GaWx

I didn't say it is over but that the chance for notable cold had dropped a lot based mainly on the warmer EPS trend and that a cold reversal was needed, stat! Since then, two GFS runs have come out with their longest mid March cold periods in the SE in many runs (3/14-18, 19). RDU to N GA have five straight freezes 3/14-18 along with 5+ days straight of sub 0C at 850 mb. Even down here there's 3.5 straight days of that. That's all quite impressive but they're just two GFS runs out 8-14 days, which get well into fantasy land. So, I'm still monitoring. I really need to see the Euro suite go back colder ASAP! The teens of March are put up or shut up time! That's still 7-13 days out. So, not over yet. Edit for 3/6 0Z EPS: coldest of run at RDU/ATL 35/39 on 3/15 making it even warmer than the prior run, which had been the warmest run for mid March, and thus not good if one prefers the longest/most intense cold. Comparing the 35/39 to the much colder two 31/30 runs of three and five days ago, respectively, doesn't exactly point to an increasing threat of long/strong cold in mid March. What's very odd is that while the GEPS has remained cold for midmonth, the GFS (cold now vs milder earlier) and Euro (milder now vs cold earlier) suites have literally switched positions! I bet that, alone, will cause some cold loving folks to favor the GFS suite over the Euro suite after previously favoring the Euro due to bias. I don't expect to do that and instead expect to continue to consider both with a little more weighting to the better performing Euro.

Here are the coldest mean lows for each EPS run back to the 2/28 0Z run for RDU/ATL, which shows why it is a bad trend for SE cold lovers: 2/28 0Z: 35/36 on 3/13-14 2/28 12Z: 34/34 on 3/14-15 3/1 0Z: 31/30 on 3/12 (coldest tied) 3/1 12Z: 32/31 on 3/12-13 3/2 0Z: 35/36 on 3/14-15 3/2 12Z: 32/31 on 3/13 3/3 0Z: 31/30 on 3/12-13 (coldest tied) 3/3 12Z: 31/31 on 3/13-14 3/4 0Z: 31/31 on 3/13-14 3/4 12Z: 33/34 on 3/13-15 3/5 0Z: 33/36 on 3/13-14 3/5 12Z: 35/37 on 3/14 (warmest run) This is a double whammy because we're now the closest to the crucial dates of 3/12-15 and the coldest means instead of cooling further, which would be expected on an ensemble with 51 members when getting closer if there's big cold coming, have warmed considerably. So, chances of the SE getting a notable cold period in mid March have come down considerably since March 3rd. Because it is getting closer and thus we're running out of time for big ensemble mean changes back in the colder direction (the closer to the days being forecasted, the smaller the average change), the ensembles are going to need to sharply reverse to colder again within the next 3 days or so or that's going to be the ballgame imo. The 3/2 12Z and 3/3 0Z runs did get significantly colder again after a significant warmup on the 3/2 0Z run, but we're three days closer. That reduces the chance considerably for another sizable cold reversal. Not good.

I see nothing on the 12Z 3/5 runs that would likely be encouraging for cold lovers. This is especially compared to some of the really nice much colder runs of 3/2-3. It is almost as if the 3/2-3 runs were troll runs lol. The Euro is especially noteworthy to me with this reversal. 12Z Euro goes all of the way to 12Z on 3/15 and coldest it gets through entire run is middle 30s in ATL and RDU. The 3/3 runs, which only went through 3/13, were well down into the 20s. Edit to add the 12Z EPS to the discouraging trend for SE cold lovers.

The concern for cold lovers, which I think is valid, is that the EPS runs from Feb 27th through 0Z March 3rd were mainly cold in the SE early on March 11th after turning colder on March 10th. But since the 12Z March 3rd run, they've been near normal or warmer for March 10th through early on March 11th. The latest EPS runs don't get it cold til either later on March 11th or on March 12th. So, a 1-2 day delay from the coldest runs. The GEFS was slower to consistently make it cold by then but became that way by the March 1st runs with colder by March 10th. The GEFS' coldest runs were 12Z/18Z of March 2nd. The March 3rd runs were not as cold but still on the cooler side for early on March 11th. Then they suddenly became much warmer (mainly AN) starting with the 0Z March 4th run and have been that way since. The most recent GEFS runs don't make it cold til either March 12th or 13th, a longer delay than the EPS...2-3 day delay vs the coldest runs. Is this another kicking the can or just a little delay? Any educated guesses? We'll know eventually. Aren't forecasting discussions fun? For those interested, go to Tropical Tidbits and look at the maps valid for 6Z on March 11th on the Feb 27th through 0Z/6Z of March 5th runs and see for yourselves as they're still there.

