MAG5035

Steady light snow now established pretty good. Dusting and 28ºF

Some steadier lighter snow with the arrival of some enhanced echoes overhead.. still trying to work on getting some accumulation going. Flakes are of the sparkly variety (dendrites).

At the very least I think CTP's advisory lineup and numbers look pretty good across the board over the region for now. Things to watch for will be with the initial shield of warm advection precip (which is generally the primary source of the snowfall for our region) and how well it presses northeastward into PA. HRRR has looked pretty good with pressing it pretty far NE, nearly getting the 1" line at 10:1 to IPT on the latest run. Ratios will be a key to get to advisory amounts. A straight 10:1 wouldn't get there with the QPF in all but the southern tier border counties. I know in earlier CTP discos they've mentioned 13-15:1 ratios, which is good but could be better. A limiting factor mentioned was that despite good dendritic growth high up, falling through the lower levels could cause riming and accretion. So if we were to end up getting better ratios (15-18:1 type stuff), then we'd squeeze a bit more snow out on the fluff factor. So i'll be curious if we end up with some better enhancement in the JST-AOO-MDT corridor with the WAA snows. It also wouldn't take much to squeeze out an extra tenth or so of precip either, especially turnpike south. Last night from CTP: The other and more potentially impacting thing to watch is what happens when the coastal low starts to take over. For one, the models have been pretty quick to snuff out the warm advection shield over PA once that starts happening. Does it really do that? Or will it linger more, and then be part of the deform shield of the coastal low that will have the heavier precip and better forcing. The 18z NAM kind of tried to do that, and illustrated how it's possible that the border counties join in with the Mid-Atl forum in getting warning snows. It'll be interesting to watch this unfold tonight. It's a moisture laden Gulf Storm, and these types of events always seem to find a way to squeeze out more snowfall.

And we're off, very light snow falling.

Echoes are just getting overhead here, nothing to the ground yet. Should be soon, snow is visible on 511pa cams in JST. 30ºF

If your talking about Raystown Lake (southern Huntingdon County) you might end up in about the best spot in the forum for this storm other than maybe the PA/MD border with the good ratios and heavier precip creeping north. The models have been pretty solid on the central counties having slightly better QPF even before the NAM started NAMing.

The classic pre-snow sunshine behind high clouds

CTP has expanded advisories up a tier or so, as has PBZ now including Pittsburgh metro. 2-4" for the central counties (JST,AOO, Lewistown region) and 1-3" advisories for the next tier of Sus Valley counties including Harrisburg. Recall that advisory criteria is now 2" in 12 hours in the LSV. Things seem pretty set now with northward extent and QPF with some possibility of some minor shifts. Just starting to get into range for using near term guidance. This isn't going to be the biggest snowfall ever for the part of the subforum that sees it but it is something.. and the longer term is starting to look pretty promising with regard to storm possibilities and sustained cold air. D8-10 range has been looking like a window to watch for the next system. CTP discussion below:

An actual look at overnight and 6z guidance would have shown some improvement overall with getting precip into central and LSV locations, esp on the Euro. I fell asleep early last night or I would’ve posted about it. Right now it’s looking like a general 1-3” snowfall under I-80 with some possibility of 4-5” in the southern tier (esp west).

I think the high is in a pretty good spot but we have issues to overcome in terms of the features in the pattern. The active Pac pattern undercuts the western ridge as this thing blossoms and it gets pushed east and thus we have an amplification problem. With that, the storm has generally been progged to "peak" in the midwest where the highest snow totals have been showing up in esp MO and IL. If we could slow the pattern down and amplify, we would have no problem pressing a solid event into our region even with just the southern stream wave. But instead we press the storm east and force secondary development that has nothing for the high to the north or confluent flow to the NE. Probably going to have to get all the players fully on the field and this storm initiated off the Rockies to see where we're at with getting this to come north a bit. The overnight Euro was really messy at 500mb while the GFS for now was a bit more defined with the shortwave. For us we are likely going to live and die with whatever initial warm advection snows make it through the area before the coastal low develops unless there is a pretty sold shift north in the short term. If there is a pretty robust precip shield from that, we'd probably be fine and at least score some kind of an advisory event (Sus Valley criteria) with the cold air in place and good ratios.

