Alert archive / Maryland / Mesoscale Discussions in 2012

Mesoscale Discussion 1408

July 5, 201212 counties in Maryland; 12 counties in Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Jul 5, 2012, 4:37 PM EDT for 12 counties in Maryland; 12 counties in Pennsylvania. It was in force for 113 min.

The area

The outline as issued.

The facts

Issued: Jul 5, 2012, 4:37 PM EDT (20:37 UTC)
Expired: Jul 5, 2012, 6:30 PM EDT
In force: 113 min
Issued by: the Storm Prediction Center
Chance of a watch: 40%

All 24 counties

Anne Arundel County, MD, Baltimore County, MD, Carroll County, MD, Cecil County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Queen Anne's County, MD, Washington County, MD, Adams County, PA, Blair County, PA, Centre County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Mifflin County, PA, Perry County, PA, York County, PA

The radar

The Sterling radar (KLWX), 111 km from the middle of the area, began a volume at 20:39 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

Washington/Dulle, VA (KIAD), launched 12:00Z, 8.6 hours before the alert went out and 112 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: 0 m above ground
0-6 km bulk shear: 6 kt
0-1 km storm-relative helicity: 37 m²/s²
0-3 km storm-relative helicity: 64 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 5.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

713 
ACUS11 KWNS 052037
SWOMCD
SPC MCD 052037 
PAZ000-MDZ000-DCZ000-WVZ000-052230-

MESOSCALE DISCUSSION 1408
NWS STORM PREDICTION CENTER NORMAN OK
0337 PM CDT THU JUL 05 2012

AREAS AFFECTED...CNTRL/SCNTRL PA...NRN MD

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 052037Z - 052230Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...THUNDERSTORM DEVELOPMENT EXPECTED NEXT 1 TO 2 HOURS IN
CNTRL PA.  DAMAGING WIND SHOULD BE MAIN THREAT INTO LATE AFTERNOON
WITH ISOLATED LARGE HAIL.

DISCUSSION...ALTHOUGH SFC WINDS ARE W/NWLY...TEMPERATURE HAVE
CLIMBED INTO THE MID 90S AND DEWPOINTS ARE IN THE UPPER 60S TO NEAR
70.  MLCAPE IS IN EXCESS OF 3000 J/KG.  MODEL FORECASTS THE CAPPING
INVERSION OVER THE AREA SHOULD CONTINUE TO WEAKEN ALLOWING STORMS TO
DEVELOP.  SATELLITE ALSO INDICATES CU FIELD IS BECOMING MORE
ENHANCED ON VIS IMAGERY.  DAMAGING WINDS AND ISOLATED LARGE HAIL
COULD BE POSSIBLE ONCE THE STORMS FORM AND A WATCH IS POSSIBLE.

..BOTHWELL/THOMPSON.. 07/05/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...CTP...LWX...

LAT...LON   39487770 39807818 40067839 40297847 40577857 40787852
            41007840 41087810 41037782 40867744 40707718 40497686
            40257648 40127635 39817613 39617594 39427587 39217583
            39047594 38907610 38797634 38837660 38987707 39487770

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 4, 8:05 PM EDT	Mesoscale Discussion	SPC	Allegany, Garrett, Washington	55 min
Jul 5, 3:29 AM EDT	Mesoscale Discussion	SPC	Calvert, Charles, Saint Mary's, Somerset	91 min
Jul 4, 9:48 PM EDT	Mesoscale Discussion	SPC	Beaver, Lawrence, Washington	87 min
Jul 4, 10:19 PM EDT	Severe Thunderstorm Watch	SPC	Allegheny, Beaver, Butler, Greene, Lawrence, Mercer and 2 more	4 hr
Jul 5, 6:16 AM EDT	Severe Thunderstorm Watch	SPC	Crawford, Erie, Lawrence, Mercer	3 hr

Nearby

Mesoscale Discussions in Maryland, 2012 Mesoscale Discussions in Pennsylvania, 2012 Every mesoscale discussion in 2012

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.