SWODY1
SPC AC 171236
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0736 AM CDT MON OCT 17 2011
VALID 171300Z - 181200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
AMPLIFICATION OF THE LARGE SCALE PATTERN IS UNDERWAY AS A DEEP
OCCLUDED LOW PERSISTS NEAR JAMES BAY...AND A PRONOUNCED SHORTWAVE
TROUGH OVER UT/WY/NW CO DIGS SEWD TO TX. AN INITIAL LEE CYCLONE
WILL DEVELOP SEWD ACROSS THE TX SOUTH PLAINS THROUGH LATE
AFTERNOON...AND THEN CONTINUE GENERALLY EWD ACROSS N TX EARLY
TONIGHT TO SRN AR BY EARLY TUESDAY IN ADVANCE OF THE MIDLEVEL
TROUGH. IN THE WAKE OF THE CYCLONE...A STRONG COLD FRONT WILL SURGE
SEWD ACROSS OK/TX.
...SRN/ERN OK AND VICINITY LATE THIS EVENING INTO EARLY TONIGHT...
LOW-LEVEL FLOW IN THE WARM SECTOR WILL REMAIN RELATIVELY WEAK SINCE
THE PRESSURE GRADIENT WILL BE REDUCED BY THE TROPICAL LOW NEAR THE
YUCATAN. STILL...VERTICAL SHEAR WILL BECOME SUFFICIENT FOR
ORGANIZED LINE SEGMENTS AND SUPERCELLS. HOWEVER...THE UNSTABLE WARM
SECTOR WILL BE LIMITED IN SPATIAL EXTENT BY MARGINAL MOISTURE RETURN
INTO TX. THUNDERSTORM DEVELOPMENT SHOULD ALSO BE CONFINED TO A LINE
ALONG THE COLD FRONT WHERE FOCUSED LOW-LEVEL ASCENT WILL BE
NECESSARY TO OVERCOME THE CAP BY LATE EVENING. THE WINDOW OF
OPPORTUNITY FOR DAMAGING WINDS AND LARGE HAIL APPEARS TO BE TOO
NARROW...AND THE MAGNITUDE OF THE THREAT TOO MARGINAL...TO WARRANT A
SLIGHT RISK AT THIS TIME FOR AREAS NEAR/SE OF I-44 IN OK/N TX.
...FL KEYS TODAY...
BANDS OF CONVECTION PERSIST ACROSS THE KEYS AND FL STRAITS TO THE
E/NE OF A TROPICAL LOW OVER THE EXTREME SE GULF OF MEXICO /N OF THE
YUCATAN CHANNEL/. RADAR DATA HAVE SHOWN SEVERAL SMALL SUPERCELLS
THIS MORNING AROUND THE KEYS...AND VERTICAL SHEAR REMAINS SUFFICIENT
FOR SUPERCELLS PER VWP OBSERVATIONS FROM KEY WEST. THE LONGER TERM
SUPERCELL/BRIEF TORNADO THREAT IS IN QUESTION...BUT WILL ADD A LOW
PROBABILITY TORNADO THREAT FOR THE FIRST HALF OF THE DAY...WITH
LATER ADJUSTMENTS PENDING THE EVOLUTION OF THE SE GULF LOW.
..THOMPSON/BOTHWELL.. 10/17/2011
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