Alert archive / Pennsylvania / Dense Fog Advisories in 2018

Dense Fog Advisory 19, NWS Philadelphia/Mount Holly

December 28, 2018Berks County, Chester County, Delaware County, Pennsylvania; New Castle County, Delaware

NWS Philadelphia/Mount Holly issued this dense fog advisory at Dec 28, 2018, 8:57 PM EST for Berks County, Chester County, Delaware County, Pennsylvania; New Castle County, Delaware. It was in force for 9 hr.

The area

The counties it named.

The facts

Issued: Dec 28, 2018, 8:57 PM EST (01:57 UTC)
Expired: Dec 29, 2018, 6:00 AM EST
In force: 9 hr
Issued by: NWS Philadelphia/Mount Holly

Counties New Castle County, DE, Berks County, PA, Chester County, PA, Delaware County, PA

The radar

The Philadelphia radar (KDIX), 108 km from the middle of the area, began a volume at 02:01 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

Wallops Is Stn, VA (KWAL), launched 00:00Z, 2.0 hours before the alert went out and 228 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 892 m above ground
0-6 km bulk shear: 54 kt
0-1 km storm-relative helicity: 181 m²/s²
0-3 km storm-relative helicity: 188 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this dense fog 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 dense fog advisory went out at Dec 28, 7:22 PM EST, 1 hour 35 minutes earlier.

Area forecast discussion, Dec 28, 7:22 PM EST, 1 hour 35 minutes before

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Hazardous weather outlook, Dec 28, 7:19 PM EST, 1 hour 38 minutes before

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In the hours before

Local storm report, Dec 28, 4:20 PM EST, 4 hours 37 minutes before

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Local storm report, Dec 28, 4:25 PM EST, 4 hours 32 minutes before

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Local storm report, Dec 28, 4:50 PM EST, 4 hours 7 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
450 PM EST FRI DEC 28 2018

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

0432 PM     FLOOD            2 NE WINSLOW TWP        39.68N 74.83W
12/28/2018                   CAMDEN             NJ   DEPT OF HIGHWAYS

            NJ DOT - TOC SOUTH: FLOODING ON US 30 BOTH
            DIRECTIONS AT CR 723/FLEMING PIKE (WINSLOW
            TWP) ALL LANES CLOSED.

&&

MPS

The office that day

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

Issued	Product	Office	Counties	Lasted
Dec 28, 10:48 PM EST	Areal Flood Warning	PHI	Cumberland	6 hr
Dec 29, 3:31 AM EST	Small Craft Advisory	PHI		12 hr
Dec 29, 6:42 AM EST	Areal Flood Warning	PHI	Cumberland, Salem	4 days
Dec 29, 4:11 PM EST	River Flood Warning	PHI	Essex, Morris, Passaic	7 days

Nearby

Dense Fog Advisories in Pennsylvania, 2018 Dense Fog Advisories in Delaware, 2018 Every dense fog advisory in 2018

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.