[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 260049
SWOMCD
SPC MCD 260049
OHZ000-KYZ000-INZ000-TNZ000-260315-

MESOSCALE DISCUSSION 2202
NWS STORM PREDICTION CENTER NORMAN OK
0749 PM CDT SUN SEP 25 2011

AREAS AFFECTED...NWRN TN...WRN KY...CNTRL/SRN IND...FAR SWRN OH

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 260049Z - 260315Z

A MARGINAL SVR THREAT WILL EXTEND NNEWD INTO THE OHIO VALLEY REGION
DURING THE EVENING INTO THE OVERNIGHT HOURS...AND THE ISSUANCE OF A
WW IS UNLIKELY.

LATEST SFC ANALYSIS DEPICTS A WAVY FRONT EXTENDING FROM SWRN OH INTO
CNTRL/SWRN KY TO A 1004-MB SUBSYNOPTIC LOW OVER NWRN TN AND
EXTENDING FARTHER SWWD INTO ERN AR. STRONG SFC PRESSURE FALLS...ON
THE ORDER OF 2-3 MB PER 2 HRS...LIE WITHIN A NNE-SSW-ELONGATED ZONE
FROM CNTRL IND INTO WRN KY. THESE PRESSURE FALLS ARE IN RESPONSE TO
ASCENT OFFERED BY AN APPROACHING MID-LEVEL IMPULSE PIVOTING AROUND
THE SRN PERIPHERY OF THE LARGER CYCLONIC GYRE OVER THE MID-MS
VALLEY. THIS ASCENT IS BEING AUGMENTED BY MASS CONVERGENCE AT THE
EXIT REGION OF AN INTENSE SSWLY LOW-LEVEL JET /50 KT AT 1.5-KM-AGL
PER HOPKINSVILLE KY VWP DATA/...ENHANCED BY UPPER-LEVEL DIVERGENCE
WITHIN THE RIGHT-ENTRANCE REGION OF A JET MAX OVER NRN IND. AS THE
SFC LOW DEVELOPS TOWARD THE REGION OF MAXIMUM PRESSURE FALLS...AND
SFC WINDS ENE OF THE LOW CENTER VEER FROM ELY TO SLY/SSELY IN
RESPONSE TO ISALLOBARIC FORCING...THE FRONT WILL RETREAT NWD THROUGH
THE COURSE OF THE EVENING AND OVERNIGHT HOURS. THIS WILL ADVECT
MODESTLY RICHER BOUNDARY-LAYER MOISTURE /SFC DEWPOINTS IN THE MIDDLE
60S/ INTO THE OH VALLEY...POTENTIALLY RESULTING IN VERY WEAK
DESTABILIZATION. REGARDLESS...WIDESPREAD STRATIFORM
PRECIPITATION...ALONG WITH NOCTURNAL COOLING...WILL LARGELY SUPPRESS
ANY APPRECIABLE IN SITU DESTABILIZATION CONTRIBUTED BY MOISTURE
ADVECTION IN THE ABSENCE OF WEAKER MID-LEVEL LAPSE RATES.
FURTHERMORE...THE BULK OF DEEP-LAYER FORCING FOR ASCENT AND
CONVECTION WILL LIKELY BE CONFINED TO THE COOL SIDE OF THE
AFOREMENTIONED FRONT OWING TO THE STATIONARY NATURE OF THE MID-LEVEL
GYRE.

GIVEN THESE FACTORS...AN UPTICK IN ELEVATED/FORCED CONVECTION WILL
LIKELY PROGRESS NNEWD DURING THE NEXT SEVERAL HRS...POTENTIALLY
REACHING AS FAR NORTH AS THE I-70 CORRIDOR BY 03Z PER THE LATEST RUN
OF THE EXPERIMENTAL HRRR. STORM-SCALE ROTATION WILL BE POSSIBLE WITH
THE MORE VIGOROUS UPDRAFTS...OWING TO LONG/CLOCKWISE-CURVED
HODOGRAPHS PER AREA OBSERVED SOUNDINGS AND RUC FORECAST SOUNDINGS
/0-3 KM SRH VALUES EXCEEDING 300 M2 S-2/. STORMS WILL LIKELY REMAIN
ROOTED ABOVE THE STABLE BOUNDARY LAYER...OFFERING A VERY MINIMAL SVR
THREAT. HOWEVER...SHOULD A SUSTAINED STORM MANAGE TO INTERACT WITH
THE RETREATING FRONT AND BECOME ROOTED AT THE SFC...A BRIEF/WEAK
TORNADO OR SVR WIND GUST CANNOT BE ENTIRELY RULED OUT. WHILE
CONVECTIVE TRENDS WILL BE MONITORED...THE MARGINAL NATURE OF THE
THREAT WILL LIKELY PRECLUDE THE ISSUANCE OF A WW.

..COHEN.. 09/26/2011

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

ATTN...WFO...ILN...LMK...OHX...IND...PAH...MEG...

LAT...LON   39988462 38978489 37568600 36248719 36378850 37728793
            39558692 40188583 39988462


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