OBS-NOWCAST for potential significant 6 hour Thursday morning (1/20/22) commute impact general 1-3" snowfall.

[wdrag]

While uncertainty exists on the target for a rain to hazardous brief commuter significant snow event, a thread has been started to take the load off January.

Thursday morning I84-NYC-PHL: Looks like 1-3" of snow in a 6 hour period centered on sunrise, with potential significant impact to morning travel due to temps falling to freezing during snowfall. There is model uncertainty on amounts. Snow could fall for an hour at 1/2-1". I84 itself seems to be on the northern fringe where snowfall could be less than 1". Amounts also depend on how fast the preceding predawn rain showers change to snow but I am confident of a snow event, just not confident who gets the biggest impact. Tomorrow morning we should have a much better idea of travel impact. 

I would add that climo on something like this probably favors an inch or less NYC CP, but I do think there is going to be a narrow lane of more than 1" per multiple model indications. NWS ensemble risk of greater than 1" is less than 30%, so that is the reasoning for calling this Potential, in the headline. 

 

656PM: adjusted Title to OBS-NOWCAST.  Added freezing rain and rain to the tags.

First batch of mixed precip should arrive ne PA, extreme nw NJ and se NYS around 1-2A as snow freezing rain-rain, but the primary batch is slated to occur between 5AM and Noon as snow north and west of NYC til NYC-Li and NJ I95 changes to snow around 7-830A. It ends from northwest to southeast, first in nw NJ by 11A and then NYC by 1P and further southeast during mid afternoon.  Amounts near I84 of a dusting to possibly 2" with a general 1.5-4" in the core of the event from near NYC/LI-down I95 in NJ.  It may briefly snow 1/2mi moderate for an hour or so.  Still a little uncertain where the 4 inches are...probably NJ/LI. 

[wdrag]

Didn't realize this topic was started as Anafront etc. Stay there. I won't comment further here. If you wish delete this particular topic thread. Thanks, Walt

[NEG NAO]

really looking better

at 18Z

[SnowGoose69]

Don't take it as gospel and this range but the 00Z HRRR coming in even more amped with this...this may be the biggest event of the next 5 days in the end

[eduggs]

5 minutes ago, SnowGoose69 said:

Don't take it as gospel and this range but the 00Z HRRR coming in even more amped with this...this may be the biggest event of the next 5 days in the end

I'm pretty confident it will be. This is our event. I think it will pound for a few hours. I'm a little worried about surface temperatures initially, particularly at low elevations, but all indications are that it cools sufficiently before the precipitation shuts off. I'd be curious to hear how the best lift is aligning with respect to snow growth temperatures. 

This could catch people off guard, especially with some people looking to the weekend for the big one.

[eduggs]

I think there is a low-medium chance this ends up the biggest snow event of the year to date for parts of the subforum (WNJ, NENJ, Rockland etc). I'm rooting for a slight delay in timing so a decent amount can occur after sunrise.

[HeadInTheClouds]

This is definitely the best shot of show through the weekend. Looking like nice little 1-3/2-4 inch type event for most although I'm on the northern edge of things. 

[the_other_guy]

7 minutes ago, eduggs said:

I think there is a low-medium chance this ends up the biggest snow event of the year to date for parts of the subforum (WNJ, NENJ, Rockland etc). I'm rooting for a slight delay in timing so a decent amount can occur after sunrise.

Marginal temps initially. you want as much of this to fall before sunrise if you want to maximize accumulation on all surfaces

[eduggs]

1 hour ago, the_other_guy said:

Marginal temps initially. you want as much of this to fall before sunrise if you want to maximize accumulation on all surfaces

I don't want any of it to fall before sunrise, because then I won't see it. And also it's mid January. The sun has a very minor affect on snow accumulations unless intensity is too light to matter anyway. Once the front passes it won't matter what time of day it is. If there is precipitation behind the front it will accumulate.

[SnoSki14]

1 hour ago, the_other_guy said:

Marginal temps initially. you want as much of this to fall before sunrise if you want to maximize accumulation on all surfaces

Start time is pretty good (5-7am) and it ends before midday. 

[wdrag]

Okay, what I mess on the dual thread, i never saw the ANA thread... My apology.

Anyway,  We are going to have minor to moderate impact snow event in the subforum because of occurrence during the Thursday rush hour and temps falling below freezing after initial rain showers (all snow nw NJ per NAM).  I'll stay with 1-3" through the subforum with I84 on the northern fringe. 

The appended 21z NWS ensemble now shows a good risk of 1+, pops too low but going in the right direction. I will not be surprised at some 4-5" amounts w NJ e PA nw of I95.  

Good idea to be preparing for morning delays for travel and school starts (non remote). 

[wdrag]

HRRR was mostly real good on the 16th event and will be again... slightly amped but the idea is there. It's a warm model so when it says snow... better pay attention if snow is your concern.

Will try and comment at 6AM..depends: am on-call.

[eduggs]

The GFS was disappointing. Dry and almost all before sunrise. Crossing my fingers for an HRRR type outcome.

[SnoSki14]

15 minutes ago, eduggs said:

The GFS was disappointing. Dry and almost all before sunrise. Crossing my fingers for an HRRR type outcome.

Mesos will be the ones to watch. Very rarely do globals get these smaller systems right. 

Nam/HRRR is the one to watch

[eduggs]

5 minutes ago, SnoSki14 said:

Mesos will be the ones to watch. Very rarely do globals get these smaller systems right. 

