Preliminary Storm Forecast : Friday 3/2/18

Warm air is entrenched over the eastern half of the United States.  The Hudson Valley has been a solid 10° to 15° above average all week so far.  So that fact that we’re about to talk about discuss the likelihood for a snowstorm on Friday may seem a bit hard to believe.  But a dynamic upper level low pressure system will interact with rapidly intensifying nor’easter.  The timing will be crucial… but the expectation is that a sizeable snowstorm will impact the Hudson Valley on Friday.

Timing:
– 8pm to 11pm Thursday: Rain develops from SW to NE
– 12am to 7am Friday: Rain mixes with & changes to wet snow from NW to SE
– 7am to 4pm Friday:  Snow falls moderate to heavy at times
– 6pm to 11pm Friday: Snow tapers off from west to east

Snow Accumulation:
– Catskills (Zone 1 & 2): 10 to 18 inches
– Southern Catskills, Shawangunks, Hurley Highlands (zone 5 & 6): 6 to 12 inches
– Majority of the Hudson Valley (Zone 3, 4, 7 & 8): 4 to 8 inches
– Extreme Lower Hudson Valley (Zone 9): 2 to 5 inches

Discussion:

In the midst of a very warm pattern, we are going to witness the power of an upper low pressure system, as it single handedly tries to cool the region substantially enough to take temperatures in the mid 50s… and turn them into temperatures in the mid 30s in 24 hours.  There is no arctic cold front, no source of cold… Canadian air.  If it’s going to snow… and we believe that it will… it’s going to do so under the power of a strong area of upper level low pressure.

This map shows the upward motion in the atmosphere.  There is projected to be a very large area of strong to intense upward motion just to the north of the upper low.  As a result, we should see rapidly cooling air temperatures, and moderate to heavy precipitation.  The entire logic behind this storm being a snow maker for the Hudson Valley… is that the tremendous upward motion is THE ingredient that cools the air mass enough to support snow.

This shows the projection by the European model, for temperatures at cloud level (in degrees Celsius).  With the progression of the Upper Level Low pressure eastward Thursday night into Friday morning… you can see that the cloud level temperatures are projected to respond in kind.  At sunset on Thursday, cloud level temperatures are above freezing in the Hudson Valley (star)… but by sunrise on Friday, cloud level (850mb) temperatures are projected to be below freezing (white color).

If this scenario is correct… and we believe that the European & NAM model solutions have the right idea… by sunrise on Friday… a moderate to heavy snow is expected to be falling across the Hudson Valley.

Based on the factors we’ve laid out… this is what the weather map could look like Friday morning.  It would set the stage for a very snowy Friday across the Hudson Valley.

Important Notes

This is an extremely complex setup, and all the pieces of the puzzle need to come together just right, for us to see snow.  If any of the factors change… it could have major implications on the end result of our weather.  Here are a couple of extra items we want to highlight related to this storm and forecast…

… The track of the upper level low pressure is critical.  It needs to track just to our south, but not too far to our south.  This is how we’re going to get our cold air, and if the upper level low is too far away, the influence of cold air will not take hold.

… Temperatures are extremely marginal… meaning near or above freezing through the duration of this event.  That will mean variations in accumulations.  Snow could struggle to stick to paved surfaces, and even on grassy areas.  So travel conditions will vary across the region.

… The data we’re seeing remains VERY conflicted at this time.  The uncertainty level with this forecast is VERY HIGH.  We are talking about a very dynamic situation.  Upper level low pressures are notoriously difficult to forecast, only adding to the uncertainty level.

… There is a STRONG block over Greenland at this time.  That will prevent this storm (rain or snow) from exiting the area quickly.  The result will be the storm getting trapped just offshore on Friday, and for the Hudson Valley and Northeast US, it means an extended period of snow (or rain)… possibly leading to very high accumulations of snow in some places (especially the mountains like the Catskills).

BOMBOGENESIS!  This storm is projected to go from 1001mb at 7pm Thursday to 971mb at 7pm Friday night.  When a storm’s central pressure drops by more than 24mb in 24 hours… the storm is said to have “bombed out” or undergone Bombogenesis.  This is another indicator of just how dynamic and powerful this storm is.

… Thanks to Bombogenesis… we’ll have very strong winds.  We’re seeing indications that sustained winds between 10 and 15mph are possible, with frequent gusts over 30mph possible.  There is a high wind watch for Westchester County, and if this storm transitions to snow as the Euro and NAM models suggest… we could see Blizzard Watches posted, or blizzard conditions experienced in some parts of the area.

… Power Outages?  Sadly… when dealing with potential blizzard conditions, due to such strong wind gusts… power outages may become a concern.  Temperatures will be mild, barely getting to the point where snow can be supported by the atmosphere.  With temperatures relatively mild, we’ll be looking at a heavy, wet snow.  When we combine wet snow and wind gusts over 30mph… we could see elevated concerns about downed tree branches and power lines.

… And Finally…WE ARE EXTREME!!… we anticipate our forecast to ruffle a lot of feathers.  To our knowledge, nobody is forecasting anything close to the snowfall map we have issued.  The National Weather Service has Winter Storm Watches posted for the Catskills, but the valleys are not projected to see much if any snow by other outlets.  You don’t have to agree with our forecast… but we would appreciate criticism be constructive.  We’re not issuing this forecast lightly… we see considerable data that supports our ideas.  We are trying to get our viewers out ahead of what will likely be a rapidly developing situation on Thursday… as more data comes out.  We do not hype storms to cause panic and worry… this storm has dynamic elements that could lead to unusual and extreme weather.

So in conclusion… there are A LAUNDRY LIST of complex items surrounding this storm and it’s forecast.  Expect there to be substantial changes to our final forecast.  We could see a scenario where we have to increase the snowfall forecast for the entire Hudson Valley… and we could also envision a scenario where the snowfall forecast gets reduced substantially.  We will have updates through the day on Thursday, as more and more data becomes available.

Thank you for reading… and we greatly appreciate all of your support!

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