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| CATEGORICAL OUTLOOK |
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| TORNADO OUTLOOK |
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| WIND OUTLOOK |
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| HAIL OUTLOOK |
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0800 PM CDT FRI JUN 29 2012
VALID 300100Z - 301200Z
...THERE IS A MDT RISK OF SVR TSTMS PORTIONS EXTREME ERN
WV...VA...MD...DC..EXTREME SRN PA...
...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM ERN WV TO
COASTAL SRN MID-ATLC AND VA/MD/DE TIDEWATER....
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SWRN MN AND IA TO NWRN
INDIANA...
...SYNOPSIS...
UPPER-AIR PATTERN WILL REMAIN DOMINATED BY MEAN RIDGING ACROSS MOST
OF SRN 1/2 OF CONUS. RIDGING EXTENDS FROM AZ-SC AND BEYOND...BUT IS
BREACHED SOMEWHAT BY COL/TROUGH OVER OK EXTENDING NWD FROM
BROAD/WEAK/QUASISTATIONARY/UPPER LOW OVER S TX. GEN RIDGING ALOFT
ALSO EXTENDS FROM 4-CORNERS REGION NNWWD OVER NRN ROCKIES TO AB AND
WILL MOVE SLOWLY EWD OUT OF NRN ROCKIES BY 12Z. SYNOPTIC-SCALE
TROUGHING IS EVIDENT OVER HUDSON BAY REGION...AND OFFSHORE PAC
COAST. SHORTWAVES EMBEDDED IN INTERVENING FLOW WILL INFLUENCE THIS
FCST...INCLUDING NEARLY-PHASED TROUGHS NOW OVER SWRN MN/NWRN IA AND
S-CENTRAL/SERN IA. LATTER PERTURBATION WAS CONVECTIVELY ENHANCED
LAST NIGHT OVER CENTRAL PLAINS...AND MAY EXPERIENCE FURTHER
CONVECTIVE VORTICITY GENERATION WITH ONGOING IA ACTIVITY. COMBINED
TROUGHS SHOULD MOVE ESEWD ACROSS UPPER MS VALLEY AND IL TO INDIANA
BY END OF PERIOD. UPSTREAM...MOISTURE CHANNEL IMAGERY INDICATES
SHORTWAVE TROUGH PENETRATING MEAN RIDGE POSITION OVER AB...WHICH
WILL PIVOT EWD/ESEWD ACROSS SK/MB OVERNIGHT...INFLUENCING ELEVATED
TSTM POTENTIAL LATE IN PERIOD OVER ND.
AT SFC...23Z ANALYSIS SHOWED COLD FRONT FROM SRN QUE ACROSS WRN
MAINE THEN SWWD OVER CENTRAL/SRN PA...BEING OVERTAKEN BY NRN PORTION
OF DERECHO-PRODUCING MCS OVER SWRN PA. OUTFLOW BOUNDARY FROM THAT
MCS EXTENDS FROM ERN KY NWWD ACROSS SWRN INDIANA TO ERN
IL...BECOMING QUASISTATIONARY ALONG ERN IL/INDIANA SEGMENT.
BOUNDARY BECOMES DIFFUSE NWWD ACROSS CENTRAL IL TO LOW OVER SERN
IA...INTERSECTING OUTFLOW FROM ONGOING IA CONVECTION. THAT
BOUNDARY...IN TURN EXTENDED FROM LOW SWWD NEAR IA/MO BORDER THEN
WNWWD ACROSS EXTREME SRN IA AND ERN NEB. QUASISTATIONARY
FRONT/TROUGH EXTENDED FROM HEAT LOW OVER KS/CO BORDER REGION ENEWD
ACROSS KS/NEB BORDER TO NWRN MO.
...WV TO DELMARVA COAST...
SVR MCS...CONTAINING LARGE BOW ECHO...SHOULD CONTINUE ONGOING
DERECHO EVENT ESEWD ACROSS APPALACHIANS/PIEDMONT TOWARD VA/MD
TIDEWATER REGION. SOME UNCERTAINTY EXISTS WITH RECOVERY AFTER
CURRENT/SLGT WEAKENING TREND DURING ITS PASSAGE ACROSS RELATIVELY
DRY AIR IN HIGHEST TERRAIN...HOWEVER
1. SUBSTANTIAL COLD POOL HAS BEEN BUILT WITH INTENSE ISALLOBARIC
TENDENCIES TO DRIVE STG LOW-LEVEL FORCING ONTO LOWER TERRAIN...AND
2. FOREGOING BOUNDARY-LAYER AIR MASS WILL REMAIN SUITABLY
MOIST/UNSTABLE PER IAD RAOB THAT CONTAINED 2 INCH PW AND OVER 5500
J/KG MLCAPE.
EXPECT CONTINUED/REJUVENATED DAMAGING WIND POTENTIAL...INCLUDING
OCNL SIGNIFICANT/65+ KT GUSTS...AT LEAST AS FAR E AS I-95 CORRIDOR.
