DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 101942
SWODY1
SPC AC 101940

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0240 PM CDT SUN MAR 10 2013

VALID 102000Z - 111200Z

...NO SVR TSTM AREAS FORECAST...

...DISCUSSION...
ONGOING FORECAST REMAINS ON TRACK...WITH A WEAK CONVECTIVE LINE NOW
ENTERING WRN TN/WRN MS AND CROSSING CENTRAL LA. DESPITE AMPLE SHEAR
AHEAD OF THE LINE...A LACK OF APPRECIABLE INSTABILITY PRECLUDES ANY
MORE THAN A VERY LOW-PROBABILITY SEVERE THREAT.

ELSEWHERE...ANY APPRECIABLE LIGHTNING POTENTIAL REMAINS UNLIKELY.

..GOSS.. 03/10/2013

.PREV DISCUSSION... /ISSUED 1106 AM CDT SUN MAR 10 2013/

...SYNOPSIS...
WITHIN A SEPARATE BELT OF WESTERLIES ACROSS CANADA...ONE VIGOROUS
SHORT WAVE TROUGH IS BEGINNING TO ACCELERATE NORTHEASTWARD OUT OF
NORTHWESTERN ONTARIO...AWAY FROM THE CENTRAL PLAINS CLOSED LOW...
WHICH IS EMBEDDED WITHIN LARGE-SCALE TROUGHING IN A MORE AMPLIFIED
BELT OF WESTERLIES ACROSS THE UNITED STATES. HOWEVER...IN THE
NORTHERN STREAM...ANOTHER STRONG SHORT WAVE TROUGH IS BEGINNING TO
DIG TOWARD THE CENTRAL CANADIAN/U.S. BORDER AREA...AND MODELS
SUGGEST THAT THIS WILL CONTRIBUTE TO THE NORTHEASTWARD ACCELERATION
OF THE CLOSED LOW TOWARD THE UPPER MIDWEST/UPPER GREAT LAKES REGION
LATER TODAY AND TONIGHT. AS THIS OCCURS...AN ASSOCIATED SURFACE LOW
OVER THE LOWER MISSOURI VALLEY IS FORECAST TO REDEVELOP
NORTHEASTWARD INTO THE GREAT LAKES REGION BY LATE TONIGHT. A
TRAILING SURFACE COLD FRONT SHOULD SURGE INTO THE LOWER MISSISSIPPI
VALLEY SOMETIME LATE THIS EVENING OR OVERNIGHT...OVERTAKING AN
INITIAL WEAK COLD FRONT GENERATED BY OVERNIGHT CONVECTION...WHICH IS
ALREADY BEGINNING TO ADVANCE INTO THE LOWER MISSISSIPPI VALLEY. AT
THE SAME TIME...UPPER TROUGHING TRAILING TO THE SOUTHWEST OF THE
MID-LEVEL LOW APPEARS LIKELY TO TAKE ON MORE OF A NEUTRAL TILT AS IT
PIVOTS ACROSS THE SOUTHERN PLAINS TOWARD THE LOWER MISSISSIPPI
VALLEY.

...LOWER MISSISSIPPI VALLEY...
THE LATEST MODEL AND OBSERVATIONAL DATA DO NOT OFFER MUCH IN THE WAY
OF ANY GREATER CERTAINTY CONCERNING SEVERE WEATHER POTENTIAL TODAY.
A WINDOW OF OPPORTUNITY DOES APPEAR TO EXIST FOR WEAK
DESTABILIZATION ALONG A NARROW AXIS FROM SOUTH CENTRAL LOUISIANA
COASTAL AREAS NORTHWARD ALONG THE MISSISSIPPI RIVER...THROUGH AT
LEAST THE NATCHEZ/VICKSBURG AREAS BY EARLY AFTERNOON. THIS MAY
ROUGHLY COINCIDE WITH THE SOUTHERLY 850 MB JET AXIS...BUT GUIDANCE
SUGGESTS THAT THE STRONGER JET CORE WILL BE IN THE PROCESS OF
SHIFTING NORTHWARD INTO THE LOWER OHIO VALLEY. FLOW COULD STILL
REMAIN AS STRONG AS 30-50 KTS...HOWEVER WINDS ARE EXPECTED TO BECOME
MORE UNIDIRECTIONAL WITH HEIGHT...ALSO CONTRIBUTING TO SHRINKING
LOW-LEVEL HODOGRAPH SIZE. MID/UPPER FORCING FOR UPWARD VERTICAL
MOTION ALSO REMAINS AN UNCERTAINTY DURING THE PERIOD OF PEAK
BOUNDARY LAYER DESTABILIZATION. UPPER FLOW IS AT LEAST WEAKLY
DIFLUENT ACROSS THE LOWER MISSISSIPPI VALLEY...BUT FORCING
ASSOCIATED WITH AN INITIAL IMPULSE PIVOTING AROUND THE CENTRAL
PLAINS CLOSED LOW WILL CONTINUE TO GENERALLY SHIFT NORTH OF THE
REGION DURING THE DAY...WHILE STRONGER MID-LEVEL HEIGHT FALLS
ASSOCIATED WITH THE UPSTREAM IMPULSE DO NOT OCCUR UNTIL AFTER DARK.

IT IS POSSIBLE THAT BOUNDARY LAYER WARMING/MOISTENING ALONG THE
LEADING EDGE OF MID-LEVEL COOLING /AROUND 700 MB/...AND CONVERGENCE
ALONG THE EASTWARD ADVANCING SURFACE COLD POOL...COULD CONTRIBUTE TO
THE REGENERATION OF A NARROW LINE OF THUNDERSTORMS ROUGHLY BY THE
20-22Z TIME FRAME. IF THIS OCCURS ...SOME RISK FOR POTENTIALLY
DAMAGING WIND GUSTS MAY EXIST... MAINLY DUE TO DOWNWARD MOMENTUM
TRANSFER. BUT THE SEVERE THREAT STILL SEEMS TOO MARGINAL/UNCERTAIN
FOR SLIGHT RISK PROBABILITIES AT THE PRESENT TIME.

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