New Month Brings Threat of Storms

As if working on cue, the change of the calendar brings with it a change in the weather pattern. January went down as a cold but relatively dry month. Two periods of below average temperatures sandwiched a 10 day period of above average warmth in the middle of the month. In Boston, the monthly average temperature in January ended up at 27.4 degrees which was almost 2 degrees below normal. That now makes 3 straight months of below average temperatures.

While experiencing some modest snowfall this winter, we have been spared of any large coastal storms. That figures to change very quickly as large scale atmospheric features that have been in place for many weeks start to break down.

A large high pressure ridge stationed over the western US is responsible for extreme drought conditions in California and record high temperatures in Alaska. This feature is breaking down, and will alter weather pattern of the entire country.  Without knowing much about weather, a quick glance at the upper air set up for this week should give you an idea of whats to come.

 

Following my arrows, we can see that a newly formed trough in the West will allow for Pacific moisture to flow over the Alaskan ridge, southward towards the Gulf.  The moisture rich Gulf will feed several surface waves, which will have the benefit of a tight pressure gradient between the strong cold High to the north and a strengthening Bermuda High to the south. All of the ingredients are in place for an active storm pattern. Notice where all of these ingredients converge? 

By my count, no less than 3 systems will make a run at us this week. The first one on Monday night will be limited in strength and impact with most snow falling south of the Mass Pike. The more concerning storms will occur on Wednesday night and next Saturday. 

There is already excellent agreement amongst long range models in both of these systems having some sort of significant impact on New England. Questions remain about the track and precipitation types, but enough cold air should be in place to support a 6 + inch event for most, with a good chance of even higher snowfall totals for some. 

Back to back storms like this bring up memories of January 2011, when 4 back to back storms created massive snow banks and a severe lack of space, especially in the city.  No way to forecast snowfall totals at this point, but with such a favorable pattern, I would anticipate poor weather conditions for both Wednesday and Saturday of next week.

Winter Storm Details

Our wild January continues. After several days of above average temperatures, cold air is currently working its way back into New England. It should be no surprise that the arrival of that cold air will coincide with a potent coastal storm, poised to bring us some significant snowfall.

A low pressure system currently over the upper Midwest will carve a path to the mid- Atlantic before moving off shore and passing to the southeast of New England. As is typical with these storms, rapid strengthening will occur once the system hits the water.

The storms exact path, through not set in stone, looks to take a similar path to the January 6th storm that gave most of eastern Massachusetts a fluffy 10-15 inches of snow.  This system doesn't look like it will have as much moisture associated with it, dropping a general 0.35-0.5 inches of precipitation. Once again, surface temps will be quite cold which means our snow to liquid ratio will be on the order of 15:1.

A blizzard watch is currently up for Cape Cod and the extreme southeast portion of Massachusetts. These areas will experience the highest snowfall totals (with some ocean enhancement) as well as winds gusting from 20-40 mph. As such, blizzard criteria will likely be met somewhere in this zone.

All of the major cities along the East Coast will be affected by this system. Washington DC, Baltimore, Philadelphia and New York will receive a good 4-8 inches before all is said and done. As such, you can imagine that travel up and down the coast tomorrow will be heavily impacted.

Snowfall will start towards the end of the evening commute tomorrow night, around 6 or 7 PM.  This storm will be a progressive system, much like the January 6th event. Heaviest snowfall will occur overnight with all precipitation clearing the region by mid morning on Wednesday. The timing of the storm will likely cause many school closings and delays. Behind the departing storm, bitter temperatures and a stiff wind will cause lots of blowing snow and dangerous wind chill values. Here are my expected totals below. Tweet me or message me with any questions!

Update on Snowstorm

Complex and powerful nor'easter will impact the area over the next 24 hours. Unique set up with extremely cold surface temperatures and a persistant NE wind direction over the warm ocean created  strong ocean effect snow bands over Essex and eastern Middlesex counties earlier. Some areas already reported 20 inches of accumulation! The area of best ocean effect banding is now over Plymouth county.


Main storm center has formed off the Mid-Atlantic coast and will rapidly intensify as it moves to the north east. This will be a relatively progressive storm and the track will keep the heaviest effects offshore. Nevertheless, the extremely cold temperatures will create impressive snowfall ratios, on the order of 15:1 or above. Anywhere from 0.4 to 1 inch of precipitation will fall, resulting in widespread 14-18 inch snowfall totals with 24+ inches likely in areas of heavy ocean effect banding. Extreme temperature gradient between the surface and the ocean combined with the northeast wind direction will result in strong ocean effect banding.


