Saturday, March 22, 2014

Forecast Thoughts For Potential Major Nor'easter Tues-Weds 3/25-26

   Highs today were near 60° for portions of the area but all eyes continue to be on what now appears to be a significant early Spring Nor'easter for much of the region later on Tuesday into Wednesday morning with the brunt of the effects expected over the eastern sections of Southern New England.
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   OVERVIEW: Arctic air looks to settle in Sunday eve and especially Monday where we could see record low maximum temps and begin to set the stage for a decent snowstorm  and what looks to be the first significant one since Feb 18th I believe. Northern energy for the pending storm is now entering the Pacific Northwest and will dive SE towards the Southeastern US states and merge with a southern based sub-tropical jet and form a storm off the Carolina's early in the day on Tuesday as the upper levels of the atmosphere dig a deep amplified trough over the East Coast Tuesday eve sending a phased storm off to the north/northeast that will undergo meteorological bombgenesis in response to rich Atlantic Ocean moisture and a clash of above normal sea surface temperatures and below normal SST's along its track and an assist from the Gulf Stream. Low pressure will pass just outside the 40/70 benchmark early Wednesday somewhere around 970 millibars, perhaps even lower  before heading towards Nova Scotia late Wednesday.
   TIMING : Flurries and light snow could break out as early as Tuesday am as upper level energy over the Ohio River Valley starts to interact with building moisture off to the south as the main storm takes shape near or off the Outer Banks of North Carolina. Flurries, perhaps a period of light snow should continue through the daylight hours before intensity will pick up south to north through the evening hours with the peak of the storm occurring overnight Tuesday into early Wednesday before  it pulls off to the northeast.
   IMPACTS & EFFECTS: Very strong signals continue to indicate the most significant effects and impacts will be felt near coastal locations. The heaviest snow and strongest winds are likely near the coastal plain. Banding of heavy snow is likely for eastern SNE especially near and inside interstate 495 in eastern Massachusetts as this area will be closest to the storm center and in the area of greatest signaled vertical motion. Unlike previous storms where there had been a sharp cutoff due to incredibly dry air contrast to the north and northwest of the storm, this one will have decent mid level moisture at least at the get go to spread light accumulating snow to the entire region before the storm really blows up and pulls the heaviest snow and banding closer to the coast and especially over the Cape and Islands. It will be very hard to see thermal profiles rise to the point where any mix would be involved so this is a predominantly snow event. Winter Storm warning headlines are very possible and even a Blizzard Watch could be warranted near the eastern Shores. The other issue and it could be a BIG one is the potential for powerful sustained  winds, again affecting the coast the most. There are strong signals of potentially damaging wind gusts along the immediate shore to Cape Cod and the Islands as the storm continues to intensify passing by.  There is a big difference between a weakening storm system and an intensifying one  like this will be . Enough signals have been there that I feel  *High Wind Warnings* are likely near the shores with even  *Wind Advisories* possibly further inland. Images below show the sustained and gust potentials during the brunt of the storm overnight Tuesday into Wednesday morning.
Wave heights are expected to grow to 15-20 feet near or just off our coastlines. The Wednesday high tide cycle will have to be closely monitored for likely splash over and potential for moderate coastal flooding. This aspect is very dependent on exactly how close that low center comes. There is great agreement as of now but slight shifts are still likely.
   So now to answer the big question I am sure many of you are asking. How much snow?  Its still a bit early to tag numbers for certain locations, however,  I believe I will be able to estimate further by this time tomorrow. In the map below it shows the best probability of seeing and exceeding 6" of snow. Confidence is quite high here, and if it  all comes together, as it has the potential to do so, someone will come away with a foot, perhaps a bit more when all is said and done Wednesday ino mid-day over eastern SNE.
Thats the skinny on the system as I see it right now. I do not expect many drastic changes but do stay tuned to me on twitter and facebook if they should arise between now and then. The good news is we could hit 60° by Friday with a better chance Saturday and we may finally be able to put the snow behind us and move forward to enjoy 'Spring'. Thank you for reading     ~Anthony

