Alert archive / Virginia / Flash Flood Warnings in 2001

Flash Flood Warning 39, NWS Baltimore/Washington

August 11, 2001Nelson County, Virginia

NWS Baltimore/Washington issued this flash flood warning at Aug 11, 2001, 12:36 PM EDT for Nelson County, Virginia. It was in force for 114 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline the Iowa Environmental Mesonet reconstructed for it; the warning itself named whole counties.

The facts

Issued: Aug 11, 2001, 12:36 PM EDT (16:36 UTC)
Expired: Aug 11, 2001, 2:30 PM EDT
In force: 114 min
Issued by: NWS Baltimore/Washington
Area: Whole counties; the outline is the Mesonet’s reconstruction

County Nelson County, VA

The radar

The Roanoke radar (KFCX), 144 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

Roanoke, VA (KRNK), launched 12:00Z, 4.6 hours before the alert went out and 85 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: 1252 J/kg
Mixed-layer CIN: -25 J/kg
Mixed-layer LCL: 689 m above ground
0-6 km bulk shear: 11 kt
0-1 km storm-relative helicity: 10 m²/s²
0-3 km storm-relative helicity: 37 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

000 
WGUS51 KLWX 111637
FFWLWX
VAC125-111830-

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE BALTIMORE-WASHINGTON
1236 PM EDT SAT AUG 11 2001

THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A

* FLASH FLOOD WARNING FOR...
  NELSON COUNTY IN CENTRAL VIRGINIA

* UNTIL 230 PM EDT

* AT 1229 PM EDT...WEATHER SERVICE DOPPLER RADAR INDICATED A
  THUNDERSTORM WITH VERY HEAVY RAINFALL OVER NELSON COUNTY.  THE AREA
  OF HEAVY RAIN WAS NEARLY STATIONARY.

RADAR ESTIMATES UP TO 3 INCHES HAS FALLEN IN FAR WESTERN NELSON 
COUNTY IN THE PAST HOUR. ADDITIONAL RAINFALL WILL RESULT IN FLOODING.

IF WATER IS FLOWING ACROSS A ROADWAY TURN YOUR VEHICLE AROUND AND
FIND AN ALTERNATE ROUTE. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW
YOUR CAR TO CROSS SAFELY. VEHICLES CAUGHT IN RISING WATER SHOULD BE
ABANDONED QUICKLY. MOVE TO HIGHER GROUND.

A FLASH FLOOD WARNING MEANS THAT FLOODING IS IMMINENT OR OCCURRING.
IF YOU ARE IN THE WARNING AREA MOVE TO HIGHER GROUND IMMEDIATELY.
RESIDENTS LIVING ALONG STREAMS AND CREEKS SHOULD TAKE IMMEDIATE
PRECAUTIONS TO PROTECT LIFE AND PROPERTY. DO NOT ATTEMPT TO CROSS
SWIFTLY FLOWING WATERS OR WATERS OF UNKNOWN DEPTH BY FOOT OR BY
AUTOMOBILE. IF YOUR VEHICLE STALLS, ABANDON IT IMMEDIATELY AND SEEK
HIGHER GROUND.

LAT...LON 3783 7916 3777 7909 3793 7887 3796 7887

What forecasters said that day

The local office's own words before this flash flood warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Baltimore/Washington wrote its last area forecast discussion before this flash flood warning went out at Aug 11, 10:16 AM EDT, 2 hours 20 minutes earlier.

Area forecast discussion, Aug 11, 10:16 AM EDT, 2 hours 20 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON
1016 AM EDT SAT AUG 11 2001

CDFNT NOW OVR SRN PA WITH THE COOL DRY AIR WELL N OF THE FNT. WITH
THE FNT NOW ALG THE SRN EDGE OF THE WESTERLIES PARALLEL TO THE UPR
LVL FLOW...IT IS NOT EXPECTED TO PUSH ANY FURTHER S THIS AFTRN.

DWPTS ACRS THE AREA ARE STILL IN THE 70S WITH PRECIP H20 AT 2.15
INCHES AT IAD THIS MORNING. VERY MOIST AIR MASS IN PLACE OVR THE
AREA. MODIFIED SOUNDING FOR IAD GIVES US A CAPE OF 2400 THIS AFTRN
WITH AN LI OF -6 SO THERE WILL ALSO BE QUITE A BIT OF INSTABILITY
OVR THE AREA.

VIS SATELLITE IMAGERY SHOWS QUITE A BIT OF SUNSHINE OVR THE AREA
THIS MRNG. WITH AFTERNOON HEATING... INSTABILITY AND VERY MOIST AIR
MASS EXPECT CONVECTION TO FIRE THIS AFTRN OVR THE CWA. WITH HIGH PWS
TSTMS COULD CONTAIN VERY HEAVY RA AND THIS IS ALREADY HIGHLIGHTED IN
THE ZNS. WE HAVE PLENTY OF INSTABILITY AND MOISTURE BUT NO DYNAMICS
AND NO SHEAR THIS AFTRN. IN ADDITION WET BULB ZERO IS AROUND 14K.
OVERALL THINK THE POTENTIAL FOR STORMS TO BE SVR IS LOW. HOWEVER...
COULD NOT RULE OUT AN ISOLD PULSE TYPE SVR TSTM ESP LATE AFTRN.