E OF THERE...ACROSS CHESAPEAKE BAY AND DELMARVA...AIR MASS WILL BE
MORE STABLE...BOTH WITH EWD EXTENT AND WITH TIME. HOWEVER...FORCED
ASCENT ALONG COLD-POOL SLAB MAY OVERCOME RELATED CINH AND MAINTAIN
DAMAGING-WIND THREAT TO COAST. GIVEN THOSE
UNCERTAINTIES...PROBABILITIES RAMP DOWN SOMEWHAT FROM BAY EWD...BUT
REMAIN ABOVE THRESHOLDS FOR CATEGORICAL SVR-WIND OUTLOOK. REF SPC
WW 438 AND RELATED MESOSCALE DISCUSSIONS FOR NEAR-TERM FCST INFO ON
THIS EVENT.
...UPPER MS VALLEY TO PORTIONS IL/INDIANA...
SVR POTENTIAL IS CONTINUING ACROSS MS RIVER INTO IL WITH TSTMS OVER
ERN IA...WITH ADDITIONAL RISK FOR LARGE HAIL FROM TRAILING
CONVECTION BEHIND INITIAL OUTFLOW BOUNDARY. ORGANIZATION WILL BE
AIDED BY LARGE-SCALE ASCENT ACCOMPANYING MCV...LOW-LEVEL INFLOW AIR
MASS CONTAINING TEMPS 80S/90S F AND DEW POINTS UPPER 60S/LOW 70S N
OF BOUNDARY...AND 40-50 KT EFFECTIVE SHEAR MAGNITUDES ALSO AIDED BY
PERTURBATION ALOFT. FOR MORE NEAR-TERM DETAILS...REF SPC WW 437 AND
RELATED MESOSCALE DISCUSSIONS. UNCERTAINTIES INCREASE WITH EWD
EXTENT REGARDING DURATION/STRENGTH/COVERAGE OF THIS ACTIVITY PAST
NRN IL...GIVEN GROWING STATIC STABILITY RELATED TO EARLIER MCS
PASSAGE...AND EXTENT OF NEARLY SFC-BASED AIR MASS RECOVERY ALONG AND
N OF BOUNDARY. AS SUCH...UNCONDITIONAL PROBABILITIES DIMINISH EWD
TOWARD INDIANA...BUT CONDITIONAL SVR THREAT MAY PERSIST TO END OF
PERIOD.
...MAINE...
SCATTERED TSTMS ALONG PREFRONTAL CONVERGENCE LINE ARE MOVING OVER
NEW BRUNSWICK AND DOWNEAST MAINE ATTM...AND THEIR SVR POTENTIAL WILL
DIMINISH THROUGH REMAINDER EVENING WITH STABILIZATION OF
PRECONVECTIVE BOUNDARY LAYER. MEANWHILE...ISOLATED SVR HAIL/GUSTS
STILL MAY OCCUR WITH CONVECTION CLOSER TO SFC COLD FRONT OVER NRN
MAINE. THREAT HAS DIMINISHED ENOUGH THAT SUB-CONDITIONAL SVR
PROBABILITIES CAN BE PULLED BELOW CATEGORICAL OUTLOOK LEVELS...WHILE
KEPT FOR MRGL POTENTIAL REMAINING.
...CENTRAL/NRN PLAINS...
ALTHOUGH ISOLATED/MRGL SVR POTENTIAL EXISTS ACROSS BROAD SWATH OF
CENTRAL/NRN PLAINS AS OUTLINED BY 5% AREA...MAIN CONCERN FOR
EVENING/OVERNIGHT ACTIVITY IS FROM NERN SD/SWRN MN SEWD ACROSS IA.
SFC ANALYSIS SHOWED WELL-DEFINED MOIST PLUMES/AXES FROM CENTRAL IA
SWWD ACROSS SRN NEB...AND NWWD OVER SWRN MN TO ERN SD. SRN MOIST
PLUME MAY SUPPORT SOME SVR POTENTIAL...BUT MLCINH DERIVED FROM
MODIFIED OAX/TOP/LBF RAOBS SHOULD STRENGTHEN WITH ONSET OF
APPRECIABLE SFC COOLING THIS EVENING...ALONG AND N OF
QUASISTATIONARY FRONT. FARTHER NW...HOWEVER...UPPER-LEVEL
SUPPORT/DESTABILIZATION AHEAD OF NRN-STREAM PERTURBATION WILL BECOME
JUXTAPOSED WITH LOW-LEVEL MOISTURE PLUME...CONDITIONALLY SUPPORTING
CLUSTERED TSTM DEVELOPMENT AND FORWARD PROPAGATION. THERE COULD BE
SOME SPATIAL SEPARATION BETWEEN ERN EDGE OF THIS REGIME AND CURRENT
LOCATION OF ERN IA COMPLEX...HOWEVER WILL AVOID INTRODUCING NARROW
GAP BETWEEN 15%/SLGT AREAS GIVEN THAT UNCERTAINTY.
..EDWARDS.. 06/30/2012
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z
CURRENT UTC TIME: 0110Z (8:10PM), RELOAD THIS PAGE TO UPDATE THE TIME
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