Re: Sunday-Monday Snowstorm - 2nd Call Snow Map

by **Frank_Wx** Sat Feb 28, 2015 4:50 pm

lglickman1 wrote:Hoe long is this event supposed to be?

Figure 1pm until 5am.

by **Frank_Wx** Sat Feb 28, 2015 4:53 pm

I'm moving the chat up to 10am tomorrow and releasing a final call snow map by the morning.

by **nutleyblizzard** Sat Feb 28, 2015 4:57 pm

If this trends any colder we could be looking at 6+ area wide.

by **snow247** Sat Feb 28, 2015 4:59 pm

RGEM looks like it cut back for north of NYC like last weekend.

by **Frank_Wx** Sat Feb 28, 2015 5:01 pm

by **RJB8525** Sat Feb 28, 2015 5:03 pm

thats a nice snow map right there

hopefully not much ice will get in

by **aiannone** Sat Feb 28, 2015 5:04 pm

GFS is cold as it can get

by **snow247** Sat Feb 28, 2015 5:04 pm

Second call, though if the usual south trend continues I'll have to move the heavier area further south, especially on LI, again.

Frank, would you mind putting my map in the first post or something so it doesn't get buried in the thread? Thanks.

Sunday-Monday Snowstorm - 2nd Call Snow Map - Page 3 Second10

Sunday-Monday Snowstorm - 2nd Call Snow Map - Page 3 Second10

by **jimv45** Sat Feb 28, 2015 5:06 pm

I know what some models are showing higher amounts but I am sticking with 3to6 south to north plus this is starting earlier so coast will have sticking issues for sometime.

by **Frank_Wx** Sat Feb 28, 2015 5:07 pm

snow247 wrote:Second call, though if the usual south trend continues I'll have to move the heavier area further south, especially on LI, again.

Frank, would you mind putting my map in the first post or something so it doesn't get buried in the thread? Thanks.

Create a maps only thread and I'll pin it

by **aiannone** Sat Feb 28, 2015 5:09 pm

18z RGEM Close-up
Sunday-Monday Snowstorm - 2nd Call Snow Map - Page 3 Rgem_s11

by **snow247** Sat Feb 28, 2015 5:10 pm

aiannone wrote:18z RGEM Close-up

What's with the screw zone in the mid-upper HV?

by **rb924119** Sat Feb 28, 2015 5:20 pm

Hmmmm anybody notice the quasi-northwest to southeast orientation of the swath of heaviest snows? I have a hunch that this is picking up on a HIGHLY MESO-SCALE band that may be induced by (extremely low-level) 925-850 hPa frontogenesis. My reasoning for this is that this is SWFE, so that fits the general orientation of the thermal profile as well as the wind profile (winds crossing the east-west tightening thermal gradient from southwest to northeast). Can anybody get 925/850 temperature and wind maps to possibly confirm?

by **rb924119** Sat Feb 28, 2015 5:24 pm

This would also make sense if a coastal develops earlier because then you would begin to have a northerly component to the low-level winds, especially north of NYC which would further enhance to the frontogensis. If this is what the RGEM is still showing, then I'd bet anything that's why we're seeing this very narrow band of heavier snow oriented and located this way.

by **snow247** Sat Feb 28, 2015 5:24 pm

I'm supposed to go from Rockland County (where I live) to Dutchess County tomorrow to visit family, I'm going at around 11AM and coming back home at around 2-3PM, It's about an hour drive to and from.

Should I go?

by **Frank_Wx** Sat Feb 28, 2015 5:29 pm

You can go but be prepared to drive in snow. Heaviest though won't be till later in the afternoon.

by **Frank_Wx** Sat Feb 28, 2015 5:31 pm

rb924119 wrote:Hmmmm anybody notice the quasi-northwest to southeast orientation of the swath of heaviest snows? I have a hunch that this is picking up on a HIGHLY MESO-SCALE band that may be induced by (extremely low-level) 925-850 hPa frontogenesis. My reasoning for this is that this is SWFE, so that fits the general orientation of the thermal profile as well as the wind profile (winds crossing the east-west tightening thermal gradient from southwest to northeast). Can anybody get 925/850 temperature and wind maps to possibly confirm?

Sunday-Monday Snowstorm - 2nd Call Snow Map - Page 3 Gfs_mslp_uv850_us_8

Sunday-Monday Snowstorm - 2nd Call Snow Map - Page 3 Gfs_uv250_us_8

by **snow247** Sat Feb 28, 2015 5:33 pm

Frank_Wx wrote:You can go but be prepared to drive in snow. Heaviest though won't be till later in the afternoon.

