GaWx

I mean relative to normal/solid BN temperatures. In the first half of March, especially, solid BN can still be quite cold and last awhile in much of the SE US. See history for examples. That doesn’t at all mean anywhere near record lows for DJF, of course, but you don’t need that to be very cold. I don’t know what your definition of “very cold” is though and don’t know where you’re located.

The new (2/7) Euro Weeklies 10 mb stratospheric 60N wind run’s mean hangs around -5 for a week and then never rises back above +5 (through Mar 23)! Most of the wind reversal dates (major SSW) are within Feb 15-17 and the members imply a good chance for a dip to sub -10. This is even more support favoring a cold SE US along with more winter storm opportunities well into March.

Wow! This may end up being one for the record books if this is any indication. This (2/7) Euro Weeklies run’s mean hangs around -5 for a week and then never rises back above +5 (through Mar 23)! Most of these reversal dates are within Feb 15-17 and the members imply a good chance for a dip to sub -10.

The awesome setup at 240 on both the 12Z Euro and 12Z/0Z CMC would imply lots of potential for the SE for 2/18-19. Those are both screaming widespread major winter storm potential with the classic split flow working in tandem with high latitude blocking. Fwiw of course since this is out 240 on operationals and thus will keep changing for awhile as no operational gets set on a solution that far out.

Latest 12 run averaged CFS ensemble looks quite nippy for early March based on 500 mb heights and actually has lower heights than the 3 weeks preceding it! For example, this shows 554 dm for RDU. That’s actually 6 dm lower than the normal for January! So, the implication based on this forecast is that the first week of March would quite possibly end up BN for January!

The -AO isn’t quite as strong as it was on yesterday’s GEFS, when it averaged -3.5 for 2/13-20. Today the period averages near -3.0. The chance for a sub -4 daily isn’t as high. Hopefully it won’t trend less negative in the coming days. A -3.0 would still make it the 3rd most negative for the period during El Niño. Also, the PNA prog for the period has risen from yesterday’s +0.5 to today’s +0.8. Strongest -AO El Niño averaged 2/13-20 (lowest daily) out of 25 Ninos since 1952: 1969: -4.8 (-5.1) (PNA: -0.1) 2010: -4.4 (-5.1) (PNA: +0.7) 1978: -2.6 (-4.8) (PNA: +0.8) 1958: -2.5 (-4.0) (PNA: +1.1) 1970: -2.4 (-4.0) 1964: -2.4 (-3.4) 1987: -2.4 (-3.3) 1966: -2.2 (-3.5) 1952: -2.1 (-2.5) 1983: -2.0 (-2.7) 1977: -1.2 (-2.1) 2007: -1.2 (-1.9) 2005: -1.1 (-1.7)

-0Z EPS much wetter than prior runs and thus the most wintry precip of any EPS in the SE -0Z and 6Z GEFS snowier overall SE largely due to more qpf -Things seem to be falling into place, which makes sense based on how consistent the big picture has been. MJO progs for mid to late month (weak left side possibly going into COD) continue to be supportive among other factors. But regardless, nothing is even close to being certain. -As a bonus the fun may very well carry well into March based on the weakening SPV

1. After having backed off the last couple of days with the lowest mean only down to +7 yesterday, the 0Z 2/6 GEFS mean low now drops to the lowest yet for mid-month, -4. Also, the GEPS dropped from +6 to -9, where the GFS also is. FNMOC dropped from +2 to -4. These models are suggesting the major SSW date/reversal would likely be within 2/15-17. 2. The new Euro Weeklies also have its lowest yet by far after having backed off slightly yesterday, when the mean rose back from a lowest of +4 two days ago to +8 yesterday. Today’s is down to -1 and also is its weakest yet from then through well into Mar, increasing the chance for a cold E US March. The members are suggesting a most likely reversal date of 2/16-18. Note that the mean hugs the 0 line for over a week!

The new Euro Weeklies are significantly colder along with more widespread cold vs recent runs for the period Feb 19-Mar 18. There’s now a solid signal for cold for much of the E US thanks to strong blocking at high latitudes as well as moderate blocking along the W coast. This more intense cold lasting well into March is likely being aided by the most bullish run yet for a mid-month major SSW, which on its own increases the chance for a cold E US starting 1-3 weeks later and which often lasts for several weeks after it starts. Along with this forecasted cold, the Weeklies maintain an El Niño induced subtropical feed of moisture in the GOM and up along the SE coast. All of the SE is NN to wetter than normal. So, the SE may very well get more winter storm opportunities into mid March! This winter appears to be a long way from ending.

