Mar 13: Major Winter Storm Approaching!

Jonathan Carr
By Jonathan Carr March 13, 2017 16:58

Mar 13: Major Winter Storm Approaching!

Here’s our final call on the approaching major winter storm…

snowmap3-13-2017

Please click here to view full resolution winter storm impact map.

Disco: Not much has changed for New Jersey since our forecast and call from yesterday. Therefore most of this discussion will be repetitive for New Jersey. Most changes have occurred to our W in PA. I highly recommend following Eastern PA Weather Authority for anyone out that way. 3 pieces of energy (cyclonic vorticity) are moving into the E US, from the N and W, as two northern shortwaves and remnants of the winter storm that just hit the SE US. The northernmost piece of energy (polar shortwave) will phase with the middle piece (Pacific shortwave) and develop a favorable longwave trough axis for the southernmost piece to eventually and also phase in as the entire trough tilts negative. The W US is modeled with a very amped ridge which correlates to a deeper trough downstream for the E US. This all translates to an environment favorable for a major, possibly historic, winter storm. While areas away from the ocean will see the biggest snows, coastal regions have flooding and beach erosion to worry about due to higher astronomical tides (coming off a full moon) + storm surge associated with strong onshore flow. Let’s break it down even further…

Snow: I’m pretty confident in areas away from the ocean seeing a foot plus of snow and therefore the KABOOM alarm has been sounded primarily for the northern 2/3 of the state. Some guidance is suggesting 18-24 inches and therefore we’ll upgrade to “Dude where’s my car?” if that happens. But for now…KABOOM! The latest guidance trends have brought the heavier snow jackpot axis SE of the I-95 corridor which is reflected in our 2nd call map above. However, we are still weary of the SENJ coast due to late-seasonal climatology + sun angle + strong onshore warm flow off the ocean. Heavier precipitation rates can overcome these conditions however that’s expecting a lot this time of year.  There’s explosive snowfall potential across the entire state but the SENJ area should see the least amount relative to points NW. A county such as Ocean could be two different planets to the north and south (heavy snow accums in NW Ocean vs lower accums + coastal flooding for SE Ocean. The cut-off is very sharp. Blizzard criteria will be met if sustained winds of 35mph along with 1/4 mile visibility can last for 3 hours. As the map above reflects, this is possible for the entire black-dashed line.

Mixing: I’m fairly confident that much of SENJ will mix during peak onshore flow late Monday night into Tuesday morning. Therefore, we’re probably going to watch the snow/rain line first move inland over Cape May/Atlantic City from SE to NW and then eventually pull back and away as the deformation zone sets up. That means snow to mix to rain to mix to snow is possible as far inland as the I-95 corridor but for at least Atlantic City down through Cape May and Cumberland Counties. How far this snow/rain line comes inland mid-storm represents one of the most difficult aspects of this forecast. This is what can make the difference between significant and major snowfall for SENJ. I CANNOT EMPHASIZE ENOUGH how sharp of a snow accumulation cut-off is possible for SENJ. There are no mixing concerns to the NW of the I-95 corridor so therfore, this snow storm is primarily for the northern 2/3 of the New Jersey.

Winds: There is no doubt that the coast should see the heaviest winds. I would expect sustained winds of 25-35mph with gusts capable of exceeding 60mph at times. For areas away from the ocean (the rest of New Jersey), lesser winds are expected but could still be problematic. Peak wind conditions should occur late tonight through Tuesday afternoon off of the ocean. Once the system moves away, strong winds are then also expected through Wednesday but out of the NW. I see no reason why it cannot gust to 40mph behind such a powerfully phased departing system. So strong onshore winds first followed by strong NW winds once the snow stops.

Coastal Flooding: Tidal guidance is picking up on the flooding potential for Tuesday. The late-Tuesday morning high tide appears to be the highest water level of the storm. The Tuesday evening high tide should then be the second highest water level of the storm. Right now, at least moderate levels of coastal flooding and beach erosion should be expected. Tidal guidance has not yet suggested major coastal flooding but it’s hard for me to believe that’s not possible given the wind field and wind gust potential. The Jersey shore, Raritan Bay, and Long Island coasts are looking a lot of wind as mentioned before. That should push a lot of water onshore and into the back bays of the barrier islands.

Power Outages: This snow should be heavy and wet, especially on the SE side of the jackpot. Therefore excessive weight could stack up on tree branches, power lines, etc. Couple that with high winds and it’s a recipe for scattered-to-widespread power outages. I strongly suggest having some blankets and winter gear to stay warm should you loose your source of heat/power. I would imagine the coast would be most susceptible to this given the higher expected winds but power outages are a threat state-wide. The snow is expected to be a little drier (fluffier) once you get far away from the coast in NWNJ and into PA but overall, most snow should be heavy for New Jersey.

Wildcards: There’s a lot of room for curveballs with this complex of a setup. An earlier phase and trough tilt would bring warmer condition as far inland as the I-95 corridor and cripple accumulation capability. A later phase would mean lesser snow totals (still significant-to-major) but possibly not historic. There’s also the possibility that the strongest frontogenic forcing/lifting stays both to our W in W PA and to our E over the ocean. These uprights of rising air would force sinking air between (over us) which could inhibit the historic scenario from occurring. Again, a significant-to-major snow storm would still be possible but not the historic scenario. The bottom line on wildcards is that there are many. Multiple vorts are involved in phasing and therefore timing is critical. We’ll immediately post anything that is detected during live observations. These wildcards come with the game and remind us that meteorology is not a guaranteed scientific principal like gravity. It’s an incomplete data set that we do our best to utilize for prediction.

Timing: We’re going with a general start time of 8PM to Midnight tonight from SW to NE across NJ. The meat and potatoes of the storm should then occur through most of Tuesday before letting up Tuesday evening. Isolated show showers would then be possible overnight and into Wednesday given the strong and cold NW flow over the Great Lakes.

In English: KABOOM! The above map represents our current expected totals for the approaching winter storm. It should start anytime after 8PM tonight and wrap up by Tuesday night. Peak storm conditions should consume at least the first half of Tuesday. SENJ will struggle to accumulate given the rainy and mix potential. You can see how sharp the cut-off is on our map. This is just not SENJ’s storm. Flooding is a much higher concern for the SENJ coast. The N coast (and most of NNJ) is subject to both heavy snow and high winds and will likely be ground zero for blizzard conditions. Otherwise everyone to the N and W of a line drawn from Brick to the Delaware Memorial Bridge are in solid shape for major snowfall (everyone NW of the snow/rain line cutoff). That cut-off line could vary a bit so surprises are expected with such a complex system. Within 20-30 miles in either direction in SENJ can mean the difference between trace slushy accumulations/mixing and double-digit accumulations. Winds will be high, especially along the coast, and therefore flooding and beach erosion are very likely. Power outages are also likely considering the heavy wet snow coupled with the previously mentioned winds. Our final call is represented by the above map. Live casting will begin tonight once snow approaches/moves into SNJ for the start of the storm. Have a great night and please be safe. JC

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Jonathan Carr
By Jonathan Carr March 13, 2017 16:58

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