Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 261949
SWOMCD
SPC MCD 261948
ALZ000-MSZ000-LAZ000-262215-

MESOSCALE DISCUSSION 0152
NWS STORM PREDICTION CENTER NORMAN OK
0248 PM CDT THU MAR 26 2015

AREAS AFFECTED...PORTIONS OF SRN/E-CNTRL MS...SERN LA...SWRN/W-CNTRL
AL

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 261948Z - 262215Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...THE RISK FOR STRONG THUNDERSTORMS -- SOME POSSIBLY
REACHING MARGINALLY SVR THRESHOLDS -- WILL INCREASE DURING THE NEXT
COUPLE OF HOURS AND SPREAD EWD. THE MARGINAL/ISOLATED NATURE OF THE
SVR RISK SHOULD PRECLUDE WW ISSUANCE.

DISCUSSION...DESPITE WIDESPREAD CONVECTION NEAR AND OFF THE GULF
COAST...ANTECEDENT POLEWARD FLUXES OF PARTIALLY MODIFIED GULF
MOISTURE HAVE BEEN SUFFICIENT TO MAINTAIN LOWER 60S SFC DEWPOINTS
FROM SERN LA NEWD INTO SWRN/W-CNTRL AL. TRANSLUCENCY IN HIGH-LEVEL
CIRRUS DECKS AND EMBEDDED CLOUD BREAKS RELATED TO THE PREVIOUSLY
MENTIONED CONVECTION HAVE ENCOURAGED MODEST SFC-LAYER HEATING AMIDST
THE AFOREMENTIONED MOISTURE...SUPPORTING 500-1250 J/KG OF MLCAPE PER
MODIFIED 12Z RAOBS ACROSS THE LOWER MS VALLEY.

THE DIURNAL DIABATIC HEATING IS ALSO ENHANCING BAROCLINICITY ON THE
LEADING EDGE OF AN EWD-ADVANCING BAND OF MIDLEVEL ASCENT MARKED BY
SHOWERS AND ACCAS INVOF THE NATCHEZ TRACE PARKWAY CORRIDOR VICINITY.
WITH MLCINH NEARLY ERODED E OF THIS BAND...CONVECTION IS DEEPENING
WITH ISOLATED THUNDERSTORMS DEVELOPING ON THE ERN EDGE OF THE
ACCAS/SHOWERS BETWEEN BATON ROUGE AND NATCHEZ VICINITY. ADDITIONAL
CONVECTION HAS DEVELOPED FARTHER E ACROSS THE PINE BELT REGION IN
SERN MS. ALL OF THIS ACTIVITY WILL HAVE THE POTENTIAL TO INTENSIFY
WITH CONTINUED MODEST SFC HEATING...ESPECIALLY GIVEN THE EWD
ADVECTION OF H7-H5 LAPSE RATES AROUND 7.0-8.5-C/KM -- SAMPLED
UPSTREAM BY 12Z RAOBS AT SHV AND LCH RELATED TO A REMNANT EML.
INCREASING LARGE-SCALE ASCENT PRECEDING A MIDLEVEL SHORTWAVE TROUGH
AMPLIFYING INTO THE LOWER MS VALLEY WILL ALSO ENCOURAGE SUCH UPTICK
IN CONVECTION...WHILE ALSO OFFERING 45-55 KT OF EFFECTIVE BULK
SHEAR. OCCASIONALLY ORGANIZED CONVECTIVE STRUCTURES /POSSIBLE
SUPERCELLS/ WITH GENERALLY MARGINALLY SVR HAIL MAY OCCUR...AND
ISOLATED DMGG WIND GUSTS MAY ALSO BE POSSIBLE.

HOWEVER...WIDESPREAD CONVECTIVE OUTFLOW FROM GULF-COASTAL CONVECTION
IS STUNTING SFC HEATING/BOUNDARY-LAYER DESTABILIZATION TO SOME
EXTENT...WHICH MAY MITIGATE THE OVERALL SVR-TSTM POTENTIAL.
FURTHERMORE...AN APPROACHING BAROCLINIC ZONE FROM THE NW MAY ALSO
EVENTUALLY UNDERCUT CONVECTION -- SUPPORTING AN EROSION OF CAPE
AVAILABLE TO ANY ESTABLISHED UPDRAFTS. FOR THESE REASONS...WW
ISSUANCE IS UNLIKELY.

..COHEN/MEAD.. 03/26/2015

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

ATTN...WFO...BMX...MOB...JAN...LIX...

LAT...LON   30519153 31009129 32288939 32918811 32728696 31878711
            30798844 30519153



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