Carvers Gap

Take a look at the 12z NAM vs GEM after 72. NAM is amped. RGEM is much flatter. Again, short range models at range...buyer be warned.

12z RGEM at range. It will often give us clues for the upcoming GEM run. For posterity and the eventual forensics investigation into this...If I hadn't seen 0z last night, I would say is that is going to be a severe ice storm if that low kicks out late or a snowstorm if it goes with that 1050 high. Usually, 1050 highs are money for frozen in this forum. However, there is definite precedent for it to rain behind big highs like that, but still is crazy to watch.

Yeah, this winter Bam has flip-flopped more than a mackerel that just got pulled into the boat. But a broken clock is right twice a day....I think he went warm for the second half of January, and then walked it back the next day. I don't understand the fascination w/ their stuff. There are so many other great mets and met resources which don't push clicks. That is all from me on that subject. The GEM-para nailed this trend. It has been good this winter. The WPC post above is really well written. It explains some of the issues they are dealing with, and some of that we actually discussed here - I hadn't read that until about ten mins ago. Just been doing this hobby long enough to know the pitfalls w/ stuff like this. I think ultimately the mishandling of the Baja low was yet again a problem. What I will be interested in...does a cutter now set the table for the next system? If that verifies, it will change the next 5-7 days worth of tracks for vortices traversing the country.

This is Wall's X post, but cleaner and easier to read. This is the most recent WPC discussion about interaction between the northern and southern branches, the NBM being "off", and potential adjustments north(with the snow line) in their forecasts. Model guidance generally remains in good agreement with the aforementioned large scale pattern evolution, however differences in the details persist. The most notable question deals with how much interaction we see between the southern stream and northern stream energy over the Plains, and the overall depth/strength of the resultant trough. More interaction and a stronger trough would likely result in stronger downstream ridging and thus a farther north storm track. This is indeed what just about all the 00z models are trending towards. Generally a clean sweep, with the deterministic physics based models, ensemble means, and AI guidance all shifting north with the storm track. This trend really has little to no impact on the fact that a widespread and significant winter storm is going to occur...but it does play a big factor in exactly where the rain/ice/snow lines set up. So how confident are we in this trend, and will it continue or revert back to earlier runs, is the big question. Given the nearly unanimous trend in this direction, and at least a couple model runs in a row showing such a trend, it does seem like this shift has some merit. However, overall run to run consistency has shown pretty large swings with the exact handling of both the southern and northern stream energy. Suspect that the exact details of these features is far from settled upon...especially the northern stream energy which is currently strung out across much of western Canada into the arctic. Thus tend to think that the unanimous model trend could be a slight mirage and suggests more confidence in a solution than there actually is at this point. Either way, it should be stressed that in just about every outcome we get a widespread and major winter storm with many areas getting significant impacts regardless of these exact details. These details are, however, important for exactly where the maximum snow and ice totals occur. The current WPC QPF and temperatures were derived before much of this 00z guidance was available, and thus is a bit south of the new consensus. As described above, no guarantee we dont see a shift back south in later models...but assuming some persistence in the 06z/12z models then the WPC update today would likely shift north to at least some extent. Behind this system the general troughing in the east and ridging in the west will persist. There is quite a bit of run to run variability with the shortwave details which does result in quite a large spread in the max/min temperature forecast across the Plains. The NBM was in line with the model means, so we did not make any changes. However, it should be noted that we will likely have some larger than normal errors...just hard to stay whether colder or warmer wins out along this ridge/trough interface.

More likely than not...the GFS is probably mishandling the timing of the Baja low. However, none of the other models have been stellar with that area either. With one big camp calling for a lot of energy to go west of the Apps....tough for me to go against that camp. Probably have an increasingly diminishing windrow through Weds for this to adjust some. I really doubt it goes back to big snow, but hope I am wrong. The GFS standing alone(maybe some RFS and AIGFS support) rarely works out for me. I do wonder if the Euro is too amped as you noted above w/ some of its recent trends with other systems.

Yes. It has done that with many systems this winter. I don't know if there is a window where data is missing(systems going through blind spots like the Arctic Circle or eastern Pac) or if that is just a bias. OTH, the GFS has had big time problems w/ Baja energy this winter. At one point, it tried to tap a Pacific tropical system and funnel that moisture into E TN. But with trends across several models...sure looks like a warmer system(compared to yesterday's runs) is likely.

