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3/4 - 3/5 Post-Frontal Snow Chance


Capt. Adam

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If we're talking over an inch of liquid then MECS is on the table. I wouldn't be surprised to see models trend wetter with this given the massive moisture feed from the south.

All the moisture and warm air to the south can mean this ticks north and hangs up the cold front, too. I wouldn't cash anything in yet, but someone should get a very nice event out of this. 

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The snow maps are picking up the plus 1 at 700 at hour 57 and 60 in the city and LI and plus 2 in CNJ so you are seeing lower totals

The 850s at KNYC at hour 57 are -2. At hour 60 - 6 , however at 700 its plus 1 .

The good thing is at 18z those 700s were plus 2 to plus 4 so the NAM actually cooled .

A positive here is the guidance is ticking up in terms of QPF so that will help everyone.

Lastly those 700s are wrong. The NAM is making an error resolving the layer at 700

Look for that cool and come in line with the rest of the guidance.

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All the moisture and warm air to the south can mean this ticks north and hangs up the cold front, too. I wouldn't cash anything in yet, but someone should get a very nice event out of this. 

The low would have to trend stronger or the SE ridge would need to get stronger otherwise the arctic high will keep pressing east. The seasonal trend has been for the high to keep pressing and focusing the heaviest moisture further south thus some of our NW screw zones.

 

Anything can still happen 2+ days out though so I don't question those who are being cautious.

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The low would have to trend stronger or the SE ridge would need to get stronger otherwise the arctic high will keep pressing east. The seasonal trend has been for the high to keep pressing and focusing the heaviest moisture further south thus some of our NW screw zones.

 

Anything can still happen 2+ days out though so I don't question those who are being cautious.

Winds below 700 are weak so the push is an error. The 4k nam at 60 is colder and is snow at KNYC

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The low would have to trend stronger or the SE ridge would need to get stronger otherwise the arctic high will keep pressing east. The seasonal trend has been for the high to keep pressing and focusing the heaviest moisture further south thus some of our NW screw zones.

Anything can still happen 2+ days out though so I don't question those who are being cautious.

Caution is good because you have an arctic high pressing south behind the front, it's going to compress the precip field there is going to be a sharp cutoff/subsidence somewhere to the north, where that will be? Who knows at the moment
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Here's a big issue on the 0z NAM: warm mid level air. This is for JFK at 60hr:

 

5 800 1872 -3.4 -3.7 98 0.3 -3.6 196 23 287.5 288.1 280.4 298.0 3.63
6 750 2386 2.6 2.6 99 0.1 2.6 224 71 299.4 300.6 288.0 317.7 6.15
7 700 2945 1.8 1.7 99 0.1 1.8 233 89 304.5 305.7 289.8 323.2 6.19
8 650 3539 -1.5 -1.8 98 0.3 -1.7 240 94 307.3 308.2 289.7 323.1 5.1

 

Note the bolded-the last numbers are temps at those levels. That's definitely big-time sleet. Again, ignore the clown snow maps which count sleet as snow. This has to cool down quite a bit in future runs. The warmth and moisture has to be lifted up somewhere, and the heavy precip means warm air at mid levels. It's the NAM, but watch out for this on other models. 

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Here's a big issue on the 0z NAM: warm mid level air. This is for JFK at 60hr:

 

5 800 1872 -3.4 -3.7 98 0.3 -3.6 196 23 287.5 288.1 280.4 298.0 3.63

6 750 2386 2.6 2.6 99 0.1 2.6 224 71 299.4 300.6 288.0 317.7 6.15

7 700 2945 1.8 1.7 99 0.1 1.8 233 89 304.5 305.7 289.8 323.2 6.19

8 650 3539 -1.5 -1.8 98 0.3 -1.7 240 94 307.3 308.2 289.7 323.1 5.1

 

Note the bolded-the last numbers are temps at those levels. That's definitely big-time sleet. Again, ignore the clown snow maps which count sleet as snow. This has to cool down quite a bit in future runs. The warmth and moisture has to be lifted up somewhere, and the heavy precip means warm air at mid levels. It's the NAM, but watch out for this on other models. 

 

Here's my backyard in Edison same time period.

NAM_218_2015030300_F60_40.5000N_74.5000W

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Sounds like a little more than light snow then.

The GFS also gives 2-3" for many areas tmrw night, so if that is factored into the 4-8, then it's a lighter snow event.....this run actually has the precip shield more expansive and a bit further north. Looks to me like 4-6" for the NYC area and 6-8" further south into NJ. Not bad at all
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The GFS also gives 2-3" for many areas tmrw night, so if that is factored into the 4-8, then it's a lighter snow event.....this run actually has the precip shield more expansive and a bit further north

 

 

It shows .50 to .75 for late Wed night and Thur, so that's a solid 6 inch snowfall.

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