canderson

Did it push down any wind?

Finally posted DISCUSSION... KEY MESSAGE 1: Severe t-storm risk confined to southeast quadrant of CPA through early evening Focus for severe t-storms appears confined to the southeast quadrant of the CWA over the Lower Susquehanna Valley. This area is on the northern end of linear convective line evolving eastward from DCA/BWI. Within a deeply meridional wind profile, damaging winds and embedded tornadoes will be the main hazards. Latest WOFS is more bullish on severe risk (both wind and tor probs) to the south of the MD line toward Chesapeake Bay. We plan to trim the Tornado Watch #68 based on the latest SPC watch status report. KEY MESSAGE 2: Quick burst of moderate to heavy snow and sharply falling temperatures to bring slippery travel across the Alleghenies this evening into early tonight Well-defined surface/arctic cold front is on the western doorstep at 18-19Z. Observed 1hr temp drops are on the order of 10-15 degrees along with wind shift to the west. In wake of this FROPA, temperatures will continue to plummet due to strong CAA, while mid and upper level flow remains southerly in response to the strongly tilted and digging upper trough. Combined with upslope enhancement, this will cause precipitation to rapidly transition to snow from the Laurel Highlands across the western and central Alleghenies through the evening commute. While some snow accumulation may be initially limited to non- paved surfaces particularly at lower elevations, the higher elevations will see a two-part winter wx event consisting of front-end "thump" followed by lake-enhanced upslope flow. A brief period of snowfall rates surpassing 1"/hr (>60% chance) is expected btwn roughly 00-04UTC where a quick 1-4" of snow is fcst. Typically favored locations +2,000ft elevation should continue to see additional minor accums into Tuesday with local amounts 4+ possible. Pressure rises and steeper lapse rates/colder air aloft will maintain gusty winds with max gusts approaching advisory levels. KEY MESSAGE 3: Much colder with a couple of locally heavy snow showers possible Tuesday As the trailing vorticity maxima and secondary shortwave embedded within the trough over the OH Valley moves east Tuesday afternoon, convective cellular snow showers and isolated snow squalls could develop across the area. Additional snowfall accumulations will be light with any of these convective elements, but briefly heavy snow rates and gusty winds could cause local travel impacts due to rapid reductions in visibility. A SPS may be needed due to the broad coverage of locally heavy snow showers.

This line of showed moving north will dampen instability and i am not sure it can rebuild again.

2011 is the storm that brought down all those trees on Front Street.

.35” rain, sun is back out. We’ll see later how the actual front comes though.

Storm is moving N at 65 mph and still didn’t mix down the high shear we have overhead. Interesting. Boundary level rules again.

No wind at all with the passage. Not even heavy rain. Some thunder and one super local single lighting strike. Wind is picking up now it’s moving out.

Holy shit that lighting and thunder

As these storms climb N into the valley they’re hitting a wall related to anything severe

Good thunder though. The dynamics here aren’t great for lighting.

You can see the dynamics change right at the PA/MD border. Oddly we see more straighter wind than them but they have the spinning much more.

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

lol the state is closing offices at 1 - right in the middle of storms.

For watch specifically mentions widespread gusts of 80+ mph. Have our safe space ready.

Sun is out in Harrisburg.

52 was the highest I got Looks like we get a reprieve from wind starting Wednesday for at least a week.

Damaging linear/downdraft winds remain our main very strong threat today for both lines - the fropa and the squall. The squall being delayed until after sunset might mitigate that but it’ll still push down 50 mph gusts for some.

Jesus

The NAMs and HRR both keep the extreme severe stuff south of the PA border.

They’re ok - no damage - but neighbor (about 1/4 mile down - it’s Texas remember) lost a part of their roof.

Funny, my parents are currently in the storm shelter because a tornado warning there (in E Texas).

Didn’t want to clutter the other thread. Thank you for that tremendous write up. It was fantastic. Tomorrow will be rough down your way.

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

I should have mentioned that - yea he’s writing for VA/MD specifically. We don’t have the prime atmospheric conditions VA will have. But that’s mostly for tornadic activity. The QLCS will mix down major winds. LWX mentions this in this afternoon’s write up which I have to say is much more in-depth than CTP’s. Granted however their entire coverage area is in the mod risk. CTP’s isn’t and they have a more dynamic atmosphere than we do. I don’t see tornadoes as much of a thing north of BWI. Once any earlier low stratus are scoured out, expect ample diurnal heating as temperatures rise into the upper 60s to low 70s. Prolonged south to southeasterly flow should also raise dew points into the upper 50s to low 60s. The seasonably warm/moist low-levels coupled by strong forcing aloft and cyclonic turning of the winds with height will make for a very active convective day. While the degree of vertical shear is impressive on its own (0-6 km values around 55 to 65 knots), this comes with more than sufficient buoyancy levels as surface-based CAPE values push into the 500 to 750 J/kg range. The shear/instability combination will be conducive to supercell development, particularly for any discrete cells that form ahead of a likely squall line. Additionally, the degree of deep-layer shear should make this more of a quasi-linear convective system (QLCS) which will be capable of tornadogenesis. Aside from any tornado risk, the strong cloud-bearing level winds should easily mix down in convective downdrafts. With 850-700 mb winds around 60-70 knots, any of this higher momentum air being transferred to the surface could yield surface wind gusts into the 65 to 75 mph range. Thus, SPC has a broad area of significant damaging wind potential (45-74%) advertised from I-81 eastward in their latest outlook.

One of the best posts you’ll read about this event