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2022 Mid-Atlantic Severe Wx Thread (General Discussion Etc)


Kmlwx
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26 minutes ago, Kmlwx said:

I haven't looked enough to weigh in. Probably won't have time to until later tonight or tomorrow AM. But if EJ is in for now... I'm intrigued 

I'm definitely intrigued with the setup. We typically get one solid SLGT/ENH per spring and this might be it.

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6 hours ago, Eskimo Joe said:

IMO, if this continues we could see this be a ENH with the SLGT back to I-81.

When was the last time the area had moderate?

Last time I can recall was June 02, 1998.  Tornadic supercells verified with big hail.  I was on a roof and had to take cover.  Those stones were scary big!

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From Mount Holly AFD-

For Thursday...As a robust upper-level trough/closed low arrives from the west, deep surface low pressure is forecast to track well to our northwest and north. Deep southwesterly flow ahead of the cold front will continue to support strong warm air advection, and this will help to propel a surface warm front across and north of our region. Given a chilly and very dry air mass initially in place in advance of this system, any precipitation may slow the northward progression of the warm front at least some. This will be key in how warm the region gets during Thursday before the cold front arrives. It does appear that most if not all of our region gets into the warm sector by later Thursday afternoon. A 120-knot 250 mb jet is forecast to be overhead by later in the day. In addition, 850 mb flow increases to near 50 knots. The GFS BUFKIT forecast soundings show strong and deep unidirectional flow and therefore strong shear in place. These soundings also show a thin instability (CAPE) profile and also have the look for low- topped convective potential. Given the strong forcing arriving from the west with an incoming cold front later in the afternoon, a low- topped squall line may develop and race across much of our area later in the afternoon and evening. Given the wind profiles, locally strong to damaging winds may occur especially with associated line segments that may take on some bowing/surging. The severe weather risk will depend on the timing and also the amount of instability, however as of now plenty of shear is forecast along with strong forcing.

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24 minutes ago, Stormfly said:

When was the last time the area had moderate?

Last time I can recall was June 02, 1998.  Tornadic supercells verified with big hail.  I was on a roof and had to take cover.  Those stones were scary big!

June 13, 2013.

A strong morning MCS stabilized the atmosphere a bit and we were downgraded to a SLGT by the 1630z update. Parts of the region particularly from northern/central Loudoun county eastwards into Montgomery and Howard counties and perhaps beyond got decent storms that afternoon w/ 40-50 kt effective bulk shear and up to 1,000J/kg MLCAPE.

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1 hour ago, George BM said:

June 13, 2013.

A strong morning MCS stabilized the atmosphere a bit and we were downgraded to a SLGT by the 1630z update. Parts of the region particularly from northern/central Loudoun county eastwards into Montgomery and Howard counties and perhaps beyond got decent storms that afternoon w/ 40-50 kt effective bulk shear and up to 1,000J/kg MLCAPE.

2008 and 2012 had moderate risks as well. Definitely not as rare as some people think! Still unusual!

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2 hours ago, Stormfly said:

When was the last time the area had moderate?

Last time I can recall was June 02, 1998.  Tornadic supercells verified with big hail.  I was on a roof and had to take cover.  Those stones were scary big!

A good questions. I had the GIS maps on my phone but then it died so I can't find them anymore. Within the LWX CWA (this applies to only the Day 1 outlook):

1.) 15 - 17 Slight Risks per calendar year

2.) 1 - 3 Enhanced Risks per calendar year

3.) 1 Moderate Risk every 4 years.

4.) 0 High Risks

4.) Derecho climatology is one about every 4 years (we are due for one)

2 hours ago, George BM said:

June 13, 2013.

A strong morning MCS stabilized the atmosphere a bit and we were downgraded to a SLGT by the 1630z update. Parts of the region particularly from northern/central Loudoun county eastwards into Montgomery and Howard counties and perhaps beyond got decent storms that afternoon w/ 40-50 kt effective bulk shear and up to 1,000J/kg MLCAPE.

This event was painful and interesting. As George said, there was a D1 MOD Risk (Hatched 45% for wind!), then a D1 MOD Risk (Hatched 45% for win and a 10% TOR!!) and it looked great, then an early morning MCS came through and blew all the instability. As it passed through however, it deposited a boundary along Loudoun, Fairfax, Montgomery, Howard, and Prince Georges counties that acted as a trigger for a lone cell in the afternoon. That resulted in a tornado warned storm. We actually saw it on a tower cam and relayed the information back to LWX as it was happening. (Link: https://mesonet.agron.iastate.edu/wx/afos/list.phtml?source=LWX&year=2013&month=6&day=13&year2=2022&month2=3&day2=27&view=grid&order=asc) which was later confirmed as a long track (Link to PNS: https://mesonet.agron.iastate.edu/wx/afos/p.php?pil=PNSLWX&e=201306142330). That was the first tornado assessment I ever took part in. 

Link to event: https://www.spc.noaa.gov/exper/archive/event.php?date=20130613

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11 hours ago, southmdwatcher said:

Wasn't April 28. 2002 also a moderate risk for the LaPlata tornado???? Unfortunately SPC is too happy to erase their files now beyond a certain timeframe.

Yea it was an insanely large MOD Risk area. Probably the largest in these parts: https://www.spc.noaa.gov/exper/archive/event.php?date=20020428

IMO, I love SPC but they seems to be a bit wonky east of the Ohio River.

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11 minutes ago, Eskimo Joe said:

Yea it was an insanely large MOD Risk area. Probably the largest in these parts: https://www.spc.noaa.gov/exper/archive/event.php?date=20020428

IMO, I love SPC but they seems to be a bit wonky east of the Ohio River.

