SWODY1
SPC AC 112003
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0303 PM CDT SUN JUL 11 2010
VALID 112000Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN AND
CNTRL PLAINS...UPPER MIDWEST...OZARKS...LOWER OH VALLEY AND TN
VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN HIGH
PLAINS AND CNTRL PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ERN GA AND SRN
SC...
MANY CHANGES HAVE BEEN MADE TO THE OUTLOOK FOR THE 20Z ISSUANCE. THE
FIRST CHANGE IS TO MOVE THE NRN EDGE OF THE 30 PERCENT HAIL AND WIND
PROBABILITIES SWD TO THE SEVERE THUNDERSTORMS ONGOING IN NE KS AND
CNTRL MO. THE GREATEST POTENTIAL FOR AN ENHANCED SEVERE THREAT
SHOULD EXIST NEAR THE CONVECTION EXTENDING SWD ACROSS ERN KS AND
SCNTRL MO WHERE A STRONGLY UNSTABLE AIRMASS IS IN PLACE ACCORDING TO
OBJECTIVE ANALYSIS. ANOTHER CHANGE IS TO BRING THE 5 PERCENT TORNADO
PROBABILITY NWWD TO A SUPERCELL ONGOING IN FAR NE KS. THIS STORM IS
LOCATED ALONG THE NERN EDGE OF STRONG INSTABILITY VERY NEAR THE CORE
OF A MID-LEVEL JET MAX AROUND 700 MB ACCORDING TO OBJECTIVE
ANALYSIS. ANOTHER CHANGE IS TO EXPAND THE SLIGHT RISK AREA IN SRN SC
NEWD TO COVER MORE OF THE COASTAL PLAINS WHERE STRONG INSTABILITY IS
PRESENT WHERE REGIONAL WSR-88D VWPS SUGGEST DEEP LAYER SHEAR IS
SUFFICIENT FOR ROTATING STORMS. IN ADDITION...THE SLIGHT RISK AREA
IN THE HIGH PLAINS HAS BEEN ADJUSTED WWD AND NWD ACROSS ERN WY INTO
FAR SE MT WHERE MODERATE INSTABILITY HAS DEVELOPED ACCORDING TO
OBJECTIVE ANALYSIS AND LAPSE RATES ARE STEEP. ANOTHER CHANGE IS TO
BRING THE 5 PERCENT HAIL AND WIND PROBABILITIES SWD ACROSS SRN AR
WHERE STRONG STORMS ARE ONGOING IN A STRONGLY UNSTABLE AIRMASS.
ANOTHER CHANGE IS TO NARROW THE 5 PERCENT HAIL AND WIND PROBABILITY
ACROSS THE TX PANHANDLE WHERE A RELATIVELY NARROW AXIS OF STRONG
INSTABILITY IS CO-LOCATED WITH STEEPENING LOW-LEVEL LAPSE RATES. THE
REMAINING CHANGES INCLUDE THUNDER PROBABILITY ADJUSTMENTS.
..BROYLES.. 07/11/2010
.PREV DISCUSSION... /ISSUED 1129 AM CDT SUN JUL 11 2010/
...MID/LOWER MO VALLEY SWD THROUGH THE OZARK PLATEAU AND EWD INTO
THE OH/TN VALLEYS...
12Z UPPER-AIR ANALYSIS INDICATES A SEASONABLY STRONG UPPER-LEVEL JET
STREAK STRETCHING FROM THE CNTRL ROCKIES INTO THE OZARKS...TO THE
IMMEDIATE SOUTH OF A WELL-DEFINED SHORT WAVE TROUGH TRANSLATING
ESEWD THROUGH THE MID/LOWER MO VALLEYS. 12Z NUMERICAL GUIDANCE
TAKES THIS SHORT WAVE TROUGH THROUGH THE MID MS VALLEY TODAY AND
ACROSS MUCH OF THE OH VALLEY OVERNIGHT. AN ASSOCIATED WEAK SURFACE
LOW IS FORECAST TO ACCOMPANY THIS UPPER SYSTEM EWD WHILE A COUPLE OF
TRAILING COLD FRONTAL SURGES PUSH SWD THROUGH THE GREAT PLAINS AND
UPPER GREAT LAKES REGION.
A CLUSTER OF STRONG TO SEVERE TSTMS IS ONGOING THIS MORNING OVER
NWRN MO/NERN KS ALONG THE SRN FRINGE OF STRONGER HEIGHT FALLS
ATTENDANT TO ABOVE-MENTIONED MIDLEVEL TROUGH...AND WITHIN A ZONE OF
LOW-LEVEL WAA ALONG 20-30 KT WSWLY LLJ. 12Z REGIONAL SOUNDINGS AND
SATELLITE-DERIVED PW DATA INDICATE THE PRESENCE OF A VERY MOIST
INFLOW AIR MASS ACROSS THE LOWER ELEVATIONS OF THE CNTRL/SRN PLAINS
EWD INTO LOWER MS VALLEY. FURTHER...VISIBLE SATELLITE IMAGERY
SUGGESTS THAT STRONG DIABATIC HEATING WILL OCCUR ACROSS THESE SAME
AREAS...SUPPORTING THE DEVELOPMENT OF A MODERATE TO STRONGLY
UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPE OF 2000-3000 J/KG.
