Alert archive / Pennsylvania / Areal Flood Advisories in 2017

Areal Flood Advisory 118, NWS Philadelphia/Mount Holly

July 23, 2017Chester County, Pennsylvania; Cecil County, Maryland

NWS Philadelphia/Mount Holly issued this areal flood advisory at Jul 23, 2017, 4:26 PM EDT for Chester County, Pennsylvania; Cecil County, Maryland. It was in force for 3 hr.

The area

The counties it named.

The facts

Issued: Jul 23, 2017, 4:26 PM EDT (20:26 UTC)
Expired: Jul 23, 2017, 7:30 PM EDT
In force: 3 hr
Issued by: NWS Philadelphia/Mount Holly
Area: Storm-based polygon

Counties Cecil County, MD, Chester County, PA

The radar

The Dover AFB radar (KDOX), 110 km from the middle of the area, began a volume at 20:31 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, 8.4 hours before the alert went out and 161 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: 186 J/kg
Mixed-layer CIN: -43 J/kg
Mixed-layer LCL: 983 m above ground
0-6 km bulk shear: 21 kt
0-1 km storm-relative helicity: 19 m²/s²
0-3 km storm-relative helicity: 31 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

What forecasters said that day

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

NWS Philadelphia/Mount Holly wrote its last area forecast discussion before this areal flood advisory went out at Jul 23, 4:17 PM EDT, 9 minutes earlier.

Area forecast discussion, Jul 23, 4:17 PM EDT, 9 minutes before

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Hazardous weather outlook, Jul 23, 3:45 PM EDT, 41 minutes before

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      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
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        The site you requested is temporarily down for maintenance or an unexpected outage.
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In the hours before

Local storm report, Jul 23, 3:14 PM EDT, 1 hour 12 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
314 PM EDT SUN JUL 23 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0253 PM     TSTM WND GST     1 WNW SHERWOOD          38.77N  76.33W
07/23/2017  M42 MPH          TALBOT             MD   MESONET

&&

EVENT NUMBER PHI1701106

FRANCK

Local storm report, Jul 23, 3:18 PM EDT, 1 hour 8 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
318 PM EDT SUN JUL 23 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0258 PM     TSTM WND GST     1 SW PARADISE ISLAND    38.90N  76.36W
07/23/2017  M47 MPH          QUEEN ANNE'S       MD   MESONET

&&

EVENT NUMBER PHI1701107

FRANCK

Local storm report, Jul 23, 3:19 PM EDT, 1 hour 7 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
319 PM EDT SUN JUL 23 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0256 PM     TSTM WND GST     1 SE CRESCENDO          38.78N  76.28W
07/23/2017  M42 MPH          TALBOT             MD   MESONET

&&

EVENT NUMBER PHI1701108

FRANCK

Special weather statement, Jul 23, 3:27 PM EDT, 59 minutes before

Special Weather Statement
National Weather Service Mount Holly NJ
327 PM EDT SUN JUL 23 2017

DEZ001-002-MDZ008-012-232000-
Kent-New Castle-Cecil-Kent-
327 PM EDT SUN JUL 23 2017

...A STRONG THUNDERSTORM WILL AFFECT SOUTHWESTERN NEW CASTLE...
NORTHWESTERN KENT COUNTIES IN DELAWARE AND NORTHEASTERN KENT AND
SOUTHEASTERN CECIL COUNTIES IN MARYLAND...

At 325 PM EDT, a strong thunderstorm was located near Cecilton, or 11
miles southeast of Aberdeen Proving Ground, moving southeast at 20
mph.

Locations impacted include...
Cecilton, Warwick, Sassafras, Massey, Kennedyville, Townsend and
Galena.

These storms will contain gusty winds up to 45 mph, torrential
downpours and occasional cloud to ground lightning.

Locally heavy rainfall will lead to ponding of water on roadways and
poor visibility at times this afternoon. Poor drainage flooding
could also develop.

Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional
information and possible warnings from the National Weather Service.

LAT...LON 3943 7599 3945 7601 3948 7593 3940 7569
      3936 7564 3927 7581 3924 7597 3939 7605
TIME...MOT...LOC 1925Z 306DEG 17KT 3939 7593

JRK

Special weather statement, Jul 23, 3:31 PM EDT, 55 minutes before

Special Weather Statement
National Weather Service Mount Holly NJ
331 PM EDT SUN JUL 23 2017

DEZ003-MDZ019-020-232015-
Inland Sussex-Talbot-Caroline-
331 PM EDT SUN JUL 23 2017

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT SOUTHWESTERN SUSSEX...
SOUTHEASTERN TALBOT AND SOUTHERN CAROLINE COUNTIES...

At 330 PM EDT, radar indicated strong thunderstorms were located
along a line extending from near Hambleton to Trappe to near
Cambridge. Movement was east at 30 mph.

Locations impacted include...
Seaford, Laurel, Delmar, Federalsburg, Bridgeville, Trappe, Preston,
Smithville, Agner, Choptank, Hambleton, Windyhill, Blades and Bethel.

These storms have weakened below severe limits but will still
contain gusty winds up to 45 mph, torrential downpours and
occasional cloud to ground lightning.

Locally heavy rainfall will lead to ponding of water on roadways and
poor visibility. Poor drainage flooding could also develop.

Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 3846 7569 3864 7571 3869 7577 3868 7580
      3870 7580 3871 7584 3868 7594 3863 7598
      3860 7599 3857 7604 3863 7608 3862 7612
      3871 7617 3878 7582 3880 7556 3845 7557
TIME...MOT...LOC 1930Z 264DEG 24KT 3869 7611 3866 7605 3854 7603

JRK

Special weather statement, Jul 23, 4:15 PM EDT, 11 minutes before

Special Weather Statement
National Weather Service Mount Holly NJ
415 PM EDT SUN JUL 23 2017

DEZ001-002-MDZ008-012-NJZ016-021-PAZ102-232045-
Kent-New Castle-Cecil-Kent-Salem-Cumberland-Eastern Chester-
415 PM EDT SUN JUL 23 2017

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT NEW CASTLE...NORTHERN
KENT...NORTHEASTERN KENT...EASTERN CECIL...WEST CENTRAL CUMBERLAND...
SOUTHWESTERN SALEM AND SOUTHERN CHESTER COUNTIES...

At 413 PM EDT, radar indicated strong thunderstorms were located
along a line extending from near Glasgow to near Smyrna to near
Dover Base Housing. Movement was variable with each storm but
generally drifting to the east at 10 mph.

Locations impacted include...
Wilmington, Dover, Newark, Middletown, Elkton, Pennsville, Smyrna,
Elsmere, New Castle, Salem, Clayton, Delaware City, Cheswold,
Newport, Stanton, Glasgow, Bohemias Mills, Newport Meadows, Dover
Speedway and Saint Georges.

These storms will contain gusty winds up to 45 mph, torrential
downpours and occasional cloud to ground lightning.

Locally heavy rainfall will lead to ponding of water on roadways and
poor visibility. Poor drainage flooding may occur with localized
rainfall amounts of one to three inches.

Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional
information and possible warnings from the National Weather Service.

LAT...LON 3969 7585 3981 7559 3970 7553 3964 7560
      3960 7561 3959 7560 3960 7558 3957 7557
      3959 7554 3962 7557 3967 7551 3930 7530
      3935 7534 3930 7543 3921 7540 3907 7540
      3907 7546 3942 7586
TIME...MOT...LOC 2013Z 240DEG 12KT 3963 7577 3935 7558 3917 7543

JRK

The office that day

Everything else NWS Philadelphia/Mount Holly issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 22, 8:05 PM EDT	Special Weather Statement	PHI	Ocean	25 min
Jul 22, 10:52 PM EDT	Areal Flood Advisory	PHI	Hunterdon, Mercer, Middlesex, Monmouth, Somerset	4 hr
Jul 23, 12:01 AM EDT	Coastal Flood Advisory	PHI	Atlantic, Burlington, Cape May, Cumberland, Middlesex, Monmouth and 1 more	25 hr
Jul 23, 3:16 PM EDT	Flash Flood Watch	PHI	Burlington, Camden, Gloucester, Hunterdon, Mercer, Middlesex and 6 more	15 hr
Jul 23, 3:43 PM EDT	Special Marine Warning	PHI		92 min
Jul 23, 4:29 PM EDT	Severe Thunderstorm Warning	PHI	Cape May, Cumberland	26 min
Jul 23, 4:39 PM EDT	Areal Flood Advisory	PHI	Cape May, Cumberland, Salem	4 hr
Jul 23, 4:40 PM EDT	Special Marine Warning	PHI		65 min
Jul 23, 4:48 PM EDT	Areal Flood Advisory	PHI	Chester, Delaware	4 hr
Jul 23, 5:22 PM EDT	Special Weather Statement	PHI	Delaware	23 min
Jul 23, 6:08 PM EDT	Special Weather Statement	PHI	Delaware	37 min
Jul 23, 6:53 PM EDT	Flash Flood Warning	PHI	Chester, Delaware	14 hr
Jul 23, 7:20 PM EDT	Flash Flood Warning	PHI	Berks, Chester, Montgomery	6 hr
Jul 23, 7:41 PM EDT	Flash Flood Warning	PHI	Bucks, Delaware, Montgomery, Philadelphia	6 hr
Jul 22, 10:18 PM EDT	Special Weather Statement	PHI	Caroline, Talbot	72 min
Jul 22, 11:26 PM EDT	Areal Flood Advisory	PHI	Caroline, Queen Anne's, Talbot	4 hr
Jul 23, 2:38 PM EDT	Special Weather Statement	PHI	Caroline, Kent, Queen Anne's, Talbot	67 min
Jul 23, 2:47 PM EDT	Severe Thunderstorm Warning	PHI	Caroline, Queen Anne's, Talbot	43 min
Jul 23, 2:53 PM EDT	Special Weather Statement	PHI	Cecil	52 min
Jul 23, 3:27 PM EDT	Special Weather Statement	PHI	Cecil	33 min
Jul 23, 3:31 PM EDT	Special Weather Statement	PHI	Dorchester	44 min
Jul 23, 3:53 PM EDT	Areal Flood Advisory	PHI	Cecil, Kent	4 hr
Jul 23, 5:40 PM EDT	Areal Flood Advisory	PHI	Cecil	4 hr
Jul 23, 5:47 PM EDT	Special Weather Statement	PHI	Cecil	28 min
Jul 23, 6:22 PM EDT	Special Weather Statement	PHI	Cecil	38 min
Jul 23, 6:26 PM EDT	Flash Flood Warning	PHI	Cecil	4 hr

Nearby

Areal Flood Advisories in Pennsylvania, 2017 Areal Flood Advisories in Maryland, 2017 Every areal flood advisory 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.