MAG5035

First 80+ of the year here, all the way up to 82ºF currently on a stiff SW breeze. 

I already like the severe potential today more than the setup last Monday. We don’t have anywhere near the shear/helicity parameters so tornado threat will be more minimalized. Wind and hail will be the primary threats with this.  

Regarding CTP disco’s previous concerns about cloud cover, SW and SC PA I-80 and south are fully in the sun and mixed out with the warm, gusty SW winds. So I think we’re going to build some half decent CAPE as the afternoon wears on and also advect in somewhat more moist air. Low and mid-level lapses are very high as well, as noted on the SPC disco. This is the kind of setup that can yield a surprisingly strong line of storms with strong downbursts. 

Low Level Lapse Rate:

Mid-Level Lapse Rate:

Just your run of the mill +40ºF departure in the central part of the US this weekend. Looks more like 6/21 than 3/21

On 3/16/2026 at 4:43 PM, canderson said:

Has the lack of vertical instability on the storms been what caused nothing to bring down the shear winds? We had not much cape but that’s not a need when interacting with shear levels so curious why everything has been muted so much. 

I was looking back at the SPC mesoanalysis from yesterday and parameters were really not all that impressive outside of the shear and low level winds. I just don’t think we had sufficient enough mixing out of the boundary layer or daytime heating (lots of cloud cover) to really tap into much potential. DCAPE’s were only on the order of a few hundred j/kg. Standard CAPE’s were only about 500 or so at best down south where there were still a decent amount of severe wind reports. But I noticed from the SPC map ITT shared up above that they were all of the standard severe wind variety, with 0 tornado or 75mph or greater reports.

Short range meso models were hinting at these limitations some which was why I was reserved on the severe potential a bit. I was still concerned some, I was figuring on a couple spin ups so I’m surprised there weren’t any reports at all. But would I have claimed essentially the weather rapture if I had 243k followers? Probably not haha. If we would have had the air mass we had last week when we were basking in the upper 70s- upper 80s in the Mid-Atlantic this absolutely would have been a much more significant event. 

At any rate, more locally mesoanalysis had a persistent area of CIN in the Lower Sus Valley. Low level stability is going to cap transferring the really high winds to the surface. The radars not very detailed on these maps but that was the cluster that popped a couple tornado warnings in MD before it moved into southern PA. 

This map is showing mixed layer CAPE (red), CIN (blue dashed), and effective bulk shear (wind barb).

The snow squalls are feisty today. Just had a nice one go through and put down a fresh half inch and take the temp all the way from 29ºF to 22ºF. 

The cloud wall in the background is the exiting squall

Synoptic stuff is done here. Most things blacktop stayed wet for the most part, but about 2.5” on pretty much everything else. Add some thunder snow and some gusty winds to that and guess I can’t complain about an event like that. 

53 minutes ago, Jns2183 said:

Thundersnow out south @MAG5035

Sent from my SM-S731U using Tapatalk
 

Yup, I’m out and about and I saw a lightning strike in Bellwood about 20 minutes ago. I-99 is a pretty rough drive right now visibility wise and the road isn’t even snow covered yet. Very windy with the heavy snow 

4 minutes ago, canderson said:

Did it push down any wind? 
 

 

Nah, starting to get a bit breezy now behind the front. Everything’s been under 30mph so far today. 

FROPA occurred here around 330pm, temps back to 48ºF. There’s been some regeneration of the line associated with the front itself, in the form of some heavier downpours here. Pressure’s been bottomed out around 992mb for awhile as this is a pretty deep storm system. 

Now to try to reel in just the 2nd measurable snowfall in the last like 50 days. Upstream radars at PBZ and RLX (Charleston) look pretty solid. This is probably going to catch some folks off guard tonight. 

HRRR and NBM snow totals this evening. 

7 minutes ago, canderson said:

How delayed is that line now? Seems less likely to be a full QLCS later this evening. 

I think the bulk of the overall severe threat is happening right now with that line coming into the Sus Valley from MD and also the other part of the line further up northeast of State College. This was the time of the day the high res models have been surging the CAPE up and matching with the shear. The line with the frontal passage (now east of Pittsburgh) might not have much CAPE to work with. 

Back this way, I think if the weather rapture were to claim me today it’s going to by the snow and wind that is looking more and more likely this evening behind the front. 

Pretty solid couplet in the newer tornado warning to the northeast of Frederick. The business end of this line with imbedded QLCS looks to be headed for York/Lancaster. 

