SWODY1
SPC AC 221958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT TUE MAY 22 2007
VALID 222000Z - 231200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL AND
NRN PLAINS...
..CNTRL AND SRN PLAINS...
A WELL ORGANIZED UPPER-LEVEL TROUGH IS EVIDENT ON WATER VAPOR
IMAGERY OVER THE WRN STATES. A MID-LEVEL JET IS LOCATED IN THE BASE
OF THE TROUGH AND THIS FEATURE WILL EJECT NEWD ACROSS THE CNTRL
PLAINS LATE THIS AFTERNOON. LIFT WILL INCREASE AHEAD OF THIS FEATURE
SUPPORTING MCS DEVELOPMENT THIS EVENING. AT THE SFC...A 1000 MB LOW
IS LOCATED OVER FAR SE CO WITH A FRONTAL BOUNDARY EXTENDING NWD
ACROSS WRN KS INTO WCNTRL NEB. SFC DEWPOINTS EAST OF THE BOUNDARY
ARE NEAR 60 F AND OBJECTIVE ANALYSIS SHOWS MODERATE INSTABILITY IS
ALREADY IN PLACE ACROSS THE MOIST AXIS. THUNDERSTORMS ARE ONGOING IN
ECNTRL CO AND THIS ACTIVITY SHOULD MOVE EWD INTO INCREASING
INSTABILITY AND GRADUALLY INTENSIFY LATE THIS AFTERNOON. OTHER
THUNDERSTORMS SHOULD INITIATE ALONG THE FRONTAL BOUNDARY IN WCNTRL
NEB LATE THIS AFTERNOON WITH CONVECTION INITIATING FURTHER SOUTH IN
WRN KS AS A CAPPING INVERSION WEAKENS BY EARLY EVENING. HOW FAR
SOUTH INITIATION WILL OCCUR STILL REMAINS QUESTIONABLE ATTM.
THE MID-LEVEL JET APPROACHING THE REGION FROM THE WEST IS ALREADY
CREATING STRONG VERTICAL SHEAR PROFILES FROM NW KS INTO WCNTRL NEB.
THIS SHOULD BE FAVORABLE FOR SUPERCELL DEVELOPMENT AS STORMS
INITIATE. A TRANSITION TO A MORE LINEAR STRUCTURED MCS MAY OCCUR
DEPENDING ON HOW MANY STORMS INITIATE THIS EVENING. FORECAST
SOUNDINGS CONTINUE TO STEEPEN MID-LEVEL LAPSE RATES AS THE JET COMES
OUT AND THIS COMBINED WITH THE INSTABILITY AND STRONG VERTICAL SHEAR
SUGGESTS SUPERCELLS WILL BE CAPABLE OF LARGE HAIL. ISOLATED VERY
LARGE HAIL WILL ALSO BE POSSIBLE CONSIDERING THE AMOUNT OF
INSTABILITY IN PLACE. A FEW TORNADOES MAY ALSO OCCUR AS SUPERCELLS
MATURE AND LOW-LEVEL FLOW INCREASES EARLY THIS EVENING. FURTHER
SOUTH ACROSS SW KS...NW OK AND THE ERN TX PANHANDLE...THE SEVERE
THREAT THIS EVENING WILL REMAIN CONDITIONAL. IF STORMS INITIATE IN
THIS REGION...SHEAR AND INSTABILITY PROFILES APPEAR ADEQUATE FOR
ISOLATED SUPERCELLS CAPABLE OF LARGE HAIL.
CONCERNING THE OVERNIGHT THREAT...MODEL FORECASTS AGREE WITH
DEVELOPING AN MCS OVER CNTRL AND NRN KS TONIGHT. ALSO...THE NAM
SUSTAINS NOCTURNAL CONVECTION IN ECNTRL NEB. THESE TWO AREAS APPEAR
TO HAVE THE GREATEST POTENTIAL FOR AN ISOLATED SEVERE THREAT AFTER
MIDNIGHT.
..NRN PLAINS...
A WELL-DEVELOPED UPPER-LEVEL TROUGH IS EVIDENT ON WATER VAPOR
IMAGERY OVER THE CNTRL AND NRN ROCKIES. A BROAD ZONE OF LARGE-SCALE
ASCENT IS LOCATED ACROSS THE NRN PLAINS WHICH COMBINED WITH POCKETS
OF MODERATE INSTABILITY WILL SUPPORT SCATTERED TO NUMEROUS
THUNDERSTORMS LATE THIS AFTERNOON INTO THE EVENING. THUNDERSTORM
DEVELOPMENT SHOULD BE MOST NUMEROUS ALONG A BOUNDARY ORIENTED SOUTH
TO NORTH FROM SCNTRL SD TO A SFC LOW IN SERN ND. REGIONAL PROFILERS
AND WSR-88D VWPS CURRENTLY SHOW 0-6 KM SHEAR VALUES AROUND 40 KT
SUGGESTING ENOUGH SHEAR WILL BE PRESENT FOR SUPERCELLS. LARGE HAIL
SHOULD BE THE PRIMARY THREAT WITH MID-LEVEL LAPSE RATES STEEPENING
AS THE EXIT REGION OF A MID-LEVEL APPROACHES FROM THE SOUTHWEST. AS
STORM COVERAGE INCREASES AND CONVECTION MOVES INTO AREAS WITH LESS
INSTABILITY...SEVERE MULTICELLS WITH A HAIL POTENTIAL WILL ALSO BE
POSSIBLE.
..SW LA/FAR SW MS...
WATER VAPOR IMAGERY CURRENTLY SHOWS AN MCV MOVING ACROSS EAST TX AND
SCATTERED THUNDERSTORMS HAVE DEVELOPED AHEAD OF THE FEATURE THIS
AFTERNOON. INSTABILITY AND SHEAR ON FORECAST SOUNDINGS APPEAR
SUFFICIENT FOR MARGINALLY SEVERE STORMS THIS AFTERNOON. CONCERNING
MORE DETAILED INFORMATION ABOUT THIS MARGINAL SEVERE
THREAT...REFERENCE MCD 860.
.BROYLES.. 05/22/2007
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