GaWx

It would be pretty remarkable if early March is also cold with it being La Niña. That’s somewhat favored during El Niño, not La Niña. But this winter has been unusual overall with regard to ENSO. Also, the coldest periods with the TPV lobes bringing the E US cold during very strong/near record strong SPV periods has been anything but normal.

Is WXBell down for anyone else? It’s been that way for me for 1/2 hour+.

Have the weenies messed up WxBell? Meanwhile, the 12Z GFS was interesting with accumulating snow just west of ATL tomorrow near and soon after sunrise. But admittedly that’s likely overdone and is an outlier, regardless.

And Barney returns! I’d love for this to verify just for the cold. But it is just a fantasy range 12Z GFS op run which looks totally different from prior runs. So, this has no more than entertainment value, of course. It will likely be far different on the Happy Hour run.

Meanwhile, 12Z UKMET at RDU dropped back from the 2.1” of the 0Z run, to 1.5” on the 6Z and to 1.4” on the 12Z. The qpf on the 12Z is ~0.13”. It looks like to me that just about all of the precip at RDU will be snow per general model consensus.

0Z Euro: 2.5” Kuchera RDU from 0.25” qpf

Why are 0Z 12K NAM 850s 3-4C warmer than 3K NAM’s for RDU?

0Z UK for RDU: highest since 12Z of Sunday with 2.1” of pure snow from 0.2” of qpf.

At RDU, the qpf of 0.28” is ~same as the 12Z/6Z and the snow (actually a little higher at 3.1” on later map) is also similar. So, it has stabilized.

18Z Euro qpf/Kuchera: with 850s never above -1C; RDU gets 3.1” (edited) of pure snow from 0.28” qpf; 2m temps start 29 and drop to 25 most of the snow; higher ratio snows to the W/NW with 850s even colder

0.80” RDU but tight gradient

I just saw WB 12Z JMA update: the 850s do, indeed, stay just <0C at RDU through the entire event and qpf is 0.80”. Based on this, I’m going to retain my educated guess that this is giving RDU ~~6” of mainly wet snow with perhaps a small amount of sleet: 12Z JMA furthest N 850 0C line southern border of Wake county with -1C at RDU:

Are you saying that RDU got 3K NAM’d?

18Z NAM ZR ouch near RDU: 0.26”

18Z NAM has a good bit of ZR and less % that’s IP vs 12Z due to warmer atmosphere

RDU. There are no p-type maps or 2 meter temp maps for the JMA at either WB or TT. It is pretty much a given that 2m will be below 32. TT does have 850s at 24 hour intervals for today’s 12Z JMA allowing me to educatedly guess that RDU would be just about all snow (maybe a little sleet). I think that 6” of snowfall from 0.80” qpf would be doable but it is just an educated guess. Regardless, it would be a major hit. If it were mainly sleet (highly doubtful), it would still approach 3” of concrete. ***Edit: I’ll update this when it comes out on WB as they have 850s and qpf at 6 hour intervals through hour 72.

12Z JMA has was appears to be nearly all if not all snow at RDU due to 850s likely staying below 0C most if not the entire time along with ~0.80” qpf suggesting ~~6” of Kuchera snow. A 6” snowfall would be their 4th biggest in La Niña Feb-Apr back to 1886-7! The only larger than 6” were 8.0” on 3/10/1934, 6.9” on 2/6/1984, and 6.2” on 2/17-18/1989. 2/16/96 was very close with 5.6”. In contrast, there have been 8 snowstorms of 6”+ during El Niño Feb-Apr vs the 3 during La Niña at RDU.

Actually, the 12Z WB NAM output shows mainly snow (1.8”) and sleet (0.8”) with only .02” of ZR for RDU due to 850s only getting to barely above 0C for a portion and 925s being near 0C for only a short time before falling to -2 to -3 for most of the qpf: The globals keep RDU in near 100% snow.

12Z Icon qpf: 0.61” RDU

12Z Icon: all snow for RDU; this is 10:1; but even after Kuchera reduction from 6.1” it shows, would likely still be 4-5” hit/major:

12Z NAM fwiw:

12Z NAM: look how much further W is the low compared to other models. But it is the latter hours of the NAM…so take with a humongous grain:

It will still be only Feb 23-24 for the next one and with cold air still nearby.

Don’t forget that there’s another system waiting in the wings once we’re done following this one. There’s always a next time. Maybe that will be more impactful than this one. One never knows, especially since it is still out 6-7 days, a relative eternity!

From JB: Opportunity to learn: Perfect 500 mb forecast, but the surface not responding likely due to lack of focused warm advection The warm advection term is just as important as upper divergence in cyclogenesis and I thought there would be more resistance. AI looks like it will be right. That 9-day call on 500 mb was as good as I can do. In retrospect the development of heavy precip on the gulf coast shuts down any inflow north into the arctic boundary. and the precip weakens in the cold air. Once that convective feedback takes off, there is no chance for the kind of warm advection needed for the more northern route. I obviously thought this was not going to happen to this extent. But that kind of vv there means that is where this wants to form. As it moves along the snow shield to the north weakens instead of the other way. Once the focus gets to the coast its too late and only light snows from the upper low come across.