Severe Storm Outlook Narrative (AC)
Issued by NWS
ACUS11 KWNS 121537
SPC MCD 121536
Mesoscale Discussion 0170
NWS Storm Prediction Center Norman OK
0936 AM CST Sun Feb 12 2017
Areas affected...Portions of central/southern NY...southwest
CT...northern NJ...northeast PA
Concerning...Winter mixed precipitation
Valid 121536Z - 121600Z
SUMMARY...Winter mixed precipitation will continue to spread
east-northeastward across the region through the day.
DISCUSSION...Ascent preceding a midlevel shortwave impulse crossing
the southern Great Lakes region will continue to foster the
east-northeastward spread of precipitation through the day. The 12Z
soundings at Buffalo and Brookhaven NY indicate sufficiently warm
conditions aloft to result in at least partial melting of descending
hydrometeors. Observations indicate that sub-freezing temperatures
within the surface layer are facilitating re-freezing, resulting in
freezing rain across parts of the area -- especially from parts of
eastern PA through southeast NY.
Areas of sleet and snow may also occur -- particularly with westward
extent across the region into central NY, where colder midlevel
profiles exist in proximity to the wave. Marginally sub-freezing
isothermal profiles could support efficient snow aggregation in
these areas, and weak convective instability could yield locally
enhanced precipitation rates. In general across the region,
freezing-rain rates around 0.02-0.04 inch per hour,
sleet-accumulation rates around 0.05-0.10 inch per hour, and
snowfall rates around 0.5 inch per hour (perhaps locally to 1 inch
per hour associated with spotty convective elements) may occur.
After the 20Z-22Z time frame, an influx of drier air aloft should
tend to result in diminishing precipitation coverage/intensity.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 40777296 40667414 40957458 42077542 42527615 42747684
42957724 43277733 43337706 43467630 43447599 43217543
42547457 41617310 40777296