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Severe weather threat April 25th


Jessy89
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.NEAR TERM /THROUGH SUNDAY/...
 As of 145 PM EDT Saturday: Forecast for the near term still
extremely complicated. The first factor of concern is the slight
risk encompassing most of the NC mountains, Upstate SC, and the NC
Piedmont. This still appears to fit well with the area of greatest
severe risk, focusing mainly on the evening hours. With many factors
in play, however, there exists some uncertainty in the most likely
severe threat and exactly where each type of threat will evolve.

A robust upper wave and surface low are in the process of
propagating towards the area this afternoon, with a warm frontal
boundary draped over the Midlands lifting slowly northward towards
the Upstate. We`ve intermittently broken out of cloud cover ahead of
the approaching low today, and with high pressure to our northeast
shifting off the NE coast, the wedge-like pattern that has been in
place for much of today is beginning to erode across the area.
Surface flow has been generally NErly for much of the day, though,
which has limited low-level moistening, and dew points will likely
only be able to peak in the mid 50s later this evening with the
anticipated shift to Srly/SWrly flow over the next hour or so. The
lack of robust surface moisture will likely be a large factor in
limiting surface destabilization, as will the persistent cloud cover
for much of the day. 

Despite this, there is no shortage of favorable factors for severe
weather. Deep-layer shear across the area is already on the order of
approx 50kt, and both directional and speed shear (especially in low
levels) will increase through the afternoon as surface flow veers to
S-SWrly. Additionally, a 500mb speed max is on approach towards the
southern Appalachians, and the arrival of an upper jet exit region
will encourage plentiful upper forcing later this evening, close to
00Z. The sharpening upper trough aloft over the southeast will also
decrease temperatures aloft, manifesting in steep mid-level lapse
rates this evening. Despite SBCAPE likely limited to 500-1000 J/kg,
MLCAPE could exceed 1000 J/kg. With the excellent shear and
sufficient CAPE, the mode of convection will likely end up
supercellular, with supercells embedded in a squall line crossing
the northern 2/3 of the forecast area from 23Z-04Z this evening
looking like the most likely final outcome. All severe threats are
in play, though hail rises to the top as the most likely threat with
cool, dry air entering aloft and excellent lapse rates expected. The
potential for wind damage (especially if convection can become at
all linear) and for an isolated tornado (despite the lack of
boundary layer moisture, which keeps LCL heights questionable) is
still in play. It should also be noted that while the best forcing
will be in place across the northern 2/3 of the forecast area and
the greatest severe threat overall is there, the warm front lifting
northward from the Midlands should be watched, especially for
tornado potential as it locally enhances low-level SRH and boundary
layer moisture.

If you`ve made it this far, the good news is that the convection
should clear our area by 05-06Z overnight, though some NW flow and
wrap-around moisture will enhance shower activity in the mountains
near daybreak tomorrow. Some moisture may even break containment,
with showers possible across the majority of the NC mountains
tomorrow, not just the TN/NC border. Though no accums are forecast
at the current time, temperatures will drop enough tomorrow as upper
heights drop that some light snow may be possible at elevations
above 5000ft. the other story across the area will be wind - stout
NW flow will encourage gusts up to 25+ mph outside the mountains,
and up to 35+ mph in the mountains. Temperatures will be below
average.

GSP area forecast discussion is above!

Yes, it is becoming much less vague that there are chances for severe here today.  I think that once the beginnings of storms appear on radar there will be discussion happening! 

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BULLETIN - EAS ACTIVATION REQUESTED  
TORNADO WARNING  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
644 PM EDT SAT APR 25 2020  
  
THE NATIONAL WEATHER SERVICE IN GREENVILLE-SPARTANBURG HAS ISSUED A  
  
* TORNADO WARNING FOR...  
  NORTHWESTERN PICKENS COUNTY IN UPSTATE SOUTH CAROLINA...  
  NORTHEASTERN OCONEE COUNTY IN UPSTATE SOUTH CAROLINA...  
  
* UNTIL 715 PM EDT.  
      
* AT 644 PM EDT, A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO  
  WAS LOCATED 7 MILES NORTHEAST OF WALHALLA, OR NEAR SALEM, MOVING  
  EAST AT 35 MPH.  
  
  HAZARD...TORNADO AND QUARTER SIZE HAIL.  
  
  SOURCE...RADAR INDICATED ROTATION.  
  
  IMPACT...FLYING DEBRIS WILL BE DANGEROUS TO THOSE CAUGHT WITHOUT   
           SHELTER. MOBILE HOMES WILL BE DAMAGED OR DESTROYED.   
           DAMAGE TO ROOFS, WINDOWS, AND VEHICLES WILL OCCUR.  TREE   
           DAMAGE IS LIKELY.  

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