SWODY1
SPC AC 281959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT TUE JUL 28 2009
VALID 282000Z - 291200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CNTRL AND SRN
PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE LOWER MS
VALLEY INTO CNTRL GULF STATES...
...CNTRL/SRN PLAINS...
AS OF 18Z...PRIMARY COLD FRONT EXTENDED FROM S OF MKC SWWD TO ICT TO
LBL TO TAD. DIABATIC HEATING COUPLED WITH DEWPOINTS IN THE 50S TO
LOW/MID 60S AND ERN EDGE OF STEEPER MIDLEVEL LAPSE RATES HAVE
CONTRIBUTED TO A MODERATELY UNSTABLE AIR MASS WITH MLCAPE OF
1500-2500 J/KG. COMBINATION OF FRONTAL FORCING AND GLANCING
INFLUENCE OF MIDLEVEL IMPULSE OVER NEB/KS ARE RESULTING IN SCATTERED
TSTM DEVELOPMENT ALONG THE HIGHER TERRAIN OF SERN CO/NERN NM.
CURRENT TUCUMCARI NM PROFILER INDICATES THAT A GRADUAL STRENGTHENING
OF WINDS HAS OCCURRED TODAY ABOVE 5-6 KM...RESULTING IN 40-50 KT OF
DEEP-LAYER SHEAR ACROSS THE PLAINS OF SERN CO/NERN NM. AS
SUCH...SETUP WILL FAVOR THE DEVELOPMENT OF ORGANIZED STORMS
/INCLUDING SUPERCELLS/ WITH THE THREAT FOR LARGE HAIL...DAMAGING
WINDS AND PERHAPS A TORNADO OR TWO. MORE DISCRETE STORMS WILL
LIKELY CONSOLIDATE INTO ONE OR MORE CLUSTERS TONIGHT WITH A
CONTINUED THREAT FOR HAIL AND DAMAGING WINDS ACROSS WRN PARTS OF TX
AND OK.
ADDITIONAL STRONG/SEVERE TSTMS WILL BE POSSIBLE FARTHER E ALONG OR
IN IMMEDIATE WAKE OF FRONT INTO S-CNTRL KS/N-CNTRL OK. SEE MCD 1702
FOR ADDITIONAL NEAR TERM GUIDANCE.
...LOWER MS VALLEY INTO CNTRL GULF STATES...
NOCTURNAL MCS WHICH MATURED EARLIER TODAY OVER THE ARKLATEX HAS
SINCE DECAYED WITH NUMEROUS TSTMS DEVELOPING ALONG CONVECTIVE
OUTFLOW AND/OR DIFFERENTIAL HEATING BOUNDARIES. 18Z JAN SOUNDING
INDICATES THAT AIR MASS IS MOIST AND MODERATELY UNSTABLE WITH MLCAPE
OF AROUND 2000 J/KG. BASED ON AREA PROFILERS AND VWPS...IT APPEARS
THAT STRONGER WIND FIELDS ASSOCIATED WITH MIDLEVEL VORTICITY MAXIMUM
WILL REMAIN GENERALLY N OF THE I-20 CORRIDOR THROUGH TONIGHT.
SHOULD POCKETS OF STRONGER DESTABILIZATION OCCUR WITHIN THIS ZONE OF
STRONGER SHEAR...SOME POTENTIAL WILL EXIST FOR MARGINAL SUPERCELL
AND/OR BOWING STRUCTURES CAPABLE OF DAMAGING WINDS AND PERHAPS A
BRIEF TORNADO OR TWO.
...4-CORNERS REGION...
SCATTERED TSTMS HAVE DEVELOPED WITH MIDLEVEL MOIST PLUME /PER WV
IMAGERY/ IN A STEEP LAPSE RATE ENVIRONMENT WITH MODEST /40 KT/
MIDLEVEL FLOW. A FEW OF THE STRONGER STORMS WILL BE CAPABLE OF
LOCALLY DAMAGING WIND GUSTS. SEE MCD 1701 FOR ADDITIONAL NEAR TERM
GUIDANCE.
...MID MS VALLEY INTO SRN GREAT LAKES...
SCATTERED TSTMS DEVELOPING ALONG/AHEAD OF FRONT WILL POSE AN
ISOLATED WIND/HAIL THREAT INTO THIS EVENING. REGIONAL VWP/PROFILER
DATA INDICATE THAT MARGINAL VERTICAL SHEAR SHOULD LIMIT A MORE
ORGANIZED SEVERE THREAT.
..MEAD.. 07/28/2009
.PREV DISCUSSION... /ISSUED 1129 AM CDT TUE JUL 28 2009/
...SYNOPSIS...
BROAD UPPER TROUGH...CENTERED OVER THE MS VALLEY...WILL RESIDE OVER
MUCH OF THE NATION THIS FORECAST PERIOD. SEVERAL SHORTWAVE TROUGHS
EMBEDDED WITH THE CYCLONIC FLOW ALOFT WILL AID IN PRIMARILY
DIURNALLY-ENHANCED STORMS. THE EXCEPTION IS WITH A PERSISTENT AND
SLOW MOVING IMPULSE CURRENTLY MOVING THROUGH THE ARKLATEX...WHERE
CONVECTION PERSISTED THROUGH THE NIGHT AND INTO THE MORNING HOURS.
