Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 1864
The Storm Prediction Center issued this mesoscale discussion at Oct 15, 2021, 12:36 PM EDT for 7 counties in Pennsylvania. It was in force for 84 min.
The area
The outline as issued.
The facts
- Issued
- Oct 15, 2021, 12:36 PM EDT (16:36 UTC)
- Expired
- Oct 15, 2021, 2:00 PM EDT
- In force
- 84 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Cameron County, PA, Centre County, PA, Clarion County, PA, Clearfield County, PA, Elk County, PA, Forest County, PA, Jefferson County, PA
The radar
The State College radar (KCCX), 48 km from the middle of the area, began a volume at 16:38 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 12:00Z, 4.6 hours before the alert went out and 156 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
- 685 J/kg
- Mixed-layer CIN
- -15 J/kg
- Mixed-layer LCL
- 658 m above ground
- 0-6 km bulk shear
- 43 kt
- 0-1 km storm-relative helicity
- 38 m²/s²
- 0-3 km storm-relative helicity
- 117 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 1.0
The text
As transmitted.
212
ACUS11 KWNS 151636
SWOMCD
SPC MCD 151636
PAZ000-151800-
Mesoscale Discussion 1864
NWS Storm Prediction Center Norman OK
1136 AM CDT Fri Oct 15 2021
Areas affected...Portions of central PA
Concerning...Severe potential...Watch unlikely
Valid 151636Z - 151800Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated storms capable of hail and locally damaging wind
are possible into early afternoon.
DISCUSSION...A small thunderstorm cluster is moving across parts of
western/central PA as of 1630Z, with the southernmost storm in the
cluster displaying some supercell characteristics. This activity is
likely being driven by a low-amplitude midlevel shortwave trough
moving across the lower Great Lakes and an associated weak low-level
warm advection regime. VWPs from PBZ and CTP show relatively weak
low-level flow, with only modestly favorable midlevel flow noted
from the CTP VWP, so ongoing activity may tend to weaken with time
as it moves eastward into a generally less unstable environment, and
watch issuance is not anticipated in the short term.
Later this afternoon, additional storms may develop across a larger
portion of the region, within a gradually improving CAPE/shear
parameter space, so some severe threat will persist across the area
in the wake of the ongoing activity.
..Dean/Grams.. 10/15/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CTP...PBZ...
LAT...LON 40877931 41217949 41517946 41697908 41727851 41617797
41507777 41177765 41007767 40767785 40707796 40587832
40587878 40877931SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 15, 1:59 PM EDT | Mesoscale Discussion | SPC | Crawford, Erie, Mercer | 91 min |
Nearby
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.