GaWx

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.

Indeed, the fact that the best models can and do miss so badly even just a few days out makes this far more interesting than it would otherwise be due to higher uncertainty. Can you imagine how boring forecast discussions would be if the models were perfect?

Yeah, it hasn’t had as big jumps as the Euro op run to run on this.

6Z EPS 10:1 RDU still gets a real nice hit of 4-4.5”

As bad as some in the SE are feeling about the Euro changes, can you imagine how bad the NE is feeling? 6Z 2/16 Euro: 6Z 2/17 Euro: instead it went way SE: 6Z 2/16 Euro: JB still yesterday evening thought even this was going to trend W to W of Hatteras 6Z 2/17 Euro instead trended way east:

JB’s prediction of the low going W of Hatteras on life support now. Meanwhile, here’s the 0Z EPS 10:1 snow. RDU actually rose from 5” on the 18Z to 6” on the 0Z, which is tied with the 0Z of 24 hours ago for the highest!

The 0Z Euro went even further SE… significantly further! The 1” and 0.5” qpf lines have moved 200 miles E/SE vs the 0Z of 24 hours ago! New 0Z Euro Kuchera: RDU down to 4.9” (~1/2 the 18Z); DC down to 0.5” vs 16.7” 24 hours ago: Old 0Z Euro Kuchera:

Look how far the Euro heaviest qpf has trended the last 3 runs. In NC, the 0.5” and 1” lines have shifted E/SE a whopping 100-150 miles! It is due to shift back west some at 0Z. Anyone want to make a prediction of what the 0Z will show? 0Z Euro 18Z Euro

Ok maybe calling it a “major” outlier is too strong. But the UK/CMC have 5-6”. Isn’t that a pretty large difference from 9.8”?

You need JB’s expectation of the low going W of Hatteras due to cold model biases/NW trend to verify.

Wow, 9.8” at RDU! I wouldn’t bet on that much as it is a major outlier to other models and La Niña climo says the chance of that much this time of year there is very low.

Per a video JB released around 11AM today, he’s insisting that the low will go W of Hatteras (100-150 miles W of the model consensus). He’s been insisting on this. His reasoning is that he thinks the models are pushing the cold air boundary out too far due to a bias. He’s saying bet on the common NW trend we talk about. Any chance he’s going to be right? I believe that all of the latest models are well E of Hatteras except the 18Z Icon and NAM, which are only barely off Hatt: 18Z Icon: 18Z NAM:

18Z GFS Sleet: ZR:

The 18Z Icon looks great for RDU: 0.92” qpf. Of this ~0.35” is with snow (say ~3” Kuchera) and ~0.57” is with sleet..1.7” of sleet. Total of ~4.7” snow/sleet RDU with hardly any, if any, ZR.

I see that Dry Fork is only ~6 miles S of Chatham. The following link has Chatham snowfall and other data back ~100 years: https://www.weather.gov/wrh/Climate?wfo=rnk 2”+ Chatham snowfalls 2/15-3/10 during La Niña: there is data going back 30 La Niñas 2/18-19/1989: 10.3” from ? 2/25-26/1934: 9.0” from 1.60” liquid 3/2/2009: 7.7” from 1.09” liquid 2/15/1965: 6.0” from 0.48” liquid 2/24/1989: 5.0” from ? 2/18-19/1972: 4.5” from 0.71” liquid 2/20/2012: 3.2” from 0.40” liquid 2/23/2001: 2.0” from 0.26” liquid 3/2/1939: 2.0” from 0.20” liquid The other 21 La Niñas had no storm of 2”+ during 2/15-3/10. Median largest snow during 2/15-3/10 in any one of the 30 La Niñas was actually <0.5”! -Chance for 0.5”+ storm during La Niña 2/15-3/10 <50% -Chance for 2”+ storm during La Nina 2/15-3/10: 9 out of 30 or 30% chance -Chance for 4”+: 20% -Chance for 7”+: 10% -Chance for 10”+: 3% So, for example: if you get a 4” snowfall, which is looking like a good possibility, you will have done better than 80% of La Niñas during 2/14-3/10. With the current storm threat, you’re in better shape than in most La Ninas this time of year. Regarding snow to liquid ratio for the seven 2”+ snows the liquid is available for: only one storm was >10:1, 2/15/1965. It was at 12.5:1. It was cold with a high of 29 and low of 23. What matters most is the temp aloft like at 850. I bet that was a good bit below 0C. Best to look at Kuchera instead of 10:1 if available.

One of the best ways to learn imo is to study wx maps of storms of the past as well as station data and indices (like MJO, PNA, AO, NAO, EPO) to get a good idea for each person’s area. The study of climo is fascinating to me. It takes time but is worthwhile if you have enough spare time.

Aren’t you still getting multiple inches on all models?

This storm will occur during a rapidly retreating -AO toward neutral (4-5 days after a sub -5), a +PNA, a retreating -NAO moving to neutral, and a weak to moderate MJO phase 8.

12Z Euro 24 hour qpf:

12Z Euro: Big hit RDU kuchera 7.9”

Thanks, Brick. For Fayetteville, that 2.9” is really mainly 0.7” of ZR/icestorm with 850s +3+ and sfc temps starting near 32 and falling to high 20s.

UK snow map: 5-6” N Wake at 10:1 (further south not accurate especially well south because counts all wintry precip as snow) https://www.pivotalweather.com/model.php?m=ukmo_global&p=sn10_024h-imp&rh=2025021612&fh=93&r=us_ma&dpdt=&mc=

12Z UK: slightly colder vs 0Z with RDU area near snow/sleet line vs almost all sleet on 0Z early. Thus, the snow maps on Pivotal for N Wake county should be pretty accurate this time for 10:1. S Wake: not quite as accurate