Yes, indeed, that's common in winter when the average wavelengths are longest. But what causes these west coast troughs (-PNA)? The record warm MC and La Niña are often touted as the main reasons. But also, there's speculation that the SER can be more than just a "forcee" but also do its own forcing at times thanks to the record high AMO of recent years.

I'm looking forward to a walk this evening with the lowest dewpoints in this region in quite some time. We had 80s today with only 40s dewpoints. This reminds me of a midsummer day in Colorado. If all days were similar in summer, I'd enjoy being outside a lot. But alas, these are very rare during summer. Regarding the persistent SER from what I've read from pro mets, it has been dominant the last few years due to a combo of La Niña, record warm MC SSTs favoring longer and stronger MC phases (though in Feb it was short) as well as MC-like forcing even when the MJO isn't there, and the very strong AMO making the Atlantic warmth act like a block in the form of a SER.

0Z GEFS based AO forecasts are still trending lower for Mar 6th and 10th (though at a slower pace as we get closer). The NAO has changed little and remains solidly negative through then. So, the models being less aggressive since yesterday with the change to a colder E US isn't due to the AO/NAO levels: For March 6th: 2/26 run: -0.1 2/27 run: -0.5 2/28 run: -1.3 3/1 run: -1.5 3/2 run: -1.9 3/3 run: -2.2 3/4 run: -2.3 For March 10th: 2/28 run: 0.0 3/1 run: -0.9 3/2 run: -2.0 3/3 run: -2.1 3/4 run: -2.4

0Z GEFS based AO forecasts still trending lower for Mar 6th and 10th though at a slower pace as we get closer For March 6th: 2/26 run: -0.1 2/27 run: -0.5 2/28 run: -1.3 3/1 run: -1.5 3/2 run: -1.9 3/3 run: -2.2 3/4 run: -2.3 For March 10th: 2/28 run: 0.0 3/1 run: -0.9 3/2 run: -2.0 3/3 run: -2.1 3/4 run: -2.4

Thanks for posting. What's amazing is that in addition to plentiful upslope snow for the mountains, the 18Z GFS has not one, not two, but three different systems (in a row) bringing significant wintry precip to parts of the SE (mainly NC to NE GA) during just the period March 13-18! I know it is just the operational GFS way out in the 11-15 but the prospects for the upcoming pattern are so way out there that this kind of thing is actually believable.

The 18Z GFS has a whopping 1060 mb surface high west of Hudson Bay at hour 138! Other runs and models have shown something similar for then. This kind of thing being repeatedly shown and it now being only 6 days out tells me that the pressure may not be overdone. For comparison, the record highest SLP for all of Canada in March is only 1 mb higher and that is way up in northern Nunavut! Also, the highest SLP on record for that area west of Hudson Bay is only ~1058 mb for all months, not just March. That alone is enough to tell me we're likely dealing with a very highly anomalous setup, which may lead to something historic for the US down the road in terms of cold and wintry weather. The map below has the all time record highest SLPs in Canada for all months. Note the 580 just N of NW Manitoba (1058 mb): https://www.wpc.ncep.noaa.gov/research/roth/SLPrecords.html

That's just an ordinary 1060 mb high at hour 138 of the 18Z GFS plunging down. Nothing to see here. Move along.

Not everybody wants the same thing. I try to leave my feelings out of these discussions as much as possible. For example, I don't want tornadoes anywhere near me, but don't complain if they're discussed. Discussing them doesn't make them occur and if anything it increases awareness of the danger. Anyway, the 12Z Euro was unreal but likely overdone as I said. Cold is often dry. Nothing unusual about that at all. Of course, that doesn't mean it will play out that way ultimately.

What Met1985 said. This is literally a wx forecasting discussion thread. Why wouldn't we discuss this stuff, especially with it being so different from almost the entire winter and potentially highly anomalous for mid March? It is what it is. Besides, this discussion may allow some people to prepare for the cold to mitigate potential damage.

The 12Z Euro has 850 temps down to -10 to -11 C in my area at 12Z on March 12th! Although it is likely overdone, that could very well be the coldest 850 so late in the season. I mean that's very cold for midwinter, much less March 12th.

Freezes are showing on the 12Z GFS for many inland areas March 10-12. That would be the first time for three in a row since very early February should they verify. Plus some areas get another on March 16th. Would at least feel like winter for a change. Also, great upslope snow potential is showing for the NC mountains at least. 12Z GEFS is the coldest run yet for March 9th-11th+.

I'm not believing the 12Z ICON's 1060 SLP just west of Hudson Bay at 144 (for 12Z on March 8th). That would beat the alltime high SLP record of ~1058 mb in that area for ANY month, much less just for March. It also would be near the 1061 March record for all of Canada, which is way up north in N Nunavut per this site: https://www.wpc.ncep.noaa.gov/research/roth/SLPrecords.html But the model consensus has been for very high SLPs (1050+) in that region for then, regardless of how high it will actually get. So, that will be interesting to follow.

