Alert archive / Pennsylvania / Mesoscale Discussions in 2016

Mesoscale Discussion 1541

August 16, 20164 states

The Storm Prediction Center issued this mesoscale discussion at Aug 16, 2016, 1:40 PM EDT for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 16, 2016, 1:40 PM EDT (17:40 UTC)
Expired: Aug 16, 2016, 3:45 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 47 counties

Baltimore County, MD, Carroll County, MD, City of Baltimore, MD, Frederick County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Washington County, MD, Adams County, PA, Blair County, PA, Centre County, PA, Clinton County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Lancaster County, PA, Lebanon County, PA, Lycoming County, PA, Mifflin County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Snyder County, PA, Union County, PA, York County, PA, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Manassas, VA, City of Manassas Park, VA, City of Winchester, VA, Clarke County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Loudoun County, VA, Prince William County, VA, Shenandoah County, VA, Warren County, VA, Berkeley County, WV, Jefferson County, WV, Morgan County, WV

The radar

The Sterling radar (KLWX), 66 km from the middle of the area, began a volume at 17:43 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Severe Thunderstorm Watch 447Aug 16, 3:20 PM EDT

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 5.7 hours before the alert went out and 70 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: 364 J/kg
Mixed-layer CIN: -175 J/kg
Mixed-layer LCL: 773 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 117 m²/s²
0-3 km storm-relative helicity: 98 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 16, 3:20 PM EDT	Severe Thunderstorm Watch	SPC	Anne Arundel, Baltimore, Carroll, Cecil, Frederick, Harford and 6 more	4 hr
Aug 16, 4:55 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Cecil, Harford, Howard, Kent and 3 more	95 min
Aug 16, 6:40 PM EDT	Mesoscale Discussion	SPC	Allegany, Garrett	2 hr
Aug 16, 2:57 PM EDT	Mesoscale Discussion	SPC	Beaver, Butler, Crawford, Erie, Lawrence, Mercer and 2 more	2 hr

Nearby

Mesoscale Discussions in Pennsylvania, 2016 Mesoscale Discussions in Virginia, 2016 Mesoscale Discussions in Maryland, 2016 Every mesoscale discussion in 2016

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.