Alert archive / Pennsylvania / Mesoscale Discussions in 2012

Mesoscale Discussion 1302

June 29, 201224 counties in Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Jun 29, 2012, 12:45 AM EDT for 24 counties in Pennsylvania. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: Jun 29, 2012, 12:45 AM EDT (04:45 UTC)
Expired: Jun 29, 2012, 2:15 AM EDT
In force: 90 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 24 counties

Armstrong County, PA, Blair County, PA, Butler County, PA, Cambria County, PA, Cameron County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Crawford County, PA, Elk County, PA, Forest County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lycoming County, PA, Mercer County, PA, Mifflin County, PA, Perry County, PA, Snyder County, PA, Union County, PA, Venango County, PA, Warren County, PA

The radar

The State College radar (KCCX), 98 km from the middle of the area, began a volume at 04:47 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

Pittsburgh, PA (KPIT), launched 00:00Z, 4.8 hours before the alert went out and 126 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: 624 J/kg
Mixed-layer CIN: -472 J/kg
Mixed-layer LCL: 2198 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 82 m²/s²
0-3 km storm-relative helicity: 178 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

244 
ACUS11 KWNS 290446
SWOMCD
SPC MCD 290445
PAZ000-290615-

MESOSCALE DISCUSSION 1302
NWS STORM PREDICTION CENTER NORMAN OK
1145 PM CDT THU JUN 28 2012

AREAS AFFECTED...NWRN/CNTRL PA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 290445Z - 290615Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...WHILE CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED
ACROSS NWRN/CNTRL PA THROUGH THE OVERNIGHT HOURS...THE ANTICIPATED
ISOLATED NATURE OF THE SVR THREAT IS CURRENTLY EXPECTED TO PREVENT
THE NECESSITY OF WW ISSUANCE.

DISCUSSION...ISOLATED TO SCATTERED CONVECTION CONTINUES TO DEVELOP
ACROSS NWRN PA WITHIN A ZONE OF WEAK WAA AT 850 MB AND WITHIN THE
WARM SIDE OF A 700-MB THERMAL GRADIENT. SUBTLE FORCING FOR ASCENT
ASSOCIATED WITH THE GLANCING INFLUENCE OF A SHORTWAVE TROUGH
CROSSING PARTS OF SRN ONTARIO. MUCAPE VALUES IN EXCESS OF 3000 J/KG
OWING TO STEEP MID-LEVEL LAPSE RATES MAY SUPPORT ROBUST CONVECTIVE
UPDRAFTS. HOWEVER...TO THE SOUTH OF THE 700-MB GRADIENT...700-MB
TEMPERATURES OVER 15C AND THE COOLING BOUNDARY LAYER ARE
CONTRIBUTING TO APPRECIABLE SFC-BASED CINH ACROSS THE DISCUSSION
AREA. WHILE STATE COLLEGE VWP DATA INDICATE MODERATE DEEP SHEAR IN
PLACE GIVEN 40 KT OF MID-LEVEL WNWLY FLOW...CONVECTION MAY STRUGGLE
TO BE SUSTAINED AS IT IS STEERED ESEWD INTO/ACROSS CNTRL PA. UNLESS
A MORE ORGANIZED CONVECTIVE THREAT EVOLVES OWING TO MERGING COLD
POOLS AND UPSCALE GROWTH...THE SVR THREAT WILL LIKELY REMAIN
ISOLATED WITH A FEW ELEVATED STORMS CAPABLE OF PRODUCING MARGINALLY
SVR HAIL BEING THE MAIN CONCERN.

..COHEN/HART.. 06/29/2012

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

ATTN...WFO...CTP...PBZ...CLE...

LAT...LON   41967996 41927967 41637701 40657684 40297719 40117816
            40327909 40988013 41518041 41738040 41928025 41967996

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 28, 8:53 PM EDT	Mesoscale Discussion	SPC	Erie	97 min
Jun 29, 3:41 AM EDT	Mesoscale Discussion	SPC	Berks, Bucks, Carbon, Chester, Columbia, Cumberland and 19 more	94 min
Jun 29, 4:34 AM EDT	Severe Thunderstorm Watch	SPC	Bucks, Chester, Delaware, Montgomery, Philadelphia	3 hr
Jun 29, 3:07 PM EDT	Mesoscale Discussion	SPC	Greene, Washington	53 min
Jun 29, 6:03 PM EDT	Mesoscale Discussion	SPC	Fayette, Greene, Somerset, Washington	87 min
Jun 29, 6:34 PM EDT	Severe Thunderstorm Watch	SPC	Allegheny, Bedford, Fayette, Franklin, Fulton, Greene and 3 more	6 hr
Jun 29, 7:51 PM EDT	Mesoscale Discussion	SPC	Adams, Bedford, Fayette, Franklin, Fulton, Greene and 2 more	114 min

Nearby

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.