Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 28

January 17, 20117 counties in Maryland; 25 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Jan 17, 2011, 7:44 PM EST for 7 counties in Maryland; 25 counties in Virginia. It was in force for 6 hr.

The area

The outline as issued.

The facts

Issued: Jan 17, 2011, 7:44 PM EST (00:44 UTC)
Expired: Jan 18, 2011, 1:45 AM EST
In force: 6 hr
Issued by: the Storm Prediction Center

All 32 counties

Anne Arundel County, MD, Baltimore County, MD, Charles County, MD, City of Baltimore, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Albemarle County, VA, Arlington County, VA, Buckingham County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, Culpeper County, VA, Cumberland County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Goochland County, VA, Greene County, VA, King George County, VA, Louisa County, VA, Madison County, VA, Nelson County, VA, Orange County, VA, Prince William County, VA, Spotsylvania County, VA, Stafford County, VA

The radar

The Sterling radar (KLWX), 43 km from the middle of the area, began a volume at 00:47 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, 0.7 hours before the alert went out and 39 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: 1527 m above ground
0-6 km bulk shear: 53 kt
0-1 km storm-relative helicity: 234 m²/s²
0-3 km storm-relative helicity: 306 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.

105 
ACUS11 KWNS 180045
SWOMCD
SPC MCD 180044
MDZ000-DCZ000-VAZ000-180645-

MESOSCALE DISCUSSION 0028
NWS STORM PREDICTION CENTER NORMAN OK
0644 PM CST MON JAN 17 2011

AREAS AFFECTED...NRN VA...CNTRL MD...WASHINGTON D.C.

CONCERNING...WINTER MIXED PRECIPITATION

VALID 180044Z - 180645Z

A SWATH OF PRECIPITATION WILL EXPAND NWD INTO NRN VA/MD AND THE
WASHINGTON D.C. METRO AREA THIS EVENING...WITH INITIAL P-TYPES OF
SNOW/SLEET EXPECTED TO TRANSITION TO FREEZING RAIN. LIQUID
PRECIPITATION RATES OF 0.05-0.10 IN/HR WITH LOCALLY HIGHER AMOUNTS
SHOULD PERSIST INTO THE EARLY MORNING.

WEAK ASCENT OCCURRING WITHIN A LOW-LEVEL WARM ADVECTION REGIME
/PRIMARILY CONFINED TO THE 900-800 MB LAYER/ WILL RESULT IN AN
EXPANSION OF A LARGE SWATH OF PRECIPITATION CURRENTLY OBSERVED OVER
SERN VA. SFC OBSERVATIONS INDICATE LARGE T-TD SPREADS VARYING
BETWEEN 10-20 DEG F ACROSS MUCH OF NRN VA AND CNTRL MD...WITH
TEMPERATURES GENERALLY IN THE LOWER-MID 30S. 00Z IAD RAOB INDICATES
THE THERMODYNAMIC PROFILE IS ENTIRELY BELOW FREEZING /SUPPORTIVE OF
SNOW/...AND IS SLIGHTLY COLDER IN THE 900-850 MB LAYER THAN NEARLY
ALL MODEL POINT FORECAST SOUNDINGS. AS LOW-LEVELS CONTINUE TO
MOISTEN AND WEAK ISENTROPIC ASCENT OCCURS COINCIDENT WITH
STRENGTHENING WARM NOSE NEAR 850 MB...THERMODYNAMIC PROFILES SHOULD
BECOME SUPPORTIVE OF FREEZING RAIN WITH TIME...WITH NEAR-SFC COLD
LAYER REINFORCED BY WET-BULB COOLING. CURRENT FORECAST SCENARIO IS
AN INITIAL P-TYPE OF SNOW /OCCASIONALLY MIXED WITH SLEET/
TRANSITIONING TO PREDOMINANTLY FREEZING RAIN.

..ROGERS.. 01/18/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PHI...AKQ...LWX...RNK...

LAT...LON   38697667 38217722 37727767 37497808 37407855 37727895
            38437839 39047758 39347712 39507682 39587660 39487631
            39187617 38697667

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jan 18, 12:29 AM EST	Mesoscale Discussion	SPC	Cecil, Harford	6 hr

Nearby

Mesoscale Discussions in Virginia, 2011 Mesoscale Discussions in Maryland, 2011 Every mesoscale discussion in 2011

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.