WILL UPDATE ZNS TO REMOVE THE MENTION OF MORNING FOG. WITH SOME
SUNSHINE THIS MORNING...TEMPS HAVE RISEN NICELY AND WITH SOME SUN
INTERMINGLED WITH THE CLOUDS THIS AFTRN EXPECT TEMPS TO RISE A BIT
ABV PREVIOUS FCST SO WILL RAISE MAX TEMPS ACROSS THE BOARD. WILL GO
WITH V/C SKIES. EVEN THOUGH RADAR IS VOID OF ECHOES IN THE CWA
ATTM...EXPECT ACTIVITY TO FILL IN DURING THE AFTERNOON.

FRONT HANGS UP JUST TO OUR N TNGT AND SUN WITH WAVES OF LOW PRES
MOVING EWD ALG THE FNT. AREA REMAINS IN VERY MOIST AIR MASS SO
SHRA/TSRA LIKELY THRU SUN BUT EXPECT SOME DRY TIME AS WELL SO IT
WILL NOT BE A TOTAL WASHOUT. NO CHGS 2ND PD AND BEYOND ATTM.

FCSTID = 15 / DMW

.LWX...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

In the hours before

Local storm report, Aug 11, 11:15 AM EDT, 1 hour 21 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON
1115 AM EDT SAT AUG 11 2001

TIME(EDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0350 PM    LANDOVER                  MD   WIND DAMAGE
08/10/01   PRINCE GEORGES                 TREES AND WIRES DOWN

0427 PM    WARRENTON                 VA   WIND DAMAGE
08/10/01   FAUQUIER                       LARGE TREES DOWN
                                          REPORTED BY METEOROLOGIST

0440 PM    NEW BALTIMORE             VA   WIND DAMAGE
08/10/01   PRINCE WILLIAM                 LARGE TREES DOWN
                                          REPORTED BY SPOTTERS

0450 PM    CITY OF MANASSAS          VA   WIND DAMAGE
08/10/01   CITY OF MANASSAS               TWO TREES DOWN
                                          REPORTED BY EMERGENCY
                                          MANAGEMENT

0458 PM    GAINESVILLE               VA   WIND DAMAGE
           PRINCE WILLIAM                 TREES DOWN AND A TRAILER
                                          FLIPPED OVER

0524 PM    5 N FREDERICKSBURG        VA   WIND DAMAGE
08/10/01   STAFFORD                       TREES DOWN IN MICROBURST
                                          PATTERN NEAR RT 17 AND I95
                                          REPORTED BY PILOT                                          REPORTED BY PILOT

0630 PM    COUNTYWIDE                MD   WIND DAMAGE
08/10/01   CALVERT                        EOC HAD SEVERAL REPORTS OF
                                          TREES DOWN COUNTYWIDE.

0645 PM    5 E OF LA PLATA           MD   WIND DAMAGE
08/10/01   CHARLES                        TREES DOWN ON ROUTE 6
                                          5 MILES E OF LA PLATA

WALSTON

Local storm report, Aug 11, 11:15 AM EDT, 1 hour 21 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE/WASHINGTON
1115 AM EDT SAT AUG 11 2001

TIME(EDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0350 PM    LANDOVER                  MD   WIND DAMAGE
08/10/01   PRINCE GEORGES                 TREES AND WIRES DOWN

0427 PM    WARRENTON                 VA   WIND DAMAGE
08/10/01   FAUQUIER                       LARGE TREES DOWN
                                          REPORTED BY METEOROLOGIST

0440 PM    NEW BALTIMORE             VA   WIND DAMAGE
08/10/01   PRINCE WILLIAM                 LARGE TREES DOWN
                                          REPORTED BY SPOTTERS

0450 PM    CITY OF MANASSAS          VA   WIND DAMAGE
08/10/01   CITY OF MANASSAS               TWO TREES DOWN
                                          REPORTED BY EMERGENCY
                                          MANAGEMENT

0458 PM    GAINESVILLE               VA   WIND DAMAGE
           PRINCE WILLIAM                 TREES DOWN AND A TRAILER
                                          FLIPPED OVER

0524 PM    5 N FREDERICKSBURG        VA   WIND DAMAGE
08/10/01   STAFFORD                       TREES DOWN IN MICROBURST
                                          PATTERN NEAR RT 17 AND I95
                                          REPORTED BY PILOT

0630 PM    COUNTYWIDE                MD   WIND DAMAGE
08/10/01   CALVERT                        EOC HAD SEVERAL REPORTS OF
                                          TREES DOWN COUNTYWIDE.

0645 PM    5 E OF LA PLATA           MD   WIND DAMAGE
08/10/01   CHARLES                        TREES DOWN ON ROUTE 6
                                          5 MILES E OF LA PLATA

WALSTON

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 11, 4:16 PM EDT	Flash Flood Warning	LWX	Arlington, Culpeper, Fairfax, Fauquier, Loudoun, Prince William and 5 more	2 hr
Aug 11, 5:43 PM EDT	Flash Flood Warning	LWX	Clarke, Loudoun	2 hr
Aug 11, 6:10 PM EDT	Flash Flood Warning	LWX	Frederick, City of Winchester	110 min

Nearby

Flash Flood Warnings in Virginia, 2001 Every flash flood warning in 2001

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.