Disc: 90% or more of this discussion will be dedicated to the upcoming storm and very little will be focused on the long term, although it does appear that a pattern conducive to more major storms with a strong -NAO feature is in place, so I will write something about it.
Also, special thanks to my cohorts Spencer and Don for great coordination today, and Don for writing a "teaser" discussion. I personally wanted to wait until the various NWS offices (CT is served by OKX, BOX, and ALY) had time to specify their hazards because they will be mentioned in this discussion.
There are currently a smorgasbord of products in effect from the National Weather Service, so let's break them down:
A Winter Storm Warning has been issued for Northern Litchfield County.
A Winter Weather Adivsory is in effect for much of the state, EXCEPT the Northeast corner and farSo Southern CT (and obviously not Northern Litchfield).
Advisories have not yet been issued, but likely will later tonight or early tomorrow morning, for NE CT.
Flash Flood Watches are in effect for the entire state EXCEPT Litchfield County (where much of the precipitation will be frozen).
A Coastal Flood Advisory is in effect for the Western half of the South Coast.
A High Wind Warning is in effect basically south of the Merritt Parkway/
A Wind Advisory is in effect for the rest of the state except Litchfield County...
So what should we expect in terms of impacts on our sensible weather? The hardest part to forecast for this storm is going to be snow accumulations, but I will detail that further down in the discussion. First, flooding rains... the ground is already moist, as is typical for this time of year. Rainfall on the order of 2 to 3 inches should be common, with locally higher amounts. For example, the GFS model, which typically has a dry bias in these type of situations, has between 2.1" and 3" of liquid equivalent precipitation through the state.
Minor coastal flooding is possible along the western half of the south coast during the midday high tide cycle tomorrow.
Wind gusts should be in the 50 to 60 MPH range for all of the state, with some gusts to 70 MPH possible along the I 395 corridor out east. These winds, when combined with the amount of rain we are expecting, will create scattered to possibly widespread power outages. Another factor which could exacerbate power problems is the duration of these winds. When a severe thunderstorm passes by, you get a 60 MPH wind gust for a minute and then the wind calms. We could be looking at 50-70 MPH wind gusts across the state for 18 to 24 hours! Any accumulating, heavy, wet snow, would make the problems even worse.
Snow: This is, by far, the hardest part of the forecast. Winds, heavy rain, and coastal flooding are all pretty much givens. They are going to happen. We have a strong, rapidly deepening low with a good moisture feed, etc, etc. All the boxes are checked. Now, for snow. Temperatures above the surface will drop to just below freezing. Normally, in March. this might not be enough to get it done in terms of changing over to snow. However, a low bombing rapidly to under 970 MBs is not exactly a normal situation. It will create heavy precipitation and convective banding type features. Under heavier bands of precipitation, temperatures will crash, and precipitation will change to snow. In interior areas and elevated areas, it is a given we will see snow, and significant accumulations. Near the coast and in lower elevations is where the bigger questions loom. Will we only see some snow mix with the rain? Will we see a changeover to snow with minor accumulations? Or will we see several hours of an all-out snowstorm with near blizzard conditions and significant accumulations? Any one of these scenarios is possible and it is really impossible to tell where the best banding will set up until you see it set up on radar. For now, our snow map has taken a "middle ground" solution. A "smoothed out" solution like this is not likely- BUT for one, we have software limitations, and for another thing, we do not have the meteorological capabilities to sort out where some mesoscale banding might set up. Therefore, we've gone with localized 6-12" accumulations in the NW Hills above 1000 feet, 3-6" for the NE hills and far northern areas, and tapering down to a coating-3" for much of the rest of the state, with little or nothing along the SE coast. This is subject to a lot of change, as are the NWS headlines.
Here's the above in map form.
Also, special thanks to my cohorts Spencer and Don for great coordination today, and Don for writing a "teaser" discussion. I personally wanted to wait until the various NWS offices (CT is served by OKX, BOX, and ALY) had time to specify their hazards because they will be mentioned in this discussion.
There are currently a smorgasbord of products in effect from the National Weather Service, so let's break them down:
A Winter Storm Warning has been issued for Northern Litchfield County.
A Winter Weather Adivsory is in effect for much of the state, EXCEPT the Northeast corner and farSo Southern CT (and obviously not Northern Litchfield).
Advisories have not yet been issued, but likely will later tonight or early tomorrow morning, for NE CT.
Flash Flood Watches are in effect for the entire state EXCEPT Litchfield County (where much of the precipitation will be frozen).
A Coastal Flood Advisory is in effect for the Western half of the South Coast.
A High Wind Warning is in effect basically south of the Merritt Parkway/
A Wind Advisory is in effect for the rest of the state except Litchfield County...
So what should we expect in terms of impacts on our sensible weather? The hardest part to forecast for this storm is going to be snow accumulations, but I will detail that further down in the discussion. First, flooding rains... the ground is already moist, as is typical for this time of year. Rainfall on the order of 2 to 3 inches should be common, with locally higher amounts. For example, the GFS model, which typically has a dry bias in these type of situations, has between 2.1" and 3" of liquid equivalent precipitation through the state.
Minor coastal flooding is possible along the western half of the south coast during the midday high tide cycle tomorrow.