Winds from the northeast will increase later, gusting to 45 mph in coastal areas and from 15-25 mph everywhere else. Coastal flooding concerns for coastal Essex county and along the South Shore, specifically with the Friday noon high tide. Light nature of the snow will make it easy for wind driven snow to create blizzard conditions.


Most snow should be over by the early afternoon on Friday. Behind it, extremely cold air will rush into all of New England. Friday night and Saturday morning lows are likely to shatter records all around the area. Much of Massachusetts will be several degrees below 0, even in metro areas such as Boston. Breezy NW winds will create wind chill values of -25 and below! This type of cold is life threatening as hypothermia can set in quickly. No doubt, this will be one of the coldest air masses that New England has seen in decades.


Temperatures will moderate on the weekend. Another system will approach the region late Sunday into Monday. A storm track to the west will keep us on the warm and rainy side of the event. Some freezing rain is definitely a possibility for interior areas, especially at the onset of the storm.

Snowstorm Thoughts

Alright, I am going to organize my thoughts into bullet points to make it easier for both me and you.

- Snowstorm will affect the area from Thursday through Friday. This much I can say with 100% confidence.  I've mentioned this time frame of Jan 2/3 for a few weeks now as having very good potential for a coastal storm and things appear to be playing out as planned.

- I do not think we are talking about a "blockbuster" event. This piece of energy is going to have a lot of juice with it and it will be feeding off some amazing temperature contrasts. But the track of the storm appears to be trending further south east and away from New England.

- Despite an offshore track, temps will be plenty cold, which will result in a higher snow to liquid ratio. Perhaps as high as 20:1 in some spots. (1 inch of rain = 20 inches of snow)

-Early indications are anywhere from 0.3-0.6 inches of moisture will fall, which translates to a 6-12 inch event. Snow will be light and fluffy. Easy to shovel.

- This appears to be a long duration event, as the developing storm runs into an Arctic front draped across SNE. Snow will likely start early on Thursday morning and lasting through Friday morning. That amounts to a 36 hour snow event. 

-Snowfall rates won't be particularity heavy, with the exception of overnight on Thursday night into Friday morning, when the storm undergoes rapid intensification. As such, much of Thursday should be manageable in terms of snow removal. The early half of Friday looks troublesome. Likely a no school day for Friday. 

- Wind direction and wind speed will be a factor with this storm. Very tight pressure gradient will result in strong NE winds to develop on Thursday. Combined with astronomically high tides, coastal flooding is a concern.

- A north east wind direction will allow for some ocean enhanced snowfall totals as well.Typically, areas around Cape Anne, the South Shore and Cape Cod get more snow in these events. 12+ inches looks very plausible in these areas.

- Perhaps the most overlooked part of this timeframe will be the immensly cold air that rushes in on Friday night into Saturday. We are talking record cold, with many areas seeing surface temps well below 0. Even in Boston, we could be talking about low temperatures that some of us have never seen in our lifetimes. Combined with gusty winds, wind chill values on Saturday morning will be DANGEROUSLY cold.

As we are still over 48 hours away from this event, plenty of time for things to change. This afternoon's model suits are in and seem to be coming into agreement on the storm timing and track. Now all that's left is to sort out the finer details. I will try to get an update up later, but as it is NYE I can make no promises!

Happy 2014!

6:30 Storm Update

Previous forecast is generally on track. Some of the higher resolution model runs from the afternoon continue to push for a warmer solution with the storm track. At this point, will have to just wait and see. The time has come to stop watching models and start watching conditions!

Taking a look at current surface temps across the region, you can clearly see where ocean influenced warming has already occurred. Cold air is fully entrenched away from the coast. And despite the low level warming this afternoon, even cold air at the coast will be hard to eject at the onset of the storm.

It appears more likely now that everyone will see a changeover by tomorrow morning as mid level warming becomes too much to sustain any frozen precipitation at the surface. The biggest question at this point is what time does this happen?

Here we see the 1am projected radar. Heavy snow extends from south shore all the way into northern New England. But that 32 degree line is oh so close to the city! This 1-4am time frame is when we will experience our heaviest precipitation rates. So a change over closer to 1am means less snow. A changeover closer to 4am will mean more snow, potentially significantly more snow considering the rate.

Need to keep an eye on NYC to see what time they transition. Also need to closely watch secondary low development and wind direction over the next 6 hours. As for now, keeping my snowfall map the same

Storm Update

Here is where we stand:

A strong surface low is currently situated over Tennessee Valley. At the same time, an extremely strong and cold High pressure is situated over southern Quebec. This High pressure has sent 3 reinforcing shots of cold air into New England over the past 48 hours in the form of weak cold fronts. As such, very cold air is settled in all across New England.