CURRENT THINKING IS THAT ONGOING STORMS WILL MOVE/DEVELOP SEWD ALONG
OR ON THE IMMEDIATE COOL SIDE OF A LOW-LEVEL BAROCLINIC ZONE
EXTENDING SEWD FROM THE VICINITY OF THESE TSTMS THROUGH SERN MO INTO
NWRN TN. GIVEN THE DEGREE OF INSTABILITY...BACKGROUND FORCING FOR
ASCENT ATTENDANT TO MIDLEVEL TROUGH AND VERTICALLY-VEERING WIND
PROFILES...SETUP SHOULD FAVOR THE DEVELOPMENT OF A
FORWARD-PROPAGATING MCS/BOW AND/OR SUPERCELLS WITH THE THREAT FOR
DAMAGING WINDS AND HAIL AND PERHAPS A TORNADO OR TWO.
ADDITIONAL STORMS ARE ALSO LIKELY TO DEVELOP WITHIN THE LOW-LEVEL
WAA REGIME ALONG THE WRN FLANK OF THIS SYSTEM /AND ALONG SRN-MOST
SYNOPTIC-SCALE FRONTAL SURGE/ OVER PARTS OF KS AND EVENTUALLY INTO
OK. GIVEN SIMILAR THERMODYNAMIC AND KINEMATIC CHARACTERISTICS TO
THOSE MENTIONED ABOVE...THE THREAT WILL EXIST FOR SUPERCELLS OR A
SECONDARY...SWD-PROPAGATING MCS WITH ATTENDANT THREATS FOR A TORNADO
OR TWO...LARGE HAIL AND HIGH WINDS.
...IA INTO THE UPPER MIDWEST...
THE COMBINED EFFECTS OF MID VALLEY SHORT WAVE TROUGH AND
LARGER-SCALE TROUGH DIGGING SEWD THROUGH MANITOBA/ONTARIO INTO THE
UPPER GREAT LAKES WILL PROVIDE FAVORABLE BACKGROUND FORCING FOR
ASCENT FOR TSTM DEVELOPMENT THIS AFTERNOON INTO TONIGHT. THE
PRIMARY UNCERTAINTY IS THE DEGREE OF AIR MASS DESTABILIZATION AHEAD
OF SEWD-MOVING COLD FRONT GIVEN THE WIDESPREAD CLOUD COVER. 12Z
MODEL GUIDANCE SUGGESTS THAT POCKETS OF STRONGER HEATING WILL
COMBINE WITH A RELATIVE MOIST BOUNDARY LAYER /I.E. DEWPOINTS IN THE
60S/ TO SUPPORT AREAS OF MODERATE INSTABILITY LATER TODAY. AS
SUCH...THE THREAT WILL EXIST FOR STRONG TO SEVERE TSTM DEVELOPMENT
ALONG THE FRONT OVER MN/WI...AS WELL AS IN ADVANCE OF PRONOUNCED
CYCLONIC CIRCULATION /PER RADAR IMAGERY/ PROGRESSING EWD THROUGH
CNTRL IA. VERTICAL SHEAR WILL REMAIN SOMEWHAT MARGINAL FOR
ORGANIZED/SUSTAINED STORMS...THOUGH A THREAT FOR HAIL AND STRONG
WIND GUSTS WILL EXIST IN AREAS WHERE STRONGER DESTABILIZATION CAN
OCCUR.
...ERN WY INTO SD/NEB...
12Z 500 MB ANALYSIS AND CURRENT WATER VAPOR IMAGERY SUGGEST THE
PRESENCE OF ONE /OR PERHAPS MULTIPLE/ SHORT WAVE TROUGH/S/ EMBEDDED
WITHIN WNWLY FLOW REGIME OVER THE NRN INTERMOUNTAIN REGION INTO NRN
HIGH PLAINS. WHEN COUPLED WITH A STEEP LAPSE RATE ENVIRONMENT AND
RESIDUAL BOUNDARY LAYER MOISTURE IN THE WAKE OF FRONTAL
PASSAGE...SETUP WILL FAVOR THE DEVELOPMENT OF A FEW SEWD-MOVING
SEVERE STORMS CAPABLE OF DAMAGING WINDS AND HAIL.
...SERN ATLANTIC COAST...
THE PRESENCE OF A HOT...HUMID AND MODERATELY UNSTABLE AIR MASS ALONG
WITH A WEAK FRONTAL BOUNDARY SHOULD SUPPORT THE DEVELOPMENT OF
NUMEROUS TSTMS THROUGH THE DIURNAL HEATING CYCLE. 12Z FFC SOUNDING
SHOWED THE PRESENCE OF SLIGHTLY STRONGER WLY FLOW /I.E. 25-30 KT/ IN
THE 3-6 KM AGL LAYER. THIS COMBINED WITH THE MODERATE INSTABILITY
MAY PROMOTE THE ORGANIZATION OF A FEW STORM CLUSTERS WITH THE MAIN
THREAT FOR WET MICROBURSTS/DAMAGING WIND GUSTS.
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