MESO: Mesoscale Discussion 0475

ACUS11 KWNS 192248
SWOMCD
SPC MCD 192247
ILZ000-MOZ000-200015-

MESOSCALE DISCUSSION 0475
NWS STORM PREDICTION CENTER NORMAN OK
0547 PM CDT TUE APR 19 2011

AREAS AFFECTED...E-CNTRL/S-CNTRL MO...CNTRL IL

CONCERNING...TORNADO WATCH 154...

VALID 192247Z - 200015Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 154 CONTINUES.

LATEST SURFACE ANALYSIS PLACES LOW PRESSURE 45 NNW STL WITH A WARM
FRONT EXTENDING EWD FROM THE LOW TO NEAR SPI AND THEN EWD INTO WRN
IND 30 ENE HUF. A COLD FRONT EXTENDS S-SWD FROM THE LOW TO 10 NNW
TBN TO 15 SSE OF UMN. THE MOST VIGOROUS AND WIDESPREAD CONVECTIVE
DEVELOPMENT /INCLUDING DISCRETE AND SEMI-DISCRETE SUPERCELLS/ OVER
THE PAST HOUR HAS BEEN NOTED IN THE ERN SEMICIRCLE OF THE LOW WITHIN
60 NM OF THE LOW CENTER. BACKED SFC FLOW IN THIS REGION...ESPECIALLY
INVOF THE WARM FRONT...IS SUPPORTING STRONG LOW-LEVEL VERTICAL WIND
SHEAR AND EFFECTIVE SRH VALUES OF 300-400 M2/S2. THE SFC LOW IS
FORECAST TO SHIFT E-NEWD INTO CNTRL IL DURING THE NEXT COUPLE OF
HOURS...WHERE PRESSURE FALLS AROUND 2 MB PER 2 HRS HAVE BEEN NOTED.
CORRESPONDINGLY...THE GREATEST THREAT FOR SUPERCELLS WITH DMGG WINDS
AND VERY LARGE HAIL /SUPPORTED BY MLCAPE VALUES AOA 2000 J PER KG
AND STRONG CLOUD-BEARING WIND SHEAR/ WILL OCCUR WITHIN A 60-NM-WIDE
AREA CENTERED ALONG A LINE FROM 45 WSW STL TO 5 ESE DEC THROUGH 00Z.
THIS INCLUDES THE ST LOUIS METRO AREA /ESPECIALLY NRN SECTIONS/
BETWEEN 23Z AND 00Z. TORNADOES WILL REMAIN A CONCERN...AS
WELL...ESPECIALLY WITH ANY SUPERCELLS THAT CAN REMAIN DISCRETE AND
MOVE EWD NEAR THE WARM FRONT.

FARTHER SOUTH ALONG THE COLD FRONT...THE PRESENCE OF SOME CINH HAS
RESULTED IN FAIRLY MORE ISOLATED COVERAGE OF STORMS...EXCEPT IN
S-CNTRL MO WHERE MID-LEVEL ASCENT IS MORE PRONOUNCED. THIS ACTIVITY
WILL MOVE NEWD AROUND 35-40 KT WHILE TRAVERSING STRONG INSTABILITY
AND EFFECTIVE BULK SHEAR MAGNITUDES AOA 45 KT...WITH BOTH LINEAR AND
DISCRETE SUPERCELL MODES FAVORED. DMGG WINDS...VERY LARGE HAIL...AND
TORNADOES WILL REMAIN THREATS WITH EFFECTIVE SRH VALUES OF 200-300
M2/S2.

..COHEN.. 04/19/2011

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

ATTN...WFO...PAH...ILX...LSX...SGF...

LAT...LON 36639334 37029352 37889301 39219169 40078987 40148779
39558755 38818782 38598878 38208970 37219104 36669171
36639334

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.