ZCZC SPCSWOMCD ALL
ACUS11 KWNS 161506 
SPC MCD 161506 
NYZ000-PAZ000-161700-

Mesoscale Discussion 1870
NWS Storm Prediction Center Norman OK
1006 AM CDT Sat Oct 16 2021

Areas affected...Central/Eastern PA...South-Central NY

Concerning...Severe potential...Watch possible 

Valid 161506Z - 161700Z

Probability of Watch Issuance...60 percent

SUMMARY...A narrow line of stronger storms is expected to move
northeastward into more of eastern PA and south-central NY over the
next few hours. Convective trends will be monitored for possible
watch issuance.

DISCUSSION...Recent radar trends show increasing reflectivity within
the line of showers and thunderstorms just ahead of the front in
central PA. Recent lightning data shows an increasing trend in
flashes within this line as well. This matches forecast expectations
with storms expected to gradual strengthen amid continued lift along
the front, increasing large-scale forcing for ascent, and modest
diurnal destabilization. 

Low to mid-level flow is also strengthening across the region, shown
well by the BGM VAD, which recently sampled 45-50 kt at 1 km AGL
increasing to 60 kt between 2-3 km AGL. The resulting vertical
profile had 0-1 km bulk shear around 35 kt and 0-1 km storm-relative
helicity near 250 m2/s2. 

The resulting combination of ascent, modest buoyancy, and strong
vertical shear is forecast to result in a narrow line of deeper
convection capable of producing damaging wind gusts and maybe even a
brief embedded tornado or two as it moves northeastward.

..Mosier/Grams.. 10/16/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...ALY...PHI...BGM...CTP...

LAT...LON   41547731 42467639 43167557 42797445 41897459 39917606
            40107789 41547731 

NNNN