ACUS02 KWNS 220520
SWODY2
SPC AC 220519
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1219 AM CDT SUN APR 22 2007
VALID 231200Z - 241200Z
..THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CNTRL AND SRN
PLAINS...
..SYNOPSIS...
MID AND UPPER-LEVEL TROUGH OVER THE GREAT BASIN IS EXPECTED TO
AMPLIFY THROUGH THE PERIOD AS IT TRANSLATES EWD INTO THE CNTRL AND
SRN ROCKIES BY TUESDAY MORNING. AS THIS OCCURS...DOWNSTREAM RIDGE
WILL IN TURN AMPLIFY OVER THE ERN GREAT PLAINS INTO MS
VALLEY...SUPPORTING EWD PROGRESSION OF WEAKENING SHORT WAVE TROUGH
FROM THE UPPER GREAT LAKES INTO NEW ENGLAND.
IN THE LOW-LEVELS...BROAD TROUGHING OVER THE HIGH PLAINS WILL
CONSOLIDATE INTO A LEE CYCLONE OVER SERN CO MONDAY AFTERNOON WITH
THIS FEATURE DEVELOPING GENERALLY EWD INTO SWRN KS OR THE OK/NRN TX
PNHDL. ATTENDANT WARM FRONT INITIALLY FROM SERN CO THROUGH
NRN/CNTRL OK AND NRN AR WILL LIFT NWD...REACHING THE KS/NEB BORDER
MONDAY NIGHT. MEANWHILE...DRYLINE WILL BECOME INCREASINGLY DEFINED
MONDAY OVER THE CNTRL/ERN TX/OK PNHDLS INTO SWRN KS. FARTHER TO THE
NE...COLD FRONT WILL RAPIDLY PUSH EWD THROUGH THE GREAT LAKES AND OH
VALLEY...EVENTUALLY REACHING THE NEW ENGLAND AND MID ATLANTIC COAST
TUESDAY MORNING.
..CNTRL/SRN PLAINS...
LATEST SHORT TERM MODEL GUIDANCE CONTINUES TO INDICATE THE POTENTIAL
FOR AN ACTIVE SEVERE WEATHER EPISODE ACROSS THE REGION MONDAY
AFTERNOON AND MONDAY NIGHT. HOWEVER...CONSIDERABLE UNCERTAINTY
EXISTS IN CONVECTIVE EVOLUTION WITHIN EXPANDING WARM SECTOR. GIVEN
THIS UNCERTAINTY /AS REFLECTED IN A BROADER AREA OF LOWER SEVERE
PROBABILITIES/...A CATEGORICAL SLIGHT RISK WILL BE MAINTAINED.
22/00Z OBSERVED SOUNDINGS FROM CRP/BRO INDICATE THAT THE QUALITY OF
BOUNDARY LAYER MOISTURE /MEAN MIXING RATIOS OF 12.5-13 G PER KG/ IS
GRADUALLY INCREASING ACROSS S TX...WITH THIS TYPE OF MOISTURE
PROFILE DEVELOPING NWD THROUGH TX AND OK INTO SRN KS DURING THE DAY
TWO PERIOD. THIS INCREASING MOISTURE BENEATH STEEP MID-LEVEL LAPSE
RATES ARE EXPECTED TO CONTRIBUTE TO THE DEVELOPMENT OF A MODERATELY
UNSTABLE AIR MASS WITH MLCAPES INCREASING TO 1000-2500 J/KG WITHIN
PRIMARY INSTABILITY AXIS.
AS MENTIONED ABOVE...CONSIDERABLE UNCERTAINTY EXISTS WITH REGARD TO
CONVECTIVE INITIATION MONDAY AFTERNOON AND EVENING WITHIN THIS AXIS
OF STRONGEST INSTABILITY. THE OPERATIONAL NAM/WRF REMAINS
CONSISTENT IN SUGGESTING THAT A WEAK LOW-LATITUDE SHORT WAVE TROUGH
WILL TRANSLATE FROM SWRN TX INTO OK...INITIATING TSTMS BY AFTERNOON
FROM THE VICINITY OF THE DRYLINE FROM W-CNTRL TX INTO THE ERN TX
PNHDL EWD INTO NWRN TX/CNTRL OK AND S-CNTRL KS. THE LATEST GFS ALSO
INITIATES A BAND OF DEEP CONVECTION A DISTANCE E OF THE DRYLINE FROM
NWRN TX THROUGH WRN/CNTRL OK INTO S-CNTRL KS. FINALLY...INDIVIDUAL
SREF MEMBERS INDICATE A WIDE ARRAY OF SOLUTIONS.
DESPITE THE UNCERTAINTY IN LOCATION OF STORM DEVELOPMENT...FORECAST
SOUNDINGS INDICATE THAT THE AMBIENT ENVIRONMENT WILL BE QUITE
FAVORABLE FOR SUPERCELLS CAPABLE OF TORNADOES AND LARGE HAIL /SOME
SIGNIFICANT/ OVER A FAIRLY LARGE AREA MONDAY AFTERNOON INTO NIGHT.
ADDITIONAL STORMS WILL BECOME INCREASINGLY LIKELY MONDAY NIGHT ALONG
RETREATING WARM FRONT FROM NERN CO ACROSS NRN KS INTO SRN NEB AS
ISENTROPIC ASCENT AND WAA ARE ENHANCED ALONG NOSE OF STRENGTHENING
LLJ. WHILE THE MAJORITY OF THIS ACTIVITY WILL LIKELY BE SLIGHTLY
ELEVATED WITH THE MAIN THREAT BEING LARGE HAIL...POTENTIAL WILL
EXIST FOR ISOLATED TORNADOES WITH ANY STORMS REMAINING SURFACE BASED
INVOF WARM FRONT.
..LOWER GREAT LAKES INTO OH VALLEY...
A MOIST AND WEAKLY UNSTABLE AIR MASS IS EXPECTED TO PERSIST AHEAD OF
COLD FRONT MONDAY WITH MLCAPES INCREASING TO 300-700 J/KG.
CONVERGENCE ALONG THIS BOUNDARY COUPLED WITH FORCING FOR ASCENT
ASSOCIATED WITH WEAKENING UPPER TROUGH SHOULD SUPPORT AN INCREASE IN
TSTM DEVELOPMENT BY AFTERNOON FROM ERN LOWER MI SWWD INTO SRN IND.
STORMS WILL MOVE/DEVELOP EWD THROUGH MUCH OF OH INTO WRN PARTS OF
NY/PA MONDAY EVENING.
WHILE LAPSE RATES AND RESULTANT INSTABILITY WILL NOT BE PARTICULARLY
STRONG...THE MODEST VERTICAL SHEAR WILL BE SUPPORTIVE OF A FEW
ORGANIZED STORMS CAPABLE OF LOCALLY DAMAGING WINDS AND PERHAPS A
TORNADO. SHOULD LATER MODEL RUNS INDICATE A MORE UNSTABLE
PRE-FRONTAL AIR MASS...PORTIONS OF DISCUSSION AREA MAY NEED TO BE
UPGRADED TO A SLIGHT RISK.
.MEAD.. 04/22/2007
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