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March 13-14th Nor'easter Threat


NJwx85
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38 minutes ago, jm1220 said:

The upper air system on the GGEM is not matured so there is not a mechanism to spread snow/precip well west of the center. Note on the 500mb chart how the flow is from the SSE mainly near the low, and the closed low is well west of it. 

Can you illustrate that difference?  Not an expert on upper air patterns, thanks...

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13 minutes ago, RU848789 said:

UK way east with limited precip for NJ, except near the coast and into NYC, with most of the precip NE of NYC; also too warm for snow for the 95 corridor...

sn10_acc-imp.us_ne.png

 

qpf_acc-imp.us_ne.png

An inch of liquid still woulda been a foot of snow if we had a cold airmass meh or got a track like this in Jan/Feb. 

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3 minutes ago, HeadInTheClouds said:

I was speaking in general terms, not just this storm. I don't trust that model. Actually I don't trust any 1 model. 

It’s not perfect but the RGEM usually isn’t way off and if anytung is usually too warm so it’s a good model to rule in snow chances if it shows somehung good. 

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39 minutes ago, RU848789 said:

Can you illustrate that difference?  Not an expert on upper air patterns, thanks...

Notice here at 72hrs when the low is SE of Montauk, the direction of the 500mb flow. The low is about to mature but the flow is generally out of the SE. That doesn't really allow a mature CCB/comma head to develop and spread snow well west of the low. We want all this to happen sooner. The focus of the moist feed is into New England.

image.png.da6802536051de5b9d8ea2bf53b48bf6.png

Here by 78hr the 500mb low is closed off and there's a mature CCB with moisture being brought west around the closed low. From here the surface low stacks and starts to weaken since there is no longer a way to evacuate air aloft over top of the low. But see how where it closes off is a great spot for interior New England. We want that 75 miles SSW or so. The crashing upper air heights as you can see there also brings cold air down to the surface.

image.thumb.png.c0c4d89ab65366ef51902a0a7bbebc3b.png

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5 minutes ago, jm1220 said:

Notice here at 72hrs when the low is SE of Montauk, the direction of the 500mb flow. The low is about to mature but the flow is generally out of the SE. That doesn't really allow a mature CCB/comma head to develop and spread snow well west of the low. We want all this to happen sooner. The focus of the moist feed is into New England.

image.png.da6802536051de5b9d8ea2bf53b48bf6.png

Here by 78hr the 500mb low is closed off and there's a mature CCB with moisture being brought west around the closed low. From here the surface low stacks and starts to weaken since there is no longer a way to evacuate air aloft over top of the low. But see how where it closes off is a great spot for interior New England. We want that 75 miles SSW or so. The crashing upper air heights as you can see there also brings cold air down to the surface.

image.thumb.png.c0c4d89ab65366ef51902a0a7bbebc3b.png

I love stacked lows because it means we no longer have to deal with a pesky warm layer and it's going to be all snow as long as you're west of the surface low.

 

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Another way to look at it-the 700mb low and vertical velocity (lift). Notice how it is well placed for New England because these dynamics get going a little too late for NYC. You want to be just NW of the 700mb low to get into the really good/intense banding. Here's 72hr

image.thumb.png.f896bdef20cf06871b2dd5a730263506.png

78hr-at this point we're probably getting some wraparound snow around the closed/stacked upper low but you can see overall the lift is weakening because the low is stacked. We can see clearly how we want this dynamic happening sooner/SW for our subforum. It's the problem we have all the time with these late developing Miller B type lows. But this is the GGEM outcome, GFS was more favorable.

image.png.5512e1984d274239df2ebff88fc305fb.png

And before 72hr we're too warm in the preceding airmass, and we don't get the benefit of strong lift/dynamics to help overcome it unless you're inland and above probably 500-600ft.

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7 minutes ago, jm1220 said:

Another way to look at it-the 700mb low and vertical velocity (lift). Notice how it is well placed for New England because these dynamics get going a little too late for NYC. You want to be just NW of the 700mb low to get into the really good/intense banding. Here's 72hr

image.thumb.png.f896bdef20cf06871b2dd5a730263506.png

78hr-at this point we're probably getting some wraparound snow around the closed/stacked upper low but you can see overall the lift is weakening because the low is stacked. We can see clearly how we want this dynamic happening sooner/SW for our subforum. It's the problem we have all the time with these late developing Miller B type lows. But this is the GGEM outcome, GFS was more favorable.

image.png.5512e1984d274239df2ebff88fc305fb.png

And before 72hr we're too warm in the preceding airmass, and we don't get the benefit of strong lift/dynamics to help overcome it unless you're inland and above probably 500-600ft.

Great analysis!

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