SPC Day 1 update introduces slight risk from LA up to northern MS and northwestern AL:
http://DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0659 AM CST THU MAR 11 2010
VALID 111300Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF FL...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE LWR MS AND TN
VLYS...
...SYNOPSIS...
BROAD UPR CYCLONE CENTERED OVER THE LWR MO VLY WILL PERSIST OVER THE
CNTRL U.S THIS PERIOD AS SHORTWAVE IMPULSE NOW OVER AZ/NM CONTINUES
E/SE TO S TX AND THE LWR MS VLY. FARTHER S...SUBTROPICAL JET ALSO
WILL PERSIST FROM S TX ACROSS THE NRN GULF OF MEXICO INTO NRN FL.
AT THE SFC...IA LOW WILL OCCLUDE OVER THE UPR MS VLY AS TRAILING
COLD FRONT DECELERATES OVER LWR PORTIONS OF THE OH...TN...AND MS
VLYS. A SECONDARY LOW SHOULD FORM OVER THE LWR MS VLY LATER IN THE
PERIOD WITH THE APPROACH OF AZ/NM UPR IMPULSE. IN THE MEAN
TIME...WEAK WAVE ON W/E STNRY FRONT JUST S OF THE FL PANHANDLE
SHOULD TRACK E ALONG THE FRONT ACROSS NRN FL TO THE GA CSTL WATERS
BY EVE.
...FL AND SRN PARTS OF THE GULF COASTAL STATES TODAY/TONIGHT...
40+ KT SWLY LLJ ASSOCIATED WITH AFOREMENTIONED SFC WAVE AND BENEATH
EXIT REGION OF STRONG SUBTROPICAL JET WILL SHIFT E ACROSS THE NERN
GULF AND THE FL PENINSULA TODAY. THIS WILL ALLOW FAIRLY RICH
MOISTURE /SFC DEWPOINTS IN THE MID 60S F AND PW AOA 1.50 IN/ TO
OVERSPREAD NRN AND CNTRL FL S OF STALLED W/E FRONT/RAIN-REINFORCED
BOUNDARY. WEAK MID LVL LAPSE RATES AND CLOUDS
WILL...HOWEVER...LIMIT SBCAPE TO AOB 1000 J/KG.
LOOSELY-ORGANIZED CONVECTIVE SYSTEM NOW OVER THE CNTRL FL PANHANDLE
SWD INTO THE NERN GULF EXPECTED TO MOVE/DEVELOP SLOWLY EWD WITH
ASSOCIATED SFC WAVE THROUGH THE DAY. ADDITIONAL SHOWERS/STORMS
LIKELY WILL FORM S AND E OF THE MCS IN RESPONSE TO SFC HEATING OF
MOIST/CONFLUENT FLOW OVER THE FL PENINSULA.
DESPITE MODEST CAPE...GIVEN INCREASINGLY MOIST LOW-LVL ENVIRONMENT
AND DEGREE OF BOTH LOW-LVL AND DEEP SHEAR...SETUP WILL SUPPORT SHORT
LINES/CLUSTERS OF STORMS WITH EMBEDDED LEWPS/SUPERCELLS. THESE MAY
PRODUCE BOTH TORNADOES AND DMGG WIND GIVEN STRENGTH OF LWR
TROPOSPHERIC FLOW AND LARGE LOW-LVL HODOGRAPHS...ESPECIALLY DURING
THE AFTN. WHILE THE SVR THREAT MAY DIMINISH THIS EVE...THE THREAT
MAY INCREASE AGAIN LATER TONIGHT/EARLY FRI AS THE LLJ REDEVELOPS
AHEAD OF APPROACHING UPR IMPULSE.
...MID MS/LWR OH VLYS THIS AFTN...
LOBE OF ASCENT ROTATING AROUND MO VLY CLOSED LOW WILL MOVE ACROSS
THE IL AREA LATER THIS MORNING/EARLY THIS AFTN...ATOP NARROW
CORRIDOR OF LOW LVL MOISTURE /DEWPOINTS IN THE LWR 50S F AND PW
AROUND 1 IN/. SFC HEATING IN ASSOCIATED DRY SLOT MAY BOOST SBCAPE
TO AROUND 750 J/KG GIVEN COOL MID LVL TEMPERATURES. SETUP MAY
SUPPORT EARLY AFTN DEVELOPMENT OF STORMS ALONG SECONDARY COLD FRONT
NOW OVER E CNTRL MO AS THE BOUNDARY MOVES E OF THE MS RVR.
HOWEVER...12Z SGF RAOB AND SOME MODEL THERMAL FORECASTS SUGGEST THAT
A WARM LAYER MIGHT MOVE INTO THE REGION AROUND THE 700 MB LVL THAT
COULD LIMIT DEVELOPMENT. AT ANY RATE...ALTHOUGH WIND PROFILES WILL
NOT BE VERY CONDUCIVE TO SUPERCELLS...GIVEN THE THERMODYNAMIC
ENVIRONMENT...ONE OR TWO BANDS OF STRONG STORMS MAY FORM IF WARM
LAYER IS BREACHED. THESE COULD YIELD HAIL AND PERHAPS A SPINUP-TYPE
TORNADO OR TWO. ANY SUCH THREAT SHOULD END LATER IN THE DAY.
...
LWR MS AND TN VLYS LATE...
TRAILING PORTION OF STALLING COLD FRONT MAY SERVE AS A FOCUS FOR
STORM DEVELOPMENT LATE TONIGHT/EARLY FRI AS ASCENT WITH AZ/NM UPR
IMPULSE OVERTAKES MOIST AXIS LIKELY TO REMAIN PRESENT E OF THE MS
RVR. COUPLED WITH STEEP MID LVL LAPSE RATES AND MODERATE TO STRONG
DEEP SHEAR...STORMS MAY YIELD LARGE HAIL AND POSSIBLY DMGG WIND AS
THEY CONSOLIDATE INTO ONE OR TWO CLUSTERS. ..CORFIDI/SMITH.. 03/11/2010
Activity weakened to a band or rain and showers (without thunder for the most part) as it moved through Middle TN this morning. But, we might have to keep an eye out for any redevelopment later.
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