GaWx

Out of 16 runs, today’s Euro Weeklies for 2/26-3/4 came in by far the warmest yet for that week!

@Stormchaserchuck1 has a very good chance at getting his +PNA for 2023-4 (assuming that’s what he predicted). More on that below. Also, according to the NOAA monthly PNA table for DJFM, 1963-4 and 2009-10 both averaged +PNA with 1963-4 at +0.5 and 2009-10 at +1.0. It has 1972-3 at neutral (+0.1). Only 1965-6 of these 4 averaged a -PNA (-0.4): https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.pna.monthly.b5001.current.ascii.table 2023-4 is so far averaging +PNA with both Dec and Jan positive. Feb 1-11 has also averaged +PNA. The forecast through Feb 18 is for more +PNA before dropping to neutral and then moderately negative. (See image below) So, there’s a very good chance that Feb overall will average a modest +PNA with a small chance to end up neutral. Thus with only March to go, 2023-4 has a very good chance to end up averaging +PNA in the table though I give it a small chance to end up neutral (that would obviously require a strong -PNA in Mar). I consider neutral to be +0.25 to -0.25:

And then that second shortwave produces an offshore low that is at first too warm but then winds up at the end…will have to check when maps out if that produces coastal NC/VA snow. *Update: evidently not but it’s a close call with 850s falling below 0C before the very last little bit of coastal NC rain finished. However, the surface is in the 40s. But more importantly, this is another model hint that there may be two shortwaves to watch for 2/17-20.

Similar changes 12Z Arpege, JMA, and now Euro with the cold high getting in front thanks to the N stream regaining influence/back to split flow.

Indeed, the 12Z UK 144 is drastically different from the prior run as it has a near textbook split flow implying wintry potential after 144. This shows how much uncertainty about next weekend/early next week remains. The split flow seems to be coming back on model consensus thanks to the N stream/Canadian high regaining influence in advance of the first shortwave after having weakened so much. And there may be two different shortwaves to deal with during 2/17-20 as the 12Z GFS and especially CMC illustrate. The 3+ sigma -EPO being forecasted is a pretty big deal and would be the strongest of this winter.

The 12Z CMC (I know isn’t credible that far out but it can show what’s reasonably possible) does much more with the 2nd shortwave.

I see the 540 line during hours 192-201 as far S as the NC/VA border. So, even that’s too far N. But sometimes the 546 line can be the snow line and that line stays just offshore 192-204 while that second shortwave and associated surface low is just off FL with its rain not far from the SE coast.

12Z GFS: note the subsequent sfc low just off FL at 192. Close call for the coast.

The King says “no, sorry” to the SE snow starved. This was a much different run from prior Euros (TPV even visits Lake Superior with sub 495 dm 500 mb heights) and combined with the others at 0Z means early next week is still way up in the air. A week out is still a semi-eternity in model-land, especially in an unusually complex pattern of the N stream (fueled by very strong -EPO/strong -AO/moderate -NAO blocking and steered by moderate +PNA) and the ST/Pacific flow (fueled by last of the strong El Niño with recent strong -SOIs) such as we will have later this week. The MJO is progged by the GEFS/EPS to then be in/near weak phase 8, which tends to be conducive to E US cold. The latest EPO forecasts for late week/weekend are the most notable with -3 to -4 being forecasted! Fasten your seatbelts and get plenty of rest just in case. *Edit: Wake up again as the 6Z GFS is similar to the much improved 0Z GFS! The very strong -EPO (strong ridge near AK/NW Canada is such a wildcard) seems to be a big factor.

0Z GFS is the coldest in the SE in 5-6 runs when precip breaks out from the Gulf low, which has slowed back down and is the most suppressed since then. This has snow to portions of the SC/NC coasts. This is clearly not close to being settled yet with such a big shift.

Wake up! 0Z: CMC and GFS much better than the most recent runs! Edit: Cold push from Canadian high ahead of the Gulf low much stronger vs the most recent runs. More like earlier runs. That is important to allow the moisture to overrun preexisting cold instead of cold chasing moisture, which usually doesn’t work well. This is clearly not close to being settled yet.

Agreed on 18Z GEFS. I count for NC 4 big dogs and 2 moderate dogs. But for ATL, I count only 2 moderates with no biggies. So, if I were in NC, I’d still be quite interested in the potential. The mean is 1”+ for RDU W. Any talk about NC being out of this is premature imo despite the trends. Nothing shabby about that at all. OTOH, ATL’s mean is only ~0.1”. I counted about 20% of the members having suppressed low tracks. Most of the ones that have SC snow are from these 20% that are suppressed. One of these gives moderate snow from the S Gulf coast states/W FL Panhandle through S & C GA, and SE half of SC. So, with it still at 20% on this, I’m not yet giving up on the suppression option though that chance has dropped a lot since just yesterday.

