February 24/25 Potential Winter Storm

[wthrmn654]

Lol the trusty icon is south and fairly icy going into nyc region. 

[wthrmn654]

0.14 ice near the airports looks like. 30 west of NY in parts of jersey. 

[HVSnowLover]

I think we saw from the last storm below 30 is the key temp for ice accretion however if there is some snow/sleet on the ground already I would imagine that might help increase accretion? 

[wthrmn654]

Just now, HVSnowLover said:

I think we saw from the last storm below 30 is the key temp for ice accretion however if there is some snow/sleet on the ground already I would imagine that might help increase accretion? 

Along with frozen ground as going into that one ground was warm/ thawed.  Versus this one having a coolder/ possibly frozen surface

[MJO812]

Gfs is warmer

[jm1220]

21 minutes ago, HVSnowLover said:

I think we saw from the last storm below 30 is the key temp for ice accretion however if there is some snow/sleet on the ground already I would imagine that might help increase accretion? 

With the last minor ice event it was 31 and accreting pretty efficiently with little snow left from the 1/29 storm here but that was with light precip. Heavier precip will tend to run off. 

[HeadInTheClouds]

[eduggs]

Anybody ignoring the NAM is wishcasting. The GFS and UK have the same basic idea. This could still go either way along the area of sharp snow gradient. But it's hard to see how the mid-level feature in WNY and southerly flow near 800mb doesn't push sleet pretty far up the HV. North of I-84 and east of the Hudson seem to have the best shot of damning in just enough cold air.

[USCG RS]

10 minutes ago, eduggs said:

Anybody ignoring the NAM is wishcasting. The GFS and UK have the same basic idea. This could still go either way along the area of sharp snow gradient. But it's hard to see how the mid-level feature in WNY and southerly flow near 800mb doesn't push sleet pretty far up the HV. North of I-84 and east of the Hudson seem to have the best shot of damning in just enough cold air.

I think the tri state is going to have to watch for the potential of Zr. Pretty ripe set up for ice imo. 

[HeadInTheClouds]

3 minutes ago, eduggs said:

Anybody ignoring the NAM is wishcasting. The GFS and UK have the same basic idea. This could still go either way along the area of sharp snow gradient. But it's hard to see how the mid-level feature in WNY and southerly flow near 800mb doesn't push sleet pretty far up the HV. North of I-84 and east of the Hudson seem to have the best shot of damning in just enough cold air.

Did you look at the 12z and 18z. It was a joke. 00z was a big correction and is still a warm outlier particularly north of 84. At 18z it gave my area 1.5 inches and Albany 3. Every other piece of guidance gives north of 84 up to I90 anywhere between 8 and 12. Should we ignore all the other guidance? 

[HeadInTheClouds]

[hudsonvalley21]

7 minutes ago, HeadInTheClouds said:

Did you look at the 12z and 18z. It was a joke. 00z was a big correction and is still a warm outlier particularly north of 84. At 18z it gave my area 1.5 inches and Albany 3. Every other piece of guidance gives north of 84 up to I90 anywhere between 8 and 12. Should we ignore all the other guidance? 

At this point I wouldn’t ignore anything. Who knows how much the 800mb push will make it northward and what the surface temps will be. I believe most models are showing a sharp cutoff with frozen type precipitation and just might come down to looking at current observations during the event itself.

[eduggs]

16 minutes ago, HeadInTheClouds said:

Did you look at the 12z and 18z. It was a joke. 00z was a big correction and is still a warm outlier particularly north of 84. At 18z it gave my area 1.5 inches and Albany 3. Every other piece of guidance gives north of 84 up to I90 anywhere between 8 and 12. Should we ignore all the other guidance? 

It didn't correct as much as you think. You are talking 3rd party interpreted snowfall accumulations, not model output. In reality, the modeled column cooled a degree or two near 800mb. The overall depiction is still the same - weakening primary in WNY associated with a dampening shortwave, transferring to weak coastal SLP. 

