Windy today and cooler tomorrow, weekend looks seasonable

Today we will continue to clear out as a dynamic shortwave trough moves out of the Northeast US.  Thunderstorms erupted over western Maryland and the DC region last night.  This front moved through late this morning.  Clearing will continue along with the windier conditions today through tonight, before subsiding tomorrow before another clipper  moves by to the north of the region.  The advertised potential coastal storm for Friday is no longer, upstream ridging pattern is not going to cooperate for us.  I am eyeing the 26-29th for a potential stormy period.  00z GFS and 12z GFS both hinting at a big snowstorm potentially for the interior region and rain/snow for the coastal plain.  However models are very unsure what is going to happen beyond 5 days.  A short reprieve from the colder air arrives Monday/Tuesday before a front moves through the region sometime Tuesday night into Wednesday morning ushering potentially a colder air mass into the region.  Right now weather should remain quiet for the weekend.  I will have another update tonight.

Evening Weather Update

Tonight will feature a rather warm and wet soggy night here in SNE.  Cold front will begin to approach the region as showers and storms increase in coverage across the area overnight tonight into tomorrow morning.  Some thunderstorms are possible, especially if we can get some good jet dynamics into the region and good lift.  Right now heavy downpours will be the theme across the area and into tomorrow.  Heavy rain will produce street flooding.  Interior of the SNE could see isolated rain amounts up to 2", with widespread .5 to 1" of rain expected elsewhere.  Tomorrow will feature the same weather pattern with above normal temperatures and a rather rainy day.  Eastern sections will clear out last as the front comes through here later on in the day.  Cooler air will begin to spread into the region on Thursday with highs on Friday slightly below normal.  Temperatures this weekend will be right around the normal for this time of year upper 40s to lower 50s, followed by slightly above normal temperatures into early next week ahead of the next front which should begin to bring in much cooler air masses into the region.  Perhaps our pattern changer.  I will have more on this tomorrw.

Wet tonight into tomorrow, cold arrives on Friday

Right now it is mostly cloudy in SNE with just a few passing showers we received last night are way out of the picture.  Heavier rains from a developing low pressure system originating in the Gulf of Mexico is moving into the TN Valley now and will continue to move the NNE or NE into western NY in the overnight.  Heavy rains and possible thunderstorms will arrive tomorrow morning and last through the afternoon before ending.  Heavy rains will likely cause some localized street flooding.  Cold air advection will build into the region as the front lifts northeastward, and colder than average temperatures will begin to build into the region.  Right now the weekend looks rather cold and dry.

00z/06z model update

Updated forecast for the region:

Highs the next several days: today into Wednesday will be in the upper 50s and lower 60s as return flow around a large surface high will be out of the south or southwest, before a major storm system moves to the west of the region.  This surface low will bring through a cold front producing heavy rain and maybe embedded thunder WED night into THUR morning.  This system is forecasted by the models to be further west than originally expected, and this will deter any downstream ridging over Atlantic Canada precluding any potential development of the late week clipper.  Cold air will move through the region next weekend with highs in the upper 30s and lower 40s, with lows in the mid 30s.  This cold air will be short lived as return flow out ahead of a surface clipper will come out of the south and southwest and return to normal temperatures will ensue, normals for this time of year are 48/35.  Thanksgiving week looks to start off nice, with a cold air mass in place as a frontal passage just days before will allow this cold air out of the central US to filter into the region.  With +EPO/-PNA/-NAO pattern regime still in place any storms should be pushed out to sea.  We need to start seeing a +PNA signal before any storm period can be trusted for snow and right now that does not look like the case.  I will have more tomorrow.  Heavy rain on WED/THUR could bring short lived street flooding.

Lack of Ridging Upstream ruins any snow chances

12z/18z model suite cycles have come into better agreement that the clipper for the 19-20th time period will be absorbed into the main trough of the system on the 16-17th.  Lack of any appreciable upstream ridging destroys a downstream trough and is displaced to the east as a strong -NAO block develops slowing down the progress of the first shortwave.  With the lack of ridging over the western US, the shortwave trough with the associated clipper outruns upper level support stationed over the central US and until this begins to break down, perhaps as early as Thanksgiving week, snow prospects will be few and far in between.  Have a good night and I will have an update on the longer range tomorrow.

