SnowenOutThere

BWI: 19.8 DCA: 12.9 IAD: 18.6 RIC: 9.0 ——————— SBY: 8.9

Well the latest GFS run opted for shredding the southern shortwave entirely by moving it out as the northern bowling ball crushed it. So making this an addendum to the og post but it appears that instead we need to have constructive interactions between the northern and southern energy to get a storm. So really I think watching for a stronger piece of energy out of the south which would help pull the northern stream energy souther is needed. Additionally, a stronger but further south piece of the NS diving in would be beneficial. Either way I just don't see a great likely way all of this breaks our way as we have to contend with a southern energy split, northern stream interaction, and trying to keep the 50/50 in a better position.

Here's my quick breakdown as a bit of practice for my upcoming atmosphere and weather test. I am going to start with the negatives before ending with the path to victory I can imagine. I think the more notable issue is that the high appears to go from helping to hurting before the event even starts. By Friday midday the main surface high pressure is off the coast which promotes flow in from the Atlantic (which as a reminder it is still early December). Additionally, we have no real mechanism for keeping any cold air in place for the layers below 700mb as the surface high is unhelpful. The upper level low and surface low are both in a position to eat away at the remaining cold wedge before precipitation even comes close to our area. Just take a look at this 925mb map. The flow is completely out of the south 12 hours before the event even begins. It should be noted our saving grace here is that the storm is weak so the winds are minimal. The better news is that the 850+ level is less affected by the surface high and general weak low that is "attacking" from the south. This means that the flow is firstly, not that strong; secondly, out of the southwest/westsouthwest. Once you get above 850mb the flow largely veers to be out of the west as there just isn't enough cyclogenesis to really distort the westerly flow. All of this said, I think that ultimately with currently modeling the event this Friday is not in a good spot. I believe this as in order to get a real plowable snowstorm we need two things to go right. 1. A stronger low pressure center in order to actually get lift into the area 2. A correspondingly stronger/more stubborn high. If we get 1. and not 2. all of the thermal issues I highlighted goes from bad to worse as the southern flow just becomes stronger. Meanwhile, if we get 2. but not 1. then we probably end up suppressing this storm. In the end it seems like another thread the needle event that just seems unlikely to get more than 1-3 inches. Disclaimer is that ofc I would be happy with 1-3 inches but this analysis is from a "how could we get a plowable storm" perspective. That said, I think there is room for hope as it is not impossible we get 1. and 2. to align. The 5h pattern isn't horrible after all. There is clearly a path here. Though as it stands everything is slightly off. We have a some semblance of a 50/50, though we need it to be further southwest if we want to trap the surface high pressure in. Additionally, the shortwave out west isn't in a horrible spot. However, as it stands it seemingly gets both weakened and pulled north by the larger low pressure center over central Canada. I think the path to victory here is quite simply that the low out west doesn't get stuck. Currently, the energy enters the southwest around hour 60 then languishes there through 110 before a secondary shot of energy pulls it along. I think if we're able to have the first ball of energy keep its form and progress eastwards and the second shot of energy enters faster its honestly quite possible we manage to get a stronger, more consolidated, and further south system without as much northern stream interference. Additionally, the 50/50 would naturally be in a better spot which would help offset the WAA from a stronger storm. Thank you for listening to my Ted-Talk and if any met read this through let me know if I am gonna fail my test. TDLR: As it stands I don't think Friday looks good for anything more than 1-3 inches, however, I think the path to victory for a bigger storm is still there if the energy out west is more progressive

I mean this sounding from the Catoctins really says it all. Though, it appears if you're able to keep the column cool it will be dumping with a saturated atmosphere up to 500mb and good lift in the DGZ

If you're also trying to just sit down and relax a bit instead of hiking the whole time then that trail isn't super great as theres no campsites or anything off it. Instead I would recommend https://www.alltrails.com/explore/recording/afternoon-hike-at-black-rock-via-the-appalachian-trail-7f8dfc1 (Black Rock Via Appalachian trail) as its both right off route 70 which is nice and the Annapolis rock outlook has picnic tables nearby (additionally Black rock outlook has a overhang you can stay under which is sheltered).

Before I forgot I wanted to upload some pictures I got of DC a couple days ago as a sendoff to November

This setup reminds me a bit of a hike I went on in the Catoctins last November around this time. Here is a link to the hike I went on which tried to maximize the amount of time I would stay at high elevation while reducing the amount of high elevation road I had to travel up. There's a very long stretch of +1500 feet and you get to start down at 800ft and hike up into it which was awesome. Let me know if you want more details and the link to the hike is here: https://www.alltrails.com/explore/recording/afternoon-hike-at-cat-rock-yellow-trail-to-catoctin-blue-trail-7b13b22?u=i&sh=vrjjqd

True, but if this storm was a couple degrees colder it’s quite possible we’d be looking at least a slop storm to an actual snowstorm.

Just checked radar and wow! Is anything even close to reaching the surface?

Not to preemptively call it but I don't think the GFS is going to be what we need it to be.

I think this is the bigger issue, we don't have the same cold press timing we had previously. Even on the amped runs its a lot more thread the needle cold. That said, its not worth throwing in the towel yet as I think some snow somewhere is likely unless it stays amped.

I think there's some interesting stuff going on up at the H5 levels that is leading to the surface differences between the Euro and GFS. If we look into the Euro's H5 it has a northern piece of energy which destructively interferes with the developing coastal as it seems to string it out. Meanwhile, the GFS firstly deemphasizes this piece of energy and secondly absorbs what's left of it into the system which obviously creates a more amplified storm. At this point who knows which ones is correct but I think is something to watch for

Euro looks weaker out west and slightly more confluence in the east.

I like how its a more traditional coastal look than just moisture flow from the gulf