|Mesoscale Discussion 668|
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Mesoscale Discussion 0668
NWS Storm Prediction Center Norman OK
1255 PM CDT Fri May 22 2020
Areas affected...Portions of North-Central Texs
Concerning...Severe potential...Watch likely
Valid 221755Z - 221930Z
Probability of Watch Issuance...80 percent
SUMMARY...Thunderstorm initiation is expected within the hour
somewhere near Young County, TX.
DISCUSSION...Towering cumulus have persisted along the western
portion of an outflow boundary from the morning MCS. This boundary
currently extends from near Childress to the northern suburbs of
Dallas/Fort Worth. Temperatures south of this boundary have warmed
into the mid to upper 80s with dewpoints in the upper 60s to low 70s
yielding MLCAPE around 3000 J/kg per SPC mesoanalysis. This boundary
has slowed its southern motion recently and may start to lift back
north slightly within the next hour or two as it encounters stronger
southerly flow ahead of the boundary.
The combination of short residence time along the boundary and dry
air entrainment have stunted storm development along the boundary
thus far with evidence of a few orphaned anvils. However, SPC
mesoanalysis indicates MLCIN has eroded near the boundary.
Therefore, it shouldn't be long before storms start to develop. The
most likely area for initial storm formation is in Young County, TX
where convergence is maximized along the outflow boundary. This is
further supported by the 17Z WoFS which shows a maturing storm in
this area between 18Z and 19Z. The strong instability, combined with
effective shear around 35-40 knots per SPC mesoanalysis supports
some supercellular structures. Mid-level lapse rates around 8-9 C/km
per 12Z FWD sounding will support the threat for very large hail
with these storms, especially initially.
Stretching of low-level vorticity in the region of the outflow
boundary may provide a brief tornado threat this afternoon, but
weakening low-level flow (per FWS and FDR VWP) will be a limiting
factor to the overall tornado threat this afternoon. However, later
this evening, the low-level jet is expected to strengthen
substantially which will enlarge hodographs and lead to an
increasing tornado threat.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 33570019 33949994 34139947 33759830 33319763 32659758
32539908 32619996 33090048 33090048 33570019
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