SWODY1
SPC AC 301951
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0251 PM CDT THU JUN 30 2011
VALID 302000Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN UT/CO NEWD INTO MN...
ADJUSTED SEVERE PROBABILITIES BEHIND COLD FRONT ACROSS ERN UT AND
REMOVED A PORTION OF W CNTRL WY WHERE LITTLE INSTABILITY REMAINS.
FOR MORE INFORMATION SEE MESOSCALE DISCUSSION 1452.
REMOVED LOW END WIND PROBS FROM MUCH OF FL WHERE MAINLY HEAVY RAIN
IS ONGOING...AND SHIFTED INTO GA AND SRN SC WHERE LARGER DCAPE
EXISTS AS WELL AS A MORE UNDISTURBED AIR MASS. FOR MORE INFORMATION
SEE MESOSCALE DISCUSSION 1450.
A CONDITIONAL THREAT OF SIGNIFICANT HAIL AND A TORNADO REMAINS OVER
ERN ND INTO NWRN MN AHEAD OF A COLD FRONT. PERSISTENT DEEP LOW LEVEL
CONVERGENCE MAY OVERCOME CAPPING FOR A FEW SEVERE STORMS IN THIS
AREA.
OTHERWISE...EXPECT CONVECTION TO EMERGE INTO THE NRN HIGH PLAINS AN
CONTINUE OVERNIGHT INTO THE DAKOTAS AHEAD OF EJECTING UPPER TROUGH
WITH WIND AND HAIL THREAT.
..JEWELL.. 06/30/2011
.PREV DISCUSSION... /ISSUED 1125 AM CDT THU JUN 30 2011/
...CNTRL ROCKIES INTO NRN/CNTRL HIGH PLAINS...
POTENT VORTICITY MAXIMUM OVER SWRN UT WILL PROGRESS ENEWD ACROSS THE
REGION THROUGH THE D1 PERIOD WITH A CORRIDOR OF MODEST HEIGHT FALLS
AND 40-50+ KT FLOW AT 500 MB ATTENDING THIS SYSTEM. 12Z REGIONAL
SOUNDINGS SHOWED THE PRESENCE OF A STEEP LAPSE RATE ENVIRONMENT
PRECEDING THE VORTICITY MAXIMUM AND ASSOCIATED SURFACE COLD FRONT
WITH DAYTIME HEATING AND PW VALUES OF 0.70-0.90 INCH SUPPORTING
AFTERNOON MLCAPE OF 1000-1500 J/KG. ZONE OF DEEP-LAYER FORCING FOR
ASCENT PRECEDING MIDLEVEL SYSTEM COUPLED WITH PACIFIC FRONT AND
TERRAIN INFLUENCES WILL SUPPORT UPSCALE GROWTH OF ONGOING STORMS
INTO MULTIPLE BANDS CAPABLE OF DAMAGING WINDS AND HAIL.
EXPECT STORMS TO RAPIDLY MOVE/DEVELOP EWD/NEWD THROUGH THE CNTRL
ROCKIES INTO NRN/CNTRL HIGH PLAINS THIS AFTERNOON INTO TONIGHT WITH
A CONTINUED RISK FOR MAINLY DAMAGING WINDS AND HAIL.
FOR ADDITIONAL NEAR TERM GUIDANCE...SEE WW 576.
...ERN DAKOTAS INTO UPPER MS VALLEY...
12Z SOUNDINGS OVER THE DAKOTAS SHOWED A UNIFORMLY STRONG CAP IN
PLACE AT THE BASE OF AN EML WHICH SHOULD SPREAD EWD ACROSS THE UPPER
MS VALLEY TODAY GIVEN THE LARGE-SCALE AIRFLOW REGIME. THIS CAP
COUPLED WITH INCREASING HIGH CLOUDS FROM THE W/SW --AND THEIR
POTENTIAL IMPACTS ON DAYTIME HEATING-- WILL LIKELY DELAY THE
DEVELOPMENT OF SURFACE-BASED STORM DEVELOPMENT ALONG COLD FRONT
WHERE AIR MASS WILL BECOME MODERATELY TO EXTREMELY UNSTABLE WITH
MLCAPE OF 2000-4000+ J/KG.
