SWOMCD
SPC MCD 161644
PAZ000-MDZ000-WVZ000-OHZ000-KYZ000-INZ000-161845-
MESOSCALE DISCUSSION 0318
NWS STORM PREDICTION CENTER NORMAN OK
1144 AM CDT FRI APR 16 2010
AREAS AFFECTED...PORTIONS WRN/CENTRAL PA...OH...NRN WV...SRN
INDIANA...EXTREME N-CENTRAL/NERN KY.
CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
VALID 161644Z - 161845Z
POTENTIAL WILL INCREASE THROUGH MID-AFTERNOON FOR SVR GUSTS FROM
SCATTERED/SFC-BASED TSTMS THAT ARE FCST TO DEVELOP OVER DISCUSSION
AREA. A COUPLE OF WWS MAY BE NEEDED TO COVER THIS CORRIDOR...GIVEN
BOTH ITS LENGTH AND MESOSCALE TIMING DIFFERENCES IN ENDING OF THREAT
FROM NW-SE DUE TO FROPA/CAA.
SFC MESOANALYSIS SHOWS COLD FRONT FROM SRN ONT SWWD ACROSS NWRN
OH...CENTRAL INDIANA AND SRN IL. THIS FRONT IS EXPECTED TO CONTINUE
MOVING SEWD ACROSS REMAINDER IL/INDIANA AND MOST OF OH THROUGH
AFTERNOON...AS STG NRN-STREAM TROUGH AMPLIFIES AND MOVES SEWD OVER
NRN ONT...LS AND LH. WINDS AHEAD OF FRONT WILL REMAIN NEARLY
UNIDIRECTIONAL THROUGH DEEP LAYER WITH STG SFC WLY COMPONENT.
HOWEVER...STRENGTHENING HEIGHT GRADIENT IS FCST IN 700-500 MB
LAYER...YIELDING ABOUT 50 KT FLOW...AND SPEED SHEAR FROM SFC INTO
THIS LAYER INCREASING TO 35-40 KT RANGE. MODIFIED RAOBS AND RUC
FCST SOUNDINGS SUGGEST MLCINH IS BECOMING WEAK IN POCKETS ACROSS
THIS AREA...A TREND THAT WILL EXPAND GIVEN CONTINUED PREFRONTAL/SFC
DIABATIC HEATING. MIXING ALSO WILL COUNTERBALANCE MOIST ADVECTION
ENOUGH TO KEEP SFC DEW POINT FIELD RATHER FRAGMENTED AND VARIABLE.
EXPECT UPPER 40S-MID 50S F DEW POINTS SUPPORTING MLCAPE INCREASING
TO 500-1000 J/KG RANGE...ATOP INVERTED-V SHAPES TO THERMODYNAMIC
PROFILES OF WELL-MIXED BOUNDARY LAYER SUPPORTING MAINTENANCE OF
DOWNDRAFT STRENGTH FROM CLOUD BASE TO SFC.
LACK OF MORE ROBUST LOW LEVEL CONVERGENCE AHEAD OF FRONTAL ZONE WILL
RESULT IN ERRATIC CONVECTIVE STRUCTURES...RANGING FROM DISCRETE
CELLS TO SMALL CLUSTERS AND LINE SEGMENTS. GREATEST POTENTIAL FOR
STG-SVR GUSTS WILL BE WHERE MULTICELL CONVECTION CAN GENERATE
SUSTAINED COLD POOLS...ALTHOUGH DAMAGING GUSTS CANNOT BE RULED OUT
IN BRIEF/ISOLATED DOWNBURSTS ASSOCIATED WITH SMALLER TSTMS.
DOWNDRAFTS AT ALL SCALES WILL BE TRANSFERRING MOMENTUM FROM REGION
OF STG 700 MB WINDS TO SFC.
..EDWARDS.. 04/16/2010
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...CTP...PBZ...RLX...CLE...JKL...ILN...LMK...IND...
PAH...
LAT...LON 39318751 40568390 41348027 41687836 40907746 39707950
38868161 38528288 38208494 38198692 39318751
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