DAY1SVR: Day 1 Convective Outlook Resent 1

ACUS01 KWNS 050828
SWODY1
SPC AC 050825

DAY 1 CONVECTIVE OUTLOOK RESENT 1
NWS STORM PREDICTION CENTER NORMAN OK
0225 AM CST THU DEC 05 2013

VALID 051200Z - 061200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
MODELS SUGGEST THAT STRONG MID-LEVEL HEIGHT FALLS...ASSOCIATED WITH
A VIGOROUS SHORT WAVE IMPULSE MIGRATING EAST NORTHEASTWARD OUT OF
THE NORTHERN PLAINS...WILL PROGRESS ACROSS THE UPPER GREAT LAKES
REGION EARLY IN THE PERIOD...BEFORE OVERSPREADING MUCH OF EASTERN
CANADA LATER TODAY INTO EARLY FRIDAY. AS THIS OCCURS...AN
ACCOMPANYING DEEP SURFACE CYCLONE LIKELY WILL CONTINUE TO DEEPEN
WHILE MIGRATING ACROSS SOUTHERN/EASTERN ONTARIO INTO THE VICINITY OF
JAMES BAY. IN ITS WAKE...VERY COLD SURFACE HIGH PRESSURE IS
EXPECTED TO CONTINUE TO BUILD ACROSS THE NORTHERN HIGH PLAINS...WITH
ITS SHALLOWER LEADING EDGE ADVANCING AS FAR SOUTH AND EAST AS THE
WESTERN GULF COAST/LOWER MISSISSIPPI VALLEY AND NORTHERN/CENTRAL
APPALACHIANS BY EARLY THIS EVENING...AND NORTHERN/MID ATLANTIC
COASTAL AREAS BY 12Z FRIDAY.

AT THE SAME TIME...WHILE AMPLIFIED CYCLONIC MID/UPPER FLOW PERSISTS
ACROSS MUCH OF WESTERN INTO CENTRAL NORTH AMERICA...MODELS SUGGEST
THAT SUBTROPICAL RIDGING WILL BUILD ACROSS THE SOUTHERN AND EASTERN
GULF OF MEXICO THROUGH AREAS NEAR/EAST OF THE ATLANTIC SEABOARD. ON
THE WESTERN PERIPHERY OF ASSOCIATED LOW-LEVEL RIDGING...A RETURN
FLOW OF SEASONABLY HIGH MOISTURE CONTENT AIR APPEARS LIKELY TO
CONTINUE TO DEVELOP OFF THE GULF OF MEXICO. THIS PROBABLY WILL
CONTRIBUTE TO AN INCREASE IN THUNDERSTORM PROBABILITIES TODAY INTO
TONIGHT...MAINLY ACROSS PORTIONS OF THE SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY INTO THE VICINITY OF THE CENTRAL/SOUTHERN
APPALACHIANS. THE RISK FOR SEVERE STORMS MAY NOT BE COMPLETELY
NEGLIGIBLE AHEAD OF THE SOUTHEASTWARD ADVANCING COLD FRONT...ACROSS
PARTS OF THE CENTRAL GULF STATES AND TENNESSEE VALLEY NORTHWARD INTO
THE WESTERN SLOPES OF THE CENTRAL APPALACHIANS...BUT THIS POTENTIAL
STILL APPEARS RELATIVELY LOW.

...CNTRL GULF STATES NEWD INTO WRN SLOPES OF APPALACHIANS...
A NARROW CORRIDOR OF WEAK TO MODEST BOUNDARY LAYER DESTABILIZATION
APPEARS POSSIBLE ACROSS THE REGION TODAY...PRIOR TO THE PASSAGE OF
THE SURFACE COLD FRONT. WARM SECTOR DEEP LAYER FLOW FIELDS AND
SHEAR APPEAR SUFFICIENTLY STRONG TO SUPPORT AT LEAST LOW
PROBABILITIES FOR ORGANIZED SEVERE STORM DEVELOPMENT...INCLUDING
SUPERCELLS. HOWEVER...THEY MAY NOT BE PARTICULARLY STRONG FOR THE
SEASON...AND LARGE-SCALE FORCING TO SUPPORT WARM SECTOR STORMS
REMAINS UNCLEAR. SOUTH OF THE UPPER OHIO VALLEY...THE COLD FRONT
MAY CONTINUE TO ADVANCE EASTWARD/SOUTHEASTWARD BENEATH STEADY OR
EVEN SLOWLY RISING 500 MB HEIGHTS THROUGH AT LEAST THE FIRST HALF OF
THE PERIOD. EVEN IF FRONTAL FORCING BECOMES SUFFICIENT TO SUPPORT
THUNDERSTORM DEVELOPMENT...ACTIVITY MAY TEND TO BE QUICKLY UNDERCUT
BY THE FRONT. IN FACT...PRIMARY STORM DEVELOPMENT MAY BE DURING THE
LATTER HALF OF THE PERIOD ABOVE/TO THE COOL SIDE OF THE SHALLOW COLD
FRONT...WHERE LARGE-SCALE FORCING FOR ASCENT IS EXPECTED TO INCREASE
AHEAD OF A WEAKENING SHORT WAVE TROUGH PROGRESSING EAST OF THE
SOUTHERN ROCKIES.

..KERR/THOMPSON.. 12/05/2013

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