SWODY1
SPC AC 131948
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0248 PM CDT SUN MAR 13 2011
VALID 132000Z - 141200Z
...NO SVR TSTM AREAS FORECAST...
...OREGON COAST...
RADAR IMAGERY SHOWS AN INTENSIFYING LINE OF SHALLOW CONVECTION ALONG
THE COLD FRONT NOW APPROACHING THE NRN CA/SWRN OREGON COAST. INTENSE
WIND SHEAR PROFILES AND DOWNWARD MIXING WITHIN THE STORM CORES MAY
ALLOW FOR A FEW STRONG TO SEVERE WIND GUSTS WITH THIS LINE AS IT
AFFECTS THE COAST. VAD WINDS FROM MEDFORD SHOW 50 KT WINDS AROUND
500 M AGL. FOR MORE INFORMATION REF MCD 222.
IN ADDITION...EXPANDED GENERAL THUNDERSTORM AREA FARTHER NEWD ACROSS
CNTRL AND NERN OREGON AND INTO WA AS IT NOW APPEARS COOLING ALOFT
MAY BE SUFFICIENT FOR WEAK CONVECTION AS THE COLD FRONT AFFECTS THAT
AREA MAINLY 00-06Z.
...NRN TX...SRN OK INTO THE ARKLATEX...
ADDED A SMALL SEVERE HAIL AREA FOR N TX INTO SRN OK FOR THIS
EVENING.
SURFACE ANALYSIS SHOWS SURFACE BOUNDARY FROM NWRN TX ACROSS CNTRL OK
AND INTO NWRN AR. POCKETS OF HEATING WERE OCCURRING BENEATH THICK
CIRRUS NEAR THE DRYLINE/COLD FRONT INTERSECTION AND SWD ALONG THE
DRYLINE IN N TX. WHILE CAPPING IS EXPECTED TO PERSIST FOR SEVERAL
MORE HOURS...CONVERGENCE SHOULD HELP TO FORCE AT LEAST ISOLATED
THUNDERSTORMS ACROSS N TX AND SRN OK BY ABOUT 03Z. STEEP LAPSE RATE
PROFILES ALOFT AS WELL AS SUFFICIENT DEEP LAYER SHEAR SUGGEST LOW
END SEVERE HAIL WILL BE POSSIBLE WITH ANY STRONG STORMS THAT
DEVELOP.
..JEWELL.. 03/13/2011
.PREV DISCUSSION... /ISSUED 1122 AM CDT SUN MAR 13 2011/
...CNTRL/SRN PLAINS INTO LOWER MS VALLEY...
MIDLEVEL SHORT-WAVE TROUGH OVER THE CNTRL ROCKIES THIS MORNING WILL
AMPLIFY THROUGH THE D1 PERIOD WHILE TRANSLATING ESEWD THROUGH THE
CNTRL AND SRN PLAINS. AN ACCOMPANYING SURFACE LOW PRESSURE CENTER
IS FORECAST TO BECOME BETTER DEFINED OVER N-CNTRL TX BY AFTERNOON
PRIOR TO DEVELOPING NEWD ALONG WARM OR QUASI-STATIONARY BOUNDARY
INTO W-CNTRL AR BY MON MORNING. MEANWHILE...TRAILING COLD FRONT
WILL SURGE SEWD THROUGH CNTRL TX.
12Z REGIONAL SOUNDINGS INDICATED THE PRESENCE OF A WELL-DEFINED EML
AND ASSOCIATED CAP OVER THE SRN PLAINS SITUATED ATOP A GRADUALLY
MOISTENING WARM SECTOR CHARACTERIZED BY BOUNDARY LAYER DEW POINTS IN
THE 50S TO LOWER 60S. INITIAL TSTM DEVELOPMENT IS ANTICIPATED LATER
THIS AFTERNOON OVER PORTIONS OF SERN KS AND NERN OK AS FORCING FOR
ASCENT ATTENDANT TO APPROACHING MIDLEVEL SYSTEM BEGINS TO INTERACT
WITH A WEAKLY UNSTABLE ENVIRONMENT FOR PARCELS BASED ABOVE 800-MB.
SUBSEQUENT SURFACE-BASED /OR NEAR SURFACE-BASED/ STORM INITIATION
WILL LIKELY OCCUR THIS EVENING FROM PORTIONS OF S-CNTRL/SERN OK INTO
N-CNTRL/NERN TX AS CAP IS GRADUALLY ERODED BY LEADING EDGE OF
STRONGER MIDLEVEL HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT.
WIDESPREAD CLOUDINESS SHOULD TEMPER DAYTIME HEATING AND RESULTANT
AIR MASS DESTABILIZATION WITHIN DEVELOPING WARM SECTOR.
NONETHELESS...THE PRESENCE OF THE STEEP MIDLEVEL LAPSE RATES AND
MODEST BOUNDARY LAYER MOISTURE CONTENT MAY YIELD CORRIDORS OF
MODERATE INSTABILITY /I.E. MLCAPE APPROACHING 1000 J PER KG/ BY
EARLY EVENING INVOF THE RED RIVER...SUPPORTIVE OF A FEW STRONG TSTMS
CAPABLE OF SMALL HAIL AND LOCALLY GUSTY WINDS.
...NRN CA/PACIFIC NW COASTS...
A VERY INTENSE MIDLEVEL SHORT-WAVE TROUGH OVER THE NERN PACIFIC IS
FORECAST TO REACH THE COAST LATER TODAY PRIOR TO SHIFTING INTO
INTERIOR PARTS OF WA/ORE AND BRITISH COLUMBIA TONIGHT. A BAND OF
LOW-TOPPED CONVECTION WILL LIKELY ACCOMPANY PACIFIC COLD FRONT
MOVING ONSHORE BY LATE AFTERNOON INTO THIS EVENING WITH MORE OPEN
CELLULAR CONVECTION LIKELY CONTINUING TO AFFECT COASTAL AREAS WITHIN
POST-FRONTAL AIR MASS TONIGHT. VERY COLD MIDLEVEL TEMPERATURES
ATTENDANT TO THE SHORT-WAVE TROUGH WILL RESULT IN CONSIDERABLE
STEEPENING OF LAPSE RATES WITH MLCAPE VALUES APPROACHING 100-150
J/KG OVER WRN ORE. MOREOVER...FORECAST WIND PROFILES EXHIBIT STRONG
VERTICAL SPEED SHEAR WITH MORE THAN SUFFICIENT LOW AND DEEP-LAYER
SHEAR FOR STORM ORGANIZATION.
IT STILL APPEARS THAT THE MARGINAL INSTABILITY WILL PRECLUDE A
THREAT FOR A TORNADO OR TWO AND/OR LOCALLY DAMAGING WIND GUSTS.
HOWEVER...CONDITIONS WILL CONTINUE TO BE MONITORED FOR STRONGER THAN
FORECAST DESTABILIZATION WHICH MIGHT WARRANT INCLUSION OF LOW SEVERE
WEATHER PROBABILITIES IN SUBSEQUENT FORECAST UPDATES.
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