SWODY2
SPC AC 211715
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1215 PM CDT THU OCT 21 2010
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE SOUTHERN
AND CENTRAL PLAINS...
...SYNOPSIS...
MODELS CONTINUE TO ADVERTISE A BREAKDOWN OF THE WRN CONUS REX BLOCK
DURING DAY 1 AS A SHORTWAVE TROUGH MOVES INLAND RESULTING IN HEIGHT
FALLS ACROSS THE NRN EXTENT OF THE BLOCK. THE SWRN STATES CLOSED
LOW...BEING DISLODGED DURING DAY 1...WILL REMAIN PROGRESSIVE ON
FRIDAY...TRACKING FROM THE SRN HIGH PLAINS TO WRN/CENTRAL NEB BY
23/12Z. STRONG SWLY MID-UPPER LEVEL WINDS MOVING THROUGH THE BASE
OF THE LEAD TROUGH/CLOSED LOW WILL SPREAD ACROSS THE SRN PLAINS
DURING DAY 2.
IN THE LOW LEVELS...AN AREA OF LOW PRESSURE OVER SERN CO ALONG THE
LEE TROUGH AT 22/12Z WILL DEEPEN AS IT TRACKS ENEWD THIS FORECAST
PERIOD REACHING NWRN KS/SWRN NEB BY 23/12Z. TRAILING COLD FRONT
WILL MOVE EWD ACROSS W TX AND OK/TX PANHANDLES DURING THE DAY AND
INTO SWRN KS FRIDAY NIGHT. LATEST GUIDANCE CONTINUES TO SHOW AN
AREA OF HIGH PRESSURE SHIFTING SEWD FROM THE OH VALLEY...WITH
PRONOUNCED RIDGING EXTENDING SWWD ACROSS THE CENTRAL GULF OF MEXICO.
GIVEN THE NEWD TRACK OF THE SRN HIGH PLAINS SHORTWAVE TROUGH AND
TRAJECTORIES ATTENDANT TO THE SURFACE RIDGE...LOW LEVEL MOISTURE
RETURN WILL REMAIN CONFINED TO THE SRN/CENTRAL PLAINS.
...SRN/CENTRAL PLAINS...
AT 12Z FRIDAY...AN AREA OF SHOWERS/EMBEDDED TSTMS WILL LIKELY BE
ONGOING ACROSS THE SRN PLAINS FROM WRN/NRN TX THROUGH WRN/CENTRAL OK
TO PART OF SRN KS. DESPITE SOME MODEL DIFFERENCES WITH RESPECT TO
THE TEMPORAL EXTENT TO WHICH THE MORNING ACTIVITY PERSISTS...
INCREASING LOW LEVEL WAA ACROSS N TX AND OK INVOF STRENGTHENING SLY
LLJ AND WEAK CAPPING SUGGESTS CONVECTION SHOULD CONTINUE. SURFACE
HEATING MAY BE INHIBITED ACROSS MUCH OF OK DUE TO ATTENDANT
CONVECTIVE CLOUDINESS...WITH GREATER HEATING EXPECTED FROM WRN OK
INTO THE PANHANDLES AND N-S ALONG THE EXTENT OF THE COLD FRONT. THE
STEEPEST MIDLEVEL LAPSE RATES WILL REMAIN CONFINED TO THE SRN HIGH
PLAINS AND ALONG THE TRACK OF THE CLOSED LOW/TROUGH ADVANCING TOWARD
NEB. THESE THERMODYNAMIC FACTORS WILL AFFECT THE DISTRIBUTION OF
INSTABILITY WITH THE GREATEST VALUES OF MLCAPE /UP TO 1000-1500 J
PER KG/ EXTENDING FROM THE TX HILL COUNTRY NWD INTO THE TX
PANHANDLE/FAR WRN OK ALONG AND AHEAD OF THE FRONT FRIDAY AFTERNOON.
SOME MIDLEVEL COOLING ACROSS THE SRN PLAINS FRIDAY NIGHT SHOULD
SUPPORT MODERATE INSTABILITY DEVELOPING INTO N TX/OK AND ERN KS
DURING THAT PERIOD.
ALTHOUGH INSTABILITY WILL TEND TO BE WEAK ACROSS MUCH OF OK INTO THE
AFTERNOON...INCREASING EFFECTIVE BULK SHEAR ATTENDANT TO STRONGER
FLOW ALOFT SPREADING NEWD WILL SUPPORT SOME STORM ORGANIZATION WITH
A LOW PROBABILITY FOR HAIL AND DAMAGING WINDS.
LOW LEVEL HODOGRAPH CURVATURE WILL INCREASE THROUGH THE FORECAST
PERIOD ALONG THE LLJ...SUPPORTING AN ISOLATED TORNADO THREAT.
ADDITIONAL TSTMS ARE EXPECTED ALONG THE COLD FRONT FROM PARTS OF
CENTRAL TX NWD THROUGH THE TX PANHANDLE/WRN OK TO SWRN KS AS STRONG
FORCING FOR ASCENT SPREADS ACROSS THESE AREA FRIDAY AFTERNOON/
EVENING. EFFECTIVE BULK SHEAR ORIENTATION TO THE BOUNDARY WILL BE
SUCH THAT BOTH DISCRETE SUPERCELLS AND BOWS WILL BE POSSIBLE. ALL
SEVERE THREATS WILL BE EXPECTED INCLUDING A TORNADO THREAT AS LOW
LEVEL SHEAR INCREASES ALONG WRN EXTENT OF CORRIDOR OF STRENGTHENING
LOW LEVEL WINDS. FARTHER NW INTO SWRN KS...INSTABILITY WILL BE
WEAKER...BUT STEEPER MIDLEVEL LAPSE RATES AND GREATER HEIGHT FALLS
SHOULD COMPENSATE IN SUPPORTING A SEVERE WEATHER THREAT. THERE IS
SOME MODEL INDICATION THAT A LINEAR MCS WILL EVOLVE FRIDAY NIGHT AND
SPREAD ENEWD ACROSS N TX...OK AND ERN KS...WITH THE GREATEST SEVERE
WEATHER THREAT ACROSS OK/N TX WHERE INSTABILITY WILL BE HIGHER.
..PETERS.. 10/21/2010
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