Alert archive / West Virginia / Mesoscale Discussions in 2017
Mesoscale Discussion 621
The Storm Prediction Center issued this mesoscale discussion at May 1, 2017, 11:59 AM EDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- May 1, 2017, 11:59 AM EDT (15:59 UTC)
- Expired
- May 1, 2017, 2:00 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 95%
All 56 counties
Garrett County, MD, Belmont County, OH, Carroll County, OH, Columbiana County, OH, Harrison County, OH, Jefferson County, OH, Mahoning County, OH, Monroe County, OH, Noble County, OH, Washington County, OH, Allegheny County, PA, Armstrong County, PA, Beaver County, PA, Butler County, PA, Clarion County, PA, Fayette County, PA, Greene County, PA, Indiana County, PA, Jefferson County, PA, Lawrence County, PA, Mercer County, PA, Venango County, PA, Washington County, PA, Westmoreland County, PA, Barbour County, WV, Boone County, WV, Braxton County, WV, Brooke County, WV, Calhoun County, WV, Clay County, WV, Doddridge County, WV, Fayette County, WV, Gilmer County, WV, Hancock County, WV, Harrison County, WV, Jackson County, WV, Kanawha County, WV, Lewis County, WV, Marion County, WV, Marshall County, WV, Monongalia County, WV, Nicholas County, WV, Ohio County, WV, Pleasants County, WV, Preston County, WV, Putnam County, WV, Randolph County, WV, Ritchie County, WV, Roane County, WV, Taylor County, WV, Tyler County, WV, Upshur County, WV, Webster County, WV, Wetzel County, WV, Wirt County, WV, Wood County, WV
The radar
The Pittsburgh radar (KPBZ), 125 km from the middle of the area, began a volume at 16:00 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
Pittsburgh, PA (KAGC), launched 12:00Z, 4.0 hours before the alert went out and 117 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
- 11 J/kg
- Mixed-layer CIN
- -114 J/kg
- Mixed-layer LCL
- 1435 m above ground
- 0-6 km bulk shear
- 55 kt
- 0-1 km storm-relative helicity
- 217 m²/s²
- 0-3 km storm-relative helicity
- 191 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
641
ACUS11 KWNS 011559
SWOMCD
SPC MCD 011559
PAZ000-MDZ000-WVZ000-OHZ000-011800-
Mesoscale Discussion 0621
NWS Storm Prediction Center Norman OK
1059 AM CDT Mon May 01 2017
Areas affected...eastern Ohio...West Virginia through western
Pennsylvania
Concerning...Severe potential...Watch likely
Valid 011559Z - 011800Z
Probability of Watch Issuance...95 percent
SUMMARY...Thunderstorms are expected to undergo a gradual increase
in coverage and intensity into the afternoon from eastern portions
of Ohio through West Virginia into western Pennsylvania. Damaging
wind and a few tornadoes will be the main threats. A tornado watch
will likely be needed by 17Z.
DISCUSSION...As of mid day storms have shown some increase in
intensity and organization over southeast OH. This activity is
developing along a cold front that stretches from the Great Lakes
through eastern OH into eastern KY. The downstream warm sector is
only weakly capped but marginally unstable. However trends in
visible imagery show numerous cloud breaks, and the boundary layer
should undergo destabilization next few hours supporting 500-1000
J/kg MLCAPE. Very strong deep layer winds will persist in this
region as a mid-level jet coupled with a strong low-level jet within
eastern periphery of the upper low circulation shifts northeast
during the day. Latest VWP data show 70 kt surface to 6 km shear and
large 0-1 km hodographs. This high shear-low CAPE environment will
support organized structures with mixed storm modes including bowing
line segments and supercells as activity develops east through the
destabilizing warm sector.
..Dial/Grams.. 05/01/2017
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...CTP...RNK...PBZ...RLX...CLE...
LAT...LON 38348200 39608158 41148105 41767967 41207877 39487923
37918066 37638186 38348200SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 1, 12:32 PM EDT | Tornado Watch | SPC | Garrett | 4 hr |
| May 1, 4:36 PM EDT | Mesoscale Discussion | SPC | Allegany | 84 min |
| May 1, 5:54 PM EDT | Severe Thunderstorm Watch | SPC | Allegany, Baltimore, Carroll, Charles, Frederick, Harford and 5 more | 5 hr |
| May 1, 1:41 PM EDT | Mesoscale Discussion | SPC | Bedford, Blair, Cambria, Cameron, Centre, Clearfield and 15 more | 64 min |
| May 1, 2:12 PM EDT | Tornado Watch | SPC | Bedford, Blair, Bradford, Cambria, Cameron, Centre and 23 more | 8 hr |
| May 1, 6:52 PM EDT | Severe Thunderstorm Watch | SPC | Pike, Wayne | 4 hr |
| May 1, 7:16 PM EDT | Mesoscale Discussion | SPC | Bucks, Chester, Delaware, Montgomery, Northampton, Philadelphia | 2 hr |
| May 1, 2:29 PM EDT | Mesoscale Discussion | SPC | Greenbrier, Mercer, Monroe, Nicholas, Pendleton, Pocahontas and 3 more | 2 hr |
Nearby
Mesoscale Discussions in West Virginia, 2017Mesoscale Discussions in Pennsylvania, 2017Mesoscale Discussions in Ohio, 2017Every mesoscale discussion in 2017
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.