SWODY1
SPC AC 171243
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0743 AM CDT WED AUG 17 2011
VALID 171300Z - 181200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CNTRL HIGH PLAINS...
...SYNOPSIS...
DEEP CYCLONE OVER SCNTRL CANADA WILL CONTINUE EAST WITH STRONGEST
HEIGHT FALLS AND DYNAMIC FORCING FOR ASCENT OCCURRING PRIMARILY
NORTH OF THE GREAT LAKES. IN THE WAKE OF THIS SYSTEM...A BELT OF
ZONAL/WLY MID LEVEL FLOW OF 40-50KT WILL EXIST FROM THE NRN GREAT
BASIN AND ROCKIES ACROSS THE NRN PLAINS...TO THE NORTH OF A BROAD
UPPER RIDGE CENTERED SOUTHEAST OF THE FOUR CORNERS REGION. THE COLD
FRONT ASSOCIATED WITH THE LOW IN CANADA WAS SITUATED FROM THE UPPER
MIDWEST SWWD TO KS AND THEN WWD AND NWWD...BANKED UP INTO THE HIGH
PLAINS/FRONT RANGE. A NUMBER OF WEAK PRESSURE TROUGHS AND RESIDUAL
CONVECTIVE OUTFLOW BOUNDARIES PRECEDE THE DEEPER STALLED SYNOPTIC
FRONT...FROM KS SOUTH ACROSS OK/TX/NM...BENEATH WEAKER FLOW ALOFT.
EXPECT DIURNAL STORM DEVELOPMENT AIDED BY MONSOON MOISTURE TRAPPED
WITHIN UPPER RIDGE ACROSS THE HIGHER TERRAIN OF THE SRN ROCKIES AND
MEXICAN ESCARPMENT TODAY. THE FRONT RANGE/ADJACENT HIGH PLAINS AND
SRN PLAINS WILL ALSO EXPERIENCE AT LEAST SCATTERED TSTM
DEVELOPMENT...SOME OF WHICH COULD BE SEVERE. ADDITIONALLY...A FEW
STRONGER STORMS COULD DEVELOP IN A NARROW WINDOW OF SPACE AND TIME
AS THE AFOREMENTIONED FRONT MAKES SOME EASTWARD PROGRESS ACROSS THE
MIDWEST THROUGH EARLY EVENING.
...CNTRL HIGH PLAINS...
A MOIST POST-FRONTAL AIR MASS AND SURFACE HEATING WILL RESULT IN AN
AXIS OF STRONG DESTABILIZATION FROM NERN NM ACROSS ERN CO AND INTO
THE NEB PANHANDLE THROUGH THE AFTERNOON. SBCAPE VALUES IN THIS
CORRIDOR ARE EXPECTED TO REACH 2000 J/KG BENEATH A MODEST CAP. WHILE
LARGE-SCALE FORCING FOR ASCENT WILL BE SUBTLE/WEAK...IT DOES APPEAR
THAT A WEAK PERTURBATION MAY BE MOVING EAST AROUND THE UPPER RIDGE
AXIS...OVER NV/UT THIS MORNING. BACKGROUND ASCENT WITH THIS
IMPULSE...COMBINED WITH TERRAIN INFLUENCES AND PERSISTENT
CONVERGENCE NEAR RESIDUAL FRONT...FROM ERN CO/WY INTO NEB...SHOULD
PROMOTE SCATTERED TSTM DEVELOPMENT LATER THIS AFTERNOON. ONCE
INITIATION IS UNDERWAY...VERTICAL SHEAR WILL CONTRIBUTE TO
PERSISTENT UPDRAFTS AS WEAK LOW LEVEL SLY FLOW IS TOPPED BY UP TO
40KT OF WLY TO WNWLY FLOW. A CONSISTENT SIGNAL FOR SEVERE STORM
DEVELOPMENT AMONGST LATEST GUIDANCE IS SITUATED FROM NERN CO INTO
NEB IN THE 21-00Z TIME FRAME...AND THEN INTO WRN KS DURING THE
00-03Z TIME PERIOD. THE NW FLOW/HIGH PLAINS PATTERN APPEARS
SUPPORTIVE OF SCATTERED SUPERCELLS WITH POTENTIALLY VERY LARGE HAIL
AND A COUPLE OF TORNADOES INITIALLY...THEN EVENING/LATE NIGHT
EVOLUTION INTO AN MCS OR TWO FROM SRN NEB ACROSS KS.
...SRN HIGH PLAINS/NERN NM ACROSS KS/OK...
LESS PERSISTENT AND MORE WIDELY SPACED STORMS APPEAR LIKELY FROM
NERN NM ACROSS KS/OK COINCIDENT WITH MAX HEATING NEAR RESIDUAL
BOUNDARIES...AND WITHIN/NEAR POCKETS OF GREATER INSTABILITY GIVEN
SOME AREAS OF CLOUDINESS THIS MORNING. WEAKER FLOW FIELDS ACROSS
THESE AREAS SUGGEST GENERALLY PULSE STORMS POSING A BRIEF THREAT FOR
STRONG TO DAMAGING DOWNBURSTS.
...MIDWEST...
AS MENTIONED ABOVE...A WINDOW OF OPPORTUNITY MAY OPEN FOR A COUPLE
OF STRONGER STORMS ACROSS IL/IND AS THE COLD FRONT MOVES INTO THESE
AREAS LATER TODAY. INSTABILITY WITHIN THE ZONE OF FRONTAL LIFT WILL
BE LIMITED BY MARGINAL MID LEVEL LAPSE RATES AS WELL AS LOW LEVEL
AIRMASS TRAJECTORIES EMANATING FROM DRIER/MORE STABLE REGIME
ASSOCIATED WITH RETREATING SURFACE RIDGE. ONLY A LOW PROBABILITY
WIND/HAIL THREAT WILL BE MAINTAINED ACROSS THE AREA WITH THIS
OUTLOOK.
..CARBIN/GRAMS/EDWARDS.. 08/17/2011
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