Alert archive / Virginia / Frost Advisories in 2018

Frost Advisory 4, NWS Baltimore/Washington

October 21, 201813 counties in Virginia; 13 counties in Maryland

NWS Baltimore/Washington issued this frost advisory at Oct 21, 2018, 4:05 AM EDT for 13 counties in Virginia; 13 counties in Maryland. It took effect at Oct 22, 2018, 12:00 AM EDT. It was in force for 10 hr.

The area

The counties it named.

The facts

Issued: Oct 21, 2018, 4:05 AM EDT (08:05 UTC)
In effect from: Oct 22, 2018, 12:00 AM EDT
Expired: Oct 22, 2018, 10:00 AM EDT
In force: 10 hr
Issued by: NWS Baltimore/Washington

All 26 counties

Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Carroll County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Saint Mary's County, MD, Washington County, MD, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, King George County, VA, Loudoun County, VA, Orange County, VA, Spotsylvania County, VA, Stafford County, VA

The radar

The Sterling radar (KLWX), 30 km from the middle of the area, began a volume at 08:07 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 00:00Z, 8.1 hours before the alert went out and 22 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: 24 J/kg
Mixed-layer CIN: -68 J/kg
Mixed-layer LCL: 1927 m above ground
0-6 km bulk shear: 115 kt
0-1 km storm-relative helicity: 57 m²/s²
0-3 km storm-relative helicity: 102 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 frost advisory 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 frost advisory went out at Oct 20, 2:49 PM EDT, 13 hours 16 minutes earlier.

Area forecast discussion, Oct 20, 2:49 PM EDT, 13 hours 16 minutes before

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Hazardous weather outlook, Oct 20, 7:55 PM EDT, 8 hours 10 minutes before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Oct 20, 9:02 PM EDT	Special Marine Warning	LWX		88 min
Oct 20, 9:02 PM EDT	Special Marine Warning	LWX		88 min
Oct 20, 9:51 PM EDT	Special Marine Warning	LWX		46 min
Oct 20, 9:52 PM EDT	Special Marine Warning	LWX		44 min
Oct 20, 10:23 PM EDT	Special Marine Warning	LWX		52 min
Oct 20, 10:25 PM EDT	Special Marine Warning	LWX		50 min
Oct 20, 10:34 PM EDT	Special Marine Warning	LWX		86 min
Oct 20, 10:35 PM EDT	Special Marine Warning	LWX		85 min
Oct 21, 4:05 AM EDT	Freeze Warning	LWX	Albemarle, Amherst, Augusta, Culpeper, Fauquier, Greene and 15 more	30 hr
Oct 21, 12:45 PM EDT	Small Craft Advisory	LWX		17 hr
Oct 21, 7:17 PM EDT	Small Craft Advisory	LWX		39 hr

Nearby

Frost Advisories in Virginia, 2018 Frost Advisories in Maryland, 2018 Every frost 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.