SWODY2
SPC AC 070552
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1152 PM CST SUN JAN 06 2008
VALID 081200Z - 091200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE OH VALLEY
INTO THE MID SOUTH...
..SYNOPSIS...
MIDLEVEL TROUGH OVER THE GREAT PLAINS TUESDAY MORNING IS FORECAST TO
INTENSIFY WHILE LIFTING NEWD THROUGH THE UPPER GREAT LAKES AND OH
VALLEY. THIS WILL OCCUR AS UPSTREAM JET STREAK/VORTICITY MAXIMUM
ROTATES THROUGH THE TROUGH BASE WITH SYSTEM BECOMING NEGATIVELY
TILTED DURING THE LATTER HALF OF THE PERIOD.
IN THE LOW LEVELS...INITIAL SURFACE LOW OVER LAKE MI/LOWER MI WILL
WEAKEN WITH TIME AS SECONDARY CYCLOGENESIS OCCURS BY TUESDAY
AFTERNOON/EVENING OVER IL/IND. THIS LOW WILL CONTINUE TO DEEPEN
TUESDAY NIGHT WHILE DEVELOPING NEWD INTO SWRN ONTARIO.
MEANWHILE...TRAILING COLD FRONT WILL ALSO STRENGTHEN TO THE S OF THE
DEEPENING CYCLONE...WITH THIS BOUNDARY RAPIDLY PUSHING THROUGH THE
MID MS VALLEY EWD ACROSS THE OH VALLEY BY WEDNESDAY MORNING. SRN
EXTENSION OF BOUNDARY IS NOT EXPECTED TO BE QUITE AS STRONG WITH A
SLOWER...MORE SWWD MOVEMENT THROUGH THE LOWER MS VALLEY.
..OH VALLEY INTO MID SOUTH...
MODEL GUIDANCE HAS TENDED TOWARD A MORE PROGRESSIVE AND LESS
AMPLIFIED CHARACTER TO ABOVE-MENTIONED TROUGH. MOREOVER...
SUBSEQUENT MODEL RUNS HAVE SHOWN A NWD SHIFT IN A PROGRESSIVELY MORE
UNSTABLE AIR MASS AHEAD OF COLD FRONT. THEREFORE... CONSIDERABLE
CHANGES HAVE BEEN MADE TO THIS FORECAST SINCE THE PRIOR DAY THREE
ISSUANCE.
CURRENT GOES SOUNDER IPW LOOP AND SURFACE OBSERVATIONS INDICATE THAT
A RELATIVELY WARM AND MOIST BOUNDARY LAYER HAS ALREADY BEEN
ESTABLISHED FROM THE LOWER MS VALLEY NWD INTO THE OH VALLEY AND SRN
GREAT LAKES WITH MID 50S DEWPOINTS INTO THE LOWER OH VALLEY AND 50 F
DEWPOINTS AS FAR N AS CNTRL LOWER MI. PERSISTENT SLY/SWLY LOW LEVEL
FLOW AHEAD OF COLD FRONT SHOULD MAINTAIN SIMILAR BOUNDARY LAYER
CONDITIONS INTO TUESDAY AFTERNOON WITH AIR MASS BECOMING AT LEAST
MARGINALLY UNSTABLE WITH MLCAPES GENERALLY LESS THAN 1000 J/KG.
TSTMS ARE EXPECTED TO BE ONGOING TUESDAY MORNING WITHIN PRE-FRONTAL
WARM SECTOR FROM PORTIONS OF IL/IND SWWD INTO THE LOWER MS VALLEY.
WHILE ISOLATED SEVERE WEATHER WILL BE POSSIBLE THROUGH THE MORNING
HOURS...MARGINAL INSTABILITY AND FORCING FOR ASCENT SHOULD LIMIT A
MORE SUBSTANTIAL THREAT. POTENTIALLY MORE SIGNIFICANT TSTM
DEVELOPMENT IS ANTICIPATED BY AFTERNOON OVER THE LOWER OH VALLEY
INTO THE MID SOUTH AS DEEP LAYER FORCING FOR ASCENT ASSOCIATED WITH
MIDLEVEL JET STREAK AND STRENGTHENING FRONTAL CIRCULATION BEGIN TO
ACT ON DESTABILIZING AIR MASS. FORECAST SOUNDINGS INDICATE THAT
VERTICAL SHEAR PROFILES WILL BE QUITE SUPPORTIVE OF EMBEDDED BOWING
STRUCTURES AND SUPERCELLS CAPABLE OF MAINLY DAMAGING WINDS AND
PERHAPS A FEW TORNADOES.
UPSCALE GROWTH INTO A STRONGLY FORCED SQUALL LINE IS ANTICIPATED
ALONG THE FRONT TUESDAY EVENING WITH THE DAMAGING WIND AND TORNADO
THREAT RAPIDLY SHIFTING EWD ACROSS SRN PORTIONS OF IL/IND AND WRN
PARTS OF KY/TN. THE POTENTIAL FOR LOCALLY DAMAGING WIND GUSTS MAY
CONTINUE INTO TUESDAY NIGHT INTO PARTS OF OH...CNTRL/ERN KY AND
MIDDLE TN...THOUGH IT APPEARS THAT ANY CONVECTIVE INSTABILITY WILL
BE QUITE SMALL AND ONLY LOW PROBABILITIES WILL BE INCLUDED ATTM.
..LOWER MS VALLEY...
AS MENTIONED ABOVE...CONSIDERABLE CHANGES HAVE BEEN MADE TO FORECAST
GIVEN RECENT MODEL TRENDS. ENVIRONMENT WILL REMAIN SUPPORTIVE OF
ORGANIZED...SEVERE STORMS INCLUDING SUPERCELLS GIVEN THE MOIST
BOUNDARY LAYER CONDITIONS AND MODERATELY STRONG VERTICAL SHEAR.
HOWEVER...THE STRONGER LARGE-SCALE FORCING FOR ASCENT IS FORECAST TO
REMAIN N OF THE REGION WHICH MAY TEND TO LIMIT THE COVERAGE AND
INTENSITY OF STORMS. IT APPEARS THAT A MORE ORGANIZED SEVERE THREAT
WILL LIKELY EXIST FROM NRN MS NWD...WITH MORE ISOLATED...SEVERE
STORM POTENTIAL OVER CNTRL/SRN MS INTO LA.
.MEAD.. 01/07/2008
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