SWODY1
SPC AC 300056
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0756 PM CDT SUN APR 29 2007
VALID 300100Z - 301200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF WEST...WCNTRL
AND NCNTRL TX...
..WEST/WCNTRL AND NCNTRL TX...
LATEST WATER VAPOR IMAGERY SHOWS AN UPPER-LOW CENTERED NEAR EL PASO
TX WITH A LARGE MCS DEVELOPING OVER WEST AND NORTHWEST TX.
WIDESPREAD LARGE-SCALE ASCENT ASSOCIATED WITH THE UPPER-LOW AND
MODERATE INSTABILITY LOCATED ACROSS WEST AND CNTRL TX WILL SUSTAIN
THUNDERSTORM ACTIVITY OVERNIGHT. THE MCS SHOULD GRADUALLY MOVE EWD
WITH TIME REACHING THE HILL COUNTRY AND THE VICINITY OF DALLAS/FORT
WORTH BY LATE TONIGHT.
THE LATEST OBJECTIVE ANALYSIS SHOWS A 55 KT MID-LEVEL JET MOVING
NEWD AROUND THE BASE OF THE UPPER-LOW WITH A BROAD EXIT REGION OF
THE MID-LEVEL JET SPREADING ACROSS WEST-CNTRL TX ATTM. THE MID-LEVEL
JET IS CREATING MODERATE VERTICAL SHEAR ACROSS THE REGION AND THIS
COMBINED WITH THE INSTABILITY IN PLACE WILL BE SUFFICIENT FOR
SUPERCELLS. A SEVERE THREAT SHOULD CONTINUE OVERNIGHT AS THE
UPPER-LOW MOVES GRADUALLY EWD.
LATEST WSR-88D VWPS SHOW FAVORABLE LOW-LEVEL SHEAR ACROSS THE REGION
FOR TORNADOES. LOW-LEVEL SHEAR ON THE DEL RIO TX 00Z SOUNDING IS
IMPRESSIVE AND THIS SUGGESTS THE GREATEST TORNADO THREAT WILL EXIST
FROM THE DEL RIO TX AREA EXTENDING NWD TO NEAR SAN ANGELO TX THIS
EVENING. IN ADDITION...THE 00Z DEL RIO TX SOUNDING SHOWS STEEP
MID-LEVEL LAPSE RATES AROUND 8.0 C/KM WITH 0-6 KM SHEAR VALUES
AROUND 40 KT. THIS APPEARS REPRESENTATIVE OF THE ENVIRONMENT ACROSS
WCNTRL TX AND LARGE HAIL SHOULD ACCOMPANY SUPERCELLS THIS EVENING
AND POSSIBLY OVERNIGHT. THE GREATEST THREAT FOR LARGE HAIL SHOULD
EXIST OVERNIGHT IN THE DEL RIO AND EAGLE PASS TX AREAS AS LAPSE
RATES AND VERTICAL SHEAR INCREASE DUE TO THE EJECTING MID-LEVEL JET.
ISOLATED WIND DAMAGE WILL ALSO BE POSSIBLE WITH THE MORE ORGANIZED
STORM CLUSTERS AND BOWING LINE-SEGMENTS OVERNIGHT.
..MT AND WRN ND...
LATEST WATER VAPOR IMAGERY SHOWS WNWLY FLOW ACROSS THE NRN ROCKIES
AND A SUBTLE SHORTWAVE TROUGH IS LIKELY PRESENT IN THE FLOW. MODEL
FORECASTS IDENTIFY THIS TROUGH AND MOVE THE TROUGH EWD ACROSS THE
REGION THIS EVENING. LATEST OBJECTIVE ANALYSIS SHOWS A POCKET OF
MODERATE INSTABILITY LOCATED ACROSS CNTRL MT WHERE MLCAPE VALUES ARE
CURRENTLY AROUND 1000 J/KG. LARGE-SCALE ASCENT ASSOCIATED WITH THE
APPROACHING SHORTWAVE TROUGH AND THE INSTABILITY CURRENTLY PRESENT
SHOULD RESULT IN AN INCREASE OF THUNDERSTORM COVERAGE THIS EVENING.
A CLUSTER OF THUNDERSTORMS MAY DEVELOP AND MOVE EWD ACROSS ERN MT
INTO WRN ND DURING THE OVERNIGHT PERIOD.
FORECAST SOUNDINGS ACROSS THE REGION THIS EVENING SHOW STRONG
VERTICAL SHEAR PROFILES ASSOCIATED WITH A MID-LEVEL JET OVER THE NRN
ROCKIES AND SRN CANADA. IN ADDITION...LOW TO MID-LEVEL LAPSE RATES
ARE STEEP AND SFC TEMP-DEWPOINT DEPRESSIONS ARE LARGE. THIS SHOULD
RESULT IN HIGH-BASED THUNDERSTORMS CAPABLE OF PRODUCING STRONG GUSTY
WINDS AND HAIL. AS THE SHORTWAVE TROUGH MOVES EWD OVERNIGHT...A
MARGINAL SEVERE THREAT MAY AFFECT AREAS AS FAR EAST AS DICKINSON ND
ALONG THE I-94 CORRIDOR.
..UPPER MIDWEST...
LATEST SFC ANALYSIS SHOWS A COLD FRONT EXTENDING WSWWD ACROSS SRN WI
INTO NRN IA. AHEAD OF THE FRONT...AN AXIS OF INSTABILITY IS PRESENT
FROM CNTRL IA EXTENDING ENEWD INTO NW IL AND SRN WI. OBJECTIVE
ANALYSIS CURRENTLY SHOWS A LOW-LEVEL JET AHEAD OF THE FRONT AND
SCATTERED THUNDERSTORMS ARE DEVELOPING IN THE ENTRANCE REGION OF
THIS LOW-LEVEL JET. IN ADDITION...THE DAVENPORT IA 00Z SOUNDING
SHOWS A VEERED WIND PROFILE WITH VERY STEEP LOW-LEVEL LAPSE RATES
NEAR 9.0 C/KM. THIS WILL BE ENOUGH FOR A MARGINAL WIND DAMAGE THREAT
THIS EVENING AS STORMS MOVE ESEWD ACROSS THE REGION. MID-LEVEL LAPSE
RATES ALSO APPEAR SUFFICIENT FOR HAIL WITH THE STRONGEST STORMS. THE
THREAT SHOULD DIMINISH THIS EVENING AS TEMPS COOL AND INSTABILITY
DROPS ACROSS THE REGION.
.BROYLES.. 04/30/2007
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