Total snowfall from the late afternoon snow squalls ended up being 2.3".. just enough to get the snowblower out and make sure it actually works properly for the next bigger storm. That's pretty decent for lake effect snow here off the Laurel's and might see some more overnight. The top of the mountain 5 miles from here had at least 3 or 4" on the ground when I went up there after the first squall around 3pm.

So far initial looks at the 0z suite have the GFS and CMC looking better with northern extent of precip from the weekend system.

Yea it had a somewhat better shield of warm advection snows, which is good to see as that could be the main precip we get from this system. It seems this storm could peak in it's high snow totals out in the midwest and upper OH valley and then the storm forms a new low off the Carolina coast and that's where the bulk of precip stays south. There's definitely overachieving potential to be had, especially from good ratios. Best lift would be fairly high (700mb and above), so the temps in that layer would be conducive for higher ratios and that would translate to the ground since there's no thermal issues. I'll be curious to see how this evolves as we get into short range. This storm looks to have a good fetch from the Gulf of Mexico so perhaps we could see an uptick in QPF. Just 0.3"-0.5" would make for a solid event and the Euro had a lot of 0.2's in the Sus Valley. I wouldn't completely disregard it.. I'm going to keep monitoring it for this upcoming storm. I don't think any actual weather data input such as balloon launches from the NWS to help with initialization has been affected but I could be wrong. The model hasn't really been showing anything insanely different or questionable with this storm, although it did switch today to line more up with other guidance after being pretty far north and our biggest fan in terms of giving most of our region a heavier snow event. I think the main thing with that is just maintaining the model and making adjustments to compensate for verification scores. With the shutdown in the middle of week 3, it's probably not having an extreme effect on that type of stuff quite yet. But if it lasts for an extended period of time (months) I could def see some issues. One of those articles mentioned the hurricane forecast models and that they use the winter months to study the previous season's hurricanes and try to improve the hurricane models off of them. The math and computer science behind the models aren't my area of expertise, but I do know there's a lot of work that on a daily basis goes into maintaining/adjusting/improving the model we love to yell at. And those people aren't able to do that right now. Another thing that hasn't been available is all the data pertaining to the National Climatic Data Center. So there's no availability to a primary source of historical weather data that is useful in generating analogs or comparing past patterns and etc. That's also the only site I'm aware of that still generates the EPO index.

Another very intense squall coming through right now, very low visibilities. The squalls are potent today, reaching pretty deep into central PA.

Update: One inch from the squall (1.2” on the day)

Working a half decent squall right now, starting to get things whitened back up.

I doubt this storm is going to get squashed south as far the Dec 9th storm was. We do have a stronger high but it's north of us vs pretty much over our heads (the case on Dec 9). So I think the DC gang will probably see this but it remains to be seen how much we can get into our region. I don't think the high positioning is as much an issue as amplification of the southern wave and interaction with the northern stream. Most guidance gets initial overrunning lighter snows into PA but have kept the bulk of precip south of the region. The GFS had been the flagship for a C-PA strike but it has shifted that axis south especially in the 6z and new 12z guidance. I guess I'd be lying if I didn't admit that seeing southern VA get hit with another significant winter storm would be brutal after throwing away December with cutter after cutter after that last southern storm. Still 3-4 days out though and different setup. These gulf storms usually have pretty decent shields and can creep north with time... or I guess BACK north. We would have a solid cold airmass and likely at least climo average snow ratios (about 12-13:1 depending on where in C-PA this time of year so just a few tenths of precip would give us a solid advisory. There is the NAM at range right now.. I'm sure that'll never let us down haha. Sidenote with regard to modeling... I've saw some discussion in other threads about the impact of the Gov't shutdown as it pertains to the GFS model. Been trying to look for some sourcing to get a better picture on if that is really affecting that model adversely. With the partial shutdown, the scientists responsible on a daily basis with keeping the model in line with updates and adjustments has not been going on (apparently the maintenance of the American tools for essential forecasting duties is deemed not essential). I'm sure that probably involves the NAM too. This may be affecting the FV3-GFS more adversely than the op GFS right now too. Either way this is something to keep in mind with trying to get a handle on this upcoming system. Some sources: https://www.nbcphiladelphia.com/weather/Government-Shutdown-Means-Some-Weather-Forecasting-Tools-are-at-Risk-504065431.html https://www.scientificamerican.com/article/another-casualty-of-the-government-shutdown-hurricane-preparedness/