Tuesday, March 18, 2014

A Few Forecast Thoughts

 Though we do have a couple weather ‘systems’ approaching before , my eyes continue to be fixed on the March 25-27th timeframe. I have shared a few images on twitter in recent days, but the fact is they are only one run of one operational model. Take note though that there have been signals of this in guidance for almost 5 days now ! Regardless if they have been strong signals (some very intense) or weak, the fact remains that it looks to be an upper level pattern that is prone to producing right into earl April and continued strong signals of anonymously cold air as well. That has not changed. And when you have cold in late winter and early Spring, some pretty dramatic occurrences can occur whether it be a severe weather outbreak or even a major winter storm.  There are many past events of such and some in New England need no introduction. Its just the nature of the pattern , temperature gradients across the CONUS during this time of year. It is more volatile than any other part of the calendar year. Always need to be on your toes this time of year even though most seasons the transition from Winter to Spring does goes fairly smooth.
  Its important to note that it is ok to share model images of potential and I would not do it out of just the fantasy of wanting a storm or because it is the most dramatic solution on the table. I am not lazy like that and have been observing (30yrs) and forecasting weather for quite some time and know better and have a great , deep respect of weather. When I see signals I mention potential whether it is 10 days out or a sneak attack in a much shorter timeframe. Aside from just many operation model runs and signals of such through global ensemble guidance signals for the 3/25-27 timeframe there have been signals of a potentially brief but importantly timed pattern change in the upper levels of our atmosphere. Two of importance. A building of a western US ridge with indication of a building positive PNA (Pacific/North American Pattern) . This in turn sends/keeps a deep trough over the eastern US. Yes this has occurred  recently and we have escaped potentials but when there are also signals of the North Atlantic Oscillation (NAO) at least trending towards a negative phase (downstream Greenland blocking) or potentially going slightly negative near the time frame it is certainly a potential to keep an eye on . It is a formula/combination that has not  occurred much this year despite the above normal snowfall for most.  In fact the last time such occurred was mid January . Could I be dead wrong? Of course I could and have been quite a few times this year but it will not stop me from moving forward.
  There really are no details set in stone being still a week or so out but feel it would be best to surely keep at least an eye on this due to the time of year and certain plans, some vital that many people and businesses make as we transition from Winter to Spring. Thank You for reading and stay tuned.    ~Anthony

Tuesday, March 11, 2014

OVERVIEW: Big winter storm approaching the Northeast. Anomalously strong March low pressure currently located over Missouri will track east/north east and pass over Southern New England early Thursday am around 978mb ! This storm will bring a major snowfall to northern New England. With the storm track expected to track over/just south of Long Island this brings mild temperatures both at the surface and aloft to begin with rain changing to a period of wintry precipitation with crashing temperatures on the back side of strengthening low pressure moving over and northeast of Southern New England early Thursday am. This a a huge snowstorm and great news for ski country. Have a look at the 6 hr snowfall animation I put together for Weds-Thurs

SNE IMPACTS & TIMING: Heaviest snowfall expected to remain north of SNE. That does not mean we will escape impacts from this storm. It appears as though 1-2" of rainfall is likely across the region. The potential is there for a gusty thunderstorm as well Wednesday evening . South winds ahead of the storm may gust 35-45mph along south coastal locations Weds eve/early Thurs.  Light rain showers break out Wednesday morning from SW-NE and become steadier as the day goes on as low pressure approaches from the WSW. With low pressure moving over and eventually starting to pull off the the north east, rain will start to turn into a wintry mix over western SNE Weds eve into pre-dawn Thursday as colder air rushes in behind the departing storm. This creates an issue with a potential flash freeze. Even a small amount of snow or mix with temperatures crashing can create big problems. The Thursday morning commute looks rough. Light snow/mix showers could continue right into the early afternoon Thursday near the coast. Not much accumulation expected anywhere across SNE, but it wont take much with the expected crash in temperatures. Below is a graphic showing general precipitation types and timing potential with the upcoming storm.
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