We will see how long and strong the cold period will be, assuming it comes at all. The models have been cold biased for most of the last few winters due largely to under forecasted SE ridging. Maybe the cooldown will end up being weak and short per what wncsnow just posted. It will be mid-March by then after all. Nobody knows of course and that's the kind of speculation this thread is here for. Regardless of what ends up happening, I think it will be noteworthy in that there will at the very least be a major pattern change to sharply colder for an unknown period of time starting after the next week or so vs how it has been most of this winter to date due to the very weak SPV (see AO forecast info below). The model consensus is still calling for the longest period of chill by far since the last half of December. Regarding wintry precip, that is always a crapshoot in the SE, especially outside of the mountains, especially south of NC, and even moreso for all of the non-mountainous SE in mid March. Hopefully, some locations will luck out and get some of note with good upslope snow for the mountains at the very least with any luck. Meanwhile, the trend toward a stronger and longer -AO period during the first half of this month (likely due to the lagged effects of a very weak and displaced SPV) continues with today's 0Z update: 0Z GEFS based AO forecasts for March 6th: 2/26 run: -0.1 2/27 run: -0.5 2/28 run: -1.3 3/1 run: -1.5 3/2 run: -1.9 For March 10th: 2/28 run: 0.0 3/1 run: -0.9 3/2 run: -2.0 Also, the EPS has continued its downward trend of the AO since its 0Z 2/27 run.

The trend toward a stronger and longer -AO period during the first half of this month (likely due to the lagged effects of a very weak and displaced SPV) continues with today's 0Z update: 0Z GEFS based AO forecasts for March 6th: 2/26 run: -0.1 2/27 run: -0.5 2/28 run: -1.3 3/1 run: -1.5 3/2 run: -1.9 For March 10th: 2/28 run: 0.0 3/1 run: -0.9 3/2 run: -2.0 Also, the EPS has continued its downward trend of the AO since its 0Z 2/27 run.

The trend toward a stronger and longer -AO continues.

I think that the seemingly ever-present NW trend of storm tracks from run to run as well as an overall cold E US bias of models much past 5 days and especially out 10+ days is probably partially related to the warm Atlantic fighting back. But if so, why do the models not get adjusted in updates to take these biases into account after all of these years? Is sparse initialization data over the Atlantic the main issue keeping the models largely clueless?

I've read from pro mets that the SER is enhanced by the record warmth in the MC of the W Pacific in addition to it being enhanced during La Nina. But is the SER also made stronger by the AMO? The AMO has been about as high during the last few years as during any other period: https://psl.noaa.gov/data/correlation/amon.us.long.data If the high AMO, itself, is also a significant SER strengthening factor, I could see your idea being plausible. Could it be that the overall warm Atlantic (including GOM) from the equator to 70N (one definition of the AMO) is resisting and thus providing its own blocking (manifested by the persistent SER)?

Tropospheric NAM = AO 0Z GEFS based AO forecasts for March 6th show that the trend is downward: 2/26 run: -0.1 2/27 run: -0.5 2/28 run: -1.3 3/1 run: -1.5 For March 10th, yesterday's 0Z GEFS had 0. Today's had -0.9. The 12Z EPS has a stronger -AO through most of its run through March 14th and that continues its downward trend since the 0Z 2/27 run.

Tropospheric NAM = AO 0Z GEFS based AO forecasts for March 6th: trend is downward: 2/26 run: -0.1 2/27 run: -0.5 2/28 run: -1.3 3/1 run: -1.5 For March 10th, yesterday's 0Z GEFS had 0. Today's had -0.9. The 12Z EPS has a stronger -AO through most of its run through March 14th and that continues its trend since the 0Z 2/27 run.

1. The 12Z EPS held consistent with the prior colder E US trend and has a stronger PNA trend in the 11-15 vs prior runs. 2. The -AO continues to trend in the stronger direction on the EPS and other models out near day 10. I wouldn't be surprised if this continues. I suspect this is because of the very weak SPV. The 10 mb winds at 60N dipped all of the down to -19 m/s yesterday, indicative of a very weak strat. A strong -AO is a primary effect of a successfully down-welled weak strat onto the troposphere.

The -AO continues to trend in the stronger direction out near that time. I wouldn't be surprised if this continues. Could this be because of the very weak SPV? The 10 mb winds at 60N dipped all of the down to -19 m/s yesterday, indicative of a very weak strat. A strong -AO is a primary effect of a successfully down-welled weak strat onto the troposphere.