Nam/HRRR is the one to watch

Probably true. But it was still better seeing the GFS spit out .2" liquid instead of a trace to a few hundredths. The CMC looked so so. I'm afraid the PVA and lift max out in KY and then decrease for us.

[wdrag]

This Thursday morning event continues. Expect a few 4-5" amounts northern NJ, se NYC, sw CT. Follow HRRR I think is best, Definitely going to impact the Thursday morning commute as temps fall to freezing or below by 9AM. Added an experimental  impact graphic. My last on this til late today when I'll update the thread and make it OBS-NOWCAST. Should be a sweet morning snowfall for some of us. Have a day. 

[Northof78]

6Z NAM good for a nice 2-4”

[MJO812]

6z Euro bumped up totals 

[North and West]

This Thursday morning event continues. Expect a few 4-5" amounts northern NJ, se NYC, sw CT. Follow HRRR I think is best, Definitely going to impact the Thursday morning commute as temps fall to freezing or below by 9AM. Added an experimental  impact graphic. My last on this til late today when I'll update the thread and make it OBS-NOWCAST. Should be a sweet morning snowfall for some of us. Have a day. 

I always look forward to your reasonable and logical posts. Thank you for that!


.

[jm1220]

Should be a decent snow event for most of us that will do enough to lay the white carpet down for much colder air. Always nice when you have some snow cover to welcome in an arctic airmass that can overperform due to snow cover, and just to have the snow to make it more wintery. Could be 3-5” where it’s all/mostly snow and it comes down moderate for a few hours. 

[wdrag]

28 minutes ago, North and West said:

I always look forward to your reasonable and logical posts. Thank you for that!


.

Try... not all work out. I still haven't given up on 1/21-24.  Something has to happen here.  

[LibertyBell]

8 hours ago, eduggs said:

The GFS was disappointing. Dry and almost all before sunrise. Crossing my fingers for an HRRR type outcome.

it's why all the locals are going with 1" of snow, best to keep expectations low.

 

[gravitylover]

2 minutes ago, wdrag said:

Try... not all work out. I still haven't given up on 1/21-24.  Something has to happen here.  

Yeah right. All of these bits of energy moving through the cold, something of consequence should pop. I have a feeling that if it does it will be as the cold air is leaving our side of the planet.

[LibertyBell]

18 minutes ago, jm1220 said:

Should be a decent snow event for most of us that will do enough to lay the white carpet down for much colder air. Always nice when you have some snow cover to welcome in an arctic airmass that can overperform due to snow cover, and just to have the snow to make it more wintery. Could be 3-5” where it’s all/mostly snow and it comes down moderate for a few hours. 

Probably more like 1-2 for us here on the south shore, most of our outlets are talking about rain for a few hours at the beginning.

 

[LibertyBell]

1 minute ago, gravitylover said:

Yeah right. All of these bits of energy moving through the cold, something of consequence should pop. I have a feeling that if it does it will be as the cold air is leaving our side of the planet.

Thats right and if it means the cold air has to go to make it happen, that's a nice trade off.  Nothing worse than worthless cold air.

 

[wdrag]

18 minutes ago, LibertyBell said:

Probably more like 1-2 for us here on the south shore, most of our outlets are talking about rain for a few hours at the beginning.

 

Yes...that looks correct.  best should near I95 westward.  My last post til this evening.

What i do from this time forward is use the SPC HREF meanssnowfall...axis should be very good. It will be available by 11A.

and of course the HRRR 12z and 18z versions.  Have a great day! Let's look forward to an even nicer looking landscape tomorrow morning. 

 

The evening visit will start the OBS-NOWcast of this thread, probably a straight conversion of this one.

 

Also, for the many of us who do not use the term ana front, katafront.  One reason i don't is that its a bit confusing. In my opinion, I view the ANAfront as a warm front...(despite its cold front southward passage) frequently will be a wave of pressure falls rippling along it to generate the qpf.

[LibertyBell]

8 minutes ago, wdrag said:

Yes...that looks correct.  best should near I95 westward.  My last post til this evening.

What i do from this time forward is use the SPC HREF meanssnowfall...axis should be very good. It will be available by 11A.

and of course the HRRR 12z and 18z versions.  Have a great day! Let's look forward to an even nicer looking landscape tomorrow morning. 

 

The evening visit will start the OBS-NOWcast of this thread, probably a straight conversion of this one.

 

Also, for the many of us who do not use the term ana front, katafront.  One reason i don't is that its a bit confusing. In my opinion, I view the ANAfront as a warm front...(despite its cold front southward passage) frequently will be a wave of pressure falls rippling along it to generate the qpf.

Thanks so much Walt.... why don't people just call it an arctic front snowfall? That's what we called it in the 90s.

 

[wdrag]

39 minutes ago, LibertyBell said:

Thanks so much Walt.... why don't people just call it an arctic front snowfall? That's what we called it in the 90s.

 

Well, in part because it is technically correct as ANA. But my take on science is try to simplify into language that cost of us understand. There is also lots of met technics that are beyond my clear understanding, that re purportedly better than old school.  Fortunately old school still works. 

So, arctic cold front snow can work...  (myself I likely to reserve arctic for 0F cold in NYC). However, I flex to not lose a persons interest.

Back tonight.

 

[ILoveWinter]

Should we expect advisories for a portion of the region today? I'd assume so considering a 2-4ish type of event...

[MJO812]

15 minutes ago, ILoveWinter said:

Should we expect advisories for a portion of the region today? I'd assume so considering a 2-4ish type of event...

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