DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 131924
SWODY1
SPC AC 131922

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0222 PM CDT WED MAR 13 2013

VALID 132000Z - 141200Z

...NO TSTM AREAS FORECAST...

...DISCUSSION...
TSTMS ARE NOT EXPECTED IN THE CONUS THROUGH TONIGHT.

..GRAMS.. 03/13/2013

.PREV DISCUSSION... /ISSUED 1100 AM CDT WED MAR 13 2013/

...SYNOPSIS...MID ATLANTIC COAST REGION...
MODELS INDICATE THAT THE AMPLIFIED UPPER TROUGH OVER THE EASTERN
U.S. WILL GRADUALLY SHIFT EASTWARD ACROSS MUCH OF THE ATLANTIC
SEABOARD BY EARLY THURSDAY. AT THE SAME TIME...THE AXIS OF BROAD
UPSTREAM RIDGING...ENCOMPASSING MUCH OF THE WESTERN U.S. AND
ADJACENT EASTERN PACIFIC...APPEARS LIKELY TO SHIFT INLAND OF THE
PACIFIC COAST STATES. ASIDE FROM A PLUME OF HIGHER MOISTURE CONTENT
AIR IMPINGING ON PARTS OF THE PACIFIC NORTHWEST COAST...ON THE
NORTHWESTERN PERIPHERY OF THE RIDGE...PRECIPITABLE WATER IS
GENERALLY LOW ELSEWHERE. AND THE LARGE-SCALE PATTERN DOES NOT FAVOR
APPRECIABLE MOISTENING THROUGH REMAINDER OF THIS FORECAST PERIOD AND
BEYOND.

LOW-LEVEL LAPSE RATES...HOWEVER...ARE IN THE PROCESS OF BECOMING
RATHER STEEP ACROSS THE CENTRAL APPALACHIANS...AND TO THE EAST OF
THE BLUE RIDGE MOUNTAINS...IN RESPONSE TO SURFACE HEATING BENEATH
VERY COLD MID-LEVEL AIR ASSOCIATED WITH THE UPPER TROUGH.
ASSOCIATED DESTABILIZATION IS CONTRIBUTING TO WEAK CONVECTIVE
DEVELOPMENT THAT PROBABLY WILL OVERSPREAD MUCH OF THE MID ATLANTIC
COAST REGION BY EARLY THIS EVENING. DURING THE PEAK HEATING
HOURS...STRONGEST MID-LEVEL HEIGHT FALLS ARE FORECAST TO OVERSPREAD
EASTERN VIRGINIA/MARYLAND AND THE DELMARVA PENINSULA...WHERE THE
RISK FOR THUNDERSTORMS MAY NOT BE COMPLETELY NEGLIGIBLE.
HOWEVER...DUE TO THE SHALLOW NATURE OF THE CONVECTIVE
DEVELOPMENT...AND THE LOW SUPERCOOLED WATER CONTENT...SUGGESTED BY
FORECAST SOUNDINGS...PROBABILITIES APPEAR LESS THAN THE MINIMUM 10
PERCENT THRESHOLD FOR A CATEGORICAL THUNDERSTORM OUTLOOK.

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