Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 532
The Storm Prediction Center issued this mesoscale discussion at May 4, 2021, 3:28 PM EDT for 20 counties in Pennsylvania. It was in force for 62 min.
The area
The outline as issued.
The facts
- Issued
- May 4, 2021, 3:28 PM EDT (19:28 UTC)
- Expired
- May 4, 2021, 4:30 PM EDT
- In force
- 62 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Bradford County, PA, Cameron County, PA, Clarion County, PA, Clearfield County, PA, Clinton County, PA, Columbia County, PA, Elk County, PA, Forest County, PA, Jefferson County, PA, Lackawanna County, PA, Luzerne County, PA, Lycoming County, PA, McKean County, PA, Montour County, PA, Potter County, PA, Sullivan County, PA, Susquehanna County, PA, Tioga County, PA, Union County, PA, Wyoming County, PA
The radar
The State College radar (KCCX), 77 km from the middle of the area, began a volume at 19:31 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
Buffalo Intl Airport, NY (KBUF), launched 12:00Z, 7.5 hours before the alert went out and 199 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 535 m above ground
- 0-6 km bulk shear
- 27 kt
- 0-1 km storm-relative helicity
- 37 m²/s²
- 0-3 km storm-relative helicity
- 84 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
172
ACUS11 KWNS 041929
SWOMCD
SPC MCD 041928
PAZ000-NYZ000-042030-
Mesoscale Discussion 0532
NWS Storm Prediction Center Norman OK
0228 PM CDT Tue May 04 2021
Areas affected...Portions of northern Pennsylvania...far southern
New York
Concerning...Severe potential...Watch unlikely
Valid 041928Z - 042030Z
Probability of Watch Issuance...20 percent
SUMMARY...An isolated severe threat exists with some of the stronger
storms. Isolated damaging gusts and perhaps a tornado or two remain
possible over the next few hours. A WW issuance is not anticipated.
DISCUSSION...Despite large-scale upper ridging in place, an embedded
mid-level perturbation is approaching portions of central PA, with
an uptick in convective coverage and intensity noted. Relatively
steep low-level lapse rates (i.e. 7 C/km per latest Mesoanalysis)
fostering 500 J/kg MLCAPE along with modest directional low-level
shear are promoting an environment supportive of transient rotating
storms. Within the past hour, a TDS has recently been noted on a
cell in Elk County, PA, and additional transient circulations,
potentially supporting the development of a brief tornado or two,
remain possible over the next few hours. A couple of damaging gusts
may also accompany the stronger storms. Given the isolated nature of
the severe threat, a WW issuance is not expected.
..Squitieri/Grams.. 05/04/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PHI...BGM...BUF...CTP...PBZ...
LAT...LON 41078002 41657916 42017843 42107772 42127668 42027598
41607554 41237540 40947560 40877641 40947695 40947806
41078002Nearby
Mesoscale Discussions in Pennsylvania, 2021Every mesoscale discussion in 2021
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.