SPC AC 221810
DAY 2 CONVECTIVE OUTLOOK CORR 2
NWS STORM PREDICTION CENTER NORMAN OK
0110 PM CDT THU APR 22 2010
VALID 231200Z - 241200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF AR...NRN LA AND
WRN MS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE LOWER MS
VALLEY...SRN PLAINS...OZARKS...MID MO VALLEY AND SRN PLAINS...
CORRECTED TO CHANGE WORDING LAST PARAGRAPH
...A SIGNIFICANT SEVERE WEATHER EVENT POSSIBLE LATE FRIDAY AFTERNOON
INTO FRIDAY EVENING ACROSS PARTS OF AR AND NRN LA...
...THE START OF A TORNADO OUTBREAK POSSIBLE LATE FRIDAY NIGHT INTO
SATURDAY MORNING POSSIBLE ACROSS THE ARKLATEX AND LOWER MS VALLEY...
...LOWER TO MID MS VALLEY...
A WELL-DEVELOPED SYSTEM OVER THE CNTRL ROCKIES WILL MOVE INTO THE
SRN PLAINS FRIDAY. AN IMPRESSIVE 80 TO 90 KT MID-LEVEL JET WILL
ROUND THE BASE OF THE UPPER-LEVEL TROUGH MOVING QUICKLY NEWD INTO
THE SRN PLAINS FRIDAY AFTERNOON. AS LARGE-SCALE ASCENT INCREASES
ACROSS THE ARKLATEX...A LOW-LEVEL JET IS FORECAST TO STRENGTHEN AND
MOVE NWD ACROSS LA INTO SRN AR. CONVECTION ASSOCIATED WITH THE
LOW-LEVEL JET SHOULD INITIATE ACROSS NRN LA AND SRN AR FRIDAY
AFTERNOON WITH THE STORMS EXPANDING QUICKLY IN COVERAGE ACROSS ERN
AR...NRN MS AND SRN MO. FORECAST SOUNDINGS FRIDAY AFTERNOON IN NRN
LA AND SRN AR SHOW MODERATE INSTABILITY...STRONG DEEP LAYER SHEAR
WITH 0-1 KM SHEAR AROUND 30 KT. THIS ENVIRONMENT SHOULD BE FAVORABLE
FOR SUPERCELLS WITH A POTENTIAL FOR TORNADOES ESPECIALLY IF THE
DEVELOPING STORMS BECOME SFC-BASED BY LATE FRIDAY AFTERNOON. AN
ISOLATED STRONG TORNADO ALONG WITH A SUBSTANTIAL WIND DAMAGE THREAT
WILL BE POSSIBLE AS STORMS MOVE QUICKLY NEWD OUT OF NRN LA ACROSS
ERN AR AND WRN MS FRIDAY EVENING.
DURING THE OVERNIGHT PERIOD...THE UPPER-LEVEL SYSTEM ACROSS THE
GREAT PLAINS IS FORECAST TO BECOME INCREASINGLY ORGANIZED. MODEL
FORECASTS DEVELOP A PRONOUNCED LOW-LEVEL JET ACROSS THE NW GULF OF
MEXICO FRIDAY NIGHT...MOVING THIS FEATURE QUICKLY NNEWD ACROSS LA
AROUND DAYBREAK SATURDAY. THUNDERSTORMS ARE FORECAST TO INITIATE
ALONG THE WRN EDGE OF THE LOW-LEVEL JET ACROSS EAST TX AFTER
MIDNIGHT WITH THIS CONVECTION SPREADING NEWD ACROSS THE ARKLATEX
LATE FRIDAY NIGHT INTO SATURDAY MORNING. INCREASING LARGE-SCALE
ASCENT ASSOCIATED WITH THE EXIT REGION OF AN APPROACHING MID-LEVEL
JET...STRONG VERTICAL SHEAR AND MODERATE INSTABILITY SHOULD MAKE
CONDITIONS VERY FAVORABLE FOR SUPERCELLS ACROSS THE ARKLATEX LATE IN
THE PERIOD. FORECAST SOUNDINGS ACROSS NRN LA AND SRN AR FROM 09Z TO
12Z SATURDAY SUGGEST LOW-LEVEL SHEAR WILL RAPIDLY BECOME FAVORABLE
FOR TORNADOES. THE SYNOPTIC SETUP ALONG WITH OUTPUT FROM VARIOUS
SEVERE PARAMETERS SUGGEST THAT A TORNADO OUTBREAK MAY START LATE
FRIDAY NIGHT ACROSS NRN LA...SRN AR...WRN MS AND POSSIBLY FAR NE TX.
TORNADOES WILL BE POSSIBLE WITH THE MORE DOMINANT DISCRETE
SUPERCELLS WITH A FEW STRONG TORNADOES POSSIBLE. IN ADDITION...LARGE
HAIL AND WIND DAMAGE APPEARS LIKELY WITH SUPERCELLS THAT DEVELOP
FRIDAY NIGHT.
THE MAIN UNCERTAINTY CONCERNING THE OUTBREAK POTENTIAL IS TIMING
WITH THE LOW-LEVEL JET LATE IN THE PERIOD. AT THIS POINT...MODEL
FORECASTS FOCUS THE LOW-LEVEL JET ACROSS THE ARKLATEX AND LOWER MS
VALLEY JUST BEYOND 12Z ON SATURDAY SUGGESTING THE POTENTIAL FOR A
TORNADO OUTBREAK COULD HOLD OFF UNTIL AFTER 12Z SATURDAY.
...MID-MO VALLEY/CNTRL PLAINS...
AN UPPER-LEVEL LOW IS FORECAST TO MOVE INTO THE CNTRL PLAINS FRIDAY
AS A CORRIDOR OF LOW-LEVEL MOISTURE SETS UP FROM ERN KS NWWD ACROSS
SRN NEB WHERE SFC DEWPOINTS SHOULD BE IN THE MID 50S TO LOWER 60S F.
MODEL FORECASTS DEVELOP MODERATE INSTABILITY FRIDAY AFTERNOON FROM
CNTRL NEB SEWD ACROSS ERN KS AND WRN MO. THUNDERSTORMS APPEAR LIKELY
TO INITIATE ALONG THE INSTABILITY AXIS LATE FRIDAY AFTERNOON WHERE
FORECASTS SOUNDINGS SHOW STEEP MID-LEVEL LAPSE RATES AND MODERATE TO
STRONG VERTICAL SHEAR FAVORABLE FOR SUPERCELLS. MLCAPE VALUES AROUND
2000 J/KG AND 850 TO 500 MB LAPSE RATES BETWEEN 7.0 AND 7.5 C/KM
SHOULD BE SUFFICIENT FOR LARGE HAIL. IN ADDITION...A THREAT FOR 2
INCH AND GREATER SIZE HAIL WILL BE POSSIBLE WITH THE MORE DOMINANT
SUPERCELLS ACROSS ERN NEB...FAR NE KS AND NW MO AS THE EXIT REGION
OF A MID-LEVEL JET MOVES INTO THE REGION FROM THE SOUTH LATE FRIDAY
AFTERNOON. A WIND DAMAGE THREAT MAY ALSO DEVELOP WITH SUPERCELLS AND
SHORT LINE-SEGMENTS EARLY FRIDAY EVENING.
..BROYLES.. 04/22/2010
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
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