A long duration and dangerous storm will impact the region over the next 48 hours, with an extended period of snow,very cold temps,near blizzard conditions and dangerous wind-chills possible.
•Light snow begins possibly, as early as later this afternoon into the early evening from west to east.
•Scattered light snow will overspread the entire region by tonight,snow will be mostly light and scattered,accumulations may vary widely across the region .
•Accumulations of 1-2 inches possible by morning, may be a very sharp cutoff with no accumulations across parts the lower HV.
•Scattered light to moderate snow falls for the morning,followed by a possible lull. Snow picks back up again in the afternoon with additional accumulations possible before sunset.
•Snow and wind intensity begin to pick up Thursday evening into the overnight as we begin the worst part of the storm.
•High ratio snow combined with 20-30 mph winds means, near blizzard conditions possible Thursday Night into pre dawn Friday, with lots of blowing and drifting snow.
•Single digits temps and 20-30 MPH winds will result in dangerous negative 15-25 degree wind chills, Thursday night into early Friday.
•Accumulations of 8-15 inches possible region wide,localized higher amounts possible, no need for the zone map.
•Very cold temps and blowing snow means roads will be difficult to maintain, travel will not be recommended.
•School closings and Thursday Morning commute up in the air, evening commute and Friday Morning commute a larger concern.
-STILL ALOT OF UNCERTAINTIES AND WILDCARDS WITH THIS SYSTEM,IT WILL BE ALOT OF NOWCASTING AND THE FORECAST IS SUBJECT TO CHANGE-
Below is a very detailed look into how this forecast came to be, and a look into the difficulties that exist with this storm. If you like to learn and love long winded geek stuff, then please read on…
A very complicated forecast to say the least, lets start by taking a look at the most recent HVW live radar, overrunning snowfall will continue to spread along a stationary front, from Ohio to New England later this afternoon and tonight. You can see the snow already starting to break out along this boundary, red area is where you will continue to see the snow fill in through the rest of the day.As I look out the window you can see clouds quickly streaking in from the West.
The latest NAM Model’s Simulated Radar below shows snowfall breaking out early this afternoon, at the moment this seems a bit to early considering its 2pm now. Sometime between mid afternoon and early evening is a more likely start time for the light snow to develop across the region. Notice the similarities of the NAM simulated radar when compared to the current live radar?
So lets talk about what has been one of the challenges forecasting this storm, it’s something called Snow Ratio’s, and its basically a calculation based on air temperatures to determine how much snowfall can occur from a specific amount of moisture. For example, one inch of rain=10 inches of snow at 28-34 degrees, make sense? Basically this storm isn’t forecasted to bring a tremendous amount of moisture into our region, as we have been stating for a few days, the track is a bit to far South and East for a ton of moisture to push into the HV. Which may end up being a blessing for those who don’t like historic snowfall! Below we have posted to short range models, which are designed to pick up on the smaller details that the longer range models tend to struggle with. We have posted the NAM and RGEM snowfall forecast, I want to call your attention to a few things, as you look at these models it seems pretty clear that a 6-12 inch forecast is pretty safe correct? Not so fast, notice at the top of the NAM model a circled what says (10:1 liquid equivalant)? What that means is that this model, and all other models have snow maps set to a 10:1 snowfall ratio be default, remember are short lesson?
Now that we have some projected snow totals, based on a 10:1 ratio, lets take a look at the temperatures in our region during the overnight on Thursday, when the heaviest snow should be falling.
Yes that is negative three to negative five degrees during the snow, curious as to what kinda snow ratio you can get out of those temps? Ofcourse I have that info…
See what a difference the temps can have on a snowfall forecast? An 8″ storm can become a very significant snowfall, now are we forecasting that much snow? No it best to be reserved on the forecast and tweak it up if needed, but the potential exists for the storm to be quite an overachiever. Next point to discuss is the possibility for near blizzard conditions for Thursday night, we will start by highlight the criteria for a storm to be considered a blizzard or for blizzard conditions.
“THE NATIONAL WEATHER SERVICE DEFINITION OF A BLIZZARD IS A WINTER STORM WHICH PRODUCES THE FOLLOWING CONDITIONS FOR 3 HOURS OR LONGER: SUSTAINED WINDS OR FREQUENT GUSTS 35 MPH OR GREATER…AND FALLING AND/OR BLOWING SNOW REDUCING VISIBILITY FREQUENTLY TO LESS THAN ONE-QUARTER MILE ON A WIDESPREAD OR LOCAL BASIS”
Now we know the criteria, so the question is will we achieve it? Lets take a look at the forecasted winds during the worst part of the storm, below is the European model projected winds/gusts for late Thursday into early Friday. As you can see, winds will be 20-30 knots which is about 23 to 35 mph, add in a light fluffy snow and we will certainly near blizzard conditions, we will lack these conditions being sustained, so it may not fully earn the title. Since we have covered the temps, and now the winds, I call your attention to the last image. This is a wind chill chart, as you can see with air temps around zero, and winds up to 35 mph, we will certainly be dealing with dangerous wind chills overnight Thursday into Friday morning down to 20-30 below.
All sounds pretty simple right? Not really,there are also a few models showing much less precip which means there are still a lot of things that can go wrong with the forecast.These are the joys of forecasting and also the reason why its always safer to stay conservative.