Still trying to gauge the degree of which the severe potential gets realized tomorrow. High res guidance seems to be tightening the window when the best shear coincides with the surge of some modest CAPE into the Sus Valley, more in the late morning/early afternoon. HRRR looked like it was toying around with some discrete and/or quasi linear convection during that timeframe, while the 3k NAM doesn’t have much at all until the frontal passage. FROPA looked slated for roughly the 4-8pm timeframe west to east in C-PA. Discrete development out ahead depends on if there’s any kind of ample daytime heating via some breaks in the clouds, something I’m not quite sure happens in earnest in PA. Line with the FROPA will be more purely dynamics driven, but we’ll have to see how well it gets organized 

Also lost in all the attention to the severe is energy rounding the base of the trough during tomorrow generating a secondary wave of heavier precip riding up behind the front. So suddenly it looks quite snowy in at least the western half of PA early to mid Mon evening. This could drive a changeover to a period of snow all the way into the Sus Valley. Given the broad model support I’d be surprised if CTP didn’t at least headline the Laurels and north central Alleghenies for advisories. There’s support for the I-99 corridor as well. That will also be interesting to watch evolve tomorrow in addition to the severe threat. 

GFS vs Euro

3k NAM vs RGEM

7 hours ago, canderson said:

Thanks for this. Remarkable this occurred up here back then. Today? Much more likely with climate changes. 

The May 31st, 1985 tornado outbreak was more severe and remarkable than 1998 or any other more recent PA involved outbreak by a pretty sizeable margin. That outbreak spun up 43 tornadoes and killed 89 people (1000 injured) in PA, NY, OH and Ontario (65 alone in PA), produced PA’s only ever EF5 tornado (Wheatland), and also produced what I’m pretty sure was one of the widest tornadoes ever recorded in the US at the time (Moshannon State Forest). 

Couple screen grabs below but there’s some really informative links about this outbreak 

CTP’s 35th anniversary link- https://www.weather.gov/ctp/TornadoOutbreak_may311985

New interactive link they made for the 40th anniversary last year collaborated with NWS Pittsburgh, State College, Buffalo, and Cleveland  https://storymaps.arcgis.com/stories/e8c12f670d5648a9b64877f42660eeeb

3 hours ago, Itstrainingtime said:

A severe weather expert met in the MA sub (high risk) still has a few reservations about the extent and level of severe tomorrow. I hope his concerns play out.

Count me in on this thinking as well, in PA at least. Certainly dynamics look very favorable in terms of shear/helicity, along with very high low level winds to tap down. Whether or not south-central/Sus Valley cracks all the way into the warm sector ahead of the front to take fuller advantage of those dynamics seems to be a main potential limiting factor. 18z 3k NAM never really builds much CAPE in the Sus Valley (cloud cover), having a narrow corridor of modest CAPE further west in the south-central counties. Newest high res model runs doesn’t look particularly organized with any kind of solid QLCS line, which would be the primary threat here over discrete cells… though I wouldn’t rule those out completely, esp with any breaks to help with daytime heating.

As a side note the 18z 3k NAM was a prolific snow maker behind the front in western/central PA and other high res like the HRRR has at least a couple inches mainly in the Laurels/north-central. 

As another side note, this is occurring tomorrow literally one year to the date last year that we had a QLCS type line come through mainly the western and central part of the state with many tornado warnings and an 89mph wind gust at Latrobe. 

2 hours ago, Summit Snow said:

https://www.tornadotalk.com/may-31-1998-pa-ny-tornado-outbreak/

For those new to PA I remember this like yesterday. Those three days were off the charts in terms of storm potential. I was Tornado warned twice on 6/2 with the second warning being the Lake Carey tornado that killed two and injured dozens.

I was just playing around with the archived radar data that’s on RadarScope Pro the other day. Here’s that tornado, that’s a pretty pronounced velocity couplet for 1998 NEXRAD data. It was roughly reading 110-115mph gate to gate on the data. 

I think you had an upload error

Here’s an archived radar image I could get on board with. Some other March 13th a while back.

10 hours ago, mahantango#1 said:

Found this on facebook I didn't know NWS was doing a storm survey.

Nepa Storm Chasers 

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Dauphin County Tornado Update 

Some followup on the tornado warned storm in Dauphin County on Wednesday. I have actually drive on the exact road in the exact rural area it struck and there's a solid chance it missed every home as it's extremely rural in Shermans Dale and Blain, PA.

The storm would have only been on the ground for a short time maybe 10-15 mins, 3-8 miles max before lifting. This may have hit a house or just tore up some woods but there was clearly evidence to suggest it was causing damage.

I clipped a photo of the debris ball with the overlay of the general area it would have been. It's all thick woods and very rural homes. I personally stayed in a cabin about 2-4 miles from the exact spot this storm happened at. I'm very curious to see what the NWS survey team determines when they conclude their investigation.