Early and Late Morning Model Cycles show potential for storm late next week

A large snowstorm is impacting the upper Midwest/Western Great Lakes, where isolated amounts of up to 12" of snow can be expected in western WI and eastern MN.  A large comma head has developed with this system and heavy snowfall rates of 1-3"/hr is possible throughout today.  Ridging is taking place across the eastern US as well as over the western US where a large trough has been stationary the past week or so.  Temperatures will probably rebound into the lower 60s regionwide this afternoon across SNE as return flow from the south and southwest will bring warm temps northward admist strong warm air advection ahead of the occluded front that will try to progress eastward.  However given that the storm will become occluded at some point on Monday, the front will not make full progress to the coastline until sometime Wednesday, where strong tropical moisture transport ahead of the strong longwave trough, will produce a large area of moderate to heavy precipitation.  Pattern is progressive so no more then 1.5" of rain will fall in any given area.  Flooding should not become a major problem with some regular street flooding in low lying regions.  As the storm intensifies over the region and heads into the Canadian Maritimes return flow from the low will bring in strong cold air advection and will bring the air temperatures slightly below normal.  Strong northwest winds will be common on Thursday and will settle down come Friday as yet another shortwave trough disturbance comes through the mid level flow.  Models have been hinting at a slight, short-lived pattern change in which the NAO heads towards negative and the persistent +EPO the last few weeks breaks down as a strong mid level trough enters the NE Pacific Ocean.  This will in turn, allow ridging to develop out ahead of it over the western US.  The flow over the Pacific and western North America is progressive so the ridging will be short lived.  However the -NAO and -AO coincide with a slight positive PNA ridge present as a clipper system drops out of Canada into the central US Plains.  Models are in two camps: the progressive out to sea camp of the 00z EURO/12z GFS which show a frontal passage followed by cold air advection into the region from northwest winds as a large low pressure center is present over the Canadian Maritimes.  The second camp involves the 12z NAM/00z GGEM and to an extent the 00z/06z GFS ensemble means.  While the NAM does not reach this time table for next Friday, the NAM offers a few suggestions to what could possibly come out of this system just from hour 84, of the short range model.  One thing is for certain and that is the NAM is stronger with the secondary shortwave trough then the 12z GFS has been which leads to better chance of amplification of the shortwave.  The GFS is progressive as well as strung out with the mid level energetic disturbance and does not allow secondary cyclogenesis to take place.  It looks to be a mainly rain event, unless future model runs bring the 700mb/850mb circulations further south, more so south of the SNE South Coast.  Western CT, MA and VT could see some accumulating snow from this system if the current models are right.  The GGEM is the most robust with secondary cyclogenesis as the storm deepens down to the lower 980s just south of Martha's Vineyard, MA.  Chances are we would see rain initially over the coastal plain followed by a changeover to potentially accumulating snow over eastern MA if the 00z GGEM is correct.  However we still have a lot of time in weather forecasting before this system becomes a threat.  Precipitation chances occur on the 16-17th and 18-19th.  Still some time to decide the details, but the pattern is favorable for at least rain/snow showers.

00z GFS update

00z GFS came in further south and more amplified with the northern jet stream disturbance which is good news if one wants a snowstorm in SNE.  Problem is that the surface temperatures warm up because the 850mb and 700mb level circulations move right overhead leading to an initial warm up in temperatures with a south to southeasterly surface flow ahead of the circulation.  Surface thicknesses are really good.  We will end up with snow with verbatim on the 00z GFS.  Good news considering that initially the setup looks unfavorable for snowfall.  However cooler air invades the region as the surface low deepens and heads sea-ward.  The blocking over Greenland takes place and gives SNE a good 24 hours of precipitation.  We just need the surface to 700mb circulations to move in tandem to the south of the region.  We also need the initial clipper low to move further to the south.  It should not be hard given the nature of the pseudo +PNA ridging that coincides with this period.  Again this is the system for 18-19th of November.

Nice Weather until Wednesday, frontal passage and then onto the real fun

Model consensus agrees for the next 5 days that sunshine and seasonable temperatures will be the norm.  However around Tuesday/Wednesday a southern stream shortwave will move out of the GOM and up the Eastern US seaboard bringing heavy rain before a front moves through the region bringing below normal temperatures into the region.  Models disagree afterwards on the pattern for the weekend.  12z GFS shows a possible secondary low developing too far northeast of the region to bring significant precipitation to the region.  A few GFS ensemble members as of the 12z runs showed potential amplification of the northern jet stream with some signals of a +PNA developing quickly and exiting in the Nov 18-20th timeframe which is the time for the best chance of accumulating snowfall.  Best chances in New England remain in NE Maine coastline as a comma head develops and produces some good precipitation to the northwest of the surface low.  Again there is a good week before anything comes with better certainty.  Pattern resembles 50/50 low placement and -NAO Greenland ridging which will force at least a period of amplification, and the reflection of a +PNA ridging present in this period should allow better amplification of the polar jet shortwave trough.  If the models are right at this time as a consensus this system will just bring in the colder air stored over Ontario, Canada in this timeframe.  Again major amplification is difficult given the orientation and placement of the central US trough.  If this trough was closer to the OH Valley, then we would have a greater chance at snowfall.  However with the 850mb and surface circulations traveling to the north of the region, chances are the precipitation will be cutoff to the region so no substantial precip is likely.  Again this is still a low confidence forecast as the 00z EURO shows a large Great Lakes low, with the GFS family models showing a clipper moving through the Lakes and creating secondary cyclogenesis to the NE of New England.  Again big discrepencies in the forecast model family.

