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SPC MD 1956


MD 1956 Image

Mesoscale Discussion 1956
NWS Storm Prediction Center Norman OK
0657 PM CST Thu Nov 17 2022

Areas affected...portions of extreme western New York

Concerning...Heavy snow 

Valid 180057Z - 180700Z

SUMMARY...2+ inch snowfall rates are expected to accompany a primary
snowband near or just south of the Buffalo, NY area this evening
into early tomorrow morning. Reduced visibility and crippling travel
conditions are possible through the night.

DISCUSSION...A mid-level impulse embedded within the broader
cyclonic upper flow is traversing the Lower MI peninsula and is
approaching Lakes Erie/Ontario and far western NY, with broader
deep-layer ascent gradually increasing over the Upper Hudson Valley.
The approach of this impulse is causing surface-700 mb winds to veer
more southwesterly, paralleling the long axis of Lake Erie. As such,
a primary snowband (also paralleling Lake Erie) is beginning to
mature and align in a manner that is favorable for a long-duration
heavy lake-effect snow event for or immediately south of the
Buffalo, NY area. Mesoanalysis trends also show surface-700 mb
cold-air advection over Lake Erie, with the -12C to -17C dendritic
growth zone deepening and saturating. The cold-air advection atop a
warmer water surface is also contributing to 7.5 C/km low-level
lapse rates near the Lake Erie shoreline (per the 00Z BUF observed
sounding), which may possibly steepen further to near 8.5 C/km
tonight, increasing SBCAPE over water to near 250 J/kg. 

The increase in CAPE and deepening/saturating of the dendritic
growth zone may support convective snow development within the
primary snow band, with 2+ inch/hr snowfall rates and near-zero
visibility possible. The heaviest snowfall is most likely after 03Z
and may continuing to 12Z Friday morning (based on the latest runs
of the HRRR and the 12Z HREF ensemble consensus). Should a prolonged
period of 1-2 inch/hr snowfall rates occur, potentially crippling
travel conditions may develop.

..Squitieri.. 11/18/2022

...Please see for graphic product...


LAT...LON   42617916 42697906 42757894 42817889 42907892 42937895
            43037898 43087892 43097878 42977862 42747851 42577868
            42527886 42517910 42617916 

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