More on how much the progged H5/sfc has changed for the pre-storm setup: This was EPS from a week ago for 0Z 2/18: clearcut split flow with cold high coming in at the sfc in advance of any GOM storm thanks to WNW flow over MW (H5 flow ND to VA) Compare that to today’s 12Z EPS for same time: cold high held back due to more zonal N jet and now cold has to wait in many cases for earlier non-suppressed GOM low to first scoot by along cold front (H5 flow ND to MA) Still time to shift back, however, though not much time.

You saying “nothing was showing” on the ensembles was what I was responding about, which is so far from reality. And that includes non-mtn NC, for which many GEFS had 50-75% of members with wintry. NC had more action than any other state, which is normal.

This assessment (bolded) isn’t accurate imo because many GEFS runs (and GEPS for that matter) had until recently been showing a large % of members with wintry precip over the non-mountain SE as I had posted about. There were quite a few GEFS with 2/3-3/4 of members doing so and with ~30-50% even down in GA/SC/FL due to numerous having suppressed southern sliders. I was even counting the # with wintry in N FL with many runs having 3-5 members and 1 having an amazing 10 (33%) with wintry, unheard of that far out. Also, for a number of days, more than 50% of GFS runs had significant wintry somewhere in the non-mountain SE. My posts are all there for the record if anyone doesn’t recall these %s. That’s one of the reasons I post details about model/ens runs. I’m thinking ahead to if/when folks want to look back.

12z EPS continues with the trend of less and less sfc high pressure to the north out ahead of any Gulf low to allow already established cold air to meet up with overrunning moisture (split flow). The number of ENE moving suppressed/S slider GOM members meeting up with the cold continues to drop and instead there are more lows that are scooting out earlier on a more NE trajectory along the cold front as the cold comes in from the NW (cold chasing moisture). As a result, there’s little snow outside of NC. NC still has some big dogs (6 out of 50) and 3 moderate dogs, but ATL (and much of GA/SC) has but one big dog (4”) and then one 2” and one 1” out of 50. So, today’s trend has not been kind at all to winter lovers overall. However, we still have another 1-2 days or so for the last chance to turn things back around.

The 12Z UK is significantly warmer than the 0Z that I showed last night. So, the overall warmer trend of models vs yesterday continues. The flow is overall now being dominated by the moist subtropical/Pacific flow instead of a true split flow of a nice mix of N cold and ST moist. Suppressed low tracks well into GOM are gone for now.

Look how different H5/sfc is prestorm on the 12Z GEFS vs just 24 hours ago: 24 hours ago- split flow with sfc Canadian high pressing into upper SE from N stream ahead of storm while suppressed low forms well down in W Gulf on ST stream; note H5 hts flow (follow lt blue, for example) from Dakotas ESE to Mid Atlantic states, a perfect pattern to provide just enough cold to the SE without an overpowering plunge of cold, dry: Latest: N stream instead gives up with Canadian high no longer pushing cold air into SE; H5 hts flow, including lt blue, from Dakotas E to NEng instead of ESE to MidAtlantic; W GOM low much further N/no longer suppressed

The 2/13-20 0Z 2/10 GEFS predicted AO rose quite a bit again to -2.2 (see image below) vs -2.7 on 2/9, -3.2 on 2/8, -3.0 on 2/7, and -3.5 on 2/6. Also, the NAO is higher. So, not good trends for 2nd day in a row at 0Z on the GEFS: Today’s AO: 2/13-20 at -2.2 Compare to just 2 days ago: 2/13-20 at -3.2

Did someone say 0Z UKMET?

12Z EPS has a good number of suppressed low tracks, not too unlike prior runs. Suppressed would obviously give a good portion of the SE more opportunities.

Major snowfall 2/18 E NC to the coast on 12Z Euro! Edit: There’s also followup light precip breaking out deep S on 2/19 within a strong wedge associated with a second weak GOM low.

The 12Z GEFS mean was the coldest run for 2/17-18 in much of the SE in many runs due largely to an increase in the number of suppressed low tracks. As a result, much of the SE has increased qpf and mean wintry precip vs the 6Z (especially ATL-GSO south), and there’s a notable increase in the deep south. N FL is back up to two with wintry. So, at 12Z, the GFS, GEFS, and the not yet mentioned CMC have a similar setup on 2/18 with a suppressed Miller A/slider Gulf low. Also, the 12Z GEPS had a similar change.

You picked the perfect time to live on the coast as Jan of 2018 was the biggest SE coastal winter storm since Dec of 1989 for many! Here, there was ~0.5” of ZR (probably the most in one storm in nearly 100 years…it stopped just before widespread outages were about to start) and 2” of a combo of sleet and snow. A good portion of that 2” hung on in shady areas for 4 days, a very rare feat! There being sleet in it combined with it being several degrees below freezing during most of the storm and very cold to follow allowed it to stick around for so long.

Going 6 years without even a T of wintry in this area is the longest since at the very least the 1940s and possibly even since the 1870s-80s! There’s missing snow data between the traces of Dec of 1944 and Nov of 1950. So, there’s a slight chance there was none then although that would still be just under 6 years. So, the current drought of 6 years, 1 month is for sure the longest since at the very least the 1880s.