SWODY1
SPC AC 122000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT MON JUL 12 2010
VALID 122000Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN MT/WRN ND...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL HIGH PLAINS
SEWD INTO THE MID MS/WRN TN VALLEYS...
...THERE IS A SLGT RISK OF SVR TSTMS FROM NC SWD INTO SERN GA...
...THERE IS A SLGT RISK OF SVR TSTMS DELMARVA NWWD INTO CENTRAL AND
ERN PA...
...DELMARVA NWWD INTO CENTRAL/ERN PA...
A SHORTWAVE TROUGH MOVING ENEWD ACROSS WRN PA/NRN WV HAS AID IN
SCATTERED STORMS ACROSS THE REGION. THE MOIST BOUNDARY LAYER ALONG
WITH 20-30 KT OF DEEP LAYER SHEAR WILL BE SUFFICIENT FOR A FEW
SEVERE MULTICELL STORMS THE NEXT FEW HOURS. THEREAFTER...OUTFLOW
FROM STORMS SHOULD LIMIT THE BOUNDARY LAYER INSTABILITY AND THE
STORMS SHOULD WEAKEN BEFORE DARK.
...SRN PLAINS...
AN MCV OR WEAK UPPER WAVE OVER SWRN OK HAS MAINTAINED A BAND OF
CLOUDS/PCPN FROM SWRN OK INTO NWRN AR INTO THE EARLY AFTERNOON
HOURS. AS THIS SYSTEM TRACKS SLOWLY EWD...EXPECT SUBSIDENCE TO LIMIT
CONVECTIVE DEVELOPMENT BEHIND IT...SO HAVE TRIMMED PORTIONS OF
CENTRAL/WRN OK FROM SLIGHT RISK. HOWEVER...OTHER STORMS ARE EXPECTED
TO DEVELOP EAST OF THIS SYSTEM. THOUGH DEEP LAYER IS NOT THAT
STRONG...STRONG INSTABILITY IS FAVORABLE FOR A FEW SEVERE STORMS
THIS AFTERNOON.
...CENTRAL HIGH PLAINS...
THE SLIGHT RISK HAS BEEN EXTENDED NWWD FROM KS INTO SWRN SD AND WRN
NEB ALONG INSTABILITY AXIS. ALTHOUGH FORCING WILL BE WEAK... ANY
STORMS THAT DEVELOP WILL ALSO ENCOUNTER DEEP LAYER SHEAR NEAR 40
KT...DUE TO SELY BOUNDARY LAYER WINDS VEERING TO NWLY AND
STRENGTHENING WITH HEIGHT. A SUPERCELL OR TWO IS POSSIBLE WITH HAIL
THE MAIN THREAT...AND POSSIBLY AN ISOLATED TORNADO.
...ERN TN VALLEY SWD INTO AL/NRN GA...
NUMEROUS THUNDERSTORM WERE LOCATED ACROSS GA AND WRN SC...AHEAD OF
WEAK IMPULSE MOVING THROUGH THE AREA. LOWERED THE SLIGHT RISK TO LOW
PROBABILITIES ACROSS THE REGION DUE TO WIDESPREAD CONVECTION OVER GA
STABILIZING THE BOUNDARY LAYER AND SUBSIDENCE TO THE NORTH AND WEST
OF THIS CONVECTION.
..IMY.. 07/12/2010
.PREV DISCUSSION... /ISSUED 1128 AM CDT MON JUL 12 2010/
...SYNOPSIS...
A BROAD BELT OF CYCLONIC MID- AND HIGH-LEVEL FLOW WILL BE MAINTAINED
THROUGH THE PERIOD FROM THE NWRN CONUS THROUGH THE ERN TWO-THIRDS OF
THE NATION. EMBEDDED WITHIN THIS LARGE-SCALE REGIME...MORNING WATER
VAPOR IMAGERY AND 12Z UPPER-AIR ANALYSIS SHOW SEVERAL IMPULSES...THE
MOST NOTABLE OF WHICH BEING A STRONG SYSTEM DIGGING SEWD THROUGH
B.C. INTO THE PACIFIC NW...AND OTHERS OVER THE NRN HIGH
PLAINS...KS/NEB...UPPER OH VALLEY. IN ADDITION...A SERIES OF WEAK
RIPPLES IN THE FLOW ARE NOTED FROM THE LOWER MS VALLEY INTO
CNTRL/SRN APPALACHIANS.
