GaWx

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

Agree 100%! A 4-6” late Feb storm in La Niña at RDU would be a rarity. 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).

0Z GFS:

Plus it has a 1060 mb high.

The week 2/19-25 has a good chance to end up the coldest week of the winter at GSO (and at other NC cities). If so, it would be the latest coldest week there since way back in 1993! Then the coldest was 3/13-19/1993 due to the superstorm. Going back to 1959-60, the only two other winters with a later coldest week were 2/21-27/1967 and 3/4-10/1960.

The new Euro Weeklies for 2/17-23 is the coldest yet for that week in the SE. In terms of anomalies, this would be the coldest of the winter in most of NC if it were to verify. In terms of absolutes, it would be close to Jan 20-26 for coldest in much of NC. For S GA/SC, it would be either 2nd or 3rd coldest in terms of anomalies/3rd coldest in terms of absolutes. For N GA/upstate SC, it would be ~a tie with Jan 20-26 for coldest anomaly and would be 2nd or 3rd coldest in terms of absolutes:

In addition to 2/13-14/1960, it appears that the terrible 2/2/1996 icestorm was from a Miller A. I don’t even see a wedge! https://products.climate.ncsu.edu/weather/winter/event/?e=159 At the time it was the worst ever in Hickory and Statesville for outages: “By 1500 EST, many major population centers such as Hickory and Statesville were reporting 50 percent power outages. The storm became the "worst ice storm ever" in local power company records. By late night most customers had lost power. Many customers did not have power restored for up to a week during extremely cold weather.” @StantonParkHoya

I see the 1/2” of ZR on WB Euro. However, I recently posted that the WB Euro algos for ZR vs IP appear to be off in that it has too much ZR at the expense of IP. In S Franklin Cty in case you didn’t see this, the 925s never get above -3C and the 850s never rise above +2C. That imo would mean little ZR RDU/Franklin Cty and 1.5-2” more IP than what’s on the Euro output.

GEPS (2/22-3):

This next SW is mildly interesting on the 12Z Euro as at face value it is a close call for a light wintry event here and nearby (coastal SE) with the low going across S FL in combo with lingering Arctic air to the N: EPS has a decent Miller A storm signal:

The WB Euro algos for ZR vs IP appear to me to be too tilted to ZR and too little for IP. Note that the GFS and CMC on WB both tend to have more IP than Euro. Looking at the 12Z Euro qpf/850s, it has for RDU ~10 times as much qpf as ZR vs IP. But that’s despite highest 850’s staying near +1C and warmest 925s being -3C! I believe that if the algos were corrected that nearly all of the ZR at RDU is really IP. Thus the Euro’s sleet map showing 0.2” should imo be ~2.2” of sleet to go along with the 4.1” of Kuch snow meaning 6.3” of snow/IP with almost no ZR at RDU.

12Z Euro

YW. Total 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.

Based on 850s, RDU gets ~1” of snow in the first few hours. But then it changes to a short period of sleet followed by a long period of ZR with even a short period of rain at the very end (33F).

I’m checking this link’s worst icestorms for the E Piedmont and am looking for wx maps to see: http://americanlifelinesalliance.com/pdf/IceStormSummaries.pdf Per this link, 2/13-15/1960 was worst icestorm in 33 years in much of NC. Here is a link to the 2/12-14/60 wx maps, suggesting a Miller A: https://library.oarcloud.noaa.gov/swm.docs.lib/1960/19600212.pdf https://library.oarcloud.noaa.gov/swm.docs.lib/1960/19600213.pdf https://library.oarcloud.noaa.gov/swm.docs.lib/1960/19600214.pdf Per this snow map from Webb, it also was a big snow producer for much of NC, with 3.7-5” in RDU area: