Alert archive / Pennsylvania / Mesoscale Discussions in 2018

Mesoscale Discussion 340

May 3, 201812 counties in New Jersey; 4 counties in New York; 14 counties in Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at May 3, 2018, 6:03 PM EDT for 12 counties in New Jersey; 4 counties in New York; 14 counties in Pennsylvania. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: May 3, 2018, 6:03 PM EDT (22:03 UTC)
Expired: May 3, 2018, 8:30 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 5%

All 30 counties

Bergen County, NJ, Essex County, NJ, Hudson County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Morris County, NJ, Passaic County, NJ, Somerset County, NJ, Sussex County, NJ, Union County, NJ, Warren County, NJ, Bronx County, NY, New York County, NY, Rockland County, NY, Westchester County, NY, Berks County, PA, Bucks County, PA, Chester County, PA, Dauphin County, PA, Delaware County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Perry County, PA, Philadelphia County, PA, Schuylkill County, PA

The radar

The Philadelphia radar (KDIX), 110 km from the middle of the area, began a volume at 22:04 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.

The nearest sounding before it

Brookhaven, NY (KOKX), launched 12:00Z, 10.1 hours before the alert went out and 205 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2245 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 79 m²/s²
0-3 km storm-relative helicity: 133 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

423 
ACUS11 KWNS 032203
SWOMCD
SPC MCD 032203 
CTZ000-NYZ000-NJZ000-PAZ000-040030-

Mesoscale Discussion 0340
NWS Storm Prediction Center Norman OK
0503 PM CDT Thu May 03 2018

Areas affected...Parts of southern and eastern PA/central and
southern NJ/southeast NY

Concerning...Severe potential...Watch unlikely 

Valid 032203Z - 040030Z

Probability of Watch Issuance...5 percent

SUMMARY...Locally strong wind gusts should be generally sub-severe,
though one or two gusts could approach 50 kt, across parts of
southern and eastern Pennsylvania into western New Jersey to
southeast New York.  Coverage of stronger storms is expected to
remain quite low, precluding the need for a watch.

DISCUSSION...A couple clusters of convection with embedded
thunderstorms have been observed across east-central PA and a second
area approaching central PA.  Thus far, the strongest gust of 47 kt
occurred at KIPT at 1950Z.  Forcing for ascent attendant to a
midlevel impulse tracking east across PA at this time and within the
entrance region of a 50-60-kt westerly 500-mb jet over northern New
England is likely aiding in the ongoing convective development that
has spread across the higher terrain in PA.  Weak instability
especially with eastward extent toward the Atlantic coast should
continue to limit the coverage of thunderstorms.  Strong surface
heating (temperatures up to 90 F) in the lower elevations from
southeast PA into NJ and southeast NY are resulting in steep 0-3 km
lapse rates up to 8.5 C/km and DCAPE exceeding 1000 J/kg.  Although
weaker instability will limit storm coverage, the aforementioned
favorable low-level thermodynamics suggest a stronger wind gust or
two could occur from southeast PA into western NJ to southeast NY
until the storms weaken this evening or move offshore.

..Peters/Edwards.. 05/03/2018

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

ATTN...WFO...OKX...PHI...BGM...CTP...

LAT...LON   41247532 41327429 41287377 41167334 40767372 40547426
            39997442 39847497 39907614 40167707 40487735 40707703
            40737641 40797579 41247532

Nearby

Mesoscale Discussions in Pennsylvania, 2018 Mesoscale Discussions in New Jersey, 2018 Mesoscale Discussions in New York, 2018 Every mesoscale discussion in 2018

Sources

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.