Wind gusts should be in the 50 to 60 MPH range for all of the state, with some gusts to 70 MPH possible along the I 395 corridor out east. These winds, when combined with the amount of rain we are expecting, will create scattered to possibly widespread power outages. Another factor which could exacerbate power problems is the duration of these winds. When a severe thunderstorm passes by, you get a 60 MPH wind gust for a minute and then the wind calms. We could be looking at 50-70 MPH wind gusts across the state for 18 to 24 hours! Any accumulating, heavy, wet snow, would make the problems even worse.
Snow: This is, by far, the hardest part of the forecast. Winds, heavy rain, and coastal flooding are all pretty much givens. They are going to happen. We have a strong, rapidly deepening low with a good moisture feed, etc, etc. All the boxes are checked. Now, for snow. Temperatures above the surface will drop to just below freezing. Normally, in March. this might not be enough to get it done in terms of changing over to snow. However, a low bombing rapidly to under 970 MBs is not exactly a normal situation. It will create heavy precipitation and convective banding type features. Under heavier bands of precipitation, temperatures will crash, and precipitation will change to snow. In interior areas and elevated areas, it is a given we will see snow, and significant accumulations. Near the coast and in lower elevations is where the bigger questions loom. Will we only see some snow mix with the rain? Will we see a changeover to snow with minor accumulations? Or will we see several hours of an all-out snowstorm with near blizzard conditions and significant accumulations? Any one of these scenarios is possible and it is really impossible to tell where the best banding will set up until you see it set up on radar. For now, our snow map has taken a "middle ground" solution. A "smoothed out" solution like this is not likely- BUT for one, we have software limitations, and for another thing, we do not have the meteorological capabilities to sort out where some mesoscale banding might set up. Therefore, we've gone with localized 6-12" accumulations in the NW Hills above 1000 feet, 3-6" for the NE hills and far northern areas, and tapering down to a coating-3" for much of the rest of the state, with little or nothing along the SE coast. This is subject to a lot of change, as are the NWS headlines.
Here's the above in map form.
So for tonight, rain should slowly develop from SW to NE. Tonight is mostly uneventful, with just some light rain spreading in and an increasing NE breeze. Temperatures by morning should be around 40 degrees.
Tomorrow: Winds will rapidly increase during the morning hours, becoming very strong by late in the day. Temperatures will not rise during the day and probably fall. Expect rain to mix with and change to snow first in the NW Hills, then for much of interior CT, and maybe down to everywhere except the SE coast by the end of the day. By around noon tomorrow, we should have an idea if the colder/snowier solutions like the NAM are verifying or if the warmer/less snowy models like the GFS are verifying. If most of the state is snowing at that hour, then the colder solutions are prevailing. If it is still raining in all of the state except the NW Hills, then the warmer solutions are verifying. It should be noted that the favored models in this setup are the NAM and RGEM, because of their higher resolutions. It should also be noted that the RGEM has a warm bias and the NAM tends to be too strong with storms like this, which would produce a colder solution in this setup. It should also be noted that the NAM has vastly outperformed the RGEM this year. So this forecast is waited 2/3 toward the NAM and 1/3 or so to the RGEM, with most globals, especially the GFS and GGEM, being ignored.
Tomorrow Night/Sat: By tomorrow night, there will be a full-blown gale in progress, with raging winds and snow for most of the state, with some type of mixed precipitation near the south coast, and mostly rain in the far SE. Keep in mind, any west snow on top of the wind and rain will significantly exacerbate any power problems, so that those who will be able to visit this page tomorrow night should consider themselves lucky! The main question is on Saturday how quickly the storm can pull out so cleanup efforts can begin. The general thinking here is that by dawn, the storm will begin to pull out from SW to NE.
Longer Term: I have to say that with all the effort put into this storm, very little time was devoted t the long term. But Sunday and Monday should be fair, with near normal temperatures for this time of year. Expect high temperatures in the 40 to 45 degree range on Monday and mid 40s on Tuesday . There could be a few snow flurries in the NW Hills on Monday.
Another coastal storm could effect the region later Tuesday into Wednesday. Although details are generally fuzzy at this range and I really didn't look into it that deeply at this point, thermal profiles appear colder, which would favor a snowier solution. It also appears that it could be another very strong storm. The bigger question with that system might be how far north the precipitation is able to make it, given the strength of the block.
Beyond that, it appears the weather turns more fair to close out the work week, but chilly, with temperatures 5-10 degrees below normal.
Looking very briefly into the long range, yet another very strong coastal low, that at a very quick glance looks sort of similar to this one, may be poised to affect the area March 12-13. That date has had several doozies historically, plus, we'll still be well-entrenched into a strong -NAO pattern. It looks like there will be a lot of these long discussions in the coming days.
I don't really have time to add graphical maps tonight (plus the Internet connection I am using is about the speed of a two-toed sloth), but you can refer to our snow map and NWS graphics for now.
That's all for now... this product could be upated later tonight if there are any changes to current warnings. I will not personally be around until tomorrow evening, as far as tomorrow goes, so I will coordinate with my cohorts to make sure this page gets updated when needed. Take care and stay safe!
-GP!
