Alert archive / Pennsylvania / Mesoscale Discussions in 2021
Mesoscale Discussion 1870
The Storm Prediction Center issued this mesoscale discussion at Oct 16, 2021, 11:06 AM EDT for 8 counties in New York; 26 counties in Pennsylvania. It was in force for 114 min.
The area
The outline as issued.
The facts
- Issued
- Oct 16, 2021, 11:06 AM EDT (15:06 UTC)
- Expired
- Oct 16, 2021, 1:00 PM EDT
- In force
- 114 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch possible
- Chance of a watch
- 60%
All 34 counties
Broome County, NY, Chenango County, NY, Cortland County, NY, Delaware County, NY, Madison County, NY, Otsego County, NY, Sullivan County, NY, Tioga County, NY, Berks County, PA, Bradford County, PA, Carbon County, PA, Columbia County, PA, Cumberland County, PA, Dauphin County, PA, Juniata County, PA, Lackawanna County, PA, Lancaster County, PA, Lebanon County, PA, Lehigh County, PA, Luzerne County, PA, Lycoming County, PA, Mifflin County, PA, Monroe County, PA, Montour County, PA, Northumberland County, PA, Perry County, PA, Pike County, PA, Schuylkill County, PA, Snyder County, PA, Sullivan County, PA, Susquehanna County, PA, Union County, PA, Wayne County, PA, Wyoming County, PA
The radar
The Binghamton radar (KBGM), 61 km from the middle of the area, began a volume at 15:04 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Albany, NY (KALY), launched 12:00Z, 3.1 hours before the alert went out and 225 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
- 50 J/kg
- Mixed-layer CIN
- -197 J/kg
- Mixed-layer LCL
- 735 m above ground
- 0-6 km bulk shear
- 49 kt
- 0-1 km storm-relative helicity
- 279 m²/s²
- 0-3 km storm-relative helicity
- 291 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.4
The text
As transmitted.
617
ACUS11 KWNS 161506
SWOMCD
SPC MCD 161506
NYZ000-PAZ000-161700-
Mesoscale Discussion 1870
NWS Storm Prediction Center Norman OK
1006 AM CDT Sat Oct 16 2021
Areas affected...Central/Eastern PA...South-Central NY
Concerning...Severe potential...Watch possible
Valid 161506Z - 161700Z
Probability of Watch Issuance...60 percent
SUMMARY...A narrow line of stronger storms is expected to move
northeastward into more of eastern PA and south-central NY over the
next few hours. Convective trends will be monitored for possible
watch issuance.
DISCUSSION...Recent radar trends show increasing reflectivity within
the line of showers and thunderstorms just ahead of the front in
central PA. Recent lightning data shows an increasing trend in
flashes within this line as well. This matches forecast expectations
with storms expected to gradual strengthen amid continued lift along
the front, increasing large-scale forcing for ascent, and modest
diurnal destabilization.
Low to mid-level flow is also strengthening across the region, shown
well by the BGM VAD, which recently sampled 45-50 kt at 1 km AGL
increasing to 60 kt between 2-3 km AGL. The resulting vertical
profile had 0-1 km bulk shear around 35 kt and 0-1 km storm-relative
helicity near 250 m2/s2.
The resulting combination of ascent, modest buoyancy, and strong
vertical shear is forecast to result in a narrow line of deeper
convection capable of producing damaging wind gusts and maybe even a
brief embedded tornado or two as it moves northeastward.
..Mosier/Grams.. 10/16/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ALY...PHI...BGM...CTP...
LAT...LON 41547731 42467639 43167557 42797445 41897459 39917606
40107789 41547731SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 16, 12:09 PM EDT | Mesoscale Discussion | SPC | Albany, Clinton, Essex, Fulton, Hamilton, Montgomery and 6 more | 2 hr |
| Oct 16, 12:35 PM EDT | Severe Thunderstorm Watch | SPC | Albany, Clinton, Columbia, Delaware, Dutchess, Essex and 15 more | 6 hr |
| Oct 16, 2:55 PM EDT | Mesoscale Discussion | SPC | Albany, Columbia, Delaware, Dutchess, Greene, Rensselaer and 7 more | 95 min |
| Oct 16, 5:39 PM EDT | Mesoscale Discussion | SPC | Nassau, Suffolk | 2 hr |
| Oct 16, 1:50 PM EDT | Mesoscale Discussion | SPC | Berks, Bucks, Carbon, Chester, Delaware, Lancaster and 4 more | 115 min |
Nearby
Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in New York, 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.