[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 051550
SWOMCD
SPC MCD 051550
INZ000-KYZ000-ILZ000-TNZ000-MSZ000-MOZ000-ARZ000-051745-

MESOSCALE DISCUSSION 0398
NWS STORM PREDICTION CENTER NORMAN OK
1050 AM CDT SUN APR 05 2009

AREAS AFFECTED...SE MO...IL...IN...WRN KY/TN

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 051550Z - 051745Z

AN APPRECIABLE INCREASE IN THE SEVERE THREAT THROUGH 18-19Z IS NOT
CURRENTLY ANTICIPATED.  HOWEVER...TRENDS WILL CONTINUE TO BE
MONITORED.

DESPITE A WEAK GULF MOISTURE RETURN...THE ENVIRONMENT IS
SUFFICIENTLY UNSTABLE FOR SCATTERED THUNDERSTORMS...WITH MID-LEVEL
FORCING FOR UPWARD VERTICAL MOTION SPREADING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...IN ADVANCE OF A VIGOROUS CLOSED LOW AND
ASSOCIATED UPPER TROUGH.  MUCH OF THE CONVECTIVE DEVELOPMENT HAS
BEEN FOCUSED AND BASED WITHIN A PRE-FRONTAL ELEVATED WARM ADVECTION
REGIME...EVEN SOUTH OF ST. LOUIS INTO SOUTH CENTRAL
ILLINOIS...WITHIN THE WARM SECTOR OF THE SURFACE LOW NOW MIGRATING
FROM EAST CENTRAL MISSOURI INTO CENTRAL ILLINOIS.  HOWEVER...FAIRLY
STEEP MID-LEVEL LAPSE RATES AND STRONG SHEAR WITHIN THE CONVECTIVE
LAYER...DOWNSTREAM OF A 100 KT 500 MB JET STREAK...HAVE CONTRIBUTED
TO OCCASIONAL STRONG/SEVERE CELLS WITH HAIL.

THIS ACTIVITY APPEARS LIKELY TO PERSIST...WITH A POSSIBLE TENDENCY
TO BEGIN TO DEVELOP MORE NORTHWARD THAN EASTWARD TOWARD CENTRAL
ILLINOIS/INDIANA...AS THE LARGE-SCALE FLOW BACKS WITH TIME THROUGH
EARLY AFTERNOON.  MODELS SUGGEST THAT THIS WILL OCCUR AS A SHORT
WAVE IMPULSE PIVOTING AROUND THE MID-LEVEL CIRCULATION TAKES ON MORE
OF A NEUTRAL TO NEGATIVE ACROSS THE OZARK PLATEAU INTO THE MIDDLE
MISSISSIPPI VALLEY.  THIS FORCING IS EXPECTED TO BE ACCOMPANIED BY
INCREASING NEW STORM DEVELOPMENT ALONG A COLD FRONT ADVANCING EAST
OF THE MISSISSIPPI RIVER...SOUTH OF ST. LOUIS THROUGH MEMPHIS...BY
THE 18-20Z TIME FRAME.  BUT...BOUNDARY LAYER DESTABILIZATION
SUPPORTIVE OF A SUBSTANTIAL INCREASE IN SEVERE WEATHER POTENTIAL MAY
NOT OCCUR UNTIL CLOSER TO PEAK AFTERNOON HEATING.

..KERR.. 04/05/2009

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

ATTN...WFO...LMK...IWX...IND...PAH...LOT...ILX...MEG...LSX...
DVN...LZK...SGF...

LAT...LON   37209135 38479069 39199032 40139043 41069044 41448951
            41598673 41008505 39498573 38188698 36988802 35588841
            34918930 34929140 37209135

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