We don't have a strong mid-level low or a bombing coastal low - just a modest southerly mid-level flow and weak to moderate surface CAD. That sounds like a recipe for a broad area of mixed precipitation. Snow vs. sleet will come down to whether it's +0.5 or +2 in the warm layer and whether dynamical cooling can partially compensate.

With a strong primary I would always take the warmest solution. The NAM often leads in cases like this - in fact as others have said, sleet frequently ends up further north than modeled. And I wouldn't be shocked if BGM and ALB mix for a time. But in this case the warm surge is muted, so I'm not so sure. That's why I'm not completely writing off significant snow (i.e., 4"+) in Sussex, Orange, and Putnam counties.

[MJO812]

7 minutes ago, HeadInTheClouds said:

Alot of sleet for NYC

[MJO812]

4 minutes ago, eduggs said:

It didn't correct as much as you think. You are talking 3rd party snowfall accumulations, not model output. In reality, the modeled column cooled a degree or two near 800mb. The overall depiction is still the same - weakening primary in WNY associated with a dampening shortwave, transferring to weak coastal SLP. 

We don't have a strong mid-level low or a bombing coastal low - just a modest southerly mid-level flow and weak to moderate surface CAD. That sounds like a recipe for a broad area of mixed precipitation. Snow vs. sleet will come down to whether it's +0.5 or +2 in the warm layer and whether dynamical cooling can partially compensate.

With a strong primary I would always take the warmest solution. The NAM often leads in cases like this - in fact as others have said, sleet frequently ends up further north than modeled. And I wouldn't be shocked if BGM and ALB mix for a time. But in this case the warm surge is muted, so I'm not so sure. That's why I'm not completely writing off significant snow (i.e., 4"+) in Sussex, Orange, and Putnam counties.

But this isn't the usual SWFE with a high retreating. 

[SnowGoose69]

The SPC SREF as far as snow amount mean is something between the NAM/RGEM in the LHV and S CT...for FRZ RAIN its fairly ominous for the metro and has notably high confidence across all of WRN LI W-SW into CNJ  and the metro

[HeadInTheClouds]

17 minutes ago, eduggs said:

It didn't correct as much as you think. You are talking 3rd party interpreted snowfall accumulations, not model output. In reality, the modeled column cooled a degree or two near 800mb. The overall depiction is still the same - weakening primary in WNY associated with a dampening shortwave, transferring to weak coastal SLP. 

We don't have a strong mid-level low or a bombing coastal low - just a modest southerly mid-level flow and weak to moderate surface CAD. That sounds like a recipe for a broad area of mixed precipitation. Snow vs. sleet will come down to whether it's +0.5 or +2 in the warm layer and whether dynamical cooling can partially compensate.

With a strong primary I would always take the warmest solution. The NAM often leads in cases like this - in fact as others have said, sleet frequently ends up further north than modeled. And I wouldn't be shocked if BGM and ALB mix for a time. But in this case the warm surge is muted, so I'm not so sure. That's why I'm not completely writing off significant snow (i.e., 4"+) in Sussex, Orange, and Putnam counties.

The nam is also known to be too warm at times also. 00z was different, with the primary not being as strong and secondary further south and it was colder. The bottom line is the output was far different from other models, particulary up north, and if Albany gets 3 inches I'll eat my shorts in Macy's window. 

[USCG RS]

5 minutes ago, SnowGoose69 said:

The SPC SREF as far as snow amount mean is something between the NAM/RGEM in the LHV and S CT...for FRZ RAIN its fairly ominous for the metro and has notably high confidence across all of WRN LI W-SW into CNJ  and the metro

Thoughts on accums? 

[HeadInTheClouds]

UKIE

 

[eduggs]

12 minutes ago, MJO812 said:

But this isn't the usual SWFE with a high retreating. 

This looks like a pretty typical SWFE to me. The SWF refers to mid-levels, not surface features.

