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| Mesoscale Discussion 483 |
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MESOSCALE DISCUSSION 0483
NWS STORM PREDICTION CENTER NORMAN OK
1256 PM CDT TUE APR 16 2013
AREAS AFFECTED...MUCH OF SRN OH/SERN IND/NERN KY/PART OF WRN WV
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 161756Z - 161930Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...POTENTIAL EXISTS FOR TSTMS MOVING EWD INTO AND/OR
DEVELOPING ACROSS THE MIDDLE-UPPER OH VALLEY THIS AFTERNOON WILL
INTENSIFY AND BECOME SEVERE. WW ISSUANCE IS POSSIBLE BY MID-LATE
AFTERNOON WITH DAMAGING WINDS AND HAIL BEING THE PRIMARY THREATS.
DISCUSSION...TRENDS IN LATE MORNING-EARLY AFTERNOON SURFACE ANALYSES
ACROSS THE OH VALLEY SHOWED A COLD FRONT ADVANCING EWD INTO NORTH
CENTRAL TO WEST CENTRAL OH...AND FAR SWRN IND. THE TRAILING PORTION
OF THIS BOUNDARY HAD REMAINED GENERALLY QUASI-STATIONARY FROM FAR
SRN IL THROUGH NWRN AR AND SOUTH CENTRAL OK. OBJECTIVE ANALYSES
INDICATED DESTABILIZATION UNDERWAY ACROSS THE WARM SECTOR WHICH
EXTENDED INTO THE MIDDLE AND UPPER PORTIONS OF THE OH VALLEY WITH
SURFACE DEWPOINTS INTO THE LOWER 60S BENEATH THE ERN EXTENT OF THE
STEEPER MIDLEVEL LAPSE RATES /7-7.5 C PER KM/. DESPITE GRADUAL
HEIGHT RISES AND SOME MIDLEVEL WARMING...FURTHER LOW LEVEL
MOISTENING SHOULD PROVE SUFFICIENT IN SUPPORTING A MODERATELY
UNSTABLE ENVIRONMENT ACROSS MOST OF THE DISCUSSION AREA BY PEAK
HEATING FOR STORMS TO BECOME SURFACE BASED.
MEANWHILE...A CLUSTER OF PERSISTENT TSTMS UPSTREAM OVER CENTRAL
IND...CENTRAL IL TO FAR EAST CENTRAL MO IS LOCATED N OF THE SURFACE
FRONT AND LIKELY ROOTED AROUND 850 MB PER RECENT RAP SOUNDINGS. THIS
ACTIVITY APPEARS TO BE SUPPORTED BY LOW LEVEL WAA AND ASCENT
ATTENDANT TO A SUBTLE MIDLEVEL IMPULSE.
TRENDS IN THE HRRR THIS MORNING AND THE 12Z 4 KM WRF-NSSL...DESPITE
TIMING DIFFERENCES IN THE LATTER MODEL...SUGGEST THE IND/IL STORMS
COULD DEVELOP A COLD POOL AS THIS ACTIVITY REACHES SERN IND INTO SRN
OH. ALTHOUGH LOW LEVEL WINDS ARE WEAKENING IN THE DISCUSSION
AREA...50 KT WLY MIDLEVEL WINDS WILL MAINTAIN SUFFICIENT BULK SHEAR
FOR STORMS TO BECOME ORGANIZED WITH ACTIVITY EVENTUALLY TRACKING
TOWARD THE ESE PRODUCING A THREAT FOR PRIMARILY DAMAGING WINDS AND
HAIL.
..PETERS/KERR.. 04/16/2013
ATTN...WFO...PBZ...RLX...CLE...JKL...ILN...LMK...IND...
LAT...LON 39168572 39928454 40688239 40518121 39578055 38818121
38158229 38188357 38388531 39168572
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