GaWx

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

The 12Z GFS and CMC have a pretty close call for wintry precip in the deep SE on Feb 24th from a coastal: GFS: CMC:

12Z CMC qpf: RDU 0.5-0.6” all wintry is a major winter storm there; it is mainly a major snow as Brick showed sleet: a lot parts of E NC

0.5-0.6” qpf for RDU as shown on the 12Z GFS would be a major winter storm for them since all is wintry precip (all with temps well below 32)

12Z GFS qpf

If RDU-GSO end up getting 3-6” of snow/sleet from this, it would be near a historic high for those cities for the last half of Feb during La Niña. It’s important to look at history to keep it in perspective. 6” would be a new record for this category: RDU La Niña 4”+ snows Feb 15-28: 2/16/1996: 5.6” 2/23-4/1989: 4.2” 2/17-8/1989: 4.9” 2/25/1894: 5.0” GSO had 5.7” just after Feb (3/1-2/2009). Furthermore, if a lot of the 3-6” is sleet, that’s much more impactful. Most of these weren’t majority sleet.

Wave #2 (2/22-23) on 0Z EPS:

EPS 10:1:

UK comparison of 0Z vs 12Z at RDU: 12Z UK RDU qpf 1.5”. Of this ~0.1” is snow, ~0.1” is sleet, ~1.1” is ZR (ouch), and 0.2” is rain. 0Z UK is colder than 12Z. RDU qpf 1.0”. Of this, ~0.05” is snow, ~0.75” is sleet, and ~0.2” is ZR. So, much more sleet and way less ZR due to colder aloft.

0Z Euro huge snow hit for many: Kuchera (WB Kuchera Euro are pretty accurate) Sleet underdone on WB Euro: ZR overdone on WB euro:

The 7.6” of RDU “snow” on this Pivotal snow map is way off. Pivotal UK snow maps are typically way overdone on the S side due to counting all wintry as snow. RDU gets a lot of qpf (1.0”) but it is mainly from sleet as ~0.75” falls with 850s +1 to +2. There’s ~0.2” falling as ZR when 850s/925s warm above that. There’s ~0.05” falling as snow. So, 0.75” qpf as sleet is ~2.25” of sleet. Add 0.5” of snow to get 2.75” of an overall dense accumulation….it wouldn’t go anywhere fast! It would have the staying power of 7.6” or more of snow. I had that much sleet here in Jan. It was awesome! @wncsnow knows about the problems with Pivotal UK snow maps