Alert archive / Pennsylvania / Mesoscale Discussions in 2011

Mesoscale Discussion 77

February 1, 20114 states

The Storm Prediction Center issued this mesoscale discussion at Feb 1, 2011, 8:39 PM EST for 4 states. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued
Feb 1, 2011, 8:39 PM EST (01:39 UTC)
Expired
Feb 2, 2011, 2:15 AM EST
In force
6 hr
Issued by
the Storm Prediction Center
All 57 counties

Carroll County, MD, Washington County, MD, Hunterdon County, NJ, Mercer County, NJ, Somerset County, NJ, Warren County, NJ, Adams County, PA, Armstrong County, PA, Bedford County, PA, Berks County, PA, Blair County, PA, Bucks County, PA, Butler County, PA, Cambria County, PA, Cameron County, PA, Carbon County, PA, Centre County, PA, Chester County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Crawford County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Elk County, PA, Forest County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Indiana County, PA, Jefferson County, PA, Juniata County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Lycoming County, PA, McKean County, PA, Mercer County, PA, Mifflin County, PA, Monroe County, PA, Montgomery County, PA, Montour County, PA, Northampton County, PA, Northumberland County, PA, Perry County, PA, Philadelphia County, PA, Schuylkill County, PA, Snyder County, PA, Somerset County, PA, Union County, PA, Venango County, PA, Warren County, PA, York County, PA, Morgan County, WV

The radar

The State College radar (KCCX), 26 km from the middle of the area, began a volume at 01:42 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, 1.7 hours before the alert went out and 191 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-pSkew-T log-p diagram, Pittsburgh, PA at 00:00Z on 2011-02-02Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCLEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Pittsburgh, PA at 00:00Z on 2011-02-02The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 172 square meters per square second.1939587897117Sfc1 km3 km6 km9 kmRMLM
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
412 m above ground
0-6 km bulk shear
65 kt
0-1 km storm-relative helicity
172 m²/s²
0-3 km storm-relative helicity
272 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.

882 
ACUS11 KWNS 020139
SWOMCD
SPC MCD 020139 
NJZ000-PAZ000-DEZ000-MDZ000-WVZ000-NYZ000-OHZ000-020715-

MESOSCALE DISCUSSION 0077
NWS STORM PREDICTION CENTER NORMAN OK
0739 PM CST TUE FEB 01 2011

AREAS AFFECTED...NWRN TO SERN PA...MD PANHANDLE AND W CNTRL NJ

CONCERNING...FREEZING RAIN 

VALID 020139Z - 020715Z

FREEZING RAIN...POTENTIALLY MIXED WITH SLEET AT TIMES ACROSS CNTRL
PA...WILL INCREASE FROM W TO E TONIGHT. EXPECT RATES AROUND 0.05" TO
0.10" PER 3 HOURS EXCEPT IN ANY HEAVIER CONVECTIVE CELLS THAT MAY
DEVELOP WHERE RATES MAY BRIEFLY BE HIGHER.

01Z MESOANALYSIS INDICATED SURFACE WET BULB TEMPERATURES BELOW ZERO
ACROSS MUCH OF PA INTO W CNTRL NJ. AREAS OF LIGHT FREEZING RAIN AND
SLEET WERE MOVING INTO WRN PA AS PRECIPITATION SHIELD /ASSOCIATED
WITH WARM CONVEYOR BELT/ISENTROPIC LIFT AROUND 850 MB LOW NEAR ST.
LOUIS/ TRACKS NEWD. 23Z RUC FORECAST SOUNDINGS INDICATED AN ELEVATED
WARM NOSE AROUND 860-870 MB OF 3-6 C WITH SFC TEMPERATURES RANGING
FROM THE LOW 20S TO NEAR 30 F ACROSS THE MCD AREA. THE ONLY
QUESTIONABLE AREA IS NEAR THE MARYLAND PANHANDLE WHERE SFC
TEMPERATURES WILL REMAIN NEAR FREEZING THROUGH THE OVERNIGHT HOURS
AS SFC LOW NOW OVER SRN IND/SWRN KY TRACKS E/NEWD AND ATTENDANT WARM
FRONT APPROACHES THE AREA.

IN ADDITION TO LARGE SCALE FORCING FROM APPROACHING MID LEVEL LOW
PRESSURE SYSTEM...850 MB FRONTOGENESIS WILL INCREASE AHEAD OF LOW AS
WILL MID LEVEL JET /40-50 KT/...LEADING TO INCREASED FORCING THROUGH
THE SATURATED WARM LAYER. EXPECT RATES TO INCREASE ACROSS WRN PA BY
03Z...REACHING W CNTRL NJ BY AROUND 06-09Z.

..STOPPKOTTE.. 02/02/2011

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

ATTN...WFO...OKX...PHI...BGM...BUF...CTP...LWX...PBZ...CLE...

LAT...LON   39487725 39487804 39607861 39737903 39887914 40087923
            40327925 40547937 40707966 40817997 40948021 41058039
            41228057 41538063 41898049 42038021 42087947 41967881
            41817825 41517759 41417654 41317569 41117525 40977482
            40787457 40587445 40227442 39967469 39957484 39757537
            39487725

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Feb 1, 11:21 PM ESTMesoscale DiscussionSPCBergen, Essex, Hudson, Middlesex, Monmouth, Morris and 4 more6 hr

Nearby

Mesoscale Discussions in Pennsylvania, 2011Mesoscale Discussions in New Jersey, 2011Mesoscale Discussions in Maryland, 2011Every mesoscale discussion in 2011

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.