A LOW-LEVEL BAROCLINIC ZONE EXTENDING GENERALLY FROM THE NRN
HIGH/CNTRL HIGH PLAINS SEWD THROUGH THE OZARKS INTO THE TN
VALLEY/NRN GULF STATES AND THEN NEWD THROUGH THE PIEDMONT REGION
WILL LIKELY SERVE AS THE FOCUS FOR STRONG/SEVERE TSTMS THROUGH THE
PERIOD. ALONG AND S OF THIS BOUNDARY THE AIR MASS IS QUITE MOIST
WITH DEWPOINTS IN UPPER 60S TO LOWER/MID 70S AND PW VALUES FROM 1.50
TO IN EXCESS OF TWO INCHES.
...CNTRL/SRN PLAINS EWD INTO THE MID MS VALLEY AND OZARK PLATEAU...
SHORT WAVE TROUGH CURRENTLY OVER NEB/KS WILL PROGRESS EWD WITH AN
ASSOCIATED WEAK SURFACE LOW /ANALYZED OVER CNTRL KS AT 13Z/
DEVELOPING EWD TOWARD STL LATER TODAY. WHILE LOW TO MIDLEVEL WIND
FIELD WILL NOT BE OVERLY STRONG...THE PRESENCE OF 50-70 KT
HIGH-LEVEL FLOW IN CONJUNCTION WITH A MOIST AND UNSTABLE AIR MASS
/I.E. MLCAPE OF 1500-3000 J PER KG/ WILL RESULT IN AN ENVIRONMENT
SUPPORTIVE OF ORGANIZED STORMS INCLUDING SUPERCELLS CAPABLE OF LARGE
HAIL...DAMAGING WINDS AND PERHAPS A TORNADO OR TWO ALONG AND SOUTH
OF THE TRACK OF THE SHORT WAVE TROUGH AND SURFACE LOW.
THOUGH LARGE-SCALE FORCING WILL BE WEAKER...ADDITIONAL...DIURNAL
STORMS WILL BE POSSIBLE OVER THE HIGH PLAINS ALONG NNW-SSE ORIENTED
SURFACE FRONT WITHIN AN ENVIRONMENT OF MODERATE CONVECTIVE
INSTABILITY AND 40-45 KT OF DEEP WNWLY SHEAR. THE GIVEN ENVIRONMENT
WILL SUPPORT THE DEVELOPMENT OF SEVERE STORMS...INCLUDING SUPERCELLS
CAPABLE OF LARGE HAIL AND PERHAPS A COUPLE OF TORNADOES.
FARTHER S...STRONG/SEVERE STORMS ARE EXPECTED TO BECOME FOCUSED
LATER TODAY FROM PARTS OF THE OZARK PLATEAU EWD INTO LOWER MS VALLEY
IN ADVANCE OF MCV CURRENTLY OVER CNTRL/ERN OK. THE COMBINATION OF
DAYTIME HEATING AND BOUNDARY LAYER DEWPOINTS OF 70-75 F WILL BOOST
MLCAPE TO 2000-3000 J/KG LATER TODAY. MOREOVER...CURRENT
VWP/PROFILER DATA SHOW A BELT OF 30-40 KT MIDLEVEL FLOW ASSOCIATED
WITH THE MCV...WHICH WILL SERVE TO ENHANCE DEEP-LAYER SHEAR AND
STORM ORGANIZATION. SETUP MAY FAVOR THE DEVELOPMENT OF AN MCS OR
TWO WITH ATTENDANT THREATS FOR DAMAGING WINDS AND HAIL.
...GULF COAST STATES TO SERN ATLANTIC COAST...
