SWODY1
SPC AC 191943
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0243 PM CDT MON APR 19 2010
VALID 192000Z - 201200Z
...NO SVR TSTM AREAS FORECAST...
...PLAINS...
LITTLE CHANGE TO EARLIER FORECAST PACKAGE. DEEP CONVECTION IS STILL
EXPECTED TO DEVELOP OVER THE NEXT FEW HOURS ACROSS THE NRN/CNTRL
HIGH PLAINS...IMMEDIATELY DOWNSTREAM OF DIGGING UPPER VORT/SHORTWAVE
TROUGH. CU FIELD IS GRADUALLY EXPANDING ACROSS THE HIGHER TERRAIN
OF THE BLACK HILLS...AND ACROSS OTHER HIGHER RIDGES WHICH SHOULD
RESULT IN SCATTERED THUNDERSTORM DEVELOPMENT. GIVEN THE STEEP LAPSE
RATE ENVIRONMENT ROBUST UPDRAFTS CAPABLE OF GENERATING GUSTY WINDS
AND SOME HAIL REMAIN POSSIBLE.
...GULF COAST..
BOUNDARY LAYER HAS WARMED RAPIDLY ALONG THE GULF COAST FROM LA...EWD
INTO FL. AS A RESULT...ISOLATED THUNDERSTORMS HAVE RECENTLY
DEVELOPED A BIT FARTHER WEST THAN EARLIER EXPECTED ACROSS SRN LA.
FOR THIS REASON HAVE EXTENDED GENERAL THUNDER WWD ALONG THE I-10
CORRIDOR TOWARDS LCH. FORECAST SOUNDINGS SUGGEST UPDRAFTS SHOULD
REMAIN WEAK AND INDIVIDUAL CELLS WILL TEND TO PROPAGATE RANDOMLY
DRIVEN LARGELY BY OUTFLOW AND SEA BREEZE MOMENTUM.
..DARROW.. 04/19/2010
.PREV DISCUSSION... /ISSUED 1126 AM CDT MON APR 19 2010/
...CENTRAL HIGH PLAINS THIS AFTERNOON/EVENING...
A WEAK...BUT COMPLEX...SPLIT FLOW REGIME PERSISTS OVER THE
WRN/CENTRAL STATES WITH MULTIPLE FLOW STREAMS. THE NRN STREAM
EXTENDS WELL TO THE N IN CANADA...WHILE THE PRIMARY SRN STREAM
EXTENDS FROM NRN MEXICO TO S TX TO FL. IN BETWEEN...SEVERAL WEAK
PERTURBATIONS ARE MOVING SLOWLY EWD/SEWD FROM THE NRN/CENTRAL
ROCKIES TO THE NRN/CENTRAL PLAINS...WITH THE MOST PRONOUNCED WAVES
LOCATED OVER ERN MT AND ERN SD. IN THE LOW LEVELS...A WEAK LEE
TROUGH WILL PERSIST ACROSS THE HIGH PLAINS. THE LEE TROUGH IS
EXPECTED TO FOCUS ISOLATED TO WIDELY SCATTERED THUNDERSTORM
DEVELOPMENT THIS AFTERNOON/EVENING.
REGIONAL 12Z SOUNDINGS CONTINUE TO SHOW MIDLEVEL LAPSE RATES OF 7-8
C/KM...AND AFTERNOON TEMPERATURES IN THE MID-UPPER 60S WILL REDUCE
CONVECTIVE INHIBITION ALONG THE SURFACE TROUGH. HOWEVER...MLCAPE
WILL REMAIN RATHER MODEST /500-750 J PER KG/ AS A RESULT OF LIMITED
BOUNDARY LAYER MOISTURE /DEWPOINTS IN THE UPPER 30S TO LOWER 40S
WITH DAYTIME HEATING AND MIXING/. MEANWHILE...DEEP-LAYER VERTICAL
SHEAR WILL BE SUFFICIENT FOR SUPERCELLS WITH 30 KT WNWLY MIDLEVEL
FLOW ABOVE LOW-LEVEL SLY WINDS. THE NET RESULT WILL BE AN
ENVIRONMENT FAVORABLE FOR A FEW HIGH-BASED SUPERCELLS CAPABLE OF
PRODUCING HAIL APPROACHING 1 INCH IN DIAMETER...AS WELL AS STRONG
OUTFLOW WINDS.
...CENTRAL FL THIS AFTERNOON...
AN INITIAL WEAK COLD FRONT HAS MOVED S OF THE FL PENINSULA...WITH A
WEAK SECONDARY MOISTURE GRADIENT ACROSS CENTRAL FL. ALOFT...A WEAK
MID-UPPER TROUGH OVER THE NE GULF OF MEXICO WILL PROGRESS EWD OVER
FL THIS AFTERNOON. THE COMBINATION OF WEAK SEA BREEZE CIRCULATIONS
WITH DAYTIME HEATING...AND WEAK BACKGROUND ASCENT WITH THE
APPROACHING MIDLEVEL TROUGH...WILL PROMOTE SCATTERED THUNDERSTORM
DEVELOPMENT THIS AFTERNOON ACROSS CENTRAL FL. STILL...MIDLEVEL
LAPSE RATES REMAIN POOR OVER FL AND WILL SUBSTANTIALLY LIMIT
INSTABILITY AND ANY ATTENDANT THREAT FOR STRONG/SEVERE STORMS.
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