SPC MD 1826

MD 1826 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR THE ARK-LA-TEX AND PARTS OF EASTERN TX

MESOSCALE DISCUSSION 1826
NWS STORM PREDICTION CENTER NORMAN OK
0740 AM CST MON NOV 28 2016

AREAS AFFECTED...THE ARK-LA-TEX AND PARTS OF EASTERN TX

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 281340Z - 281615Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...THE RISK FOR SEVERE THUNDERSTORMS WILL SLOWLY INCREASE
THIS MORNING COINCIDENT WITH THE DIURNAL HEATING CYCLE AND INITIALLY
BE FOCUSED OVER NORTHEASTERN AND EASTERN TX.  THE
SEVERE-THUNDERSTORM THREAT WILL LATER SPREAD INTO PARTS OF WESTERN
LA AND SOUTHERN AR.

DISCUSSION...SUBJECTIVE SURFACE MESOANALYSIS PLACES A RESIDUAL FRONT
ADVANCING NORTH AND EAST AS A WARM FRONT OVER THE SABINE RIVER
VALLEY.  RADAR MOSAIC THIS MORNING OVER SOUTHEASTERN TX HAS SHOWN
SHALLOW CONVECTIVE STREAMERS MOVING NORTH-NORTHEASTWARD INTO
EAST-CENTRAL TX.  OBSERVED SURFACE DEWPOINTS IN THE 68-70 DEG F
RANGE ARE COINCIDENT WITH THE AFOREMENTIONED FEATURES AND THIS
INDICATES RICHER LOW-LEVEL MOISTURE SURGING POLEWARD OVER THE TX
UPPER COASTAL PLAIN.  

THE COMPLICATING FACTORS CONCERNING THIS FORECAST CONSIST OF 1)
INITIAL TIMING OF SEVERE STORM DEVELOPMENT --RELATED TO DIURNAL
DESTABILIZATION PROCESSES-- AND 2) THE MAGNITUDE OF DESTABILIZATION
WHICH WILL AFFECT THE POTENTIAL FOR WARM SECTOR SEVERE.  WIDESPREAD
CLOUDS WILL TEND TO RETARD ROBUST HEATING SO ONLY GRADUAL
BOUNDARY-LAYER DESTABILIZATION IS EXPECTED.  FORECAST SOUNDINGS SHOW
MOIST AND DEEP BOUNDARY LAYERS WITH MLCAPE RANGING FROM 200-800 J/KG
DEVELOPING LATER THIS MORNING AS SURFACE TEMPERATURES WARM INTO THE
MIDDLE 60S AND LOWER 70S.  STORM INITIATION IN THE WARM SECTOR WILL
LIKELY BE ASSOCIATED WITH ONE OR MORE PROMINENT CONFLUENCE BANDS...AS
MOISTENING OCCURS BENEATH A WEAK CAPPING INVERSION.  ONCE ROBUST
UPDRAFTS ARE BECOMING ESTABLISHED AND SUPERCELL DEVELOPMENT APPEARS
IMMINENT...A TORNADO WATCH WILL LIKELY BE NEEDED.  A RISK FOR
ISOLATED LARGE HAIL AND DAMAGING WINDS WILL BE A PROBABLE
EARLY-STAGE THREAT...BUT AS STORMS MATURE...VERY LARGE
CLOCKWISE-CURVED HODOGRAPHS YIELDING 400+ M2/S2 0-1 KM SRH WILL
SUPPORT THE POTENTIAL FOR LOW-LEVEL MESOCYCLONES BEING CAPABLE OF A
COUPLE OF TORNADOES LATER TODAY.

..SMITH/EDWARDS.. 11/28/2016

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LZK...LCH...SHV...HGX...FWD...

LAT...LON   32159544 32869508 33759366 33619313 33079290 31319347
            30809398 30679484 30979555 32159544 

Read more

from SPC Forecast Products http://ift.tt/17x69Gc