Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 192320
SWOMCD
SPC MCD 192319
IAZ000-MNZ000-NEZ000-SDZ000-200145-

MESOSCALE DISCUSSION 1733
NWS STORM PREDICTION CENTER NORMAN OK
0619 PM CDT FRI SEP 19 2014

AREAS AFFECTED...CNTRL/NERN NEB...SERN SD...CNTRL/NWRN IA...SRN MN

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 192319Z - 200145Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...THE AREA IS BEING MONITORED FOR THUNDERSTORM DEVELOPMENT
THIS EVENING...ALONG WITH SOME SVR RISK. CONVECTIVE TRENDS WILL
CONTINUE TO BE MONITORED...THOUGH WW ISSUANCE IS CURRENTLY UNLIKELY.

DISCUSSION...SFC OBSERVATIONS REVEAL A WIND-SHIFT AXIS EXTENDING
FROM A DIFFERENTIAL-HEATING INDUCED BAROCLINIC ZONE LYING W-E ACROSS
SRN MN...SWWD INTO SERN SD AND FARTHER SW THROUGH CNTRL NEB.
SFC-3-KM LAPSE RATES OF 8-9 C/KM EXTEND NEWD FROM THE CNTRL HIGH
PLAINS INTO CNTRL NEB...IN PROXIMITY TO THE WIND-SHIFT AXIS. AT THE
LEADING EDGE OF DEEP MIXING ASSOCIATED WITH THESE LAPSE
RATES...WHERE SFC TEMPERATURES HAVE BREACHED 90F IN SOME AREAS...VIS
IMAGERY INDICATES A WEAK-CONVERGENCE-MANIFESTED NARROW BAND OF
TOWERING CU. RELATIVELY REDUCED MLCINH OWING TO ANTECEDENT DIABATIC
SFC-LAYER HEATING MAY ALLOW FOR DEEPER CONVECTION TO BLOSSOM FROM
THIS CLOUD BAND IN THE NEXT FEW HOURS. HOWEVER...CAPPING ASSOCIATED
WITH AN EML THAT HAS OVERSPREAD THE AREA MAY MITIGATE THE POTENTIAL
FOR SFC-BASED CONVECTIVE DEVELOPMENT. STORMS MAY NOT MATERIALIZE
UNTIL LATER THIS EVENING TOWARD THE UPPER MS VALLEY...AS MODEST
COOLING ALOFT OCCURS IN CONCERT WITH SLIGHT AMPLIFICATION TO THE
MID/UPPER-LEVEL FLOW...THOUGH NOCTURNAL STABILIZATION OF THE PBL MAY
MITIGATE THE OVERALL SVR-TSTM POTENTIAL.

REGARDLESS...THE PRESENCE OF 1500-3000 J/KG OF MLCAPE ASSOCIATED
WITH STEEP...EML-RELATED MID-LEVEL LAPSE RATES OVERLYING
LOWER/MIDDLE 60S SFC DEWPOINTS E OF THE WIND-SHIFT AXIS BREEDS SOME
CONDITIONAL SUPPORT FOR A SVR-TSTM RISK. IF THUNDERSTORMS WERE TO
FORM...AMPLE DEEP SHEAR ASSOCIATED WITH 30-50-KT MID-LEVEL WLYS
SAMPLED BY AREA VWPS COULD SUPPORT ORGANIZED/SUSTAINED CONVECTION
WITH AT LEAST ISOLATED INSTANCES OF SVR HAIL/WIND.
ULTIMATELY...THERE IS LARGE UNCERTAINTY IN THE POTENTIAL FOR
SFC-BASED/SVR CONVECTION OWING TO THE LACK OF STRONGER DEEP-LAYER
FORCING FOR ASCENT AND THE ANTECEDENT CAPPING. AS SUCH...CONVECTIVE
TRENDS WILL CONTINUE TO BE MONITORED.

..COHEN/GOSS.. 09/19/2014

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

ATTN...WFO...MPX...DMX...FSD...OAX...GID...LBF...

LAT...LON   41200023 41480038 42049943 44109511 44179310 42899303
            41849500 41179890 41200023



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