SWODY1
SPC AC 161959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SAT JUN 16 2007
VALID 162000Z - 171200Z
..THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT
ACROSS PARTS OF CNTRL/ERN MT...FAR NWRN SD AND FAR NERN WY...
..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT FROM
THE NRN ROCKIES INTO NRN PLAINS...
..NRN ROCKIES INTO NRN PLAINS...
COMPLEX SURFACE PATTERN EXISTS EARLY THIS AFTERNOON WITH PRIMARY
SURFACE LOW OVER NERN ID AS OF 19Z WITH ASSOCIATED COLD FRONT FROM
NEAR HVR SWWD TO THIS LOW AND THEN INTO E-CNTRL ORE. A SECONDARY
LOW WAS ANALYZED OVER W-CNTRL WY WITH ATTENDANT DIFFERENTIAL HEATING
BOUNDARY/BAROCLINIC ZONE EXTENDING GENERALLY EWD ACROSS NRN WY TO
NEAR RAP TO NEAR FSD AND THEN INTO SRN MN. A TROUGH THEN EXTENDED
FROM THIS SECONDARY LOW SEWD THROUGH CNTRL WY INTO CNTRL CO.
WATER VAPOR IMAGERY AND VISIBLE SATELLITE SUGGEST THAT LEADING EDGE
OF STRONGER HEIGHT FALLS AHEAD OF PACIFIC NW SYSTEM ARE BEGINNING TO
SPREAD EWD INTO WRN PARTS OF MT/WY...AND INTERACT WITH WRN EDGE OF
LOW-LEVEL THETA-E AXIS. MODIFICATION OF 18Z GREAT FALLS SOUNDING FOR
CURRENT SURFACE CONDITIONS INDICATES THAT AIR MASS OVER CNTRL MT HAS
BECOME MODERATELY UNSTABLE WITH MLCAPES OF AROUND 1000 J/KG AND A
RATHER WEAK CAP. CONTINUED DAYTIME HEATING AND BOUNDARY LAYER
MOISTENING WITHIN STRENGTHENING ELY LOW-LEVEL FLOW REGIME SHOULD
SUPPORT FURTHER DESTABILIZATION TODAY WITH MLCAPES INCREASING TO
1000-2000 J/KG OVER CNTRL/SRN PARTS OF MT TO AS HIGH AS 2000-3000
J/KG ALONG BOUNDARY OVER NRN NEB/SRN SD.
EXPECT STORMS TO GRADUALLY INCREASE OFF THE HIGHER TERRAIN OF WRN MT
THIS AFTERNOON...WITH ADDITIONAL DEVELOPMENT OCCURRING FARTHER TO
THE SE ALONG TERRAIN AND/OR DIFFERENTIAL HEATING ZONE OVER
NWRN/N-CNTRL WY SEWD INTO SRN SD/NRN NEB. OTHER STORMS WILL LIKELY
FURTHER INTENSIFY E OF LEE TROUGH OVER SERN WY INTO THE WRN NEB
PNHDL.
GIVEN THE RELATIVELY STRONG LOW AND DEEP LAYER SHEAR /0-3 KM SRH OF
200-400 M2/S2 AND EFFECTIVE BULK SHEARS OF 45-60 KT/ N OF PRIMARY
W-E BAROCLINIC ZONE...POTENTIAL WILL EXIST FOR SUPERCELLS
CAPABLE OF A FEW TORNADOES IN ADDITION TO LARGE HAIL /SOME
POTENTIALLY SIGNIFICANT/ AND DAMAGING WINDS. THIS IS ESPECIALLY THE
CASE OVER CNTRL/ERN MT INTO NERN WY AND WRN SD. STORMS WILL LIKELY
GROW UPSCALE INTO ONE OR MORE SEVERE MCS/S TONIGHT WITH THE SEVERE
THREAT SPREADING EWD INTO THE WRN/CNTRL DAKOTAS.
..NEW ENGLAND TO MIDDLE ATLANTIC COAST...
LATEST MESOANALYSIS INDICATES WEAK PRESSURE TROUGH/CONFLUENCE ZONE
EXTENDING FROM N-CNTRL NEW ENGLAND SWWD INTO THE LOWER HUDSON
VALLEY. STRONG DAYTIME HEATING HAS ALLOWED TEMPERATURES TO WARM
INTO THE 80S INVOF THIS FEATURE...EFFECTIVELY RESULTING IN THE
DEVELOPMENT OF STEEP LOW-LEVEL LAPSE RATES AND MLCAPES OF 500-1000
J/KG. WATER VAPOR IMAGERY INDICATES NO SUBSTANTIAL IMPETUS FOR
LARGE-SCALE FORCING FOR ASCENT WITH REGION LOCATED IN A DEFORMATION
ZONE JUST TO THE W OF PRIMARY MID/UPPER-LEVEL LOW. AS SUCH...EXPECT
ONGOING STORMS TO REMAIN LARGELY TIED TO DIURNAL HEATING
CYCLE...WITH MARGINALLY SEVERE WIND/HAIL THREAT CONTINUING INTO THE
EVENING. THEREAFTER...STORMS SHOULD WEAKEN WITH THE LOSS OF DAYTIME
HEATING.
..CAROLINA PIEDMONT...
A WEAK LEE TROUGH HAS BECOME ESTABLISHED THIS AFTERNOON IMMEDIATELY
E OF HIGHEST TERRAIN. TSTMS ONGOING OVER PORTIONS OF WRN NC APPEAR
TO HAVE INITIATED ALONG THIS TROUGH OR THE COMPLEX TERRAIN...WITH
ADDITIONAL BACKGROUND FORCING ASSOCIATED WITH SHORT WAVE TROUGH
DIGGING SEWD THROUGH THE CNTRL APPALACHIANS. IMMEDIATE DOWNSTREAM
AIR MASS ACROSS THE PIEDMONT HAS BECOME MODERATELY UNSTABLE WITH
MLCAPES OF 500-1000 J/KG...LARGELY DUE TO DAYTIME HEATING AND A
RELATIVELY MOIST BOUNDARY LAYER /DEWPOINTS IN THE MID 60S/. CURRENT
VWPS ACROSS THE REGION INDICATE RATHER STRONG VEERING WINDS WITH
HEIGHT THROUGH THE LOWEST 5-6 KM AGL WITH AROUND 30 KT OF BULK SHEAR
THROUGH THIS LAYER.
EXPECT STORMS TO MOVE/DEVELOP SEWD INTO LOWER ELEVATIONS OF THE
PIEDMONT AND PERHAPS COASTAL PLAIN THIS AFTERNOON AND
EVENING...DRIVEN BY LARGE-SCALE FORCING ATTENDANT TO SHORT WAVE
TROUGH. LARGE HAIL AND DAMAGING WINDS WILL REMAIN POSSIBLE WITH THE
MOST INTENSE STORMS THROUGH THE EVENING HOURS.
.MEAD.. 06/16/2007
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