2023 Mid-Atlantic Severe Wx Thread (General Discussion)

[Eskimo Joe]

27 minutes ago, Kmlwx said:

Not anything near as intense as June 2012 - but this is the kind of event where MAYBE some of us get surprised. Models can really struggle sometimes with eastern extent of a threat in a setup like this. It will be fighting the complete opposite of peak heating by the time it gets here - but I'll be watching. 

Agreed. This event is climatologically abnormal, and we don't have the rocket fuel to really goose the storms up. Still, we have some decent mid level instability, a belt of shear, and some really solid DCAPE.

[Eskimo Joe]

@Kmlwx I lost the OU CIMMS placefile for GR. Can you post it in here please?

[Kmlwx]

1 minute ago, Eskimo Joe said:

Agreed. This event is climatologically abnormal, and we don't have the rocket fuel to really goose the storms up. Still, we have some decent mid level instability, a belt of shear, and some really solid DCAPE.

Also, in addition to not having the triple digit heat that June 2012 had, this will be arriving substantially later. In fact, it will probably arrive so late that it makes little sense to "stay up" for the storms...I'll set an alarm for 2am perhaps and see how things look. 

I do like the look of the stuff over western Ohio - based on the H5 flow I'd think that would be more likely to be our stuff versus the NW PA stuff. 

[Kmlwx]

Just now, Eskimo Joe said:

@Kmlwx I lost the OU CIMMS placefile for GR. Can you post it in here please?

Hang on - coming right up

 

https://cimss.ssec.wisc.edu/severe_conv/NOAACIMSS_PROBSEVERE

[Stormchaserchuck1]

Look at the warnings

https://radar.weather.gov/station/KCLE/standard

LI  https://ibb.co/FkpzH99

[Eskimo Joe]

1 minute ago, Kmlwx said:

Hang on - coming right up

 

https://cimss.ssec.wisc.edu/severe_conv/NOAACIMSS_PROBSEVERE

Thank you.

[mappy]

Wind threat? Should I bring in pool floats and stuff?

[Kmlwx]

8 minutes ago, mappy said:

Wind threat? Should I bring in pool floats and stuff?

If it's easy - I'm not convinced the storms will make it here with much else than showers. But - some of the models do have something coming through. 

[Stormchaserchuck1]

16 minutes ago, mappy said:

Wind threat? Should I bring in pool floats and stuff?

Lapse Rates and CAPE is pretty decent. 

Another beautiful sunset with a sliver of moon in the sky. clear skies

[mappy]

11 minutes ago, Kmlwx said:

If it's easy - I'm not convinced the storms will make it here with much else than showers. But - some of the models do have something coming through. 

Thanks! I’ll reevaluate before going to bed. 

[mappy]

3 minutes ago, Stormchaserchuck1 said:

Lapse Rates and CAPE is pretty decent. 

Another beautiful sunset with a sliver of moon in the sky. clear skies

Thank you! 

[RDM]

Currently 3 tornado warnings in nrn Ohio and NW PA.  Not good.  

[yoda]

8:30pm LWX AFD evening update

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Unsettled weather pattern is expected for tonight with strong
storms likely and severe storms possible. Current analysis
shows an MCS ahead of a cold front moving into Pennsylvania
while another area of convection approaches the Shenandoah
Valley from the southwest, which is in association with a weaker
shortwave/outflow boundary that is passing by to the south.

For this evening, the activity to our southwest will most likely
propagate into the central Shenandoah Valley and Potomac
Highlands. Note the west to southwest flow over western VA
converging into the south to southeast flow over the central
Shenandoah Valley. There is an area of higher MLCAPE over this
area as well. Therefore, showers and thunderstorms are likely to
develop this evening across this area, and with moderate
effective deep layer shear, some storms may become severe.
Damaging wind is the primary threat, but an isolated instance of
hail is possible as well. Also, there is a decent amount of
moisture pull, looking at the 925 and 850mb moisture transport
from the southwest. This, combined with a light low-level flow
means that some storms may hug terrain or convective boundaries,
causing a threat for flood/flash flooding. However, confidence
is too low for a watch at this time given a relatively stronger
steering flow. Will continue to monitor.

The other area of concern is the MCS moving through
Pennsylvania this evening. This line will most likely propagate
southeast into western MD close to midnight, before moving
through our area from northwest to southeast overnight. The
propagation of this system to the southeast is offset from the
steering flow, which is southwest to northeast as well as the
potent shortwave that will be passing by to the north.
Therefore, there is a chance that the outflow may outrun this
activity, causing it to be relatively weaker. However, there is
increasing CAPE and instability due to southerly winds ahead of
this system, despite it not being a favorable time for
convection. This increases the threat for severe storms. Given
the setup, damaging winds appear to be the primary threat,
especially near and north of Interstate 66 and US 50 into
eastern WV, northern VA, and northern/western MD, where the
forcing will be strongest. Isolated instances of flood/flash
flooding are possible due to the heavy rain and increasing
moisture ahead of this system. However, it should be
progressive (causing any training storms to be localized in
coverage). The low-level flow will be backed more to the
southeast and perhaps a bit stronger, especially near/east of
Interstate 95 in northeastern MD. An isolated tornado cannot be
ruled out as this activity approaches toward Friday morning.