Anyway, thought this may be interesting to everyone. I'll update when I found out.

- Espresso 

When I ponied up and upgraded my RadarScope to the Pro subscription this winter I forgot one of the features was archived radar data. So this is a really good example to try it out and review something. Basically, I’m not doubting the chances that this storm might have spun something weak up somewhere along the way but I think this posted screengrab of the CC labeled as a debris ball to prove a tornado on the ground is a bit of a stretch.

So here’s the 606pm image that was shared, crosshairs placed on the “debris ball” 

One thing about debris ball signatures is the area of low CC values are usually co-located to an area of high DBZ reflectivity values, which this CC signature is not. They’re also typically associated with established, strong tornadoes (>EF2), which I’m not really seeing the support for on velocity data, or obs/local storm reports. Even though this passed thru a relatively sparse area, it did still cross US 22/322 during this period. There weren’t very many reports on this storm at all looking over the LSR’s. 

This signature likely had more to do with the hail core that this cell did have with it, which will reduce the CC values and can also cause a corridor of reduced values in the downstream direction of the radar beam when there’s a pretty decent hail core.. which can be seen on the images. 

9 hours ago, Itstrainingtime said:

 

Pictures being posted in the MA thread are something else - a lot of white landscapes in areas that were around 70 degrees at 6am this morning. 

That’s just crazy how that all evolved down there this morning. The DCA ob was even registering a heat index last night when I had posted about it. 

People in there rating/upgrading their winters to A’s and such haha. If I don’t get any more snow this season beyond like a 1-2” bush bender I’m rating my winter a C-, and it’ll take a late March/early April 2018 type run for me to rate it any better than a C+. The only reason I won’t rate it worse than a C is the consistent cold + scoring the big storm on 1/25. But temps were similarly cold consistently last winter too, just without the big storm.  My snow total is sitting basically on par with the last 4 winters, which were all solidly below normal for here. So I’m grading tough. 

 I know this isn’t our area but it’s going on midnight and it’s still nearly 80ºF in and around DC, on March 11th. That’s nuts 

On 3/4/2026 at 1:50 PM, WmsptWx said:

 

 

 

Here’s the follow up on all this haha

Busted back out of the overcast/drizzle this afternoon and well into the 60s again today (as high ans 65ºF) after it had moved back in after dark last night.

The severe setup definitely escalated quickly in western PA, with temps reaching near 80 with dewpoints near 60. Decent shear/wind parameters and at least some CAPE (500-1000) along with some discrete cell formation. That will definitely need monitored over there. Obviously will remain much more stable in eastern PA at the low levels with the overcast and cool air damming but might still be some rumbles of thunder with anything that makes it over that way tonight. I do expect non-diurnal warming this evening in the spots that have been most locked in to the CAD as the approaching system/ SW flow will eventually mix some of the warmth down. 

I busted out of the clouds here, was as high as 63ºF earlier. Still around 61ºF

0.65” of rain here yesterday.

Eastern PA definitely looks to be denied a full torch this weekend as cool air damming, cloud cover and maritime flow off the Atlantic have a firm hold east of the mountains. Meanwhile from the Laurels westward, increasing breezy southwest flow is going to make for much warmer temps, likely making a run at 65-70 or so on Saturday. Sus Valley may eventually mix down 50s to near 60 later Saturday/Sat night as a weak frontal passage approaches. 

Mon-Wed is the real time frame where it looks quite warm, as it has looked consistently on models for like the last week. Tuesday is the best chance for at least the southern half of PA to make a run at 70ºF ahead of the next system. Some difference between Euro and GFS with the Euro being much more expansive in PA with the very warm temps and GFS more confined to southern PA. 

Much more uncertainty abound beyond that, big differences between the Euro and GFS. Euro has been way colder around the St Patty’s day timeframe and also has a storm on tonight’s 0z run. GFS bottles up cold air more in Canada and runs a further north storm track. Both models and ensembles develop the really negative WPO, which should put a lot more cold back in Canada. They’re also pretty firm on a pretty positive AO and NAO though, which would suggest cold intrusions into the US are limited and brief. Difference area is the PNA, where the Euro/ensembles (and Canadian) reverses a pretty negative PNA to positive to set up western ridging and a chance at the kind of storm it puts out at 0z tonight and holding a cold pattern more. The GFS op just keeps the PNA solidly negative and its ensembles do reflect the other models more with the reversal but is more neutral. I’m fairly pessimistic overall on any decent snow chances in that timeframe mainly due to the +NAO/AO, but building a western ridge even briefly would at least allow for a window to try to line something up.