SPC's Day 2 outlook:
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1148 PM CDT THU APR 23 2015
VALID 251200Z - 261200Z
...THERE IS AN ENH RISK OF SVR TSTMS ACROSS THE LOWER OH AND TN
VALLEY REGION...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENH RISK TO THE
GULF COAST...
...THERE IS A MRGL RISK OF SVR TSTMS FROM KS TO CNTL FL...
...SUMMARY...
SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP DURING THE AFTERNOON
ACROSS PORTIONS OF THE LOWER OHIO VALLEY AND TENNESSEE VALLEY. VERY
LARGE HAIL...DAMAGING WINDS...AND TORNADOES ARE POSSIBLE.
ISOLATED SEVERE THUNDERSTORMS ARE ALSO POSSIBLE ACROSS MUCH OF THE
GULF COAST REGION.
...LOWER OH/TN VALLEY REGION...
BAJA PENINSULA SHORT-WAVE TROUGH WILL EJECT NEWD INTO THE CNTRL/SRN
PLAINS DURING THE LATTER HALF OF THE DAY1 PERIOD...THEN INTO THE MS
VALLEY BY DAYBREAK SATURDAY. STRONG MID-LEVEL SPEED MAX...ON THE
ORDER OF 80KT...IS FORECAST TO TRANSLATE ACROSS AR TO NEAR THE TN/AL
BORDER BY EARLY AFTERNOON. 12HR HEIGHT FALLS NEAR 90M SHOULD SPREAD
NORTH OF THE SPEED MAX ACROSS THE LOWER OH/TN VALLEY REGION WITH
FOCUSED CORRIDOR OF FORCING FOR ASCENT EXPECTED ALONG A WARM FRONT
THAT WILL DRAPE ITSELF FROM SRN IL...INTO ERN KY.
SUBSTANTIAL WLY DEEP LAYER FLOW IS EXPECTED TO DRAW A PLUME OF STEEP
LAPSE RATES/DRY SLOT EWD ACROSS THE PLAINS INTO SRN MO/AR REGION
EARLY IN THE PERIOD. BY MID-DAY A FAIRLY WELL-DEFINED DRY LINE
SHOULD EXTEND FROM A SFC LOW OVER CNTRL MO...SWD INTO AR. STRONG
HEATING EAST OF THE DRY LINE IS EXPECTED IN THE WAKE OF
EARLY-MORNING MCS THAT SHOULD BE DRIVEN BY WARM ADVECTION. AS A
RESULT...THERE IS INCREASING CONFIDENCE THAT SUBSTANTIAL WARM SECTOR
RECOVERY WILL BE NOTED WITHIN VEERED FLOW REGIME SUCH THAT MODERATE
BUOYANCY AND STRONGLY SHEARED PARAMETER FIELDS WILL BECOME
SUPPORTIVE OF DISCRETE SUPERCELLS. WHILE THE STRONGEST FORCING IS
EXPECTED ALONG THE WARM FRONT...IMMEDIATELY AHEAD OF SFC LOW AS IT
TRACKS ESEWD ALONG THE BOUNDARY...STORMS THAT DEVELOP JUST SOUTH OF
THE WARM FRONT ACROSS KY AND TN SHOULD EASILY ROTATE AND VERY LARGE
HAIL AND TORNADOES ARE EXPECTED. CONDITIONS COULD EVOLVE SUCH THAT
A FEW STRONG TORNADOES ARE POSSIBLE. WILL CONTINUE TO MONITOR THIS
REGION FOR POSSIBLE INCREASE IN SEVERE PROBABILITIES IN LATER
OUTLOOKS.
...GULF COAST REGION...
SEVERE THREAT SOUTH OF AFOREMENTIONED MID-LEVEL SPEED MAX WILL BE
MORE NEBULOUS ACROSS THE GULF COAST STATES. LATEST THINKING IS A
SUBSTANTIAL EARLY MORNING MCS WILL TRACK ACROSS THE NRN GULF
STATES/TN VALLEY REGION WITH A TRAILING SFC BOUNDARY DRAPED SWWD
ALONG THE TX COASTAL PLAIN. STRONGEST LOW-LEVEL HEATING/STEEPEST
LAPSE RATES WILL FOCUS NORTH OF THIS REGION BUT DEEP-LAYER SHEAR
WILL PROVE SUPPORTIVE OF ORGANIZED ROTATING UPDRAFTS. IT/S NOT REAL
CLEAR HOW CONVECTION WILL EVOLVE ACROSS THIS REGION BUT CONVECTIVE
INHIBITION IS EXPECTED TO BE SUFFICIENTLY WEAK FOR SCT THUNDERSTORMS
TO INCREASE DURING THE DAY...ESPECIALLY FROM THE UPPER TX COAST INTO
PORTIONS OF SRN GA. GREATEST RISK WILL BE DAMAGING WINDS AND
PERHAPS A FEW TORNADOES...AS LAPSE RATES ARE EXPECTED TO BE WEAKER
ACROSS THIS REGION THAN FARTHER NORTH.
