Severe today (May 5): Slight risk / Possible MCS

[calm_days]

 

RAH forecast discussion

.NEAR TERM /TODAY THROUGH TONIGHT/...
As of 1130 AM Tuesday...

...The risk for severe storms across central and southern NC later
this afternoon and evening has increased...

There are lots of mesoscale features to note that will all play a
role in today`s convective evolution and thus makes it a complicated
and difficult forecast.

Lead MCV and round 1 of elevated convection has moved off the
southern NC coast with satellite imagery showing an impressive
dry slot immediately behind this feature. Meanwhile, across the
SW Va and NC, a separate upper disturbance interacting with a plume
of deeper moisture is producing an area of showers that will move
east across along the NC-VA border over the next several hours.
This rain will help to lock in a wedge of weak, but cool
high pressure(in-situ CAD) across northern sections of the NC
Piedmont and coastal plain zones. Trailing all these is yet another
MCV approaching the southern NC mtns. While there is very little
wx/rain currently accompanying this feature at the moment, it could
help to spark additional convection across southern portions of the
area later this afternoon, with associated rain-cooled air
potentially helping to stabilize things ahead of the late
afternoon/early evening convection that is expected to develop in
response to the upper trough and associated cold front moving into
the region. Finally, the quasi-stationary front across upstate SC
will be especially important, returning as a warm front into
southern NC, in advance of the trailing cold front that
move east through the area tonight/early Wednesday.

Aside from the batch of showers skirting the far northern counties,
should see a mid day lull in rain/showers, though mostly cloudy skies
will prevail. Will still have to see what becomes of the trailing
MCV coming into the NC mtns, but still expect the emergence of
a new/triple low to develop and ride east along the northward
lifting warm front. Scattered thunderstorms are expected to develop
ahead of the upper trough and cold front and will move west to east
through the area between 21 to 04z. Amidst steep mid-level lapse
rates spreading east into the area, warm moist air advection will
result in 1000 to 1500 J/Kg of elevated instability across southern
and central portions of central NC with the potential to realize
sfc-base instability of 500 to 1000 J/kg across the far southern
zones as the warm front lifts into the area. Given strongly curved
hodographs across the area, this will set the stage for some
embedded supercells to move through the area. If the warm sector
does indeed become established across the far southern zones(this
includes the areas from Wadesboro to Fayetteville to Clinton),
damaging winds, large hail and an isolated tornado will be possible.
Just north of this area, though the storms will likely be elevated,
we could see some large hail, up to baseball size possible. The
greatest threat is between 7 to 11 pm, approximately along and south
of I-40. Convection chances will decrease west to east overnight
with the passage of the cold front. QPF generally 0.25 to 0.50,
locally 1 inch possible.

~~~

GSP discussion

.NEAR TERM /THROUGH TONIGHT/...
As of 1210 PM Tuesday: The latest satellite showed low to mid clouds
gradually filling in from the west with showers and embedded
convection straddling the northern mountains. Trends towards
increased instability and updraft strength and continued likelihood
of an organized squall line this evening supports SPCs extension of
the slight risk of severe thunderstorms to more of the forecast
area. The preferred mode of severe weather may begin with damaging
hail with a few isolated tornadoes as the main threats due to the
more discrete/isolated nature of convection early on and trend
towards more of a wind threat later this evening. This is especially
true along and east of I-77 as most guidance supports upscale growth
of a broken squall line into a full blown mesoscale convective
system. HREF continues to show rotating updrafts which could support
a few tornadoes east of the mountains, however relatively high cloud
bases may limit this potential. Deep moist convection also supports
localized should training of cells occur.

[janetjanet998]

  
URGENT - IMMEDIATE BROADCAST REQUESTED  
SEVERE THUNDERSTORM WATCH NUMBER 168  
NWS STORM PREDICTION CENTER NORMAN OK  
355 PM EDT TUE MAY 5 2020  
  
THE NWS STORM PREDICTION CENTER HAS ISSUED A  
  
* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF   
  SOUTHERN NORTH CAROLINA  
  NORTHERN SOUTH CAROLINA  
  
* EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 355 PM UNTIL  
  1100 PM EDT.  
  
* PRIMARY THREATS INCLUDE...  
  SCATTERED DAMAGING WIND GUSTS TO 70 MPH LIKELY  
  SCATTERED LARGE HAIL AND ISOLATED VERY LARGE HAIL EVENTS TO 2  
    INCHES IN DIAMETER POSSIBLE  
  A TORNADO OR TWO POSSIBLE  
  
SUMMARY...A CLUSTER OF THUNDERSTORMS OVER WESTERN NORTH CAROLINA  
WILL TRACK EASTWARD ALONG A WARM FRONT, AFFECTING THE WATCH AREA  
THIS AFTERNOON AND EVENING.  LOCALLY DAMAGING WIND GUSTS AND HAIL  
ARE POSSIBLE IN THE STRONGEST CELLS.  AN ISOLATED TORNADO IS ALSO  
POSSIBLE.  

[ICEHOCEY77]

Cell near Chester, SC is starting to look better. Riding a boundary and getting the evening LLJ increase, wouldn't be surprised if it's tornado warned in a bit.  

[janetjanet998]

Quote

 

  
BULLETIN - EAS ACTIVATION REQUESTED  
TORNADO WARNING  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
638 PM EDT TUE MAY 5 2020  
  
THE NATIONAL WEATHER SERVICE IN GREENVILLE-SPARTANBURG HAS ISSUED A  
  
* TORNADO WARNING FOR...  
  SOUTHEASTERN CHESTER COUNTY IN UPSTATE SOUTH CAROLINA...  
  
* UNTIL 715 PM EDT.  
      
* AT 638 PM EDT, A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO  
  WAS LOCATED 9 MILES SOUTHEAST OF CHESTER, OR 5 MILES SOUTHWEST OF  
  RICHBURG, MOVING EAST AT 55 MPH.  
  
  HAZARD...TORNADO AND QUARTER SIZE HAIL.  

[GoAPPS]

 

[ICEHOCEY77]

I've chased in this area before, you are limited with bridges to get across the catawba river. Once you get on the other side the road network isn't great and there are a ton of trees everywhere. 

[GoAPPS]

Don't see that kind of storm around here very often.

[nwohweather]

That is an extremely impressive hail core heading towards Florence.