Mesoscale Discussion 1477
NWS Storm Prediction Center Norman OK
1241 PM CDT Sat Aug 12 2017
Areas affected...Central PA...Central NY
Concerning...Severe potential...Watch possible
Valid 121741Z - 121945Z
Probability of Watch Issuance...40 percent
SUMMARY...Thunderstorm coverage is expected to continue increasing
over the next few hours. Some hail and damaging wind gusts are
possible with the stronger, more organized cells and trends will be
monitored for possible watch issuance.
DISCUSSION...Thunderstorm activity has increased across central PA
and central NY over the past hour or so within a broad region of
surface confluence ahead of an approaching cold front. Low-level
airmass ahead of the cold front is characterized by dewpoints in the
upper 60s/low 70s, which is supporting modest instability (i.e.
MLCAPE around 1000 J/kg per the latest mesoanalysis), despite
filtered sunshine and warm mid-level temperatures. General
expectation is for MLCAPE to remain around 1000 J/kg with increasing
storm coverage as both the cold front and its parent shortwave
trough continue eastward into the region.
Despite modest the instability, occasionally strong/organized
updrafts are possible given the strengthening mid-level flow and
related moderate shear. Recent CCX VAD sampled 0-6 km bulk shear
over 45 kt and a long hodograph, favorable for storm splits. Some
hail will be possible with the any stronger/discrete cells with
gusty winds also possible as multicell storms organize in small
bowing structures. Convective trends will be monitored for possible
watch issuance.
..Mosier/Guyer.. 08/12/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ALY...PHI...BGM...BUF...CTP...LWX...PBZ...
LAT...LON 42747788 43427626 43067457 41027579 39767695 39687939
42747788
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