I should add that I would be shocked w/ a reversal. Just too many models showing the trend towards a warmer solution. However, with the Euro changing hp strength in the Plains...that could greatly affect where the phased system tracks. If the hp dives behind the system, it cuts. If it stays over the top...it might force the bulk of the energy east of the Apps w/ only a shadow pressing west. For E TN...this looks like snow to sleet to ice to rain. For now(like right this minute), it looks like 8-12 hours of frozen precip at TRI. Downslope effects are showing up on some models for sure in the Foothills - so, usual caveats apply. When I see big changes on modeling(MT hp on the 6z Euro), that usually tells me that things are not worked out. The GFS consistency gives me some weak(very weak) hope, and the 6z GEFS snow axis actually shifted south at 6z. It is possible the Euro is too amped....but the AIFS supports the Euro as does the GEM and GEM-para. Let's see what this hurricane hunter data reveals. I think the big error(and this error has been present on modeling all winter long) is trying to hold that Baja low in place too long or string it out. More often than not, that low has been poorly modeled up until about 3-4 days before reality. We have also seen energy transfer from the Rockies back to San Francisco on modeling(not this particular setup to clarify) - didn't happen. The Southwest has been a big problem for modeling this winters. Oddly, that Baja bias has been across modeling. One thing I will add...any time a Baja low is involved, the Euro struggles...until it doesn't. Then, it locks in.

For sure on the phase. And I agree. If it phases....the hp strength is minimal in terms of importance. However, how they phase will be impacted greatly by how much that hp presses. A stronger hp will suppress that system. Check out Steve's comments in the SE mountain thread. He does a better job of explaining it. I lean Euro, because it generally is a better model....and the gfs has been bad since Thanksgiving. I don't think hurricane hunter data went in last night. It looks like some data will be added today and tomorrow. We may see a big jump (could be good...could be bad)once that data is inputed.

@Maggie Valley Steveposted this in the SE Mountains Thread which @Met1985mentioned. Great disco in that thread BTW. Sounds to me like they were just moving planes around last night. Today and tomorrow, those guys get down to business. So I got some clarity from Jeremy DeHart on Twitter. Jeremy is an AF Reserve Meteorologist for the Hurricane Hunter missions for many years now. He stated that last night mission was a reposition flight back to Keesler. The mission today will sample the Baja low with additional missions sampling the Gulf tomorrow.

Below is a comparison of the 6z GFS(left) and 6z Euro(right). The differences over the Plains are noticeable. The Plains hp on the GFS is stronger and more to the Northwest. The Euro is digging the hp behind the storm - amps the slp in front. The hp in New England is more expansive on the GFS and blocks the slp from coming north...supresses the slp in the mid-South. Here are two more things I am looking at. Let's compare trends within the same model. If the GFS is going to be insistent on the Montana high being strong, is it actually maintaining its solution from run-to-run? 6z GFS(left) and 0z GFS (right). The GFS weakens the Montana hp(for lack of a better term), but only slightly and the portion of the hp is pretty much the same. The more that hp weakens, the more room is available for the slp to slip north. We need a banana high which is continuous. The New England high really stays about the same in terms of strength and position. IMPORTANT: Now, this might sound like splitting hairs, because it is. But the placement and strength of the two areas of hp is affecting synoptics big time. In turn, that is affecting p-types. I tend to lean towards the Euro as it is just a better model at this range. But...the 6z RFS surface pressure(not in this post) looks like the 6z GFS, and that gives me pause. The Euro having pretty significant differences w/ high strength and position(from 0z to 6z) in the Plains also gives me pause. The fact the 6z Euro brought back a stronger Montana hp...cannot be ignored, but it might not matter if the STJ pulse stays strong.

I think with that Euro setup as is...it is going to try to split those two highs and head for the Lakes. What I can't know for sure is if the Euro is trending back stronger w/ the hp to the Northwest. The differences, even after that slide, grow pretty massively. The GFS is just weaker (but trending stronger) w/ the STJ pulse. I would really, really like to know which models got the bulk of the hurricane date overnight, and if one model didn't get it. To me the hp differences in the Plains look like a data error or absence of it...I just don't know which model is handling that hp over the Plains correctly. That feature is drastically affecting the overall synoptics of the storm.

6z left. 0z right. 11mb difference(increase) in hp over Montana. Notice the system at 6z doesn't get as far north on this frame. It eventually gets there, but those are pretty big changes. HUGE difference between a 1028hp and 1039.

Have to go further into the run.

That loss of hp was seen across several models at 0z...and now poof...it is back on many. Trying to dig through this and see what the trend might be and what caused the iteration overnight.

FWIW, the 6z RFS model which John uses is in the 6z GFS camp(shaky, shaky camp). It also handles the hp to the northwest of the system differently than the 0z Euro, but similarly to the 6z Euro. What the Euro is doing is basically settling into a seam between to highs to the north, one over New England and one over Montana. IF the Montana high is strong and bridges over to the New England high....the system slides on across. The 0z Euro completely lost the hp to the northwest of the storm...returned at 6z. I don't know. I am guessing that we are getting better sampling of the northern features as they get closer to us.