Tuesday, December 31, 2013

SNE Snowstorm to Begin 2014

 Confidence high that snowstorm is on the way but not a blockbuster like it once had slight potential to be. The set up is driven by an energetic north branch disturbance swinging towards the northeast late Wednesday. The reason for the snow will not be the placement/track of low pressure that very often this time of year and in the winter months is so key but instead the presence of an arctic high to the north , very cold air in place and plenty of moisture in the mid to upper levels in the atmosphere. The clash of the two brings us our accumulating dry fluffy snows Thursday into at least midday Friday to Southern New England. Long duration. The image below should help to explain this showing a low much farther south and east than is typical  but an impressive "overrunning" situation with moisture into arctic. Its that process that brings the snow growth .
The good thing with this storm coming is that there is zero doubt this is a "snow" storm. Very cold temperatures will be in place at the start and hold , maybe even drop throughout the event. This is important for a few reasons, 1: The snow will add up as its falling, there will be no wasted precipitation. Snow ratio's appear to be near 20:1  perhaps more ! This is due to temperatures being only in the teens to 20's at best for many during the storm, perhaps colder. This creates a fluff factor. The bad thing to that is that with expected gusty winds at times especially neat the coast there will be blowing and drifting of snow at times. Even though it appears the snow will never really "puke", its a drawn out light to moderate perhaps heavy at times intensity to it. The blowing will create low visibility at times for motorist. Something to be aware off. This looks to be the case especially for eastern Massachusetts and Cape Cod and the Islands as that will be the area of strongest winds and still a fluffy snow.
The other issue with this storm and again especially eastern Mass. shorelines and the Cape and Islands is the potential for coastal flooding during the Friday Am high tide cycle. Winds look to be sustained out of the north/northeast between 30-perhaps as high as 40 mph for a time early Friday morning. Given this flooding could be moderate.  Again, this really does NOT hinge on the placement /intensity of storm, its likely to occur regardless. 
So how much, right? I am not going to go crazy with this but looks like a general 8-12" snowfall for the region with potential for a few places to see over a foot favoring areas of eastern Ma and RI as this area will be under the influence of a NNE (seen in wind graphic above) wind flow and with relatively mild water off the coast it acts to enhance snowfall in those areas as we have seen many times before. "Ocean Enhancement".
Here is my overall thinking. As always I urge you to look at the forecast range and not just fix to the high number. light snow starts Thursday morning. Heaviest period is late night into early Friday with light snow continuing to the east for much of Friday as well. In its wake we are left with frigid arctic air with temps below zero (some *well* below ) for much of the region both Friday and especially Saturday morning. The potential is there for another storm Sunday night and Monday. Still kinks to work out with that one. Thank you for taking the time to read the blog and Happy New Years !!  ~Anthony