Do you think it would be beneficial (doubt the funding exists) - to have center similar to the river forecast centers for severe storm related stuff? In other words, perhaps staffed with mets that are more familiar with the climo and such of smaller areas they forecast for? 

Even something broader like dividing the country into very broad regions. West Coast, Plains/Tor Alley, Southeast and Northeast. 

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56 minutes ago, Kmlwx said:

Do you think it would be beneficial (doubt the funding exists) - to have center similar to the river forecast centers for severe storm related stuff? In other words, perhaps staffed with mets that are more familiar with the climo and such of smaller areas they forecast for? 

Even something broader like dividing the country into very broad regions. West Coast, Plains/Tor Alley, Southeast and Northeast. 

No

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Recent model trends have me liking this setup a lot less.    There is lead wave that arrives midday Thursday - this has the potential to produce showers and clouds that limit afternoon heating.  It also leads to a cold front that has more of a southwest-northeast orientation;  we do better with a more south-north orientation.      There isn't much convergence along the front as currently modeled (especially on the NAM and CMC - it's better on the GFS), and the main upper system lags pretty far behind.     There is still plenty of time to get things much more favorable, but it definitely has limited potential as currently progged.  

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Afternoon LWX AFD seems to like the threat 

LONG TERM /THURSDAY THROUGH SUNDAY/...
A very dynamic system associated with a strong nearly negatively
tilted upper level trough will impact our region on Thursday. A
strong cold front associated with the trough axis is forecast to
pass through our region Thursday afternoon and into the evening
periods. Ahead of the frontal passage, strong warm air advection
will lead to temps in the mid 70s with models forecasting CAPE
values potentially over 800 J/KG. Most model guidance is also
indicating a strong wind field especially with nearly 70s knots
between the 850 and 700 mb layer. Strong speed shear along with CAPE
around 1000 J/Kg will likely lead to an increased risk for strong to
severe storms on Thursday. SPC has been highlighting areas east of
the Blue Ridge Mtns for the past two days with a 15% slight risk in
their day 4/5 outlook which they only reserve for enhanced threats.
Looking at model precipitation, it seems there will be two threats
for storms on Thursday, one associated with the strong low level jet
ahead of the front and then also when the boundary moves through our
region. We will need to monitor model trends to determine timing and
magnitude of the SVR threat for Thursday.
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2 hours ago, high risk said:

Recent model trends have me liking this setup a lot less.    There is lead wave that arrives midday Thursday - this has the potential to produce showers and clouds that limit afternoon heating.  It also leads to a cold front that has more of a southwest-northeast orientation;  we do better with a more south-north orientation.      There isn't much convergence along the front as currently modeled (especially on the NAM and CMC - it's better on the GFS), and the main upper system lags pretty far behind.     There is still plenty of time to get things much more favorable, but it definitely has limited potential as currently progged.  

Think this is probably the first solid SLGT risk regionwide for the year. That should be our benchmark. 

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19 hours ago, high risk said:

Recent model trends have me liking this setup a lot less.    There is lead wave that arrives midday Thursday - this has the potential to produce showers and clouds that limit afternoon heating.  It also leads to a cold front that has more of a southwest-northeast orientation;  we do better with a more south-north orientation.      There isn't much convergence along the front as currently modeled (especially on the NAM and CMC - it's better on the GFS), and the main upper system lags pretty far behind.     There is still plenty of time to get things much more favorable, but it definitely has limited potential as currently progged.  

Yep, it's definitely a mid atl thing especially in the north east md region.  We get dammed in the 50s while DCA and south is near 80F and sees the action.

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14 hours ago, Stormfly said:

Yep, it's definitely a mid atl thing especially in the north east md region.  We get dammed in the 50s while DCA and south is near 80F and sees the action.

        Yes, that happens, but damming isn't a concern for Thursday - strong low-level southerly flow is pretty much a certainty.     I've been less enthused about this event due to potential poor timing, but there is more hope in recent guidance.    The HRRR and some of the HiResWs have convection breaking out during the late afternoon hours.   The wind profiles will be strong, so any storms that try to take advantage of peak heating certainly have a shot to be severe.    And low-level convergence looks better than it did several model cycles ago.

         The potential for  1) widespread showers and storms forming too early and wiping out heating     and/or   2)  the front hanging back and having the main line roll through the DC/Baltimore areas after dark   are still on the table.      We need every bit of heating we can get at this time of year to maximize potential.    Storms rolling through after dark simply won't have the warm sfc temperatures and resulting larger CAPE values to work with.

 

 

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Latest take from Mount Holly-

As the entire upper-level trough gets closer later Thursday afternoon and evening, substantial flow through the atmosphere is expected to be over our area. This flow is nearly unidirectional (south to southwest) and will result in substantial shear. An examination of some model forecast sounding points from around the region shows impressive flow, however the instability profile is thin and short. These profiles tend to represent low-topped convective events. Given the shear that is forecast though, convection embedded within it will have the potential to transport the strong winds from aloft (40-60 knots at 925 mb) down to the surface. This will particularly be the case with line segments that take some some bowing/forward surging. Given the magnitude of the low-level shear (0-1 km) of around 30 knots, there is a non-zero tornado threat. Convection may start as discrete, especially to our west, but should evolve into a line or line segments with an eastward extent. Damaging straight-line wind is the main threat, however a tornado cannot be ruled out especially with any mesovortices that develop within a linear convective line. Some guidance shows that there is some potential for organized convective development near early evening in southern New Jersey to Delmarva, and the Slight Risk area (level 2 out of 5) has been expanded eastward and now covers nearly our entire area.

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1 hour ago, Stormfly said:

Just about the entire state of MD in slight risk, 15% wind.  Pretty impressive for March!

You better hope for prolonged sunshine. Without that this time of the year, your pissing in the wind lol. 

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