[BlizzardNole]

Solid arc of severe TS warnings from near Toronto/Buffalo all the way back to central Ohio.  Gotta wonder what this thing would have done in peak afternoon heating!

Hoping to score but it's tough in the rain shadow, especially with NW to SE moving stuff.

[Stormchaserchuck1]

Still have juicy LI's

https://ibb.co/m0vBQ8s

[Eskimo Joe]

Mid level lapse rates appear to have strengthened and as @Stormchaserchuck1 just mentioned, Lift Index is rather robust.

[Kmlwx]

0z HRRR kills off most of the activity for much of our area except for NE Maryland as LWX has been indicating. 

[TSSN+]

2 minutes ago, Kmlwx said:

0z HRRR kills off most of the activity for much of our area except for NE Maryland as LWX has been indicating. 

HRRR timing is not even close. Storms right now about to move into state college around 10ish and HRRR at 10 has the storms like 3 counties west of there. 

[Kmlwx]

2 minutes ago, TSSN+ said:

HRRR timing is not even close. Storms right now about to move into state college around 10ish and HRRR at 10 has the storms like 3 counties west of there. 

It also seems to interact with the activity over WV which seems to "aid" in killing off the line. Certainly the line still looks robust for right now. 

[87storms]

It also seems to interact with the activity over WV which seems to "aid" in killing off the line. Certainly the line still looks robust for right now. 

The mountains love this type of system. If I can see lightning in the distance with remnant light showers, I’ll call it a win.

[TSSN+]

1 minute ago, Kmlwx said:

It also seems to interact with the activity over WV which seems to "aid" in killing off the line. Certainly the line still looks robust for right now. 

I'm sure it will crap out though. I haven’t had a single thunderstorm this season yet. The heaviest rain I have had was late June and was only like .5” or something that day but was just a plain rainy day. Total rainfall since June 1st here only at 1.87”. 

[Kmlwx]

PBZ radar is cool to watch. You can see the outflow trying to outrun the storms. Outflow seems to be heading almost due south despite the storms trying to pull more easterly - they keep being tugged along with the outflow. 

[Stormchaserchuck1]

I've been surprised it's been raining so much here in NE MD. We have 10"+ since it started a month ago.  

[Eskimo Joe]

Looks like the best instability will be from NE suburbs of DC into Baltimore and PA. New severe thunderstorm watch for PA until 5:00 am Fri, 7/21.

[Kmlwx]

12z NAM nest goes kind of bonkers for parts of the area tomorrow afternoon - even has intense UH tracks over parts of the area. The other guidance is less impressive...but the FV3 is pretty good too. 

[George BM]

1 hour ago, Kmlwx said:

12z NAM nest goes kind of bonkers for parts of the area tomorrow afternoon - even has intense UH tracks over parts of the area. The other guidance is less impressive...but the FV3 is pretty good too. 

SLGT risk introduced for tomorrow east of the mountains. T/W/H 0/15/15

[George BM]

Wonder if we can get some W/NW flow action late this week and/or this weekend as a few models are hinting at.

[CAPE]

The depiction on the 18z 3km NAM aligns pretty well with the SPC discussion for tomorrow-

A large scale mid/upper trough oriented from the lower Great Lakes to the central Appalachians will pivot east across the Mid-Atlantic and Northeast on Tuesday. Large scale ascent coupled with modest vertical shear (effective shear magnitudes around 30 kt) atop a seasonally moist/unstable airmass will support scattered strong to severe thunderstorms from early afternoon into early evening. Elongated/straight hodographs amid large instability above 850 mb and increasing westerlies to around 35 kt between 3-6 km suggest isolated severe hail will be possible with semi-discrete cells, especially around the Delmarva/Chesapeake Bay vicinity where midlevel lapse rates are forecast to be steepest (around 6.5-7 C/km). Strong heating will aid in steepening low-level lapse rates, and low-level winds will remain fairly light. This will promote potential for strong outflow and isolated damaging gusts. Some guidance suggests a forward propagating cluster may develop via consolidating outflow across the Chesapeake Bay vicinity late afternoon/early evening. As a result of these factors, the Marginal risk (level 1 of 5) has been expanded across the Mid-Atlantic and a Slight risk (level 2 of 5) introduced across the Delmarva vicinity.

[Kmlwx]

0z HRRR does it's usual thing of bringing dews way down - even into the lower 60s for some tomorrow afternoon. The 18z NAM had richer moisture as usual. Despite that, the HRRR does deliver some storms but it looks fairly garden variety. 

[Kmlwx]

Much of the guidance is almost nothing if you are west of I-95 in most of the area. FV3 Hi-res is still decent. But east seems to be very much favored today.