The 12Z GEFS has a whopping 5 out of 30 (17%) members with wintry precip within 2/18-22 in N FL! That many members doing that is very rarely seen 12-16 days out. It is the most of any run yet this winter beating out 4 of 30 on a recent run. Two of those have a wintry mix that goes just S of @pcbjr! The strongly suppressed track usually required for this is made less improbable by a very strong -AO/extreme high latitude blocking that is being forecasted. I know that @NorthHillsWxasked where the cold air would come from. When you have forecasted for mid-month extreme blocking in the Arctic (-AO), strong blocking near AK (-EPO), moderate blocking in the N Atlantic (-NAO), a moderate +PNA (W coast blocking) to drive cold air into the SE, the most favorable MJO for cold there is (weak left sided possibly going into the COD), a strong subtropical jet (favors extra cooling from upstairs if there’s precip), and with it then still only mid Feb, you’ve got about the most loaded setup to produce cold enough air for significant wintry precip even deep into the SE as exhibited quite well by many GEFS/GFS runs. Why else would just about every GEFS run in recent days be showing members with wintry precip down into N FL? Keep in mind that we don’t need cold anomalies in Canada or even the N Plains/upper MW to get cold in the SE. Will the SE get a winter storm or maybe even two? I don’t know as I don’t have a crystal ball. But I can’t ask for a better big picture pattern consistently showing up every day to give us the chance. The big picture remains about as favorable as it ever gets that far out, especially for the deep SE. I said I was going to have fun following this and I’m having a blast. There could easily not be another period of potential like this for years to come for the deep SE at least. When other subforums are worried about “suppression”, I’m of course loving it.

The image below of today’s GEFS AO prog implies the likelihood of a few days of sub -4 within 2/13-20 along with a 25% chance for a lowest of sub -5 and 10% chance of lowest of sub -6! Whereas yesterday’s had ~-3.1 for mid-month, today’s has ~-3.5 for 2/13-20! (The PNA forecast is +0.5.) How would a -3.5 AO compare to Nino history back to 1952? Strongest -AO El Niño averaged 2/13-20 (lowest daily) out of 25 Ninos since 1952: 1969: -4.8 (-5.1) (PNA: -0.1) 2010: -4.4 (-5.1) (PNA: +0.7) 1978: -2.6 (-4.8) (PNA: +0.8) 1958: -2.5 (-4.0) (PNA: +1.1) 1970: -2.4 (-4.0) 1964: -2.4 (-3.4) 1987: -2.4 (-3.3) 1966: -2.2 (-3.5) 1952: -2.1 (-2.5) 1983: -2.0 (-2.7) 1977: -1.2 (-2.1) 2007: -1.2 (-1.9) 2005: -1.1 (-1.7) So, the prog suggests 2024 has a chance to come in as easily the 3rd most -AO of the 25 Ninos for 2/13-20 and near the average of the lowest 4. It is no wonder why we’ve seen a good number of GEFS members/GFS runs with winter storms so far south. ATL; RDU for strongest 4 -AO: 2/13-20 temps/SN 1969: -13/1.2”; -9/0.8” 2010: -11/T (3.6” on 2/12); -8/1.0” 1978: -6/0.3”; -8/T (5.6” 2/21-2) 1958: -23/2.7”; -21/3.0” AVG: -13/1.4”; -12/1.2” So, these 4 averaged very cold and snowier than avg. for 2/13-20.

The MJO ensemble mean forecasts, especially GEFS, look favorable for cold at mid-month with weak left side:

The EPS continues to be much drier and thus have much less wintry precip (mean is very unimpressive) than the GEFS/GEPS.

18Z GEFS (outside of mountains): active again -Mean wintry amount is impressive, especially in NE GA, upstate SC, and NW 3/5 of NC with 1-2.5” of snow, snowiest run yet for those areas I think -Three (10%) really big dog snows NC, with two of those extending back into N GA -70% of members have wintry precip -50% have wintry not limited to NC -10% (3) in N FL with one as far S as north-central! -30% have IP or ZR included -some early snow 2/12-14, mainly in NC; most activity 2/17-21

12Z GEFS SE US outside of mountains: -20% have wintry precip 2/13-14 mainly GA/SC with all including N GA and most including SC -70% have it 2/16-21 (mainly 2/17-21) -50% have it 2/13-21 that include states outside of NC -~40% have IP or ZR -So, the strong signal for that far out continues with a little bit more of a signal than before for 2/13-14, too. The 12Z EPS like for earlier runs has much less snow than the 12Z GEFS and GEPS.

