New Day One Is Out

Storms are already forming tonight across North Central Mississippi in advance of a warm front. Some of those will likely work their way across Northwest Alabama during the pre-dawn hours. This was expected. The Alabama storms should not become severe overnight, but will have lots of lightning and thunder, some gusty winds and even some hail.

The tornado probabilities are generally 15% across Central Alabama, severe wind probabilities are at 30% across much of central Alabama and the severe hail probabilities are at 45% over West Central and Southwest Alabama.

The new Day One Outlook from the Storm Prediction Center is out and it does have a moderate risk of severe weather for parts of our area.

Here is the text of the convective outlook…

SPC AC 150552

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1252 AM CDT FRI APR 15 2011

VALID 151200Z – 161200Z

…THERE IS A MDT RISK OF SVR TSTMS OVER PORTIONS OF MS AND AL…

…THERE IS A SLGT RISK OF SVR TSTMS OVER A LARGE PORTION OF THE
SERN STATES…TN AND OH VALLEYS…

…SYNOPSIS…

UPPER TROUGH CURRENTLY OVER THE CNTRL PLAINS WILL ADVANCE THROUGH
THE MIDDLE AND LOWER MS VALLEYS FRIDAY…REACHING THE TN AND OH
VALLEYS FRIDAY NIGHT. ATTENDANT SURFACE LOW WILL OCCLUDE OVER NRN MO
WHILE OCCLUDED/COLD FRONT ADVANCES EWD THROUGH THE MID-LOWER MS
VALLEYS. THIS BOUNDARY WILL LIKELY EXTEND FROM THE OH VALLEY INTO
THE SRN APPALACHIANS AND THE SERN STATES BY THE END OF THE PERIOD.
WARM FRONT WILL LIFT NWD THROUGH THE CNTRL GULF COAST STATES AND TN
VALLEY DURING THE DAY.

…SERN STATES…

SLY TRAJECTORIES EAST OF THE OCCLUDED LOW WILL ADVECT RICHER GULF
MOISTURE WITH MID 60S DEWPOINTS NWD THROUGH THE LOWER MS VALLEY AND
PORTIONS OF SERN STATES WARM SECTOR. THIS WILL CONTRIBUTE TO
MODERATE INSTABILITY AS BOUNDARY LAYER WARMS WITH MLCAPE FROM 1500
TO 2000 J/KG POSSIBLE FROM PARTS OF MS INTO CNTRL/SRN AL. POTENTIAL
COMPLICATING FACTOR IS LIKELIHOOD OF ONGOING STORMS FROM WRN TN
VALLEY INTO THE LOWER MS VALLEY EARLY FRIDAY. CURRENT THINKING IS
THAT STORMS MAY REINTENSIFY ALONG SRN END OF MCS AND NEW STORMS WILL
ALSO LIKELY REDEVELOP ALONG RESIDUAL OUTFLOW BOUNDARIES ACROSS MS
AND AL AS THE ATMOSPHERE DESTABILIZES.

STRONGER LLJ WILL SHIFT NWD THROUGH THE TN AND OH VALLEYS EARLY
FRIDAY IN ASSOCIATION WITH NEWD EJECTING LEAD VORT LOBE.
HOWEVER…LLJ MAY STRENGTHEN FARTHER SOUTH ACROSS MS/AL WITHIN EXIT
REGION OF UPPER JET THAT WILL ROTATE THROUGH BASE OF UPPER
TROUGH…MAINTAINING LARGE HODOGRAPHS IN WARM SECTOR AND NEAR
RETREATING WARM FRONT. POTENTIAL EXISTS FOR BOTH SUPERCELL AND
BOWING STRUCTURES AS STORMS REINTENSIFY DURING THE DAY. THREAT WILL
EXIST FOR TORNADOES…LARGE HAIL AND DAMAGING WIND WITH GREATEST
THREAT OF STRONG TORNADOES EXPECTED IN MODERATE RISK AREA. ACTIVITY
WILL SHIFT EWD THROUGH SRN PARTS OF THE GULF COASTAL STATES
OVERNIGHT WITH A CONTINUED SEVERE THREAT.

…TN THROUGH MID MS AND OH VALLEYS…

PARTIAL CLEARING IS EXPECTED FROM WRN TN…ERN MO INTO SRN AND CNTRL
IL IN WAKE OF EARLY CONVECTION ASSOCIATED WITH LEAD VORT MAX.
DIABATIC WARMING AND NWD ADVECTION OF UPPER 50S TO NEAR 60F
DEWPOINTS BENEATH COLD AIR ALOFT AND STEEP MID LEVEL LAPSE RATES
WILL CONTRIBUTE TO A RELATIVELY NARROW CORRIDOR OF MODERATE
INSTABILITY. DEEPER FORCING FOR ASCENT WITHIN DIVERGENT EXIT REGION
OF JET MAX ROTATING THROUGH UPPER TROUGH BASE WILL PROMOTE STORMS
REDEVELOPING ALONG EWD ADVANCING COLD/OCCLUDED FRONT FROM WRN TN NWD
THROUGH ERN MO AND IL DURING THE AFTERNOON. STRONG VERTICAL SHEAR
PROFILES WILL SUPPORT SUPERCELLS WITH VERY LARGE HAIL AND ISOLATED
TORNADOES POSSIBLE. ACTIVITY WILL SHIFT EWD THROUGH PORTIONS OF THE
TN AND OH VALLEYS BEFORE WEAKENING DURING THE EVENING AS THE
BOUNDARY LAYER STABILIZES.

..DIAL/COHEN.. 04/15/2011

Category: Alabama's Weather, Severe Weather