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

[yoda]

00z HRRR seems a bit more ominous IMO, though it has numerous rounds of storms... one around 17z, another at 23z, then finally one flnal sweep at 01z/02z.  The 23z ones look supercells that come up from the south

00z NAM NEST leans in the direction of the HRRR IMO

[yoda]

From the 00z NAM NEST at 19z just SW of DCA

[yoda]

5/5/15 on new Day 1

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1256 AM CDT Fri May 27 2022

   Valid 271200Z - 281200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE CAROLINAS AND MID-ATLANTIC...AND IN PARTS OF THE NORTHERN HIGH
   PLAINS...

   ...SUMMARY...
   Scattered severe thunderstorms with a threat for wind damage and
   possibly a couple tornadoes are expected to develop today from the
   Carolinas northward into the Mid-Atlantic. Severe wind gusts will
   also be possible in parts of the northern High Plains.

   ...Carolinas/Mid-Atlantic/New York/New England...
   An upper-level low will move east-northeastward across the Ohio
   Valley today. Ahead of the system, flow will be southwesterly at
   mid-levels across much to the Eastern U.S. At the surface, a
   pre-frontal trough will develop to the east of the Appalachian crest
   today, as moisture advection takes place to the east of the trough.
   Surface dewpoints should be mostly in the mid to upper 60s F from
   the eastern Carolinas northward into the Mid-Atlantic. Elevated
   storms or bands of rain may be ongoing at the start of the period
   along some sections of the Eastern Seaboard. Areas that remain
   somewhat clear of morning convection, should be able to heat up
   sufficiently for moderate destabilization.

   The latest model forecasts develop two corridors of moderate
   instability by midday. The first is forecast in eastern Virginia and
   Maryland, with the second located from southeast Georgia to central
   North Carolina. These two corridors will likely be favorable for
   isolated damaging wind gusts associated with multicell line
   segments. Supercells will also be possible, mainly from
   north-central North Carolina northward into southeastern
   Pennsylvania, where strong deep-layer shear will be present. A
   low-level jet of approximately 35 to 45 knots is forecast to move
   across Virginia during the day. This should increase low-level shear
   enough for a tornado threat with any supercells that can develop. 
   The tornado threat could extend north-northeastward across the
   Mid-Atlantic near the axis of the stronger low-level flow.

[Kmlwx]

The hires FV3 runs a line through around 15z and then another more spotty one around 01z. I guess we could recover a bit between those two time periods...but 15z is prime time to ruin our instability IMO. Messy evolution. I'm about to meh.

[yoda]

Making itself known... LWX describing the QLCS lol in their morning disco re threats today

 

.NEAR TERM /TODAY AND TONIGHT/... 
Surface low pressure is churning just west of the Ohio Valley 
early this morning, showing up nicely on IR/WV satellite 
imagery. Extending eastward from the low is a cold front sliding
south southwest into the lower Mississippi Valley with a warm 
front bisecting West Virginia and Virginia from west to east. 
This synoptic setup allows for the Gulf to be open for business 
in terms of moisture transport northward across the Southeast 
and the Mid- Atlantic. Surface dewpoints locally are in the low 
to middle 60s this morning, right on pace with temperatures in 
the mid to upper 60s. Skies are cloudy with a light southeast 
wind across much of the CWA. Precipitation so far this morning 
has been relegated west of the spine of the Blue Ridge 
Mountains, with scattered showers tracking northward. 

The remainder of the morning will feature increasing rain 
chances from west to east as the aforementioned warm front lifts
northward and the surface low/front pushes eastward from the 
Ohio Valley. With the plentiful moisture in place thanks to the 
increasing southerly flow and low level jet, allowing 
precipitation to overspread the area. With the ample cloud cover
in place and limited instability this morning, heavy rainfall 
appears to the primary concern the first half of the day as this
activity pushes across the area. PWATs will range in the 
1.5-1.75 range per latest model guidance this morning and early 
afternoon, pooling along and east of the Blue Ridge Mountains. 

Given the anomalously moist airmass in place, the approaching 
cutoff upper low and PVA, as well as favorable MBE velocities, 
do see the potential for flash flooding this morning and early 
afternoon with the first round of convective 
showers/thunderstorms. Rainfall rates of 1-2 inches, locally 
higher, will be possible in a short amount of time within the 
strongest activity, yielding flooding concerns. As such, we have
issued a Flash Flood Watch for a good portion of our CWA, 
starting this morning across our southwestern zones, extending 
north and eastward including the metro areas closer to midday 
and lingering into this evening. 

With the increasing low level jet this morning, strong to 
severe storms will be possible, even if instability is a bit 
limited with cloud cover and prior shower activity. Increasing 
wind shear and low LCL's also provide a favorable environment to
produce a tornado threat as well, particularly in any discrete 
cell structures that are able to form. Damaging wind gust do 
appear to be the primary threat given the wind field aloft, with
the potential for isolated large hail as well. 

