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Thanksgiving Eve SECS/MECS Discussion II


gkrangers

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The discontinuity continues and is even worse this morning. Winter storm watches are up for all counties west of the Delaware River in PA and for Mercer to Somerset to Union to NYC and all counties NW of there in NJ and NY, of course, skipping over my county, Middlesex, in NJ, lol. It’s a bit of a disconnect to have neighboring Mercer/Union/SI to have watches and for Middlesex (at least northern Middlesex - problem is they only have one zone for our county) to not. Just look at the map and it looks funny...

 

For what it's worth, here's what I just sent out to the folks I send my winter weather emails to. I know it's not model discussion, but thought a few might be interested. Nice to see the NWS offices in Philly and NYC have resolved the major discontinuities and I'm psyched for snow.

Yay. As people can now see from the updated snowfall maps (which I can't link here, for some reason - maybe IE8 issue), the NWS offices have collaborated much more closely and the snowfall predictions are reasonably well aligned without any significant discontinuities. NWS Philly increased accumulations almost everywhere, but especially along and to the SE of I-95 (now 2-4/4-6" depending on where one is, as opposed to 1-2/2-4"), while NYC office decreased their accumulations slightly.

Winter storm warnings are now up for counties NW of I-95 for 4-8" of snow (and 6-12" in the Poconos/Sussex/Hudson Valley) and winter weather advisories are up for the I-95 corridor from Philly to NYC for 3-6" of snow. And counties to the SE of I-95 will likely receive 1-3" with immediate coastal areas getting <1". All makes sense now. Still a highly uncertain forecast with significant bust potential. All it would take is a 25-50 mile track shift or a change in the arrival time/strength of the cold air or a change in dynamics (snowfall rates) to make significant changes to accumulations in either direction, but I still think busting high is more likely, especially near I-95, given the borderline boundary layer temps.

Should be moderate to heavy rain in most locations in the morning, changing to a heavy wet snow by late morning or mid-afternoon, depending on elevation and how far inland one is. Anywhere that gets >6" of this heavy wet paste is likely going to have downed tree limbs and power outages.

Traveling on the major roads shouldn't be much of an issue before late afternoon, except well N/W of I-95, where it will be colder and snowing for more time. However, given heavy traffic and heavily falling snow with low visibility in the late afternoon/evening in most locations, I would not want to be on the road at that time, as I could see this being gridlock on some major highways - even if there isn't that much accumulation on the roads - hell, on this day one can get gridlock with just rain.

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Ok.  So why dismiss it then and ride the NAM?

RGEM was lethal last year in a lot of storms.

 

While the NAM can often be overdone on WAA, the GFS can often underestimate the 700 mb

temperatures by a degree or so in strong WAA. So a NAM-GFS compromise still isn't great

news east of NYC.

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Perfect illistration of the heaviest snows possibly falling just nw of the rain-taint/snow line.

Lol I actually was NOT expecting to see that. I'm in that little curl of orange in NE NJ. Highly, highly doubt I see 25-30mm.....which I guess would be around 4-7" or so? My point and click is for 4-7" anyway, so ya never know. Holding just a wee bit of hope though.....always surprises with storms
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While the NAM can often be overdone on WAA, the GFS can often underestimate the 700 mb

temperatures by a degree or so in strong WAA. So a NAM-GFS compromise still isn't great

news east of NYC.

 

True.  I'm WSW (more west) of NYC in central Union County.  We're often a battle line in these setups and having to fend off the warming in the upper levels.  I think even where I am we are likely to see some sleet.

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Lol I actually was NOT expecting to see that. I'm in that little curl of orange in NE NJ. Highly, highly doubt I see 25-30mm.....which I guess would be around 4-7" or so? Holding just a wee bit of hope though.....always surprises with storms

 

Looks like it's mixing sleet and snow and counting it as snow on that eastern edge near the city.

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It's going to be so close here!

Need some serious thread right now. I'm not however jumping ship. I think mid morning during the heaviest rates everyone outside of eastern li is snowing and that includes the SS. We may well go over to rain in the afternoon but I think that's after several inches are already down.

This would be similar to last February were JM had 5" I had 7" and the NS 14"!

Cut those by half and I think that's what we get

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Perfect illistration of the heaviest snows possibly falling just nw of the rain-taint/snow line.

Is it possible that it's picking up on a mesoscale banding signature? I would think those capabilities lie with the short term players like the HRRR - But I don't know. Any input would be appreciated.

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It's going to be so close here!

Need some serious thread right now. I'm not however jumping ship. I think mid morning during the heaviest rates everyone outside of eastern li is snowing and that includes the SS. We may well go over to rain in the afternoon but I think that's after several inches are already down.

This would be similar to last February were JM had 5" I had 7" and the NS 14"!

Cut those by half and I think that's what we get

I'm starting to think it's not going to be such a happy event for our areas and the LI crew. Models last night seemed to be giving us more snow but are now catching onto both the stale airmass behind the front and the warm layer aloft. Our chance at accums might be late as the storm exits but I'm having a hard time thinking we see more than an inch or two. We'll have to see how much we radiate tonight and can evaporationally cool tomorrow.

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Let's hope the 18z/12z Rgem/12z Euro has a better handle with their 4DVAR grid.

It's the awful positioning of the 700mb low. It closes off and torches the mid levels with warm air, and the low's track is creeping closer to the coast as well. The GFS is west of other guidance but last minute shifts can still occur. Last winter was all about those. 

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I'm starting to think it's not going to be such a happy event for our areas and the LI crew. Models last night seemed to be giving us more snow but are now catching onto both the stale airmass behind the front and the warm layer aloft. Our chance at accums might be late as the storm exits but I'm having a hard time thinking we see more than an inch or two. We'll have to see how much we radiate tonight and can evaporationally cool tomorrow.

Watch the mid morning rates. The column should crash with temps going from 40 to mid 30/s. I think it just pukes snow for a while and that's when we see our accums. After that the mid level warmth does it's dirty work and we go sleet and then rain. I don't think we see any additional on the back end as rates will be to low to cut it as temps are sill mid 30s.

I don't think anyone south of the LIE needs a shovel but I think the grass and cars get a couple slushy inches

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