Friday, December 20, 2013

Warm , Wet & Windy Weekend Ahead

Click on images for a larger view
After a cold and snowy mid  December, today in Southern New England found highs into the upper 40's and low 50's ! The "bump up" continues into Saturday as well as highs will be in the 50's for many to near 60°. The same holds true for most the region on Sunday as well. With Temperature fluctuations  like this there surely will be some weather impacts expected as well. A frontal boundary is draped across the lower Great Lakes this eve and into central and northern New England and a couple waves of low pressure are expected to ride along that frontal boundary through Monday am bringing with it showers, downpours, possible thunder, strong wind gusts and warmth to the south of the boundary and potential ice , wintry mix and snow well north of the boundary.
The heaviest precipitation through Monday is expected to occur along and north of the front. If it were plain rain there would not be any issues but as temperatures skyrocket in the mid-upper levels of the atmosphere, surface temps will remain below freezing for many to the north of the front and that will bring a potential Ice storm to parts of northern New England Saturday night into Sunday especially but possibly not limited to central and eastern New Hampshire and much of Maine away from the immediate shores. South of the front surface temperatures will soar to about 20-25° above normal for this time of year with highs near or over 60° for much of SNE on Sunday. Dewpoints (measure of humidity) will be in the 50's too. It will feel almost muggy for the 1st *full* day of Winter on Sunday south of the front. The area to watch for potential *brief* icing would be extreme northern Middlesex County in eastern Ma as well as Essex County. I am not expecting any major concerns with the potential for ice but it does not take much . What is really insane is that temps near the MA/NH border will be in the 30's and near Taunton Ma and other areas in SNE it will be 30° milder! Such a short distance for such a gradient. These changes in the lower & upper levels as well as a screaming ridged Jet Stream into Canada will bring the potential for strong wind gusts into SNE late Saturday eve through Sunday on the order of 30-45 mph.  As low pressure works off to the west and north of SNE late Sunday , cold west northwest winds will start snap back in here late Monday and especially Tuesday. Monday is the transition day though with still many SNE readings in the 50's . Its from that point on though that an arctic blast of air starts to get ushered into our area with highs remaining in the upper 20's to low 30's on Tuesday. A very cold Christmas Eve is shaping up into Christmas Morning with many teens likely away from the southeast shores. As low pressure works off the Northeast coast early Weds, winds will turn north over the relatively mild waters of the Atlantic and we could even see some Ocean Effect flurries or snow showers on Christmas Eve Day over Cape Cod. For SNE High pressure will be overhead and the forecast for Christmas looks like clear skies, calm winds and cold in the 20's and 30's . Below are some modeled images for Sunday Afternoon

Monday, December 16, 2013

Alberta Clipper Approaching. Details & Whats Ahead...

Click All Images For A Larger View....Two days removed from the first significant winter storm of the 2013-2014 season and now we are watching yet another system approach us this eve as northern branch energy dives east/southeast from central Canada currently north of Lake Superior. This energy/weak broad low pressure continues approaching southern New England this eve spreading a swath of light snow along the way. It's the ingredients for what we call an "Alberta Clipper". These clippers have a history of being moisture starved and usually drop minor advisory snowfalls and for many that is exactly what this one will do. But wait, we are still left in the same Jet Stream pattern just a few days ago and enough tilt to the Jet Stream that once that energy/vorticity nears the eastern shores of New Jersey it will spawn a secondary, coastal low off south of Long Island and start to intensify as it passes just east of the southern New England coastlines Tuesday evening. It is the formation of that new low pressure system in combination will remaining arctic air to the north being drained into the storm. This is the set up that brings us our accumulating snow for Tuesday.
 If you are thinking that it seems like a while since we have seen one of these buggers, It has ! I don't have any specific dates but can tell you its been at least 2 yrs. Again, not a huge deal here but the timing could be rough for the evening commute as it is likely that moderate snow will be falling especially closer to Boston - Providence to the north /northeast into southeast New Hampshire. It is that area along with some favored higher elevations that could approach warning criteria snow of 6"/+ as this will be the area of greatest dynamics and lift being close to the center of a developing low pressure. In the image below the surface pressure trend /change shows falling pressure off the area of expected development during the mid to late morning hours.
 At that time we will start to see more organized bands of snow closer to the coastlines. The storm is all snow for all the area except south and east of the Cape Cod Canal and the Islands as they will be close to the developing low which in turn allows milder air to come in off the Atlantic a bit of mix/rain *could make it as far north as Plymouth, Ma. Areas west of RT 24 in eastern Ma will see a dry fluffy snow. It is important to note with the cold temperatures as of late that the snow will start to adhere to all surface immediately. This storm is another quick mover with once again a lack of upstream blocking near Greenland (-NAO) , so may catch a few by surprise during the late afternoon, early evening hours as it progress off to the ENE. The concern is that the strongest part of the event commute during the Pm/evening commute. There are signals from guidance of steep mid level lapse rates (change in temperature of height) these values tend to lead to heavy convective-like precipitation and banding and yes even the potential for a rumble of thunder ! Something to monitor while now-casting early tomorrow and something to keep in mind if venturing out that you could get caught in a low visibility situation in heavy snowfall especially from Providence to Boston to southeast New Hampshire . The light snow starts to spread in here during the mid morning hours first in SW Connecticut and then will advance to the NNE thereafter reaching the eastern shores by 11am give/take.

