January 25-26 Winter Storm Potential

[Newman]

Wow the 12z NAM just made a jump towards the GFS evolution, keeping things a bit more strung out and transferring to the coast sooner. Still gets the sleet line up to Central Berks county, but no further north. And then things crash back south with more to come early Sunday night. This is probably the NAM doing NAM things, but fun to see and if we see models tick that way at 12z, I might give it credence. Will need quite a few more ticks to see a lot of snow on the backside, the dry slot still kills anything past 03z

[The Iceman]

1 minute ago, LVblizzard said:

12z NAM is substantially colder north of Philly. All snow for I-78 north. Jackpot zone of 16-20” for the LV and Poconos.

It also beats back the sleet line. 18z it's pushing into the burbs, 21z its beaten back below freezing. I think it's showing it will be rate dependent there whether you stay snow or not.

[zenmsav6810]

36 minutes ago, PhiEaglesfan712 said:

I moved my Vermont trip to March 7-9. We can be sure there won't be a snowstorm that weekend, right?

 

11 minutes ago, The Iceman said:

Damn you should have left a day early, the way this ones trending, Vermont is going to be the place to be for this one.

Its not too late! Just go twice!!

[JTA66]

37 minutes ago, PhiEaglesfan712 said:

I moved my Vermont trip to March 7-9. We can be sure there won't be a snowstorm that weekend, right?

March will rock!

[LVblizzard]

1 minute ago, The Iceman said:

It also beats back the sleet line. 18z it's pushing into the burbs, 21z its beaten back below freezing. I think it's showing it will be rate dependent there whether you stay snow or not.

It actually starts out warmer. Earlier in the run I was like welp here we go again. But that sleet line just stalls on Sunday afternoon. It will come down to rates but also the development of the secondary low.

[LVblizzard]

3km NAM does the same thing with stalling the mix line, except it does it like 20 miles north right along I-78.

[Violentweatherfan]

1 hour ago, Physicsteve said:

Based on the map Paul just posted, which i had to double and triple check all the time stamps, maybe the real mets are also thinking the models are overdoing the non-snow. Paging @MGorse, as if he’s not busy or anything. 

ETA: Does that map *include sleet* as snow like some other models? Also off topic and apologize if bantery, but how does the NBM account for some including sleet as 3:1 snow and not others?

I think they are accounting for heavy snow bands, since this is still an overrunning event there will be a much wider swath of snow 

[Newman]

9 minutes ago, LVblizzard said:

3km NAM does the same thing with stalling the mix line, except it does it like 20 miles north right along I-78.

By 1pm Sunday it also has significantly more snow across the area. It doesn't look like a timing difference to me, just more QPF and better ratios/rates.

[LVblizzard]

Just now, Newman said:

By 1pm Sunday it also has significantly more snow across the area. It doesn't look like a timing difference to me, just more QPF and better ratios/rates.

Northern extent of the mix line comes down to two things:

1. Snowfall rates - heavier snow = slower progression northward

2. Formation of the secondary low - models have been killing off the primary sooner since last night which is what we want to see for a snowier solution

[ChescoWx]

Looking at the 12z 3km NAM only through 7pm but it shows what I suspect will happen - a quick 6" to 9" of snow across Chester County up to the LV and a change to sleet all the way up to ABE from noon through 3pm from south to north. Then 0.5" north to 2" south of sleet which gets totals to 7" to 10" of snow/sleet by 7pm....if this went further I believe it will show a change back to all snow later like the 12km at night with maybe a couple more inches which gets us to 9" to 12" across the area from Southern Chesco up to ABE.  

