Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 051258
SWOMCD
SPC MCD 051258
NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-051800-

MESOSCALE DISCUSSION 0124
NWS STORM PREDICTION CENTER NORMAN OK
0658 AM CST THU MAR 05 2015

AREAS AFFECTED...WV AND WESTERN/NORTHERN VA TO DC METRO/MD/SOUTHEAST
PA/NJ/DE

CONCERNING...HEAVY SNOW

VALID 051258Z - 051800Z

SUMMARY...INCREASINGLY HEAVY SNOW IS EXPECTED THROUGH LATE
MORNING/AFTERNOON WITH HEAVIER SNOWFALL RATES EXCEEDING 1
IN/HR...PARTICULARLY INCLUDING A CORRIDOR ACROSS SOUTHERN/EASTERN
WV...WESTERN/NORTHERN VA...FAR SOUTHEAST PA...THE DC METRO...NJ/MD
AND NORTHERN DE.

DISCUSSION...PRECIPITATION RATES WILL INCREASE ACROSS MUCH OF THE
CENTRAL APPALACHIANS AND MID-ATLANTIC STATES/DELMARVA VICINITY BY
MID/LATE MORNING AND AFTERNOON IN ASSOCIATION WITH AN AMPLIFYING
UPSTREAM SHORTWAVE TROUGH AND AMPLE ISENTROPIC LIFT/FRONTOGENETICAL
FORCING. NEAR-SURFACE SUB-FREEZING AIR CONTINUES TO STEADILY
PROGRESS SOUTHEASTWARD EARLY THIS MORNING...WITH THE SURFACE
WET-BULB 32F ISOLINE EXTENDING ACROSS FAR WESTERN/NORTHERN VA...NEAR
THE DC METRO AREA...TO NEAR PHILADELPHIA/CENTRAL NJ AS OF 12Z.

AS COLDER AIR IN THE LOW LEVELS CONTINUES TO TRANSITION
SOUTHEASTWARD...INCREASING FORCING FOR ASCENT COINCIDENT WITH A
FAVORABLE ELEVATED THERMODYNAMIC PROFILE FOR DENDRITIC GROWTH SHOULD
CONTRIBUTE TO A SCENARIO FAVORABLE FOR INCREASINGLY HEAVY
SNOW...WITH SOME SLEET ALSO INITIALLY POSSIBLE. SNOWFALL RATES ARE
LIKELY TO LOCALLY EXCEED 1 IN/HR WITHIN THIS CORRIDOR. THE 12Z
OBSERVED SOUNDING FROM WASHINGTON-DULLES SUBSTANTIATES THIS NOTION
WITH CONSIDERABLE COOLING HAVING OCCURRED BELOW 700 MB OVER THE PAST
12-HOURS...WITH ONLY A NEGLIGIBLE ABOVE-FREEZING ELEVATED LAYER
/AROUND 0.5C/ REMAINING AT 850 MB AS OF 12Z. OF NOTE RELATED TO
NUMERICAL GUIDANCE...THIS OBSERVED ELEVATED WARM LAYER AT KIAD WAS
AS MUCH AS 2-3C COLDER /750-700 MB/ THAN THE 06Z NAM POINT FORECAST
BUT SIMILAR TO THE 06Z GFS FORECAST PROFILE.

..GUYER.. 03/05/2015

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

ATTN...WFO...PHI...CTP...LWX...RNK...PBZ...RLX...

LAT...LON   37098013 37548142 38458163 40137779 40467420 39547430
            39267498 38447776 37098013




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