A new day dawns to the first accumulation of snow on the ground in over a month (coating)... 12 hours after having thunderstorms roll through.

Lol, thunder and lightning with the approaching showers here. That and I could've sworn I saw a tornado warning in NW PA on RadarScope earlier this afternoon. Edit @pirates21 Yep haha

0z Euro keeps it's minor event status quo much like the GFS has with it's big snowstorm one. The issue isn't really that the wave isn't there. The Euro does eject out southern energy in a similar manner and we have a breakout of snowfall with a 6-8" bullseye in the midwest (MO) which then runs a few to several inches along the OH River Valley that loses it's luster once over the Apps. It does have a 1-3" type event in the western half of PA with up to an inch or so (used Kuchera numbers). So all the major models do have this thing, but the big difference especially between the GFS and Euro is the northern branch and positioning of the ridging in central Canada. GFS has a sharper and somewhat stronger ridging up into the Hudson Bay, which buckles the northern branch in the fashion that allows enough interaction to touch off the GFS's bigger storm. The Euro's alignment doesn't buckle the northern stream and it stays largely separated, so in that case we just have the southern stream wave ejecting out on a positive tilt with progression and no dig. Adding in the Canadian, it gets there by having a much more robust and consolidated southern branch shortwave but has little NS interaction like the Euro. The differences between the three models at H5 around that 120-144hr timeframe are pretty significant... but I am becoming more confident that we see x amount of snow from this. The eventual evolution as to how much x ends up being is going to need to be sorted out a lot better the next few days. As I mentioned a couple days ago, this overall setup is a way for us to winter with an active Pac and above average 500 ridging. You have the ridging in western/central Canada and the Pac shortwaves undercutting and running thru the SW US. GFS at 126hr EURO at 126hr Canadian at 126hr

Still 32-33ish here. Nasty glaze of ice remains on untreated stuff, hard to stand on my paved driveway. Probably about 0.1" on the ice accrual. Per mesowest obs the cold air looks to be starting to retreat with above freezing obs for the most part AOO/JST south and near 50 on the other side of the Alleghenies in the Pit region.

0z GFS whacks C-PA, Pit and Mid-Atlantic gangs. Canadian more of an I-80 south event but I consider that progress for that model which was pretty disinterested in any event just a day or so ago and a decided shift into our region from 12z today.

Well the Mid-Atlantic forum did make a storm thread for this potential event so there's that haha.

It sure did back this way. A light glaze of freezing rain and sleet is likely the culprit for multiple crashes/road closures this morning up in Cambria County. One on US 219 (between Johnstown and Ebensburg) and the other on US 22 (Between Altoona and Ebensburg) https://wjactv.com/news/local/sr-219-at-new-germany-closed-for-extended-period-of-time?fbclid=IwAR0Xa5fYn061deH-HI56i8fgwGcvWjhLZvIsrFsVmGtLnrpdTPNxGkMgOUk https://wjactv.com/news/local/penndot-crash-on-rt-22-near-cresson-closes-at-least-one-westbound-lane-lane

It's going to be interesting to see if this potential storm starts looking better on the models overall (more consistency). There's been something in the timeframe off and on but nothing concrete. As modeled right now it would be an example of wintering with above normal 850ºC anomalies and high 500 heights above being undercut by shortwaves. Regardless of if we get something from this, this potential pattern change looks to be coming and relatively soon at last compared to earlier fears of punting the whole month...although I think we could have the usual transitioning pattern issues. The MJO went from the border of phase 5/6 to cracking into phase 8 in less than five days.