Thursday's Mothrazilla, Part II: First Forecast

The fury February onslaught continues as our area stares down yet another winter storm Thursday into Friday. Personally, this one snuck up on me because I did not believe it had a chance to be an area-wide significant snowstorm. The mid-level trough axis is west of here and the Atlantic ridge is overlapping onto the coast. However, Mother Nature said 'va fangul' and snow begets snow, so here we are.



One key reason why the surface low will take a path that favors colder temps staying locked into our area is because of the ULL - upper level low - spinning over SE Canada. The confluence that is draped across northern New England is preventing 500mb heights from growing above our metro. As the primary low attempts to cut into Ohio, it quickly realizes it has nowhere to move and transfers its energy to a secondary low near the Mid-Atlantic. There are several 'waves' of upper energy that are expected to pass south which may mean more than one surface low developing. Because our area is wedged between an incoming trough, SE ridge, and extremely powerful upper level jet stream to the north, the gradient and dynamics associated with this storm are going to be one of the more impressive we've seen yet this winter.



The 200mb jet streak (how many times have we seen this picture on the year?) is approaching 200 KTs. In conjunction with very potent 500mb vorticity passing through, that calls for an impressive precipitation field to develop. This is one reason why I'm not buying the EURO very much. It shows a sharp cut-off of the precip for areas N&W of NYC.



Check out this band of 700mb frontogenesis the NAM tracks from south to north across PA, NJ and NYC. This band has the potential to drop 3-4" of snow in 1 HOUR.



One possible negative is the track of the 850mb low. If it gets as far west as shown here - in NW PA - then there is a very good chance the 850mb temps along the coast rise above freezing levels. This would limit the amount of snow that falls over certain parts of our area.



Remember that sneaky warm wedge in the boundary layers during the February 1st Roidzilla that caused parts of EPA and WNJ to see sleet? You can see the NAM hints at something like that coming to fruition again. Now by this time most of the damage has already been done and we're already in a dry slow. However, be mindful that this is not the most perfect set-up and that warm wedges are possible again.





What's interesting is seeing the northern stream energy trying to phase in at the last moment. This would lengthen the duration of this storm by a few hours as additional banding tries to develop on the west side as the low pulls away. But as you can see, the immediate coast at this point is too warm for snow. However, areas N&W would end up seeing 'bonus' snow IF this comes to fruition. The overall idea here is that the storm could continue well into Friday (say 3-5pm) IF this phasing and back-building of precipitation forms.



My first forecast takes all of these factors into account. One thing I'll have to keep an eye on is the immediate coast. I'm thinking >8" is possible since the 700mb frontogenesis band tracks directly over that area. This includes NYC Metro. However, the negatives are daytime snowfall and the fact this storm is going to move very fast. I will adjust on my second forecast map if necessary.

Very nice, cannot complain about that map one bit. Just hope those pesky 850s stay away for all. So if that back end does build in the people not far NW are they go see rain wash all the snow away on Friday?

Today was the first day that I was able to actually see my whole walkway and driveway since the 2/1 storm. The last of the buildup melted in the 49 degree heatwave we had up here today.

Not that I'm complaining, mind you. Bring it on. Great explanation and write-up Frank, much appreciated as always.

00z NAM has an even more robust jet streak than 18z...madonne

By Thursday 7pm the NAM is showing the coast changing over

Total precip...that northern cut off. Gotta watch it

Frank_Wx wrote:By Thursday 7pm the NAM is showing the coast changing over

How do we have such different images for the same hour

Frank_Wx wrote:Total precip...that northern cut off. Gotta watch it

how much of that yellow around NYC is rain or IP do you think to cut into the snowfall? And yeah pivotal isnt showing same thing.

3km nam has a big area of changeover after the main snow comes through.  Man that is a fast storm, how does it put down 8-12 in literally like 6 hrs, its go snow that hard?

edit well on 3km totals are less.

It might...

aiannone wrote:

Frank_Wx wrote:By Thursday 7pm the NAM is showing the coast changing over

How do we have such different images for the same hour

Position of the low is the same. My guess is different resolutions is causing differences in how precip is shown. But that’s kinda strange.

jmanley32 wrote:

Frank_Wx wrote:Total precip...that northern cut off. Gotta watch it

how much of that yellow around NYC is rain or IP do you think to cut into the snowfall? And yeah pivotal isnt showing same thing.

Probably .20 or so.

jmanley32 wrote:3km nam has a big area of changeover after the main snow comes through.  Man that is a fast storm, how does it put down 8-12 in literally like 6 hrs, its go snow that hard?

I guess you didn’t read my post!!

SENJsnowman wrote:It might...

Someone did

NAM also shows what I said about extending the duration of the storm. Bad news for the coast is that precip that falls after 8pm Thursday may not be snow. But it helps areas N&W

Frank your map is almost identical to regular 00z NAM snow map.

Frank_Wx wrote:By Thursday 7pm the NAM is showing the coast changing over

That's more than just the coast. No?

Frank_Wx wrote:

aiannone wrote:

Frank_Wx wrote:By Thursday 7pm the NAM is showing the coast changing over

How do we have such different images for the same hour

Position of the low is the same. My guess is different resolutions is causing differences in how precip is shown. But that’s kinda strange.

jmanley32 wrote:

Frank_Wx wrote:Total precip...that northern cut off. Gotta watch it

how much of that yellow around NYC is rain or IP do you think to cut into the snowfall? And yeah pivotal isnt showing same thing.

Probably .20 or so.

jmanley32 wrote:3km nam has a big area of changeover after the main snow comes through.  Man that is a fast storm, how does it put down 8-12 in literally like 6 hrs, its go snow that hard?

I guess you didn’t read my post!!

Oh I did read your post, just so hard believe, that would be harder than we saw in last two storms, too bad its not for hours on end haha

Irish wrote:

Frank_Wx wrote:By Thursday 7pm the NAM is showing the coast changing over

That's more than just the coast. No?

Anyone east of 95 is coast in my book

Frank_Wx wrote:

Irish wrote:

Frank_Wx wrote:By Thursday 7pm the NAM is showing the coast changing over

That's more than just the coast. No?

Anyone east of 95 is coast in my book

Gotcha, close enough.

Frank_Wx wrote:Total precip...that northern cut off. Gotta watch it

Frank:

Isn't that precip as of 10PM Thursday night? If so wouldn't areas especially to the north of NYC expect more precip and snow after this?

CPcantmeasuresnow wrote:

Frank_Wx wrote:Total precip...that northern cut off. Gotta watch it

Frank:

Isn't that precip as of 10PM Thursday night? If so wouldn't areas especially to the north of NYC expect more precip and snow after this?

Yes...here’s the real total. Not a whole lot expanded north but it did some.

Icon definitely expanding the precip north.

18z



00z



Run hasn’t finished

Great potential for this storm and looking forward to what it does. Great write up Frank as usual. What are looking at with timing? Start-Finish? It's looking like it may continue into Friday as well.