All models are predicting the AO to drop to -3 or lower at mid month with the likelihood of some days dipping to near -4 being implied. The chance of a sub -2 AO averaged out during 2/15-29 is increasing and is close to becoming likely. (There’s a good chance for a +0.3+ PNA averaged out during the same period.) Here are the strongest -AOs averaged out during 2/15-28(9) for El Niño: 2010: -4.1 (PNA +0.2) 1969: -3.4 (PNA -0.1) 1958: -2.5 (PNA +0.9) 2005: -2.4 (PNA +0.4) 1952: -2.0 (PNA +0.4) 1977: -1.8 (PNA +1.0) 1987: -1.7 (PNA +0.3) 1970: -1.6 (PNA +0.7) AO lowest daily 2/15-28(9) -3 or lower during El Nino: 1952, 58, 64, 66, 69, 78, 2005, 10 AO lowest daily 2/15-28(9) -4 or lower during El Nino: 1958, 69, 2005, 10

The potential for significant SE wintry precip 2/15-20, especially 2/17-20, is not at all going away and is if anything increasing as we get closer while the big picture doesn’t change. At least 75% of the last 3 GEFS runs ending with the 6Z have SE US wintry precip outside of the mountains somewhere within Feb 15-20. About 50% of the 6Z members have it including outside of NC with 4 of the 30 even as far south as N FL. It is hard to look better than this 10-15 days out. The big picture is still very much intact with a hard to beat combo of a very strong -AO, moderate +PNA, -EPO, neutral to -NAO, strong subtropical jet/split flow, and the tendency for 50/50 lows (which tend to hold cold in longer). Moderate+ El Niño climo is quite supportive, too. It never hurts to have analogs on your side. I hope to post more about the very strong -AO later as far as El Niño analogs are concerned.

Also, GEFS has been better than GEPS. Interestingly though, 0Z GEFS today (2/4) has backed off slightly on an actual reversal with a lowest mean just above zero vs -2 on the 0Z 2/3 run. Also, it’s mean though still low edges back up to +9 later vs staying under +7 yesterday.

Today’s extended EPS mean drops to a mere +4 (vs +11 two days ago and +31 nine days ago) with numerous members having a major SSW. Also, like is the case on the extended GEFS, the SPV is now much weaker than normal from mid Feb into March. The chance for a cold E US March continues to increase!

Rainy, windy, and cool here late this afternoon. A good day to stay inside! Update: After ~7 hours of rain that included periods of heavy rain along with rumbles of thunder that I’m still hearing (there even was one cloud to ground strike a few hours ago), it is finally ending for now. I’ll get totals tomorrow. We got another period of rain on Monday but not heavy. I very roughly estimate my Sun-Mon (2/4-5) total to have been 1.75”.

12Z EPS: -Unlike the GEFS/GEPS and although there are some wet members, there are many dry members and thus the mean is dry/BN in the SE. But keep in mind that it ends 24 hours earlier though it is drier through 2/19 for sure. -Although there are a good number of very cold members, they are balanced by a good number of mild members late in the period. Thus, the mean is warmer than both of the GEFS and GEPS late in the period with the cold temps warming to mainly near normal temperatures by the end of the period. -Unlike the GEFS/GEPS means of above average snowfall in NC, the EPS has BN/little snow. So to summarize my posts regarding the 12Z ensembles for SE wintry precip potential Feb 15-19/20, the GEFS and GEPS means have AN snowfall and cold whereas the EPS mean is drier with BN snow and less cold temps late. Going to be lots of fun to see how this plays out.

-The Canadian ens map you’re showing has near normal precip (white area) for that 5 day period. Near normal is neither wet nor dry in NC in mid Feb. -1/2 of the members have snow in NC outside of the mtns -4 of the 20 (20%) have widespread 3”+ snowfall, all including heaviest of 6”+, in NC. -A good number of the wet members in NC have no wintry outside of the mountains. -2 of the 20 (10%) have wintry as far south as N FL. I haven’t yet had a chance to look at the EPS.

Nope, especially 2/17-20. From 12Z GEFS outside of the mountains 2/15-20: -21 of 30 members have wintry precip in NC. -13 have it in GA including 8 central and/or south -11 have it in SC including 7 in south -3 have it in N FL -6 have ZR and/or IP included, including part or all of the 2 of the 3 in N FL

12Z GEFS big picture in more ways than one: classic split flow has been showing for this period for weeks. This is about as good a look as I’ve seen in recent years this far out. Ingredients are there. But will they mix right? That’s always the tough part for the SE, especially.

12Z GEFS for Feb 16 is by a good margin coldest in at least the last 16 runs. Now let's see how well the ST jet/moisture interacts.