) with the average temperatures averaging 3 to 6 degrees below normal to start November.