[Newman]

Lol, the FV3 is super cold. That is its typical bias though so I wouldn't put much stock in it. It's got the sleet line still south of Philly by 0z Monday. Significant snows north of that across all of SE PA verbatim

[rcostell]

1 hour ago, MGorse said:

Looking at some of the model forecast soundings, some  of the guidance is showing freezing rain or even plain rain (depending on location) however the sounding looks more like sleet. Model snowfall graphics typically include sleet as snow and sleet are counted together. The FRAM graphic above is strictly ice accretion from freezing rain. The Kuchera snowfall maps be careful with as it only uses the maximum temperature aloft to calculate snowfall. The 10:1 ratio maps also use with caution as that ratio is not usually representative during a storm as the ratios certainly change up and down as the storm evolves.

Mike- Thanks for the insight and taking time out. Us "largely lurkers"  learn a little something with any exchange like the above.  Obliged. 

[The Iceman]

On 1/22/2026 at 10:15 AM, The Iceman said:

First call:

3-6” snow/sleet/ice shore points extreme snj

6-12” snow/sleet 95/195 corridor to SNJ

8-16” snow/sleet N and W of the fall line.

 

Still sticking with this call and I don't imagine I'll change it so this is really final call. Someone in the Pocono's will probably get 20".

[rcostell]

1 hour ago, Albedoman said:

Note this.  I am NOT chuckling:  

 

As long as the column saturates quickly enough, any snow that
falls late Saturday night and into early Sunday morning could be
very high ratio, fluffy, rapidly accumulating snow that
consists of many pristine dendrites (SLRs 15-20:1, could be
even higher if the column saturates faster but there is dry air
at low levels to overcome at onset). So after a few hours of
virga, accumulations have the potential to begin with a
vengeance in the predawn hours Sunday, especially from I-80
south.”

(The above is a State College based write up.  No arguing here- but kaeeping it real- you earlier wrote with contextual certainty for your area (not Stage College)  yesterday:  "with greater than 25:1  as a max with this storm.."   so yes, I chuckled.  Sorry if it seems to have triggered you.  I'd get over it and move on.   Back to reading.) 

[SP]

for some reason the excitement is fading......for SOMOCO

[JTA66]

My first guess for central Montco is 6-10". Obviously subject to change.

[mattinpa]

2 minutes ago, JTA66 said:

My first guess for central Montco is 6-10". Obviously subject to change.

Sounds good for now - could get a little more but likely not less than 6”.

[ChescoWx]

The latest RRFS which will replace the NAM this year comes in with a snowier less sleety solution than it's older parent...

 

[JTA66]

GFS also sticking with the colder solution. If only it were a good model...sigh.

[jrodd321]

Gfs boom. 

[Duca892]

GFS has been remarkable in its consistency IMO 

[zenmsav6810]

4 minutes ago, Duca892 said:

GFS has been remarkable in its consistency IMO 

Yes, this will be a nice storm especial for the NW crew. Its been consistent with the followup storms too. 

[Mikeymac5306]

Did I just see this come south a tick or two? Please elaborate

[RedSky]

16 minutes ago, Mikeymac5306 said:

Did I just see this come south a tick or two? Please elaborate

Woken up from a coma thought I was hallucinating you may be right

 

[RedSky]

CMC and UKMET notch south and colder

 

[RedSky]

Dr No rolling out from the bunker

 

[Hurricane Agnes]

4 minutes ago, RedSky said:

Dr No rolling out from the bunker

 

The AI one looks conservative compared to everything else.

[Newman]

I still like my Adams -> Dauphin -> Schuylkill -> Carbon -> Monroe call as to where the southern edge of the jackpot zone might set up. You want to be on the north side of the 850mb fronto and unfortunately I could see poor snow growth/crystal habit in the sinking air south of that fronto band. However, it is encouraging seeing things start to tick south and colder

[wkd]

6 minutes ago, Hurricane Agnes said:

The AI one looks conservative compared to everything else.

Need to see the Kuchera map

[zenmsav6810]

34 minutes ago, Mikeymac5306 said:

Did I just see this come south a tick or two? Please elaborate

 

13 minutes ago, RedSky said:

CMC and UKMET notch south and colder

 

Perhaps its a more ..."efficient" transfer of the primary to the costal low. That seems to be driving the earlier/faster evolution/colder/more southern solutions