Aug 5, 2011 0600 UTC Day 1 Convective Outlook | |
Updated: Fri Aug 5 05:52:08 UTC 2011 | |
Probabilistic to Categorical Outlook Conversion Table |
Categorical Graphic |
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Probabilistic Tornado Graphic |
Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point. |
Probabilistic Damaging Wind Graphic |
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point. |
Probabilistic Large Hail Graphic |
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point. |
SPC AC 050548 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1248 AM CDT FRI AUG 05 2011 VALID 051200Z - 061200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NRN PLAINS... ...SYNOPSIS... INTENSE MID-UPPER ANTICYCLONE OVER ARKLATEX REGION WILL REMAIN DOMINANT FEATURE OVER SRN HALF OF CONUS...AS ITS CENTER DRIFTS WWD ACROSS N TX. MEANWHILE...QUASI-ZONAL BELT OF NRN STREAM FLOW WILL PERSIST FROM PAC NW TO UPPER GREAT LAKES...WITH SEVERAL EMBEDDED SHORTWAVES. MOST OF THESE WILL BE LOW-AMPLITUDE IN NATURE...EXCEPT FOR TROUGHING NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER INTERIOR NWRN CONUS. LEADING ASSOCIATED VORTICITY MAX OVER ID SHOULD BECOME PRIMARY 500-MB PERTURBATION DAY-1...MOVING EWD ACROSS MT AND REACHING ND BY END OF PERIOD. MEANWHILE...CONVECTIVELY INDUCED/AMPLIFIED VORTICITY MAX OVER MID MS VALLEY REGION SHOULD DEAMPLIFY GRADUALLY AS IT MOVES EWD TOWARD OH BY 5/00Z...WHILE MCV OVER SERN AL/SWRN GA AREA DRIFTS SWWD ACROSS CENTRAL GULF COAST. ANOTHER MCV...EVOLVING FROM CONVECTION ACROSS WRN KS...IS EXPECTED TO MOVE EWD GENERALLY TOWARD MKC AREA AND NRN MO THROUGH PERIOD. AT SFC...FRONTAL ZONE NOW QUASISTATIONARY OVER ND IS EXPECTED TO REMAIN SO THROUGH 6/00Z...WITH SOME EFFECTIVE MODULATION POSSIBLE IN RESPONSE TO INTERVENING CONVECTION. AS MID-UPPER TROUGH MOVES OVER NRN HIGH PLAINS DURING LATTER HALF OF PERIOD...DEEPENING LEE CYCLONE OVER MT WILL MOVE EWD AS FRONTAL-WAVE LOW...REACHING WRN/SRN ND BY 6/12Z. FARTHER SE...BROAD/RESIDUAL BAROCLINIC ZONE WILL PERSIST THROUGH 6/00Z FROM SRN PIEDMONT/CAROLINAS SWWD OVER PORTIONS GA/AL...THEN WNWWD TO NRN OK/SRN KS. BY THAT TIME...FRONT SHOULD BE CLOSE TO...OR LINKED WITH...PROBABLE HEAT LOW OVER OK...WITH VERY HOT AND LOW-RH BOUNDARY LAYER TO ITS S OVER SRN PLAINS. ...NRN PLAINS... SCATTERED TSTMS SHOULD DEVELOP OVER PORTIONS CENTRAL/ERN MT DURING AFTERNOON AND MOVE EWD...WITH MIXTURE OF SUPERCELL AND MULTICELL MODES INITIALLY POSSIBLE. ACTIVITY SHOULD GROW UPSCALE TO MCS WITH PRIMARY THREAT EVOLVING TO DAMAGING WIND IN CORRIDOR FROM ERN MT NOT PORTIONS ND THROUGH EVENING AND