Alert archive / Virginia / Mesoscale Discussions in 2021
Mesoscale Discussion 1628
The Storm Prediction Center issued this mesoscale discussion at Aug 28, 2021, 1:05 PM EDT for 4 states. It was in force for 115 min.
The area
The outline as issued.
The facts
- Issued
- Aug 28, 2021, 1:05 PM EDT (17:05 UTC)
- Expired
- Aug 28, 2021, 3:00 PM EDT
- In force
- 115 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 5%
All 45 counties
Allegany County, MD, Frederick County, MD, Washington County, MD, Adams County, PA, Bedford County, PA, Blair County, PA, Cambria County, PA, Cumberland County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Indiana County, PA, Mifflin County, PA, Albemarle County, VA, Augusta County, VA, City of Charlottesville, VA, City of Harrisonburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, Highland County, VA, Loudoun County, VA, Madison County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Rockingham County, VA, Shenandoah County, VA, Warren County, VA, Berkeley County, WV, Grant County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Mineral County, WV, Morgan County, WV, Pendleton County, WV
The radar
The Sterling radar (KLWX), 108 km from the middle of the area, began a volume at 17:07 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
Washington/Dulle, VA (KIAD), launched 12:00Z, 5.1 hours before the alert went out and 116 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
- 425 J/kg
- Mixed-layer CIN
- -107 J/kg
- Mixed-layer LCL
- 898 m above ground
- 0-6 km bulk shear
- 9 kt
- 0-1 km storm-relative helicity
- -11 m²/s²
- 0-3 km storm-relative helicity
- 11 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
948
ACUS11 KWNS 281705
SWOMCD
SPC MCD 281705
PAZ000-MDZ000-VAZ000-WVZ000-281900-
Mesoscale Discussion 1628
NWS Storm Prediction Center Norman OK
1205 PM CDT Sat Aug 28 2021
Areas affected...South-Central Pennsylvania...Western
Maryland...Eastern West Virginia...and Northern Virginia
Concerning...Severe potential...Watch unlikely
Valid 281705Z - 281900Z
Probability of Watch Issuance...5 percent
SUMMARY...Isolated damaging wind gusts possible with the strongest
storms this afternoon.
DISCUSSION...Visible satellite shows strong insolation this morning
has given way to scattered convective development over the northern
part of region. Surface temperatures have warmed into the mid 80s F
amid rich low-level moisture (dew point temperatures in the upper
60s and low 70s F). This is yielding around 1000 J/kg of MLCAPE.
With weak convective inhibition and continued
heating/destabilization, additional pulse-like storms are expected
to develop throughout the afternoon and gradually move southeastward
with time. Weak flow throughout the atmosphere will limit storm
organization, however, a few isolated damaging wind gusts will be
possible with the strongest storms given at least marginal low-level
lapse rates near 8 C/km that should develop, particularly over parts
of northern Virginia and vicinity later this afternoon. Given the
expectation for an isolated damaging wind threat, watch issuance is
not expected.
..Karstens/Grams.. 08/28/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...AKQ...CTP...LWX...RNK...PBZ...RLX...
LAT...LON 39387920 40087891 40537913 40937915 41017832 40767758
40077712 39157722 38397754 38077818 37947903 38077944
38447964 38977948 39387920Nearby
Mesoscale Discussions in Virginia, 2021Mesoscale Discussions in Pennsylvania, 2021Mesoscale Discussions in West Virginia, 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.