Thanks

by **rb924119** Sat Feb 28, 2015 5:37 pm

Frank_Wx wrote:
rb924119 wrote:Hmmmm anybody notice the quasi-northwest to southeast orientation of the swath of heaviest snows? I have a hunch that this is picking up on a HIGHLY MESO-SCALE band that may be induced by (extremely low-level) 925-850 hPa frontogenesis. My reasoning for this is that this is SWFE, so that fits the general orientation of the thermal profile as well as the wind profile (winds crossing the east-west tightening thermal gradient from southwest to northeast). Can anybody get 925/850 temperature and wind maps to possibly confirm?

Well then never mind about that lol There clearly has to be something forcing that....

by **Frank_Wx** Sat Feb 28, 2015 5:40 pm

I just think this is a classic event with a strong upper level jet streak wedged between the PV and SE Ridge. That's where all your forcing is coming from.

by **rb924119** Sat Feb 28, 2015 5:42 pm

Frank_Wx wrote:I just think this is a classic event with a strong upper level jet streak wedged between the PV and SE Ridge. That's where all your forcing is coming from.

But we aren't located in favorable spots for that to aid us; in fact, it's kind of the opposite or a non-factor completely.

by **rb924119** Sat Feb 28, 2015 5:43 pm

I'm still not sold on these higher numbers.

by **Frank_Wx** Sat Feb 28, 2015 5:44 pm

rb924119 wrote:
Frank_Wx wrote:I just think this is a classic event with a strong upper level jet streak wedged between the PV and SE Ridge. That's where all your forcing is coming from.

But we aren't located in favorable spots for that to aid us; in fact, it's kind of the opposite or a non-factor completely.

Yes...ideally we want it south of us? Either way, the intense thermal gradients should help bring about frontogenesis.

by **Frank_Wx** Sat Feb 28, 2015 5:53 pm

Here's a good start time graphic. Channel 7 is very conservative with their snow map. Just 1-3 for NYC. Not sure why.

Sunday-Monday Snowstorm - 2nd Call Snow Map - Page 3 Screenshot_2015_02_28_17_50_26

Sunday-Monday Snowstorm - 2nd Call Snow Map - Page 3 Screenshot_2015_02_28_17_50_26

by **oldtimer** Sat Feb 28, 2015 5:57 pm

Frank 7eyewitness hasn't changed anything since 7am this morning

by **RJB8525** Sat Feb 28, 2015 6:04 pm

doesn't look like they will be changing any amounts, they like their 1-3 for the city

by **rb924119** Sat Feb 28, 2015 6:12 pm

Frank_Wx wrote:
rb924119 wrote:
Frank_Wx wrote:I just think this is a classic event with a strong upper level jet streak wedged between the PV and SE Ridge. That's where all your forcing is coming from.

But we aren't located in favorable spots for that to aid us; in fact, it's kind of the opposite or a non-factor completely.

Yes...ideally we want it south of us? Either way, the intense thermal gradients should help bring about frontogenesis.

Yeah. In the H2 image you posted, there would be three ideal locations and orientations. In the orientation that it is in on your image, we'd ideally want it located over extreme southern Ohio, Indiana and Illinois. Our second option, would be to have it oriented southwest-northeast from approximately 200 miles east of the Delmarva and stretching back to the south-southwest. Our third, and most likely only viable option if we had a coupled jet system with a second jet located where I just mentioned to stave off p-type issues) would to have it located in any orientation from around or just north of the eastern Great Lakes and stretching eastward from there.

Take a look at the following images and see if you can figure it out. I don't mean to sound rude, but I have to go for a while. I'll be back to further explain in a little bit. This is the ageostrophic circulation that I was talking about in the case study. and why you tend to see rising/sinking motion associated with different locations in jets.

Idealized jet structure:

Sunday-Monday Snowstorm - 2nd Call Snow Map - Page 3 Unknow10

Sunday-Monday Snowstorm - 2nd Call Snow Map - Page 3 Unknow10

Cross-sections representing vertical motion associated with jets. The shorter and stronger the jet streak, the stronger the vertical circulations are (because of the dynamics, which I can explain later if you'd like; let me know):

Sunday-Monday Snowstorm - 2nd Call Snow Map - Page 3 Unknow10

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