Alert archive / Maryland / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 310, NWS Baltimore/Washington

July 29, 2021Montgomery County, Prince George's County, Maryland

NWS Baltimore/Washington issued this severe thunderstorm warning at Jul 29, 2021, 4:40 PM EDT for Montgomery County, Prince George's County, Maryland. It was in force for 50 min. 4 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jul 29, 2021, 4:40 PM EDT (20:40 UTC)
Expired: Jul 29, 2021, 5:30 PM EDT
In force: 50 min
Issued by: NWS Baltimore/Washington
Area: Storm-based polygon
Tornado: Possible
Hail: 1.0 in
Wind: 60.0 mph

Counties Montgomery County, MD, Prince George's County, MD

The radar

The Sterling radar (KLWX), 46 km from the middle of the area, began a volume at 20:39 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.

What was reported inside it

Time	Report	Where	Remark
Jul 29, 5:03 PM EDT	TSTM WND DMG	1 Wsw Glenmont, MD	A TREE BLEW DOWN ONTO WIRES SNAPPING A TELEPHONE POLE IN THE 12000 BLOCK OF BLUHILL ROAD.
Jul 29, 5:03 PM EDT	TSTM WND DMG	2 S Aspen Hill, MD	LARGE TREE BRANCHES BLEW DOWN ONTO WIRES IN THE 13000 BLOCK OF TURKEY BRANCH PARKWAY.
Jul 29, 5:10 PM EDT	TSTM WND DMG	1 Wsw Glenmont, MD	LARGE TREE, TELEPHONE POLE AND WIRES DOWN NEAR THE 12000 BLOCK OF BLUHILL ROAD
Jul 29, 5:10 PM EDT	TSTM WND DMG	2 S Aspen Hill, MD	LARGE TREE BRANCHES DOWN ONTO WIRES ON THE 13000 BLOCK OF TURKEY BRANCH PKWY

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Jul 29, 3:00 PM EDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 8.7 hours before the alert went out and 40 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.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 269 J/kg
Mixed-layer CIN: -91 J/kg
Mixed-layer LCL: 893 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 62 m²/s²
0-3 km storm-relative helicity: 62 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

Open this sounding in Storm Lab

The text

As transmitted.

681 
WUUS51 KLWX 292040
SVRLWX
MDC031-033-292130-
/O.NEW.KLWX.SV.W.0310.210729T2040Z-210729T2130Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
440 PM EDT Thu Jul 29 2021

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southeastern Montgomery County in central Maryland...
  Northwestern Prince Georges County in central Maryland...

* Until 530 PM EDT.

* At 440 PM EDT, a severe thunderstorm was located over Gaithersburg,
  moving east at 25 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches 
           to fall. This could injure those outdoors, as well as 
           damage homes and vehicles. Roadways may become blocked by 
           downed trees. Localized power outages are possible. 
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Germantown, Rockville, Gaithersburg, Olney, College Park,
  Greenbelt, Langley Park, Beltsville, University of Maryland, Aspen
  Hill, North Bethesda, Montgomery Village, Laurel, North Potomac,
  Fairland, Hyattsville, White Oak, Redland, Takoma Park and East
  Riverdale.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Tornado Watch remains in effect until 900 PM EDT for central
Maryland.

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3914 7696 3913 7695 3913 7694 3912 7688
      3911 7687 3911 7685 3896 7692 3911 7728
      3918 7722
TIME...MOT...LOC 2040Z 285DEG 23KT 3912 7722 

TORNADO...POSSIBLE
HAIL...1.00IN
WIND...60MPH
 
$$

BJL

3 follow-up statements

728 
WWUS51 KLWX 292056
SVSLWX

Severe Weather Statement
National Weather Service Baltimore MD/Washington DC
456 PM EDT Thu Jul 29 2021

MDC031-033-292130-
/O.CON.KLWX.SV.W.0310.000000T0000Z-210729T2130Z/
Montgomery MD-Prince Georges MD-
456 PM EDT Thu Jul 29 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 530 PM EDT
FOR SOUTHEASTERN MONTGOMERY AND NORTHWESTERN PRINCE GEORGES
COUNTIES...

At 455 PM EDT, a severe thunderstorm was located over Aspen Hill, or
near Rockville, moving east at 25 mph.

HAZARD...65 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated.

IMPACT...Damaging winds will cause some trees and large branches to 
         fall. This could injure those outdoors, as well as damage 
         homes and vehicles. Roadways may become blocked by downed 
         trees. Localized power outages are possible. Unsecured 
         light objects may become projectiles.

Locations impacted include...
Rockville, Gaithersburg, Olney, College Park, Greenbelt, Langley
Park, Beltsville, University of Maryland, Aspen Hill, Potomac, North
Bethesda, Laurel, North Potomac, Fairland, Hyattsville, White Oak,
Redland, Takoma Park, East Riverdale and Adelphi.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Tornado Watch remains in effect until 900 PM EDT for central
Maryland.

