Mesoscale Discussion 503

Issued

Apr 16, 2017, 2:15 PM EDT (18:15 UTC)

Expired

Apr 16, 2017, 4:45 PM EDT

In force

3 hr

Issued by

the Storm Prediction Center

Chance of a watch

20%

The State College radar (KCCX), 72 km from the middle of the area, began a volume at 18:16 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

620 
ACUS11 KWNS 161816
SWOMCD
SPC MCD 161815 
VTZ000-NYZ000-PAZ000-WVZ000-OHZ000-162045-

Mesoscale Discussion 0503
NWS Storm Prediction Center Norman OK
0115 PM CDT Sun Apr 16 2017

Areas affected...Portions of eastern OH...northern
WV...western/central PA...much of upstate NY...and far southwestern
VT

Concerning...Severe potential...Watch unlikely 

Valid 161815Z - 162045Z

Probability of Watch Issuance...20 percent

SUMMARY...An isolated threat for strong to locally damaging winds
should develop this afternoon. Watch issuance is unlikely owing
mainly to weak instability and an overall marginal severe weather
threat.

DISCUSSION...A line of convection has developed within the past hour
across western NY, far northwestern PA, and into far northeastern OH
along a surface trough and downwind of Lake Erie. Visible satellite
imagery shows building cumulus along the length of the pre-frontal
trough as a low-amplitude shortwave trough moves over the Northeast,
and thunderstorms are forecast to develop along the length of the
trough this afternoon from eastern OH to northern NY. Breaks in the
clouds have allowed temperatures to warm into the mid 70s to low 80s
as of 18Z ahead of the developing line of storms, and continued
diurnal heating through the remainder of the afternoon will support
weak instability from eastern OH to upstate NY. Low-level moisture
remains limited across this region as surface dewpoints are in the
upper 40s to mid 50s, and precipitable water values generally range
from 0.75-1.00 inch. Mid-level lapse rates are also poor from area
12Z soundings, which will act in concert with the limited low-level
moisture to support only weak instability (MLCAPE generally 250-500
J/kg) across this region. Steepening low-level lapse rates and
strong mid-level flow may encourage some enhancement to convective
downdraft winds with the line of storms, and isolated instances of
strong to locally damaging surface winds will be possible. Watch
issuance remains unlikely mainly due to instability forecast to
remain weak.

..Gleason/Thompson.. 04/16/2017

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

ATTN...WFO...BTV...ALY...BGM...BUF...CTP...PBZ...RLX...CLE...
ILN...

LAT...LON   39468226 39818259 40378265 40618230 41138136 42457892
            44067473 43997365 43717290 42907323 41827498 40267808
            39378052 39468226

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The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.