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 Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point. | |
 Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point. | |
 Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point. | |
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SPC AC 151256
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0756 AM CDT FRI APR 15 2011
VALID 151300Z - 161200Z
...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF AL AND MS...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
AREA...FROM THE CNTRL GULF CST INTO THE MID MS AND LWR OH VLYS...
...SYNOPSIS...
POTENT CNTRL KS UPR LOW EXPECTED TO MOVE SLOWLY E INTO CNTRL MO THIS
EVE BEFORE CONTINUING E INTO CNTRL/NRN IL EARLY SAT. AS THIS
OCCURS...BAND OF 75+ KT 500 MB FLOW ON S SIDE OF SYSTEM EXPECTED TO
SPREAD E ACROSS THE LWR MS VLY LATER TODAY...AND NE ACROSS THE TN
VLY/SRN APPALACHIANS EARLY SATURDAY.
AT THE SFC...STRONG LOW NOW CENTERED NEAR KTOP SHOULD MOVE NNE TO
NEAR KMKE BY 12Z SAT AS ASSOCIATED COLD FRONT SWEEPS E ACROSS THE
OZARKS AND MID/LWR MS VLY LATER TODAY...AND ENE ACROSS THE OH AND TN
VLYS EARLY SATURDAY. AHEAD OF THE FRONT...A NE-SW SQLN THAT EVOLVED
FROM STORMS OVER OK AND AR YESTERDAY WILL BE ACCOMPANIED BY A
SIGNIFICANT OUTFLOW BOUNDARY THAT SHOULD BECOME QSTNRY FROM LA NEWD
INTO CNTRL MS/AL BY AFTERNOON. AT THE SAME TIME...A WEAK FRONT
MARKING THE LEADING EDGE OF RELATIVELY RICH RETURN FLOW WILL ADVANCE
ENE ACROSS MS THIS MORNING...ACROSS AL LATER TODAY...AND INTO GA
TONIGHT/EARLY SAT.
...SERN STATES...
SLY FLOW AHEAD OF COLD FRONT AND DECELERATING SQLN OUTFLOW BOUNDARY
WILL ALLOW INCREASINGLY RICH /PW AOA 1.25 INCHES/ MOISTURE TO SPREAD
NWD ACROSS THE CNTRL GULF CST REGION. COUPLED WITH MODEST DAYTIME
HEATING...THIS SHOULD YIELD MODERATE INSTABILITY WITH MLCAPE OF
1500-2000 J/KG LIKELY BY AFTERNOON FROM ERN LA AND CNTRL/SRN MS AND
AL.
ONGOING SQLN NOW IN NRN/WRN MS SHOULD CONTINUE GENERALLY ENEWD
THROUGH MIDDAY. THE NRN PART MAY SOMEWHAT WEAKEN AND BECOME
SLIGHTLY ELEVATED UPON ENCOUNTERING PARTLY MODIFIED POLAR AIR IN NRN
AL. BUT STORMS IN THE SRN PART MAY INTENSIFY AND BECOME SOMEWHAT
MORE DISCRETE AS THEY ENCOUNTER DESTABILIZING BOUNDARY LAYER OVER
ERN LA AND CNTRL/SRN MS. ADDITIONAL STORMS MAY FORM AHEAD OF THIS
ACTIVITY IN MOISTENING WARM SECTOR EWD INTO AL.
WHILE THE STRONGEST LOW-LVL FLOW IS STILL EXPECTED TO SHIFT NWD INTO
THE TN AND OH VLYS TODAY AHEAD OF KS/MO UPR LOW...AMPLE /40-50 KT/
CONFLUENT LOW-LVL FLOW WILL REMAIN/OVER MS/AL TO MAINTAIN
LONG...HOOKED HODOGRAPHS...ESPECIALLY AS STRONGER MID/UPR LVL FLOW
OVERSPREADS REGION A TOWARD MIDDAY. POTENTIAL WILL THEREFORE EXIST
FOR SUPERCELLS AND BROKEN LINE SEGMENTS/LEWPS POSING A THREAT FOR
TORNADOES...DMGG WIND...AND HAIL. ONE OR TWO OF THE TORNADOES COULD
BE STRONG AND LONG-LIVED GIVEN THE LIKELIHOOD THAT ONE OR TWO
DISCRETE STORMS WILL EVOLVE IN THE MOISTURE-RICH/STRONGLY-SHEARED
ENVIRONMENT OVER PARTS OF MS AND AL. THE SVR THREAT LIKELY WILL
PERSIST...ALBEIT IN A SOMEWHAT DIMINISHED FORM...THROUGH EARLY
SATURDAY AS THE BAND OF CONFLUENT LOW-LVL FLOW AND MOISTURE RETURN
PROGRESSES E INTO GA AND THE WRN CAROLINAS.
...TN INTO THE MID MS AND OH VLYS...
PARTIAL CLEARING SHOULD SPREAD NEWD FROM ACROSS ERN MO AND ERN AR
INTO PARTS OF IL...WRN KY...AND WRN TN IN WAKE OF OVERNIGHT SQLN.
DAYTIME HEATING AND MID-LVL COOLING /500 MB TEMPS AOB MINUS 15C/
ATOP LOW-LVL MOIST AXIS /WITH UPR 50S TO LOW 60S F
DEWPOINTS/ SHOULD YIELD A RELATIVELY NARROW CORRIDOR OF MODERATE
INSTABILITY...WITH MLCAPE AOA 1000 J/KG.
FORCING FOR ASCENT ASSOCIATED WITH UPR VORT NOW OVER NE OK WILL
OVERSPREAD REGION AROUND TIME OF MAX HEATING. THIS SHOULD FOSTER
STORM DEVELOPMENT ALONG AND PERHAPS AHEAD OF EWD-MOVING COLD
FRONT FROM FAR ERN MO/NE AR INTO WRN TN...WRN KY AND SRN/CNTRL IL BY
AFTERNOON. AMPLE DEEP SSWLY SHEAR WILL EXIST FOR SUPERCELLS...WITH
PROFILES EXPECTED TO BE MOST FAVORABLE FOR BROKEN LINE SEGMENTS.
EMBEDDED SUPERCELLS COULD YIELD LARGE HAIL IN ADDITION TO TORNADOES.
THE STORMS SHOULD MOVE E ACROSS PARTS OF THE TN AND OH VLYS BEFORE
WEAKENING DURING THE EVE.
..CORFIDI/HURLBUT.. 04/15/2011
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Originally Posted by wxchaser420
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