In the wake of this first round of showers/storms through mid 
afternoon, a secondary line of activity is expected to be 
focused along the front, making itself known during the late 
afternoon and evening hours as it crosses the region. A more 
organized QLCS structure is favored along the front, and is 
highlighted by the most recent hi-res guidance filtering in this
morning. Damaging wind gusts again will be the primary threat 
with this feature, but an embedded spin-up cannot be ruled out. 
With the multi-threats on the table today, be sure to closely 
monitor the latest trends in the forecast, as well as having a 
way to receive warnings throughout the day and evening hours as 
the Memorial Day weekend travel kicks off.

[mappy]

its muggy, but cloudy and damp. that's always a good sign on a severe day, right?

[mappy]

 

[H2O]

MDs at 6am is not normal for this area

[yoda]

3 minutes ago, mappy said:

 

@Eskimo Joe discussed this last night briefly

@Kmlwx are you mehing now?

[yoda]

Tornado Watch issued till 2pm

[H2O]

Red box at 6:30 is rare as well

[mappy]

6 minutes ago, yoda said:

Tornado Watch issued till 2pm

 

[mappy]

1 minute ago, H2O said:

Red box at 6:30 is rare as well

 I get a 630am watch too! 

[yoda]

Already TW up down by Martinsville, storm moving NE... should be entering LWX CWA in about an hour

[yoda]

50/20 tor probs are pretty beefy for a early morning tornado watch...

[yoda]

9 hours ago, Eskimo Joe said:

Keep an eye on those cells in western NC. They've been having some tendency to spin. We might get a few early AM tors.

Nice call

[kgottwald]

So much for tonight's Nats game.

[Kmlwx]

Honestly this is how we *could* get a full day under a tornado watch. Send this activity through by 16-18z and then we may be able to recover a bit of instability for a line around 0z. 

[SnowenOutThere]

Imagine if the line came through around 3/4 hours later. Either way looks like it might be an interesting day out. 

[yoda]

I know this is nothing like April 27 2011 at all.... but I was intrigued in seeing what the tor probs were on our tornado watches that day... the first was 40/20, second was 40/20... the third one was 40/20... and the final one was also 40/20.

So... i don't think we have seen a 50 prob for 2 or more tornadoes in our region... unless someone says otherwise?

[mappy]

5 minutes ago, yoda said:

I know this is nothing like April 27 2011 at all.... but I was intrigued in seeing what the tor probs were on our tornado watches that day... the first was 40/20, second was 40/20... the third one was 40/20... and the final one was also 40/20.

So... i don't think we have seen a 50 prob for 2 or more tornadoes in our region... unless someone says otherwise?

I wouldn't even know how to look to check 

[Eskimo Joe]

27 minutes ago, yoda said:

Nice call

Yup. Today is going to be a weird day. That TOR cell SW of Lynchburg has the Frederick Tornado Zone™ written all over it.

10 minutes ago, yoda said:

I know this is nothing like April 27 2011 at all.... but I was intrigued in seeing what the tor probs were on our tornado watches that day... the first was 40/20, second was 40/20... the third one was 40/20... and the final one was also 40/20.

So... i don't think we have seen a 50 prob for 2 or more tornadoes in our region... unless someone says otherwise?

Took a quick look at the SPOC archives and I agree.

[Eskimo Joe]

Secondary action appears to be over central Kentucky. If we get clearing it's behind this lead stuff then we get the next line with the cold front.

[yoda]

Rare 10% tor probs on 13z SPC OTLK?

[Eskimo Joe]

2 minutes ago, yoda said:

Rare 10% tor probs on 13z SPC OTLK?

I'd be surprised if we get that. We'd need more sun to get the updrafts rooted to the surface. 10% TOR on SWODY1 = ENH.

[Mrs.J]

11 minutes ago, Eskimo Joe said:

Yup. Today is going to be a weird day. That TOR cell SW of Lynchburg has the Frederick Tornado Zone™ written all over it.

Took a quick look at the SPOC archives and I agree.

Ugh. Just dropped the youngest off at school. Have informed her about the watch. 

[yoda]

Just now, Eskimo Joe said:

I'd be surprised if we get that. We'd need more sun to get the updrafts rooted to the surface. 10% TOR on SWODY1 = ENH.

True... just with the 50% of 2 or more tor probs on the watch I was thinking maybe.  Granted watch probs don't translate to SPC OTLK probs, but would be interesting to see

[NorthArlington101]

True... just with the 50% of 2 or more tor probs on the watch I was thinking maybe.  Granted watch probs don't translate to SPC OTLK probs, but would be interesting to see

Could be wrong but I almost think that might just because that watch is pretty darn big, lol.

[yoda]

1 minute ago, NorthArlington101 said:

Could be wrong but I almost think that might just because that watch is pretty darn big, lol.

I dunno... the watches on 4/27 were big as well for our area and the 4 were all 40/20 probs.  Probably overthinking it lol

[mappy]

3 minutes ago, yoda said:

I dunno... the watches on 4/27 were big as well for our area and the 4 were all 40/20 probs.  Probably overthinking it lol

its too early to be overthinking lol