AT THE SURFACE...A SEWD MOVING COLD FRONT WILL SHIFT THROUGH THE
GREAT LAKES/OH VALLEY...IN ASSOCIATION WITH A STRONGER UPPER WAVE
MOVING THROUGH THE NRN GREAT LAKES. SRN PORTION OF FRONT FROM MO
SWWD INTO THE TX PANHANDLE WILL MOVE SEWD...AND EXTEND ROUGHLY NEAR
A STL-END-LBB LINE BY LATE AFTERNOON.
...ARKLATEX EWD INTO THE SRN APPALACHIANS...
UPPER IMPULSE OVER THE ARKLATEX HAS THUS FAR BEEN SLOW TO MOVE EWD
MORE RAPIDLY...LIKELY DUE TO ANOTHER DISTURBANCE...ON WV
IMAGERY...THAT APPEARED TO MERGE AND STRENGTHEN SYSTEM EARLIER THIS
MORNING. FORWARD SPEED MAY INCREASE AS OTHER WAVES BEHIND IT MOVE
SEWD AND AID IN KICKING THE SYSTEM A LITTLE FASTER EWD. WIND
PROFILES LOCATED CLOSE TO THIS UPPER SYSTEM ARE FORECAST TO REMAIN
RELATIVELY STRONG THROUGH TONIGHT. THOUGH CONSIDERABLE CLOUDINESS IS
LIKELY TO REDUCE THE AMOUNT OF DAYTIME HEATING AHEAD OF THE
SYSTEM...A WARM AND MORE UNSTABLE AIR MASS IMMEDIATELY SOUTH OF THE
CONVECTION WILL FUEL THE STORMS. THOUGH MODE AND EVOLUTION OF
CONVECTION IS EXPECTED TO BE MIXED THROUGH THE PERIOD...THE VERTICAL
SHEAR WILL SUPPORT BOTH SUPERCELLS/ISOLATED TORNADOES AS WELL AS BOW
ECHOES WITH WIND DAMAGE. THIS THREAT IS EXPECTED TO SPREAD INTO MS
THIS AFTERNOON AND POSSIBLY AS FAR EAST AS AL AND NWRN GA TONIGHT.
...WESTERN PORTIONS OF THE CENTRAL/SRN PLAINS...
MORNING WV IMAGERY SHOWS FRAGMENTED UPPER WAVES MOVING SEWD FROM THE
WY/NEB BORDER SEWD INTO NRN OK. HOWEVER...ONGOING CONVECTION OVER
NRN KS AND MODEL FORECAST SUGGEST SYSTEM NEAR THE WY/NEB BORDER
SHOULD BE THE MAIN FEATURE FOR CONVECTION ACROSS THE CENTRAL/SRN
PLAINS. SUNNY CONDITIONS AND WARMING/DESTABILIZING BOUNDARY LAYER
THIS MORNING WAS OCCURRING OVER SERN CO/SWRN KS/NWRN OK AND THE TX
PANHANDLE. ACROSS THIS AREA...THE BEST OVERLAP OF LOW LEVEL FRONTAL
CONVERGENCE...WARMING AND LIFT ASSOCIATED WITH UPPER WAVE WOULD BE
OVER SWRN KS/NWRN OK AND TX PANHANDLE. OTHER STORMS ARE LIKELY TO
DEVELOP OVER THE HIGHER TERRAIN OF SERN CO/NERN NM WHERE STRONG
HEATING OF MOIST BOUNDARY LAYER WILL OCCUR. AFTER STORMS
FORM...MODERATE INSTABILITY AND 30-40 KT DEEP LAYER SHEAR SHOULD
SUSTAIN MULTICELLS AND POSSIBLY A SUPERCELL OR TWO. THE MAIN THREAT
WILL BE HAIL...THOUGH THE WIND THREAT WILL BE HIGHER THIS EVENING AS
STORMS CONSOLIDATE INTO ONE OR TWO LINEAR CLUSTERS.
...LOWER MI/IND TO IL/MO...
SCATTERED CONVECTION WAS LOCATED NEAR THE COLD FRONT AND WILL
CONTINUE TO SERVE AS FOCUS FOR STORMS FROM LOWER MI SWWD INTO THE
MID MS VALLEY/OZARKS. WHILE DEEP SHEAR WILL BE SUFFICIENT FOR
ORGANIZED AND SUSTAINED STORMS IN MI...INSTABILITY WILL BE WEAK.
FROM INDIANA TO MO...THE INSTABILITY WILL BE MODERATE TO
STRONG...BUT THE SHEAR WILL BE WEAK...DUE TO UNIDIRECTIONAL WIND
PROFILES. ALTHOUGH ISOLATED SEVERE WIND/HAIL EVENTS APPEAR
POSSIBLE...THE POTENTIAL FOR A MORE ORGANIZED SVR EVENT APPEARS LOW.
...NRN INTERMOUNTAIN/ROCKIES...
RELATIVELY MOIST /0.75 TO 1 INCH PW/ AIR IS IN PLACE FROM THE NRN
ROCKIES AHEAD OF ANOTHER SHORTWAVE TROUGH MOVING SEWD TOWARD THE
CONTINENTAL DIVIDE. THE SHEAR/INSTABILITY APPEARS MOST FAVORABLE FOR
SEVERE STORMS ESPECIALLY ACROSS WA...THOUGH MODEL RUNS APPEAR TO
DEVELOP CONVECTION IN ASSOCIATION WITH THIS SYSTEM OVER WRN MT.
INSTABILITY IN WRN MT WILL BE MARGINAL FOR SEVERE...THOUGH SHEAR
SHOULD BE STRONG ENOUGH FOR A FEW SVR STORMS LATE AFTERNOON/EVENING.
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