Alert archive / Virginia / Mesoscale Discussions in 2026

Mesoscale Discussion 2147

August 27, 20264 states

The Storm Prediction Center issued this mesoscale discussion at Aug 27, 2026, 1:52 PM EDT for 4 states. It was in force for 113 min.

The area

The outline as issued.

The facts

Issued: Aug 27, 2026, 1:52 PM EDT (17:52 UTC)
Expired: Aug 27, 2026, 3:45 PM EDT
In force: 113 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch likely
Chance of a watch: 80%

All 46 counties

Anne Arundel County, MD, Baltimore County, MD, Carroll County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Washington County, MD, Adams County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Fulton County, PA, Juniata County, PA, Perry County, PA, York County, PA, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, Loudoun County, VA, Madison County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Shenandoah County, VA, Stafford County, VA, Warren County, VA, Berkeley County, WV, Hampshire County, WV, Jefferson County, WV, Morgan County, WV

The radar

The Sterling radar (KLWX), 51 km from the middle of the area, began a volume at 17:52 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 632Aug 27, 3:15 PM EDT

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 5.9 hours before the alert went out and 54 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: 728 J/kg
Mixed-layer CIN: -107 J/kg
Mixed-layer LCL: 980 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 145 m²/s²
0-3 km storm-relative helicity: 120 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 2.7

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 27, 3:17 PM EDT	Severe Thunderstorm Watch	SPC	Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 8 more	7 hr
Aug 27, 7:26 PM EDT	Mesoscale Discussion	SPC	Baltimore, Carroll, Frederick, Harford, Howard, Montgomery and 1 more	94 min
Aug 27, 10:57 AM EDT	Mesoscale Discussion	SPC	Bucks, Delaware, Montgomery, Northampton, Philadelphia	2 hr
Aug 27, 12:51 PM EDT	Mesoscale Discussion	SPC	Bradford, Lackawanna, Luzerne, Sullivan, Susquehanna, Wayne and 1 more	114 min
Aug 27, 12:51 PM EDT	Severe Thunderstorm Watch	SPC	Berks, Bucks, Carbon, Chester, Delaware, Lehigh and 4 more	9 hr
Aug 27, 1:53 PM EDT	Severe Thunderstorm Watch	SPC	Bradford, Lackawanna, Luzerne, Pike, Susquehanna, Wayne and 1 more	7 hr
Aug 27, 2:29 PM EDT	Mesoscale Discussion	SPC	Delaware, Philadelphia	2 hr
Aug 27, 7:06 PM EDT	Mesoscale Discussion	SPC	Lackawanna, Wayne	84 min

Nearby

Mesoscale Discussions in Virginia, 2026 Mesoscale Discussions in Maryland, 2026 Mesoscale Discussions in Pennsylvania, 2026 Every mesoscale discussion in 2026

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.