AS MENTIONED IN THE SYNOPSIS...SEVERAL MIDLEVEL IMPULSES ARE EVIDENT
IN MORNING WATER VAPOR IMAGERY TRANSLATING GENERALLY EWD ALONG
LOW-LEVEL BAROCLINIC ZONE. VISIBLE SATELLITE IMAGERY SHOWS MORE
EXTENSIVE CLOUD COVER THIS MORNING ACROSS THE TN VALLEY INTO THE
CNTRL/SRN APPALACHIANS. HOWEVER...AREAS TO THE S WILL LIKELY
EXPERIENCE STRONG DAYTIME HEATING. WHEN COUPLED WITH LOWER/MID 70S
DEWPOINTS...ENVIRONMENT WILL BECOME MODERATE TO STRONGLY UNSTABLE BY
AFTERNOON. ALSO OF NOTE...12Z OBSERVED SOUNDINGS AND CURRENT VWP
DATA SUGGEST A BELT OF 30-35 KT FLOW PRESENT IN THE 3-6 KM AGL
LAYER...WHICH WHEN COMBINED WITH THE STRONG INSTABILITY WILL LIKELY
FOSTER CORRIDORS OF MORE INTENSE STORMS...PRIMARY IN ADVANCE OF THE
MORE PERSISTENT MIDLEVEL IMPULSES. THE PRIMARY HAZARD WITH THESE
STORMS WILL BE DAMAGING WIND GUSTS.
...PIEDMONT AND COASTAL PLAIN...
MESOANALYSIS SHOWS A SW-NE ORIENTED BAROCLINIC ZONE SITUATED JUST E
OF THE BLUE RIDGE. AIR MASS E OF THIS BOUNDARY IS QUITE MOIST WITH
DEWPOINTS OF 70-75 F. VISIBLE SATELLITE IMAGERY SUGGESTS THAT
INCREASING CLOUDINESS MAY TEMPER DAYTIME HEATING AND RESULTANT AIR
MASS DESTABILIZATION THROUGH THE REMAINDER OF THE DAY.
HOWEVER...WHERE POCKETS OF STRONG HEATING CAN OCCUR...THE PRESENCE
OF THE RICH BOUNDARY LAYER MOISTURE WILL RESULT IN THE DEVELOPMENT
OF MLCAPE APPROACHING 1000-2000 J/KG.
A NUMBER OF MIDLEVEL IMPULSES CURRENTLY MOVING THROUGH THE CNTRL/SRN
APPALACHIANS ARE EXPECTED TO CONTRIBUTE TO AN INCREASE IN STORM
COVERAGE AND INTENSITY TODAY AS THE STRONGER FORCING PROGRESSIVELY
OVERSPREADS THE DESTABILIZING BOUNDARY LAYER. HERE TOO...VWP DATA
SHOW A BELT OF 30-40+ KT MIDLEVEL FLOW ATTENDING THESE IMPULSES.
WHEN COUPLED WITH THE SLY LOW-LEVEL WIND COMPONENT...VERTICAL SHEAR
PROFILES WILL BE SUPPORTIVE OF A FEW ORGANIZED/ROTATING STORMS
CAPABLE OF DAMAGING WINDS AND PERHAPS A TORNADO OR TWO.
PLEASE SEE MCD 1263 ON FURTHER NEAR-TERM GUIDANCE FOR THIS AREA.
...NRN HIGH PLAINS...
STRONG DYNAMIC FORCING ASSOCIATED WITH MIDLEVEL TROUGH MOVING
THROUGH THE NRN INTERMOUNTAIN REGION IS EXPECTED TO SUPPORT THE
DEVELOPMENT OF TSTMS ALONG COLD FRONT LATE THIS AFTERNOON INTO
EVENING. FORECAST SOUNDINGS INDICATE THE PRESENCE OF STEEP LAPSE
RATES AND MODEST BOUNDARY LAYER MOISTURE WHICH WILL CONTRIBUTE TO
POCKETS OF MODERATE INSTABILITY. MOREOVER...VERTICAL SHEAR WILL
INCREASE CONSIDERABLY IN CONCERT WITH THE ARRIVAL OF THE UPPER
SYSTEM WITH ENVIRONMENT SUPPORTIVE OF HIGH-BASED SUPERCELLS AND/OR
BOWING STRUCTURES CAPABLE OF DAMAGING WINDS AND HAIL.
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