Good evening everyone!
The Storm Prediction Center in Norman OK. has issued a SLIGHT risk for Severe Thunderstorms across parts of CNTRL TO EAST TX…LA…SRN AR AND SW MS…
…SRN PLAINS/LOWER MS VALLEY… AN UPPER-LEVEL TROUGH WILL QUICKLY PROGRESS EWD INTO THE SRN PLAINS ON SUNDAY.
AT THE SFC…A STRONG COLD FRONT WILL ADVANCE SWD ACROSS THE SRN PLAINS AND ARKLATEX BEING POSITIONED FROM NEAR THE TX HILL COUNTRY NEWD ACROSS EAST TX TO NEAR THE AR-LA STATE-LINE BY AFTERNOON.
WIDESPREAD ELEVATED CONVECTION SHOULD BE ONGOING NORTH OF THE BOUNDARY FROM THE RED RIVER VALLEY NEWD INTO THE OZARKS.
FURTHER SOUTH ALONG AND JUST AHEAD OF THE BOUNDARY…THE MODELS DIFFER CONCERNING THE TIMING OF INITIATION AND CONVECTIVE COVERAGE. THE NAM AND WRF-NMM4 SOLUTIONS KEEP CONVECTIVE COVERAGE MINIMIZED THROUGH LATE AFTERNOON WHILE THE GFS AND ECMWF APPEAR TO DEVELOP A LINE OR CLUSTER OF THUNDERSTORMS ALONG THE FRONT…MOVING THIS CONVECTIVE SYSTEM SEWD ACROSS THE SLIGHT RISK AREA EARLY SUNDAY EVENING.
DUE TO THE DIFFERENCES IN MODEL SOLUTIONS…THERE APPEARS TO BE UNCERTAINTY CONCERNING THIS UPCOMING EVENT. GFS FORECAST SOUNDINGS AT 00Z/MONDAY IN SOUTHEAST TX SHOW SFC DEWPOINTS IN THE MID TO UPPER 60S F WITH LAPSE RATES FROM 700 TO 500 MB NEAR 7.5 C/KM. THIS SHOULD BE ENOUGH FOR A POCKET OF MODERATE INSTABILITY LATE SUNDAY AFTERNOON FROM NEAR COLLEGE STATION SWD TO THE UPPER TX COAST WHERE MUCAPE SHOULD REACH THE 1000 TO 1500 J/KG RANGE.
IN ADDITION…0-6 KM SHEAR WILL INCREASE TO 50 TO 60 KT ACROSS SE TX AS THE UPPER-LEVEL SYSTEM APPROACHES MAKING CONDITIONS SUPPORTIVE OF SEVERE STORMS. SUPERCELL DEVELOPMENT WILL BE POSSIBLE DUE TO THE STRONG DEEP LAYER SHEAR BUT A QUICK TRANSITION TO A LINEAR CONVECTIVE SYSTEM SEEMS LIKELY ALONG THE FRONT DUE TO STRONG LOW-LEVEL CONVERGENCE.
IF A LINEAR MCS CAN ORGANIZE…THEN A SUBSTANTIAL WIND DAMAGE THREAT MAY DEVELOP SUNDAY AFTERNOON. THE POTENTIAL FOR AN ENHANCED WIND DAMAGE THREAT APPEARS MOST LIKELY FROM AUSTIN EXTENDING EWD INTO WRN LA AND SWD TO THE HOUSTON AREA. HAIL WILL ALSO BE POSSIBLE WITH THE MORE INTENSE CELLS WITHIN THE LINE.
A TORNADO OR TWO CAN NOT BE RULED OUT IF CELLS CAN REMAIN DISCRETE FOR A FEW HOURS DURING THE AFTERNOON. AT THIS POINT…UNCERTAINTY CONCERNING SEVERE THREAT COVERAGE IS SUBSTANTIAL. IF THE COLD FRONT MOVES SWD INTO THE SRN PLAINS FASTER THAN FORECAST…THEN THE SEVERE THREAT AREA WOULD BE SMALLER IN REGIONAL EXTENT.
THIS COULD ALSO REDUCE TO AREAL EXTENT OF DESTABILIZATION IN TURN REDUCING SEVERE THREAT COVERAGE. DUE TO THESE CONCERNS…HAVE REDUCED THE SIZE OF THE 30 PERCENT SEVERE THREAT PROBABILITY TO FOCUS ON AREAS A BIT FURTHER SOUTH…
Based on my late afternoon / early evening analysis of severe weather forecast indices and parameters, and information displayed from F5 DATA Severe Weather Software, both analysis of the GFS and NAM – WRF model solutions indicate the highest potential for Severe Thunderstorms to develop, lie within the risk area, mainly over the portion for TX. AND within the 30% probability range. Current information also suggests Severe Thunderstorms may have a high potential just west of the 30% prob. area as outlined in blue area on the following map:
Cells that can maintain a supercell structure will most likely be in the blue area, with the highest probability of tornadic activity at the moment, being within the pink hatched area. This should also hold true for any QLCS that may develop. At the moment, the biggest threat appears once again to be damaging Severe Thunderstorm winds and gusts.
I am going to try and have an update very early in the a.m. as due to the job I am starting, I will not be available to update thereafter.
Have a blessed evening!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST / SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FL AMS
CERTIFIED SKYWARN OFFICIAL STORM SPOTTER (advanced)