 The other thing to watch for is some gusty winds to develop over Cape Cod & the Islands. Gusts 25-35 mph are possible into Wednesday morning. Its a cold day ! Highs only in the Teens for some , 20's for most and 30's over extreme southeast MA , the Cape & Islands. Wednesday we are left with some lingering morning clouds east before sunshine develops and we approach 30° for highs as a SNE average. The Warming trend will continue throughout the week with lots of clouds around after Thursday into the weekend , but mild ! Highs will be near/into the 50's possibly on Friday with windy conditions at times and showers developing late. 
It appears as though the big trough driven by the Canadian Polar Vortex  will work offshore towards Thursday allowing for an eastern ridge to build and bring the mild, showery conditions right into the weekend as well. Fear not though snowlovers...We need this to reshuffle things in the atmosphere and already there are indications the cold comes back in time for Santa and perhaps a storm system to watch as well. Thank you for taking the time to read the blog, I appreciate it.           ~Anthony        Oh..Winter begins Saturday ! Yup, has not even started yet. 

Thursday, December 12, 2013

Coastal Storm/Nor'easter On The Way

Its not quite "Winter" just yet but try telling that to Mother Nature. The active early to mid December pattern will roll on. It looked much different with the first few days of December  in Southern New England  averaging above normal temperatures but since we have been going nowhere but downhill and looks to be no prolonged end in sight to the cold. The change in the pattern started in its early stages towards late November and is continuing to date. It has been an impressive cold and snowy start to the season across much of the United States with relentless arctic air in the west and a nation that is now left with the highest percentage of snowcover to date going back to at least 2003.
So, this gives us an idea of where we have been and where we stand now. Now we look to the future. More snow is heading into SNE this weekend and will be the biggest, most widespread snowstorm thus far this December.
This storm will come with snow, heavy at times, some mixing near the shores and also some rain over far southeast SNE. The heaviest axis of most snow  like many set ups like this occurs just to the north/northwest of the big cities as colder temperatures will bring in the "fluff factor" there even though less moisture may be in the cards for them as opposed to locations nearer to the coast. The coast will see a wetter type snow and possible mixing at times. A situation seen many times before and the snow map will echo that likelihood. In the below image of a snapshot of the current Water Vapor, you can see the ingredients coming together now for the storm ahead. First the northern energy now diving into the northwest US from Canada and building moisture over Texas which will soon tap the Gulf Of Mexico. These two meet up over SNE on Saturday  , clash with large arctic high pressure to the north to bring us our winter storm/ Nor'easter. The included model image shows the idea of how it comes together as well.
Its still a tad too early to really get into specifics as far as timing and such but light snow looks to break out for most as early as 10am Saturday morning and will spread and intensify thereafter from SSW-NNE. The brunt of the storm comes Saturday evening into the first part of Sunday morning before tapering precipitation towards Sunday afternoon. Along with the Snow, mix and even rain for some mixing near the shores will come winds, especially but not confined to the eastern shorelines of SNE. Sustained ENE winds will develop between 20-30 mph for favored locations which the model image below gives a general idea. Wind *gusts* across much of SNE will be on the order of 30-40 mph for some and perhaps briefly approach 50mph for the Cape & Islands as the storm intensifies Sunday am off the coast heading into the Gulf Of Maine. 
Waves 7-10' will develop just offshore of east and southeast facing shorelines and in combination with the expected winds may cause some splash over and minor coastal flooding  at the times of high tide Sunday morning. So to wrap up , when all said and done the largest most impactful winter storm of the season is on the way and here is the expected snowfall map through early Sunday afternoon.

 As far as where we are headed beyond this weekend I feel our active/COLD pattern will continue into at least next week. I am monitoring the potential for more snowfall early to mid next week along with possible record cold temperatures especially early in the week. Then Winter starts officially. Enjoy. ~Anthony 
Quick Note: A few more finer details may arise and minor changes. Stay tuned to twitter and my SNE FB Fanpage for any further developments. Thank you for taking the time to read the blog.