The high doesn't "retreat" because the mid-level shortwave approaching through the midwest is dampening as it approaches, so the area of strongest upper level convergence stays in approximately the same place. This upper level convergence (converging height lines) results in an accumulation of air aloft, which is forced to descend - hence high surface pressure.

The dampening wave allows a quicker weakening of the surface low and prevents a complete torch. But if you look at h5, the shortwave is traversing Lake Ontario and northern NY on Friday. That's classic SWFE, and why we have a mix event on tap while areas north and east will be snow.

[Juliancolton]

Just now, eduggs said:

This looks like a pretty typical SWFE to me. The SWF refers to mid-levels, not surface features.

The high doesn't "retreat" because the mid-level shortwave approaching through the midwest is dampening as it approaches, so the area of strongest upper level convergence stays in approximately the same place. This upper level convergence (converging height lines) results in an accumulation of air aloft, which is forced to descend - hence high surface pressure.

The dampening wave allows a quicker weakening of the surface low and prevents a complete torch. But if you look at h5, the shortwave is traversing Lake Ontario and northern NY on Friday. That's classic SWFE, and why we have a mix event on tap while areas north and east will be snow.

Great series of posts tonight.

[SnowGoose69]

8 minutes ago, USCG RS said:

Thoughts on accums? 

I think everyone  in this subforum is 5 inches or less for sure with the 5 near SWF and 1 or less near NYC

[eduggs]

8 minutes ago, HeadInTheClouds said:

The nam is also known to be too warm at times also. 00z was different, with the primary not being as strong and secondary further south and it was colder. The bottom line is the output was far different from other models, particulary up north, and if Albany gets 3 inches I'll eat my shorts in Macy's window. 

I don't think you should focus so much on ptype interpreted accumulation maps (e.g., 3" at ALB). They can be very misleading. Yes recent NAM runs had a slightly stronger and longer-lived primary surface low. But there is broad inter-model agreement on the synoptic setup. The difference between 3 and 8 inches of snow could come down to a degree or two in the warm layer. 

[LibertyBell]

9 minutes ago, eduggs said:

This looks like a pretty typical SWFE to me. The SWF refers to mid-levels, not surface features.

The high doesn't "retreat" because the mid-level shortwave approaching through the midwest is dampening as it approaches, so the area of strongest upper level convergence stays in approximately the same place. This upper level convergence (converging height lines) results in an accumulation of air aloft, which is forced to descend - hence high surface pressure.

The dampening wave allows a quicker weakening of the surface low and prevents a complete torch. But if you look at h5, the shortwave is traversing Lake Ontario and northern NY on Friday. That's classic SWFE, and why we have a mix event on tap while areas north and east will be snow.

Yep, this isn't a VD 2007 repeat or even St Paddy's Day 2007 for that matter.

 

[USCG RS]

7 minutes ago, SnowGoose69 said:

I think everyone  in this subforum is 5 inches or less for sure with the 5 near SWF and 1 or less near NYC

Thanks for the answer.. I should have clarified... Thoughts on ice accums? 

[NJwx85]

9 minutes ago, SnowGoose69 said:

I think everyone  in this subforum is 5 inches or less for sure with the 5 near SWF and 1 or less near NYC

Can you please post SREF ZR probabilities?

[HeadInTheClouds]

1 minute ago, eduggs said:

I don't think you should focus so much on ptype interpreted accumulation maps (e.g., 3" at ALB). They can be very misleading. Yes recent NAM runs had a slightly stronger and longer-lived primary surface low. But there is broad inter-model agreement on the synoptic setup. The difference between 3 and 8 inches of snow could come down to a degree or two in the warm layer. 

and isn't that exactly what happened at 00z vs 18z therefore it looked a little more like other guidance as far as snow vs sleet. I have seen the nam be too aggressive with the warming many times and it did correct somewhat at 00z. 

[MJO812]

Euro is all rain for NYC

[HeadInTheClouds]

[MJO812]

I'm going to pray for colder trends tomorrow