..DARROW.. 04/24/2015
NWS Huntsville:
ALONG WITH HEAVY RAINFALL...A SEVERE WEATHER POTENTIAL ALSO EXISTS
WITH THIS SYSTEM. WHETHER SEVERE WEATHER OCCURS IS DEPENDENT ON HOW
MUCH INSTABILITY IS REALIZED AFTER THE HEAVIEST RAIN DEPARTS TO THE
EAST ON SAT. AM KEEPING SKY COVER AS CLOUDY...BUT A FEW BREAKS DO
APPEAR POSSIBLE LATER SAT MORNING AND IN THE AFTERNOON. THIS COULD
RAISE HIGHS INTO THE UPPER 70S/NEAR 80. THIS WARMING WILL RESULT IN
GREATER ATMOSPHERIC INSTABILITIES. VARIOUS POINT SOUNDINGS FROM THE
NAM/GFS/HIRES ALSO SHOW CAPES RISING INTO THE 2000-2500 J/KG RANGE
WITH SIMILARLY ELEVATED CONVECTIVE NUMBERS TOO. HELICITY VALUES WILL
DECREASE SOMEWHAT DURING THE DAY...AKA 0-1KM NUMBERS BETWEEN 250-450
M/S AT DAYBREAK TO 150-250 IN THE AFTERNOON. BUT WITH BULK SHEAR
NUMBERS STAYING ABOVE 50KT (MOSTLY 60-75KT 0-6KM) IT IS SUGGESTIVE
THAT SEVERE WEATHER IS NOT OUT OF THE QUESTION. STORM MODE APPEARS
TO BE CELLULAR AS OPPOSED TO QLCS. SUCH STRONG SHEAR NUMBERS OF
COURSE MEANS DAMAGING WINDS...AND WET-BULB ZERO HEIGHTS BELOW 9000FT
COULD BRING LARGE HAIL FROM THE STRONGER STORMS TOO. A TORNADO
THREAT REMAINS TOO. PARTS OF OUR AREA HAVE BEEN HIGHLIGHTED IN AN
`ENHANCED` AREA IN THE SPC OUTLOOK FOR DAY-2...WITH A
CORRESPONDINGLY HIGHER TORNADO RISK. TIMING OF THE MORE INTENSE
CONVECTION WILL TAKE PLACE FROM LATE SAT MORNING TO THE EARLY
EVENING...MAINLY NEAR AND NORTH OF THE TENNESSEE RIVER. THE SEVERE
THREAT SHOULD WIND DOWN AFTER DUSK SAT AS THE STRONGER DYNAMICS
MOVES EAST OF THE FORECAST AREA.
NWS Atlanta:
THE SECOND ROUND OF CONVECTION IS EXPECTED TO DEVELOP IN THE MID TO
LATE AFTERNOON ALONG THE COLD FRONT. SURFACE INSTABILITY WILL REALLY
BEGIN TO INCREASE WITH HEATING DURING THE AFTERNOON...ESPECIALLY IN
AREAS WHERE THE CLOUDS ARE NOT AS THICK. AFTERNOON AND EVENING
CONVECTION WILL ALSO HAVE THE BENEFIT OF SOME UPPER JET SUPPORT
WITH STRONG UPPER DIVERGENCE. MID LEVEL LAPSE RATES WILL ALSO BE
FAIRLY DECENT. STRONG LOW LEVEL SHEAR WILL ALSO BE
PRESENT...MAINLY IN THE AFTERNOON. SO...CONDITIONS WILL BE
FAVORABLE FOR TORNADO DEVELOPMENT.
NWS Nashville:
SEVERE WEATHER A GOOD BET FOR SATURDAY AFTERNOON AS SOUTHWESTERN
U.S. UPPER TROUGH LIFTS OUT INTO THE CENTRAL AND SOUTHERN PLAINS
TONIGHT WITH AN 80 KNOT SPEED MAX NOSING INTO THE MID STATE BY
NOON SATURDAY. SHORT WAVE KICKS RAPIDLY FROM WEST TO EAST ACROSS
THE MID STATE FROM ABOUT NOON THROUGH 6 PM SATURDAY AFTERNOON.
WITH THE PROXIMITY OF THE WARM FRONTAL BOUNDARY AND SURFACE LOW
RIDING ALONG A SOUTHWARD SAGGING SURFACE BOUNDARY DURING THE AFTERNOON
COUPLED WITH AFOREMENTIONED SPEED MAX...ALONG WITH STRONG THERMODYNAMIC
INSTABILITIES SUCH AS SURFACE LI`S OF -7...AND MOST UNSTABLE CAPES
CLIMBING TO > 2K. SURFACE TEMPS SATURDAY AFTERNOON WILL CLIMB TO
NEAR 80 DEGREES BUT AIR MASS DOES DRY DURING THE AFTERNOON AND
THIS MAY LIMIT THE NUMBER OF SUPER CELLS. THERE IS A CAP THAT
FORMS AROUND 21Z BUT WITH STRONG FORCING NOT LIKELY TO HINDER
STORM DEVELOPMENT. MAIN THREAT FROM SEVERE STORMS WILL BE LARGE
HAIL AND DAMAGING WINDS BUT HAVE CONCERN FOR TORNADOES AS WELL.
BEST TIMING FOR SEVERE STORMS IN MIDDLE TENNESSEE WILL BE FROM
ABOUT NOON THROUGH 8 OR 9PM SATURDAY EVENING. THIS WILL BE A QUICK
HITTER IN TERMS OF STORM DEVELOPMENT AND TRANSITIONING INTO SUPER
CELLS...SO FOLKS NEED TO STAY ESPECIALLY ALERT DURING THE DAY
SATURDAY FOR WATCHES AND WARNINGS. UPPER TROUGH AND ATTENDANT
SHORT WAVE WORKS EAST OF MID STATE SATURDAY NIGHT BUT COLD FRONT
STILL HANGING BACK INTO CENTRAL ARKANSAS AS LATE AS MIDNIGHT
SATURDAY NIGHT AND DOESN`T CLEAR PLATEAU UNTIL AFTER 12Z SUNDAY.
SO KEPT A FEW SHOWERS IN FOR OVERNIGHT SATURDAY NIGHT AND ALONG
PLATEAU FOR EARLY SUNDAY.