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3914 7696 3913 7695 3913 7694 3912 7688
      3911 7687 3911 7685 3896 7692 3908 7722
      3916 7716
TIME...MOT...LOC 2055Z 285DEG 23KT 3909 7709 

TORNADO...POSSIBLE
HAIL...1.25IN
WIND...60MPH
 
$$

DHOF

115 
WWUS51 KLWX 292113 RRA
SVSLWX

Severe Weather Statement
National Weather Service Baltimore MD/Washington DC
513 PM EDT Thu Jul 29 2021

MDC031-033-292130-
/O.CON.KLWX.SV.W.0310.000000T0000Z-210729T2130Z/
Montgomery MD-Prince Georges MD-
513 PM EDT Thu Jul 29 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 530 PM EDT
FOR SOUTHEASTERN MONTGOMERY AND NORTHWESTERN PRINCE GEORGES
COUNTIES...

At 513 PM EDT, a severe thunderstorm was located over University of
Maryland, moving southeast at 30 mph.

HAZARD...60 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated.

IMPACT...Damaging winds will cause some trees and large branches to 
         fall. This could injure those outdoors, as well as damage 
         homes and vehicles. Roadways may become blocked by downed 
         trees. Localized power outages are possible. Unsecured 
         light objects may become projectiles.

Locations impacted include...
College Park, Greenbelt, Langley Park, Beltsville, University of
Maryland, Fairland, Hyattsville, White Oak, Takoma Park, East
Riverdale, Adelphi, Colesville, Kemp Mill, Riverdale Park, Forest
Glen, Hillandale, Wheaton-Glenmont, Silver Spring, Wheaton and
Chillum.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3901 7705 3909 7700 3906 7687 3896 7692
TIME...MOT...LOC 2113Z 298DEG 27KT 3900 7696 

HAIL...1.25IN
WIND...60MPH
 
$$

BJL

383 
WWUS51 KLWX 292114
SVSLWX

Severe Weather Statement
National Weather Service Baltimore MD/Washington DC
514 PM EDT Thu Jul 29 2021

MDC031-033-292130-
/O.CON.KLWX.SV.W.0310.000000T0000Z-210729T2130Z/
Montgomery MD-Prince Georges MD-
514 PM EDT Thu Jul 29 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 530 PM EDT
FOR SOUTHEASTERN MONTGOMERY AND NORTHWESTERN PRINCE GEORGES
COUNTIES...

At 514 PM EDT, a severe thunderstorm was located over Beltsville,
moving east at 25 mph.

HAZARD...60 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated.

IMPACT...Damaging winds will cause some trees and large branches to 
         fall. This could injure those outdoors, as well as damage 
         homes and vehicles. Roadways may become blocked by downed 
         trees. Localized power outages are possible. Unsecured 
         light objects may become projectiles.

Locations impacted include...
College Park, Greenbelt, Langley Park, Beltsville, University of
Maryland, Fairland, Hyattsville, White Oak, Takoma Park, East
Riverdale, Adelphi, Colesville, Kemp Mill, Riverdale Park, Forest
Glen, Hillandale, Silver Spring, Wheaton, Chillum and Calverton.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Remain alert for a possible tornado! Tornadoes can develop quickly
from severe thunderstorms. If you spot a tornado go at once into the
basement or small central room in a sturdy structure.

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 3910 7697 3907 7687 3896 7692 3901 7705
TIME...MOT...LOC 2114Z 285DEG 23KT 3906 7694 

TORNADO...POSSIBLE
HAIL...1.25IN
WIND...60MPH
 
$$

DHOF

The office that day

Everything else NWS Baltimore/Washington issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 28, 9:30 PM EDT	Severe Thunderstorm Warning	LWX	Montgomery	45 min
Jul 28, 9:48 PM EDT	Severe Thunderstorm Warning	LWX	Montgomery, Prince George's	42 min
Jul 29, 3:31 PM EDT	Severe Thunderstorm Warning	LWX	Carroll, Frederick	44 min
Jul 29, 4:00 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Carroll	45 min
Jul 29, 4:01 PM EDT	Tornado Warning	LWX	Carroll	29 min
Jul 29, 4:16 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Carroll, Howard	44 min
Jul 29, 4:34 PM EDT	Tornado Warning	LWX	Howard	26 min
Jul 29, 4:50 PM EDT	Severe Thunderstorm Warning	LWX	Anne Arundel, Baltimore, Howard, City of Baltimore	55 min
Jul 29, 4:59 PM EDT	Severe Thunderstorm Warning	LWX	Charles	46 min
Jul 29, 4:59 PM EDT	Tornado Warning	LWX	Anne Arundel, Baltimore, Howard	31 min
Jul 29, 5:01 PM EDT	Severe Thunderstorm Warning	LWX	Montgomery, Prince George's	29 min
Jul 29, 5:30 PM EDT	Severe Thunderstorm Warning	LWX	Anne Arundel, Calvert, Prince George's	40 min
Jul 29, 5:43 PM EDT	Severe Thunderstorm Warning	LWX	Anne Arundel	17 min
Jul 29, 6:49 PM EDT	Coastal Flood Advisory	LWX	Anne Arundel	4 hr

Nearby

Severe Thunderstorm Warnings in Maryland, 2021 Every severe thunderstorm warning 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.