Alert archive / Pennsylvania / Dense Fog Advisories in 2017

Dense Fog Advisory 1, NWS Philadelphia/Mount Holly

January 21, 20176 counties in New Jersey; 10 counties in Pennsylvania; Cecil County, Maryland

NWS Philadelphia/Mount Holly issued this dense fog advisory at Jan 21, 2017, 8:58 AM EST for 6 counties in New Jersey; 10 counties in Pennsylvania; Cecil County, Maryland. It was in force for 2 hr.

The area

The counties it named.

The facts

Issued: Jan 21, 2017, 8:58 AM EST (13:58 UTC)
Expired: Jan 21, 2017, 11:00 AM EST
In force: 2 hr
Issued by: NWS Philadelphia/Mount Holly

Counties Cecil County, MD, Atlantic County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Gloucester County, NJ, Salem County, NJ, Berks County, PA, Bucks County, PA, Carbon County, PA, Chester County, PA, Delaware County, PA, Lehigh County, PA, Monroe County, PA, Montgomery County, PA, Northampton County, PA, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 79 km from the middle of the area, began a volume at 13:55 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, 2.0 hours before the alert went out and 215 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: 621 m above ground
0-6 km bulk shear: 30 kt
0-1 km storm-relative helicity: 0 m²/s²
0-3 km storm-relative helicity: 116 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 Jan 21, 4:14 AM EST, 4 hours 44 minutes earlier.

Area forecast discussion, Jan 21, 4:14 AM EST, 4 hours 44 minutes before

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Hazardous weather outlook, Jan 21, 8:53 AM EST, 5 minutes before

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In the hours before

Special weather statement, Jan 21, 4:04 AM EST, 4 hours 54 minutes before

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Special weather statement, Jan 21, 8:34 AM EST, 24 minutes before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Jan 21, 3:30 AM EST	High Wind Watch	PHI	Atlantic, Burlington, Cape May, Middlesex, Monmouth, Ocean	24 hr
Jan 21, 8:51 AM EST	Marine Dense Fog Advisory	PHI		37 hr
Jan 21, 3:29 PM EST	Dense Fog Advisory	PHI	Atlantic, Burlington, Camden, Cape May, Cumberland, Gloucester and 10 more	22 hr
Jan 21, 3:41 PM EST	Gale Warning	PHI		43 hr
Jan 21, 3:41 PM EST	Storm Warning	PHI		52 hr

Nearby

Dense Fog Advisories in Pennsylvania, 2017 Dense Fog Advisories in New Jersey, 2017 Dense Fog Advisories in Maryland, 2017 Every dense fog 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.