LATEST CONVECTION-ALLOWING AND MESOSCALE MODEL GUIDANCE SUGGESTS
THAT TSTMS WILL BECOME INCREASINGLY LIKELY BY 01/00Z OVER NWRN MN
INTO ERN ND/NERN SD ON THE FRINGE OF THE STRONGER CAP.
HERE...FORECAST HODOGRAPHS EXHIBIT VERTICALLY VEERING WIND PROFILES
WITH 30-40 KT OF DEEP-LAYER SHEAR WHICH WILL SUPPORT SUPERCELLS
GIVEN THE DEGREE OF INSTABILITY. WHILE VERY LARGE HAIL WILL BE THE
PRIMARY HAZARD...A TORNADO OR TWO IS POSSIBLE IN ADDITION TO
DAMAGING WINDS. THE NOCTURNAL STRENGTHENING OF A SWLY LLJ MAY
PROMOTE THE UPSCALE GROWTH OF STORMS INTO A FORWARD-PROPAGATING MCS
WITH A CONTINUED THREAT FOR DAMAGING WINDS AND HAIL SPREADING SEWD
ACROSS NRN MN LATE TONIGHT INTO FRI MORNING.
...WI/MI/IND...
A BAND OF ELEVATED STORMS HAS RECENTLY FORMED OVER THE WRN UP OF MI
INTO NERN WI ALONG THE EDGE OF THE CAP AND AT TERMINUS OF DIURNALLY
WEAKENING LLJ. THERE IS SOME QUESTION AS TO WHETHER THIS ACTIVITY
WILL PERSIST TODAY GIVEN THE WEAKENING LOW-LEVEL WAA/ISENTROPIC
ASCENT WITH TIME. BUT...GIVEN THE VERY STEEP MIDLEVEL LAPSE RATES
AND POTENTIALLY STRONG ELEVATED INSTABILITY UPSTREAM /REF. 12Z MPX
SOUNDING/...HAIL WILL BE POSSIBLE WITH STORMS THAT CAN PERSIST.
TONIGHT...AS MENTIONED ABOVE...EXPECT THE POTENTIAL FOR MCS
FORMATION TO INCREASE ACROSS PARTS OF NRN WI AND THE UP OF MI WITH
ADDITIONAL MORE ELEVATED TSTM ACTIVITY POSSIBLE DOWNSTREAM ACROSS
LOWER MI INTO IND IN RESPONSE TO STRENGTHENING NOCTURNAL LLJ. THESE
STORMS WILL BE CAPABLE OF LOCALLY DAMAGING WINDS AND HAIL INTO FRI
MORNING.
...SRN GA/NRN FL...
STALLED SYNOPTIC FRONT AND DEVELOPING SEA BREEZE CIRCULATIONS WILL
FOCUS NUMEROUS STORMS TODAY WITHIN A HIGH-PW AIR MASS WITH THE
POTENTIAL FOR WET MICROBURST ACTIVITY OWING TO WATER LOADING
EFFECTS.
...PORTIONS OF LOWER MS VALLEY INTO ERN OK/WRN AR...
WRN EXTENSION OF STALLED SURFACE FRONT ARCING NNWWD THROUGH THE
REGION MAY SERVE AS THE FOCUS FOR ISOLATED DIURNAL STORM
DEVELOPMENT. THE PRESENCE OF A MOIST BOUNDARY LAYER AND STEEPENING
MIDLEVEL LAPSE RATES WITH NWD EXTENT WILL YIELD A MODERATELY TO
STRONGLY UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPE OF 1000-2000
J/KG SOUTH TO 2000-3500 J/KG NORTH. WHILE VERTICAL SHEAR WILL
REMAIN RELATIVELY WEAK...THE POTENTIAL FOR SOME HAIL AND LOCALLY
DAMAGING WINDS WILL BE POSSIBLE GIVEN THE FAVORABLE THERMODYNAMIC
ENVIRONMENT.
...DEEP S TX...
NRN FRINGES OF T.S. ARLENE WILL CONTINUE TO AFFECT AREA TODAY WITH A
SMALL RISK FOR A BRIEF TORNADO WITH LAND-FALLING RAINBANDS.
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