Jan 24-26 Weekend Snow and Sleetfest Model Thread Part Tres

[clskinsfan]

Through 12z for those who dont have access:

[psuhoffman]

2 minutes ago, stormtracker said:

Still colder vs 12z...CAD dug in a little deeper as well..precip not super heavy on this panel tho

High was a little further south with better damming signal into the mid atlantic this run.  Minor but we only need minor improvements here 

[bncho]

btw the 3k NAM is ALSO noticeably colder in the upper levels than its 12z run

[stormtracker]

Sleet incoming at 42.   

[MN Transplant]

Parent NAM still changes DC over at 12z, but at least there is a bit more precip by then.  But really, we should be looking at the 3k from now to the event.

[stormtracker]

wetter than 12z so far

[jgentworth]

1 minute ago, stormtracker said:

Thermal changes level off at 42, but some good snows 12z

Yeah, pretty wild how it can go from being colder at all layers for the entire run but then at 42, the snow line is actually North of the 12z run. Overall though, I liked the steps south in the earlier hours.

[jlewis1111]

1 minute ago, jgentworth said:

Yeah, pretty wild how it can go from being colder at all layers for the entire run but then at 42, the snow line is actually North of the 12z run. Overall though, I liked the steps south in the earlier hours.

cause by then its outa range no point looking past 24 hours tbh

[SnowenOutThere]

Nam 3k is am improvement for me (mix line hits me at this panel) but man is it still a certifiably bad outcome. It does the same splotchy precip shield which just won't work out for us even it is colder.

[Maestrobjwa]

9 minutes ago, psuhoffman said:

High was a little further south with better damming signal into the mid atlantic this run.  Minor but we only need minor improvements here 

You think the ol' "models underdoing CAD" tendency may come into play here?

[MillvilleWx]

Just looked at model comparison tool on Pivotal at hr 42 and went through every model sounding I could get for DCA and NoVA. The NAM 12km is the warmest of all and most aggressive with the warm nose push. Every model, including the 12z NAM Nest is south of it, and by 30+ miles. The key this run was a much better precip shield on the WAA pattern leading in. As @psuhoffman alluded to, that is important and a good sign across all guidance that seemed to bump precip in that time for 12z runs with the NAM the only one lagging behind. It’s playing catch up in that instance, which is fine at this lead. It’s a solid signal overall. 

[Yeoman]

6 minutes ago, stormtracker said:

Thermal changes level off at 42, but some good snows 12z

Compare 850 winds and 850 0°C line at hour 42 on both runs, plus where the strongest fgen/omega sits. If the better lift shifts north or the 850 flow turns more S/SE, that’s your “colder run, warmer result” culprit.

[Yeoman]

2 minutes ago, Maestrobjwa said:

You think the ol' "models undergoing CAD" tendency may come into play here?

If low-level northeasterly flow holds longer than modeled, you can sustain snow or sleet even as the mid-levels warm, which models often don’t resolve well until you’re inside ~24–36 hours.

[MN Transplant]

The 3km NAM is the worst run so far for DC.  Only about 0.3" before the flip.  Pronounced warm nose between 750-800mb.

[snjókoma]

The 3K Nam has ~0.35" of QPF in DC before flip to sleet.

[NorthArlington101]

2 minutes ago, SnowenOutThere said:

Nam 3k is am improvement for me (mix line hits me at this panel) but man is it still a certifiably bad outcome. It does the same splotchy precip shield which just won't work out for us even it is colder.

Still just can't get over .5"/hr 10:1 on the 3k... and D.C. still flips around 9am. With all other guidance saying otherwise I really want to toss. Just can't shake the fact that it's not quite on board yet. What @MillvilleWx said is encouraging, at least.

[SnowenOutThere]

Just now, NorthArlington101 said:

Still just can't get over .5"/hr 10:1 on the 3k... and D.C. still flips around 9am. With all other guidance saying otherwise I really want to toss. Just can't shake the fact that it's not quite on board yet. What @MillvilleWx said is encouraging, at least.

It leaves all its intense precip way down in the warm sector compared to everything else. To my understanding of WAA and FGEN that's not normal. 

[NorthArlington101]

Just now, MN Transplant said:

The 3km NAM is the worst run so far for DC.  Only about 0.3" before the flip.  Pronounced warm nose between 750-800mb.

better snow to the south of us but didn't save it from a mediocre outcome. Only using Kuchera given the chatter about better than 10:1

[T. August]

3k is dry af… .4-.5 qpf before the flip even in the favored areas.

[psuhoffman]

Both NAM's were colder and better out to 36 hours then went off the rails...once they got into less reliable ranges.  

[SnowenOutThere]

I mean it has the FGEN but only bothers to bring it north after we all are sleeting. The HRRR has FGEN more spread out which makes sense imo with this setup and then its real band is right on the snow/sleet line

[DDweatherman]

2 minutes ago, psuhoffman said:

Both NAM's were colder and better out to 36 hours then went off the rails...once they got into less reliable ranges.  

The NAM kinda does truncate at hour 36 I believe? Could make sense.

[Terpeast]

2 minutes ago, psuhoffman said:

Both NAM's were colder and better out to 36 hours then went off the rails...once they got into less reliable ranges.  

By tonight/tomorrow 0z-12z we should see NAM start handling the thermals better.

[baltosquid]

4 minutes ago, psuhoffman said:

Both NAM's were colder and better out to 36 hours then went off the rails...once they got into less reliable ranges.  

Yeah I got pulled away from checking panels as the system worked up the central CONUS and was optimistic, then quite unpleasantly surprised when I was able to see the end… whatever the case I am happy to take the better cold push and punt the thermal question til later.

[MillvilleWx]

4 minutes ago, T. August said:

3k is dry af… .4-.5 qpf before the flip even in the favored areas.

This is the biggest issue for the Nest so far. It’s just so weak comparitively with the WAA precip, and precip just in general. Still time, but I have seen the Nest do this before with synoptic scale QPF distribution. Too light overall, but still shows the ultra heavy precip depictions in the mountains as it struggles with capping magnitude of upslope flow. 

[MN Transplant]

6 minutes ago, psuhoffman said:

Both NAM's were colder and better out to 36 hours then went off the rails...once they got into less reliable ranges.  

We took a step backwards with a stronger (the strongest yet) 850 low in Ohio.

[balltermen]

5 minutes ago, MN Transplant said:

The 3km NAM is the worst run so far for DC.  Only about 0.3" before the flip.  Pronounced warm nose between 750-800mb.

soundings maybe imply snow until 14-15z. it's after that that the nose goes full pinocchio.  I think it's too warm.  But if models trend toward an 8-9 am flip it's a 4-6" snow and then maybe 2-3" sleet. 

I figure a blended ratio of 12:1 for the snow portion here.   I think 6-10" incl sleet is still the right forecast for now. 

[Yeoman]

5 minutes ago, SnowenOutThere said:

I mean it has the FGEN but only bothers to bring it north after we all are sleeting. The HRRR has FGEN more spread out which makes sense imo with this setup and then its real band is right on the snow/sleet line

HRRR is worthless for predicting band placement until it's inside 18 hours

[Yeoman]

1 minute ago, MN Transplant said:

We took a step backwards with a stronger (the strongest yet) 850 low in Ohio.

Must have picked up on what's looking like this early wave break

[baltosquid]

Oof, RRFS amped up at 18z. Need one of these mesos to trend better…