EARLY OVERNIGHT HOURS. SVR POTENTIAL THEN SHOULD DIMINISH LATE NIGHT AS CONVECTION ENCOUNTERS PROGRESSIVELY WEAKER BOUNDARY-LAYER INSTABILITY...BOTH WITH TIME AND WITH EWD EXTENT. AFTERNOON INITIATION IS FCST IN REGIME OF FAVORABLY STEEP MIDDLE-LEVEL LAPSE RATES AIDED BY DCVA ALOFT...INCREASING MOISTURE WITH EWD EXTENT...FRONTAL/CYCLONIC CONVERGENCE NEAR SFC LOW...DIABATIC SFC HEATING TO STEEPEN SUBCLOUD LAPSE RATES AND CONTRIBUTE TO CINH REMOVAL...FAVORABLE STORM-RELATIVE INFLOW...AND ENHANCED LOW-LEVEL VORTICITY INVOF FRONT. GIVEN THIS ANTICIPATED JUXTAPOSITION OF FAVORABLE FOCI AND PARAMETERS...STG CONSENSUS EXISTS AMONG OPERATIONAL MODELS AND SREF MEMBERS WITH CONCENTRATED AREA OF CONVECTIVE PRECIP MOVING EWD FROM MT TO SD FROM AFTERNOON THROUGH EVENING. AGGREGATE OUTFLOW MAY RESULT IN FORWARD-PROPAGATING MCS ALIGNED NEARLY ORTHOGONAL TO DEEP-LAYER WIND VECTOR IN SUPPORT OF WIND POTENTIAL. MORE WIDELY SCATTERED TSTMS ARE POSSIBLE FARTHER S ACROSS ERN WY AND WRN SD...WITH SOME OROGRAPHIC LIFT AIDING IN INITIATION. DEEP-LAYER SHEAR WILL WEAKEN WITH SWD EXTENT...PROGRESSIVELY LIMITING POTENTIAL ORGANIZATION/LONGEVITY OF CONVECTION. ISOLATED TO WIDELY SCATTERED TSTMS ALSO MAY DEVELOP DIURNALLY ALONG FRONTAL SEGMENT ACROSS ERN ND AND NRN MN...WITH ISOLATED SVR HAIL/GUSTS POSSIBLE. WEAK LOW-LEVEL FLOW WILL LIMIT HODOGRAPH SIZE AND DEEP-LAYER SHEAR..ALTHOUGH AREA WILL RESIDE ON SRN FRINGE OF STRONGER 200-300 MB LAYER FLOW. ...CENTRAL PLAINS TO SERN CONUS... WIDELY SCATTERED TO SCATTERED TSTMS ARE POSSIBLE AGAIN THIS AFTERNOON...WITH ASSORTED FOCI INCLUDING SEA BREEZES/OUTFLOWS NEAR ATLC AND GULF COASTS...OUTFLOW/DIFFERENTIAL HEATING BOUNDARIES NEAR RESIDUAL CLOUD COVER OVER PORTIONS MS/AL OR MID-SOUTH REGIONS...AND ALONG AND N OF FRONTAL ZONE AND RESIDUAL OUTFLOWS FROM PRIOR/OVERNIGHT CONVECTION FROM OZARKS INTO CENTRAL PLAINS. RELATIVE NODES OR MAXIMA ARE PROBABLE WITHIN THIS BROAD SWATH...WHICH WILL BE UNDER GENERALLY WEAK DEEP-TROPOSPHERIC FLOW AND SHEAR IN SUPPORT OF MULTICELLULAR AND PULSE MODES. SUCH NODES ARE SO DEPENDENT ON MESOSCALE FOCI -- SOME YET TO DEVELOP -- THAT THERE IS TOO MUCH UNCERTAINTY ATTM FOR UNCONDITIONAL/15% THRESHOLD CATEGORICAL RISK AREA. ONE AREA OF CONCERN IN PARTICULAR MAY BE FROM SRN KS ACROSS SRN MO...WHERE FRONTAL AND DIABATIC ASCENT MAY COMBINE WITH ENHANCED GRADIENT FLOW S OF MCV. SHAPE/DENSITY EWD-MOVING CLOUD DEBRIS FROM ONGOING CONVECTIVE REGIME OVER WRN KS MAY EXERT CONSIDERABLE INFLUENCE ON MORE PRECISE AREAS FOR CONVECTIVE/SVR POTENTIAL. ..EDWARDS/GRAMS.. 08/05/2011 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z