[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 281758
SWOMCD
SPC MCD 281758
TNZ000-KYZ000-ALZ000-INZ000-ILZ000-281930-

MESOSCALE DISCUSSION 0318
NWS STORM PREDICTION CENTER NORMAN OK
1258 PM CDT SAT MAR 28 2009

AREAS AFFECTED...PORTIONS OF THE LOWER OH AND TN RIVER VALLEYS

CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY

VALID 281758Z - 281930Z

SCATTERED TSTMS SHOULD DEVELOP BY 20-21Z ALONG A COLD FRONT
PROGRESSING EWD ACROSS THE LOWER OH AND TN RIVER VALLEYS. VERY
STRONG DEEP-LAYER SHEAR AMIDST MODEST SURFACE-BASED INSTABILITY WILL
RESULT IN SUPERCELLS PRODUCING TORNADOES...LARGE HAIL...AND DAMAGING
WINDS. A TORNADO WATCH WILL LIKELY BE ISSUED PRIOR TO 19-20Z.

17Z SURFACE ANALYSIS PLACED A 993 MB LOW NEAR SGF WITH AN ARCING
COLD FRONT FROM CGI TO TUP. BREAKS IN LOW-LEVEL STRATOCUMULUS AND
PRESENCE OF MID-LEVEL DRY SLOT HAS ALLOWED SURFACE TEMPERATURES TO
WARM TO AROUND 70 F ALONG AND AHEAD OF THE BOUNDARY...WHILE DEW
POINTS HAVE RISEN TO AROUND 60 F GIVEN DOWNWARD MIXING/ADVECTION.
WITH CONTINUED INSOLATION...MODIFIED RUC FORECAST SOUNDINGS SUGGEST
MLCAPES OF 600 TO 1200 J/KG WILL BE COMMON.

AS THE CYCLONE OVER THE OZARKS PIVOTS NEWD...LARGE-SCALE FORCED
ASCENT WILL INCREASE AS AN INTENSE /90 KTS AT 500 MB/ S-SWLY
MID-LEVEL JET OVERSPREADS THE REGION. TSTM INITIATION SHOULD OCCUR
BY 21Z...WHICH IS SUPPORTED BY 00Z 4-KM WRF-NSSL AND 12Z GFS. WITH
BACKED S/SELY LOW-LEVEL FLOW...DEEP-LAYER SHEAR WILL BE QUITE STRONG
/AOA 60 KTS/ AND WILL PROMOTE SUPERCELL DEVELOPMENT. FAVORABLE
LOW-LEVEL HODOGRAPHS WITH 0-1 KM SRH AOA 200 M2/S2 WILL SUPPORT
POTENTIAL FOR TORNADOES. WHILE RELATIVELY STEEP MID-LAPSE RATES /AS
SAMPLED UPSTREAM BY 12Z LZK RAOB/ AND THE VERY STRONG SHEAR WILL
PROMOTE HAIL DEVELOPMENT AND LOCALLY DAMAGING WINDS.

..GRAMS.. 03/28/2009

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

ATTN...WFO...MRX...LMK...OHX...BMX...HUN...PAH...MEG...

LAT...LON   37768865 37418874 36708844 34868791 34188768 33918734
            33888682 33998633 34148605 34678581 35288564 36988595
            37948637 38238690 38188786 38108815 37768865



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