SWODY1
SPC AC 081619
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1119 AM CDT SUN MAY 08 2011
VALID 081630Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE NRN HIGH
PLAINS SEWD THROUGH THE MID MO VALLEY...
...SYNOPSIS...
PAC NW UPPER LOW WILL CONTINUE DROPPING SSEWD INTO NWRN NV BY 12Z
MON AS PRIMARY TROUGH REMAINS W OF ROCKIES. DOWNSTREAM RIDGE SLOWLY
AMPLIFIES AND SHIFTS EWD TO VICINITY MS RIVER VALLEY. WITH ONLY A
MODEST SWLY FLOW ALOFT OUT INTO THE PLAINS ON E SIDE OF WRN
TROUGH...ANY SEVERE THUNDERSTORM POTENTIAL WILL BE DRIVEN BY LOW
LEVEL FEATURES SUCH AS STRONG SURFACE HEATING AND LIFT PROVIDED BY
CONVERGENCE ALONG DRY LINE AND TO THE NORTH OF WARM FRONT CURRENTLY
FROM CENTRAL NEB SEWD TO NRN MO.
...NRN HIGH PLAINS EWD/SEWD INTO THE UPPER MS AND MID/LOWER MO
VALLEYS...
WITH SURFACE LOW DEVELOPING NWD INTO WRN NEB ASSOCIATED DRYLINE WILL
BECOME BETTER-DEFINED BY AFTERNOON...EXTENDING FROM SURFACE LOW
THROUGH WRN NEB INTO CNTRL KS. MEANWHILE...WARM FRONT CURRENTLY
LIFTING NWD SHOULD CONTINUE TO MOVE/DEVELOP NWD...LIKELY EXTENDING
FROM SURFACE LOW EWD THROUGH CNTRL NEB INTO NERN KS LATER THIS
AFTERNOON.
LATEST SUITE OF MESOSCALE AND CONVECTION-ALLOWING MODEL GUIDANCE
CONTINUES TO PROVIDE CONSIDERABLE UNCERTAINTY ON TSTM EVOLUTION THIS
AFTERNOON AND EVENING. NONETHELESS...THE MAINTENANCE OF A 30-40 KT
SLY LLJ ACROSS THE GREAT PLAINS WILL SUPPORT THE CONTINUED NWD FLUX
OF AN INCREASINGLY MOIST BOUNDARY LAYER WITH AFTERNOON DEWPOINTS
RANGING FROM MID/UPPER 50S OVER S-CNTRL SD TO MID 60S ALONG WARM
FRONT IN CNTRL/ERN NEB. WHEN COUPLED WITH MIDLEVEL LAPSE RATES
APPROACHING DRY ADIABATIC AND STRONG DAYTIME HEATING...EXPECT WARM
SECTOR AIR MASS TO BECOME MODERATELY TO STRONGLY UNSTABLE WITH
MLCAPE VALUES RANGING FROM 1000-1500 J/KG IN WRN SD TO AS HIGH AS
3000-3500 J/KG ACROSS S-CNTRL/SERN NEB.
THE ONLY SOMEWHAT CONSISTENT MODEL SIGNAL HAS BEEN FOR INITIATION OF
SEVERE THUNDERSTORMS NEAR WARM FRONT LATER THIS AFTERNOON ACROSS ERN
NEB INTO SRN SD. SUPERCELLS WILL BE THE PRIMARY INITIAL MODE THIS
AREA RESULTING IN VERY LARGE HAIL. ADDITIONALLY AT LEAST AN ISOLATED
TORNADO THREAT WOULD BE LIKELY GIVEN THE AMOUNT OF INSTABILITY...LOW
LEVEL VEERING SHEAR PROFILES VICINITY FRONTAL ZONE.
STORM FORMATION APPEARS MORE LIKELY BY THIS EVENING N OF SURFACE LOW
AND WARM FRONT FROM SERN MT EWD ACROSS ND...NRN SD INTO CNTRL/SRN MN
SEWD TOWARD THE MID MS VALLEY. THIS WILL BE IN
RESPONSE TO A BROAD SWATH OF INCREASING WAA/ISENTROPIC ASCENT
OCCURRING AS THE LOW LEVEL JET INTENSIFIES. THIS AREA WOULD SEE A
MORE ELEVATED SEVERE THREAT /INCLUDING SUPERCELLS/ CAPABLE OF LARGE
HAIL.
...CENTRAL/SRN PLAINS VICINITY DRY LINE...
ALTHOUGH RATHER...SHALLOW MOISTURE CONTINUES TO STREAM NWD TO THE E
OF SLOWLY DEEPENING SURFACE LOW CENTRAL HIGH PLAINS. A PRONOUNCED
EML WITH LAPSE RATES NEAR DRY ADIABATIC RESIDES ABOVE THE MOIST
BOUNDARY LAYER FROM SRN PLAINS NWD TO SRN SD.
DRY LINE MIXES EWD THIS AFTERNOON INTO CENTRAL KS SWD THRU WRN OK AS
TEMPS WARM THROUGH THE 90S. WHILE CINH WILL BECOME NEGLIGIBLE AS
MUCAPES CLIMB TO 3000 J/KG OR HIGHER IMMEDIATELY E OF DRY LINE
KS/OK...THE SEVERE POTENTIAL SHOULD REMAIN QUITE CONDITIONAL GIVEN
LACK OF UPPER SUPPORT. ANY STORM THAT INITIATES FROM SRN NEB TO OK
WOULD QUICKLY BECOME SEVERE WITH A LARGE HAIL/WIND THREAT. HOWEVER
EWD EXTENT OF THREAT WILL BE LIMITED AS STORMS MOVE QUICKLY EWD INTO
AREAS OF GREATER CINH THIS EVENING.
...TN VALLEY TO SERN ATLANTIC COAST...
BUILDING SURFACE RIDGE FROM THE LOWER GREAT LAKES SWD THROUGH THE
MID ATLANTIC STATES WILL RESULT IN THE SWD PROGRESSION OF A WEAK
BACKDOOR COLD FRONT THROUGH THE SRN APPALACHIANS WHICH WILL
EVENTUALLY MERGE WITH WARM FRONT LIFTING NWD THROUGH THE LOWER MS
VALLEY. THIS BOUNDARY IS EXPECTED TO SERVE AS THE FOCUS FOR
ISOLATED TO SCATTERED TSTM DEVELOPMENT THIS AFTERNOON.
12Z OBSERVED SOUNDINGS FROM AR EWD ACROSS THE GULF COAST SHOW THAT
AN EML HAS SPREAD EWD ACROSS THE REGION WITH MIDLEVEL LAPSE RATES OF
7.0-7.5 C/KM. WHEN COUPLED WITH A MOISTENING BOUNDARY LAYER AND
DAYTIME HEATING...ENVIRONMENT IS EXPECTED TO BECOME MODERATELY
UNSTABLE WITH MLCAPE VALUES RANGING FROM 1500-2500 J/KG OVER THE MID
SOUTH TO AROUND 1000 J/KG ALONG THE SAVANNAH RIVER. GIVEN THE
MODESTLY STRONG NWLY WIND FIELD OBSERVED THIS MORNING IN THE MID TO
UPPER-TROPOSPHERE...SETUP MAY YIELD A FEW FORWARD-PROPAGATING STORM
CLUSTERS CAPABLE OF DAMAGING WINDS AND SOME HAIL.
..HALES/COHEN.. 05/08/2011
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