 

As the system over the middle of the country moves East, a new surface low will develop off the New Jersey coast, as is typical of New England snow storms.  This new storm have an influx of Gulf and Atlantic moisture, providing plenty of fuel for precipitation. As the storm runs into the Arctic air mass over New England, snow will outbreak across the whole area sometime after 7PM this evening. 

This much we know. The large scale factors are in place for a decent sized snow storm. The finer details are all that is left to sort out. But those finer details can mean everything in a winter storm like this!

Main Issue: How much warm air intrusion is there?

We always here meteorologists say that the "track" of these storms is so important. That is especially true when we have such a large temperature gradient between surface land temps (in the teens/20's) and the ocean (45 degrees). The track of the storm will dictate the surface wind direction. Any wind from the east will use the warmer ocean and try to warm the lower layers of our atmosphere. Its the all important rain/snow line.

So how do we forecast this feature? Well, we really can't! This close to the storm, some of our trusted models won't be able to pick up such a finer atmospheric detail. We can certainly get some guidance by looking at "thermal profiles". Thermal profiles are basically a snapshot of the vertical atmosphere at a particular time and place.

Lets walk through this step by step:

7PM

Light snow has overtaken much of the area. Everywhere will be cold enough to start as snow.

1AM

 

Storm has redeveloped of NJ coast and is moving towards New England. Moderate to heavy snow falling everywhere. These are the EURO projected snowfall totals by 1AM. I think these might be a bit overdone, but a general 2-4 inches will have fallen by this point. Remember, the ground is extremely cold so anything that falls will stick right away. 

4AM-7AM

This will be the deciding time frame for this storm. Up until now, pretty much everyone has stayed snow, except for areas along Cape Cod and the extreme coast. This will be the time frame where we watch both the surface temps and the 850mb (5000 feet up). If the storm tracks further off shore as the euro images above suggest, there will be less of a warm surface layer intrusion. However, some short term models this afternoon are still suggesting a storm path closer to Boston, which would encourage more of an easterly wind direction and warming of the the surface layer.

 

Notice the track of the storm goes right over Cape Cod. This image is projected for 7AM tomorrow morning. Under normal circumstances, this track changes everyone inside of 128 to rain. 

The 850mb temps for the same time show temps above freezing all the way to the NH border. Now, this would of course mean rain for Boston but more of a sleet situation for somewhere like Bedford, MA

 Aforementioned thermal profile for Bedford, MA at 7AM shows surface temps at or near 32, while 850 temps have warmed to above 32. This would be a sleet situation.

So lets just get to the nitty gritty. I've already made this blog post too long so I hope you've made it this far. What do I think is going to happen?

I feel that the cold air in place over all of SNE will be hard to "push" out, even by a warmer storm track. Not to mention, we will continue to be fed cold air at upper levels for the majority of the storm, up until the surface low starts tracking closer to the area. As such, I think most of us stay snow for 80% of the storm and more importantly for 80% of the heaviest precipitation.

Eventually, warm air will win out at the surface, sometime between (4-7AM) but by then, the heaviest precipitation has already fallen. It will amount to just coating of sleet or rain on top of the already fallen snow.

So here is my snowfall map!

Timing will be from 7PM tonight to about 10AM tomorrow morning. Its all gone by tomorrow afternoon. Again, some changeover is likely after 7AM but I feel most of the snow has fallen by this point. Updates on Twitter and Facebook thoughout the day

Another Deluge On the Way

Today most certainly felt more like fall than late July. In fact, Boston's high temperature of 67 corresponds with the average high we see on October 1st! Cool air will be the least of our problems however, as a stalled off shore frontal boundary will allow a developing low pressure to push up the east coast and drench us tonight and through most of tomorrow.

A developing low pressure, currently situated off the coast of North Carolina will ride the stalled front due north, tapping into some tropical energy being provided by a cluster of thunderstorms further out in the Atlantic.

This topical energy will create a very heavy rain sheild that will rotate back into the area starting tonight. Latest models show some really heavy rain falling, especially along the south shore and coastal areas.

With the rain totals like this and the tropical downpour narture of the precipitation, the NWS has issued a Flash Flood Watch for much of eastern MA starting tonight and lasting through tomorrow afternoon.

Take a look at one models loop of the expected rainfall through 2AM. Definetly a washout!
Loop of Friday rain

Bottom line, tonight and tomorrow are not good days for outdoor activities. The sox will be lucky to finish their game tonight. Heavy rain won't start until 10/11 tonight and thankfully we should see some drier weather (but still cloudy) by late tomorrow afternoon.