Next large precip threat comes with another frontal passage sometime in the 20-23 timeframe where a monster low will travel again through the Great Lakes states and the associated frontal boundary moves through New England as strong cold air advection pushes the frontal east and southeastward.  Lake Effect snows over the Great Lakes could become a problem over there for the Thanksgiving traveling period.  Strong cold air advection will bring high temperatures down to the low to mid 30s in this time frame, and the GFS is showing a fantasy range storm system sometime that Thanksgiving holiday weekend.  We need to watch the 26-28th timeframe as models are showing potential pattern change back to a +PNA/-NAO/-AO regime which should favor New England with a snowy and cold pattern heading into DEC.

Next update will be tomorrow, unless the 18z runs show something worthy of discussing.

12z model update:

As previously mentioned the 12z GFS operational and ensemble mean continued to remain the furthest northeast with secondary formation.  12z GGEM and EURO came in with a much further southwest positioned low, however are still at odds with the development with the secondary low.  Still a lot of questions and again, I will keep you ahead of the system.

Omega Block Breaking Down, Cold Air Breaks for New England next weekend!

After yesterday's discussion, the omega blocking pattern continues to move eastward and break down as the large ocean storm that has recently been battering the region is moving seaward quickly now and will continue to allow drying and a warm air trend to begin today and throughout early next week.  Temperatures should stay in the upper 40s/lower 50s for the foreseeable future.  The next chance for a major weather maker is a Great Lakes Low Pressure center that will begin to affect the area next week.  Heavy rain looks to be the main impact as the cold front approaches.  Models are still at odds with one another.  00z EURO breaks down the low pressure center east of Cape Cod, MA by 600 miles or so the slowest with the GFS ensembles quicker.  Models agree on the magnitude of the +EPO in place, which leads to a -PNA/+NAO interaction as ridging heights build over the eastern US, and heights crash over the western US.  Cold air will be found over this region of the country where snow will likely fall on the northwest side of the Great Lakes Low Pressure system.  Heavy snow will fall across the Rockies and into the Central Plains sometime this weekend, as the large low pressure system moves northeastward.  This low will swing a cold front through the region sometime Wednesday through Thursday.  Strong Cold Air Advection will take place as the front moves through the region allowing cold air to infiltrate the region bringing highs down into the mid to upper 30s for the following weekend.  Right now models cannot be trusted with the details and are changing run to run.  There is no model run to run consistency and confidence beyond Next Monday is low.  Next update will be tomorrow.

Southern New England Forecast

Ok, I can't hold on any longer, here is my first forecast:

The next several days will belong to a large cutoff extratropical cyclone (surface low) that has been meandering off the US East Coast the last several days.  We are within a pattern called the omega blocking pattern where there are two troughs on either side of a central US ridge.  With the 500mb chart in mind, models begin to break down this block as the large storm exits out into the central atlantic Ocean where SNE weather begins to resemble rebounding temperatures and a seasonable feel to the air.  This is in large part do to a large western/central US trough that will continue to build into this region of the country as we are admist a large -PNA/+NAO pattern in which we have troughing over the western US and ridging over the central/eastern US where the rebound in our temperatures will begin as southwest flow materializes over the next 48 hours and through the weekend.  Next week resembles a tricky forecast.  Models are in large disagreements with the overall pattern, with the 00z EURO more amplified and stronger with the surface low over the Great Lakes, and the 00z GFS more progressive and weaker with the surface low over the Great Lakes.  Ridging will be present at the surface over the western Atlantic Ocean and this will the culprit for the rebounding temperatures over the weekend as surface flow becomes southerly and/or southwesterly as this system slides a cold front eastward.  The air mass behind this cold front is still within disagreement in the model consensus.  Right now it is useless to forecast beyond this and therefore will write a new update when the 00z models come in.