SPC AC 250724
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0224 AM CDT WED MAR 25 2009
VALID 271200Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN TX EWD INTO TN VALLEY
AND CNTRL GULF STATES...
...SYNOPSIS...
A SIGNIFICANT MIDLEVEL LOW IS FORECAST TO TRANSLATE EWD THROUGH THE
SRN PLAINS INTO THE LOWER MS VALLEY DURING THE DAY THREE PERIOD.
THIS SYSTEM WILL BE ACCOMPANIED BY A 100+ KT MIDLEVEL JET STREAK AND
INCREASING DIFFLUENT FLOW IN THE HIGH-LEVELS...BETWEEN CYCLONICLY
CURVED POLAR JET STREAK AND SUBTROPICAL JET SITUATED ALONG THE GULF
COAST. THE NET RESULT WILL BE INTENSE LARGE-SCALE FORCING FOR
ASCENT SPREADING EWD THROUGH OK/TX INTO THE LOWER MS VALLEY THROUGH
THE FORECAST PERIOD.
IN THE LOW LEVELS...LATEST GFS AND ECMWF DIFFER SLIGHTLY ON THE
TRACK AND INTENSITY OF ATTENDANT SURFACE LOW WITH THE GFS BEING THE
MOST PROGRESSIVE AND DEEPEST SOLUTION. BOTH MODELS HAVE INDICATED
FAIRLY GOOD RUN-TO-RUN CONSISTENCY WITH A BLEND OF THE TWO FOLLOWED
FOR THE SURFACE PATTERN. AS SUCH...IT APPEARS THE PRIMARY SURFACE
LOW WILL DEVELOP FROM N-CNTRL TX ENEWD THROUGH THE ARKLATEX BEFORE
MOVING MORE NNEWD TOWARD THE CONFLUENCE OF THE MS AND OH RIVERS.
TRAILING COLD FRONT WILL SHIFT EWD FROM ERN TX INTO THE LOWER MS
VALLEY WHILE ASSOCIATED WARM FRONT LIFTS NWD THROUGH THE TN VALLEY
TOWARD THE OH RIVER.
...ERN TX EWD INTO THE TN VALLEY AND CNTRL GULF STATES...
...POTENTIAL INCREASING FOR A SEVERE WEATHER OUTBREAK FRI AND FRI
NIGHT...
MODEL GUIDANCE CONTINUES TO INDICATE THAT A RATHER BROAD WARM SECTOR
WILL BECOME ESTABLISHED FRI FROM ERN TX EWD ACROSS THE GULF COAST
STATES WITH DEWPOINTS INCREASING THROUGH THE 60S TO PERHAPS AROUND
70 ALONG THE COAST. THIS MOISTURE WILL COMBINE WITH STEEP MIDLEVEL
LAPSE RATES...RESULTING IN A MODERATELY UNSTABLE AIR MASS BY
AFTERNOON.
TSTMS SHOULD BE ONGOING FRI MORNING BOTH WITHIN WARM SECTOR AND N OF
WARM FRONT FROM THE OZARK PLATEAU EWD INTO THE LOWER MS VALLEY.
ADDITIONAL TSTMS WILL DEVELOP THROUGH THE DAY ALONG AND AHEAD OF
COLD FRONT AS A BAND OF STRONG ASCENT ASSOCIATED WITH UPPER SYSTEM
OVERSPREADS FRONTAL ZONE. ACTIVITY WILL LIKELY CONSOLIDATE ALONG
COLD FRONT FRI NIGHT AS IT BEGINS TO ACCELERATE EWD THROUGH THE
LOWER MS VALLEY.
UNCERTAINTY STILL EXISTS WITH REGARD TO THE DOMINANT CONVECTIVE
MODE...DEGREE OF CONVECTIVE INSTABILITY...AND WHETHER ANY WEAKER
IMPULSES WILL PRECEDE PRIMARY UPPER TROUGH...POTENTIALLY INFLUENCING
THE EVOLUTION OF THE CONVECTIVE EVENT. HOWEVER...SHOULD A WARM
SECTOR ENVIRONMENT SIMILAR TO THE 25/00Z GFS ACTUALLY DEVELOP /I.E.
MLCAPE OF 1500-2500 J PER KG AND 0-1 KM SHEAR OF 30-40 KT/...THE
POTENTIAL WILL EXIST FOR A SIGNIFICANT TORNADO EVENT FRI AND FRI
NIGHT.
A CATEGORICAL SLIGHT RISK WILL BE INTRODUCED ATTM DUE TO THE
ABOVE-MENTIONED UNCERTAINTIES. HOWEVER...SHOULD MODEL GUIDANCE
REMAIN CONSISTENT WITH THE CURRENTLY FORECAST
THERMODYNAMIC/KINEMATIC PARAMETERS...AN UPGRADE TO AT LEAST MODERATE
RISK WILL BE REQUIRED IN SUBSEQUENT OUTLOOKS.
..MEAD.. 03/25/2009
CLICK TO GET WUUS03 PTSDY3 PRODUCT
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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