GaWx

0Z CMC: no SE winter storm. Run not as cold as prior run as of 12Z on 2/17. That carries over later to not as cold NW of the offshore SE low and thus not as cold a rain/not as close a call. (actually 12Z had a little bit of wintry precip).

0Z GFS has more IA and vicinity snow and a possibly related stronger push of cold. Let’s see whether this pushes moisture/storminess away from the SE or else it teams up with moisture and gets more interesting. Edit: the former though it gets close. We need the low/moisture to lag more/come in later to mix with the cold instead of riding along the cold front, which usually doesn’t work out (cold chasing moisture). Edit: This GFS is coldest in SE for 12Z on 2/18 in at least a week per TT old runs. *Corrected

The 0Z ICON looks like a no for wintry in the SE.

If the CMC weren’t so cold biased, I’d be more excited about the potential for 2/18-9 wintry deep into the SE. Keep in mind that at 12Z on 2/17, this latest run has single digit temps in the NW 2/3 of MO associated with a 1044 mb high centered to the W. In contrast, the 18Z GFS is much less cold at ~20 with a much weaker high, 1030. The 12Z Euro is way up in the 25-27 range, 20 warmer than the CMC, along with a 1032 high. The NWS forecasts for MO are all in the 20s. So, the CMC is on its own there right now. To have a halfway reasonable shot for wintry in the SE, the colder and stronger the high (like what the CMC has) the better. Although I’m not betting on it due to cold bias, I’m still hoping the CMC somehow has the right idea. With the progged very strong -EPO ridge resulting in an EPO of ~-3 setting in for the next several days, my hope is that the non-CMC models aren’t fully seeing how cold the high will be. But the current lack of mid-US snowcover may still allow it to modify rapidly like the non-CMC models have. OTOH, the models all have new snow progged for much of the Plains and Midwest just in advance of this cold air with the CMC having it all the way down to MO. Perhaps how much/how widespread the snow this week will be crucial and thus something to follow.

Look how warm the Arctic has been. What’s also interesting is that the Arctic’s coldest day in the means isn’t for another 13 days, Feb 25. Feb actually is slightly colder than Jan:

The DJ MEI came in at only +0.7 vs the +1.1 peak of ND.

Actually, I do the opposite. My walks in the park are typically more frequent during winter than in any other season. But then again, I’m down in Savannah, where unenjoyable heat and humidity dominate much of the year and thus I enjoy walking in chilly conditions. Regardless, I can usually get in a good number of enjoyable walks well into April. The treadmill usually takes over starting in May.

Compared to the improved 18Z GEFS, the 12Z GEFS has worsened substantially: -much of NC only 0.1 to 0.6” and most only 0.1-0.2” vs 0.5-1.5” -NC: only 2 moderate to big dogs vs 5 -NC: but still 70% have snow vs 75% although most light (a good number in E NC) -Other states: 30% vs 50% -ATL: only 4 with SN, all very light (~0.1”) -N FL: only 1 (3%) and that one just barely

The 2/13-20 0Z 2/12 GEFS predicted AO rose quite a bit again to -1.2 (see image below) vs -2.2 on 2/10, -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 significantly higher than yesterday with it hitting +0.7 In addition, the soon to peak PNA will be dropping to negative in ~a week. So, terrible trends again for cold lovers on the GEFS for late month: AO from just 4 days ago (2/8 run) : -3.2 for 2/13-20 and headed for a major bust AO today (2/12 run): -1.2 for 2/13-20

I think we need a ruling from the King, who is now deliberating. We’ll know soon. Edit: King says no snow for you, SE.

18Z GEFS (outside of mtns): much more wintry than 12Z -back up to 4 members with wintry precip in N FL (2 near Jacksonville) -mean is the highest it has been in N 1/2 of GA and much of SC in awhile; 50% have snow that includes outside of NC -NC: 3 biggies/2 moderate; mean is 0.5-1.5” most of state; 75% have snow -ATL: 1 with 3”+ that also includes moderate to heavy much of SC/NC with light to far NE FL

18Z GFS output has wintry mix from the two waves much of SC and NC coasts on 2/18 to early 2/19 but temps stay above 32 (middle 30s for coldest). Edit: There’s also light sleet 2/18 from south central GA to FL Panhandle.

If the models’ consensus for a dip to ~-3 EPO later this week were to verify, it would be the lowest so far this winter and thus a pretty big deal. The lowest so far has been -2.3. We’ve had only 11 -EPO days so far this winter vs 32 +EPO days and 27 neutral. (I consider sub -0.5 negative with -0.5 to +0.5 neutral.) Cold sometimes but not always accompanies and/or immediately follows a strong -EPO. Here are the last 10 winters’ lowest EPO days (average lowest -2.7): 2022-3: -3.9 on Dec 16 (just before the big Arctic plunge) 2021-2: -3.3 on Dec 20 2020-1: -1.5 on Feb 1 2019-20: -1.4 on Dec 9 2018-9: -3.0 on Feb 27 (El Nino) 2017-8: -2.2 on Dec 6 2016-7: -3.7 on Jan 3 (winter storm 4 days later) 2015-6: -1.4 on Jan 7 (El Nino) 2014-5: -3.1 on Dec 30 (El Nino) 2013-4: -3.6 on Jan 25 (3 days before snow jam) For other El Niño winters: (avg lowest ~-3) 2009-10: -3.9 on Dec 7 2006-7: -3.8 on Jan 30 (winter storm 2 days later) 2004-5: -3.3 on Jan 7 2002-3: -3.1 on Feb 7 1997-8: -1.5 on Feb 5 1994-5: -3.7 on Feb 12 1991-2: -2.2 on Feb 8 1987-8: -2.9 on Jan 2 (just before big winter storm) 1986-7: -2.5 on Dec 9 1982-3: -2.5 on Dec 10 1979-80: -4.1 on Feb 14 1977-8: -2.9 on Dec 21 1976-7: -2.5 on Jan 8 (week before severe Arctic plunge) 1972-3: -3.9 on Dec 9 1969-70: -3.5 on Feb 27 (Arctic plunges) 1968-9: -3.2 on Dec 20 1965-6: -1.7 on Dec 27 1963-4: -3.1 on Dec 11 (4 days before Arctic plunges) 1958-9: -2.3 on Dec 5 1957-8: -2.5 on Feb 2 1953-4: -2.3 on Jan 16 1951-2: -3.1 on Dec 27

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.