DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 281942
SWODY1
SPC AC 281940

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0240 PM CDT FRI JUN 28 2013

VALID 282000Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM SRN NEW ENGLAND AND THE
MID-ATLANTIC STATES SWWD INTO THE GULF COAST STATES/LOWER MS
VALLEY...

...DISCUSSION...
ONLY MINOR TWEAKS TO THE CURRENT FORECAST ARE BEING MADE
ATTM...REFLECTIVE OF THE LATEST CONVECTIVE TRENDS. OTHERWISE...THE
SITUATION CONTINUES TO EVOLVE AS EXPECTED...WITH WIDESPREAD
CONVECTION E OF THE MS RIVER -- INCLUDING ONGOING SEVERE POTENTIAL
MAINLY CONFINED TO THE ATLANTIC AND GULF COAST STATES.

ISOLATED SEVERE POTENTIAL IS ALSO FORECAST TO EVOLVE THIS
AFTERNOON/EVENING ACROSS THE HIGH PLAINS INVOF ERN CO...AS MODEST
DESTABILIZATION ON THE WRN FRINGE OF THE STRONGER BELT OF UPPER
NWLYS SUPPORTS LOCAL HAIL/WIND POTENTIAL.

..GOSS.. 06/28/2013

.PREV DISCUSSION... /ISSUED 1114 AM CDT FRI JUN 28 2013/

...SYNOPSIS...

INTENSIFICATION OF A MID/UPPER-LEVEL LOW OVER THE GREAT LAKES/SWRN
ONTARIO WILL CONTRIBUTE TO THE AMPLIFICATION OF THE LARGE-SCALE
PATTERN THROUGH THE D1 PERIOD. A BELT OF ENHANCED MIDLEVEL FLOW
WILL BE MAINTAINED BETWEEN THIS LOW AND THE WRN U.S. ANTICYCLONE
FROM THE NRN PLAINS THROUGH THE OH VALLEY TO MID-ATLANTIC COAST AND
NEW ENGLAND. A SERIES OF LOW-AMPLITUDE PERTURBATIONS WILL PROGRESS
THROUGH THIS HIGH-MOMENTUM AIR STREAM...AUGMENTING CONVECTIVE
POTENTIAL FROM PARTS OF THE UPPER-OH VALLEY TO MID-ATLANTIC COAST
AND SRN NEW ENGLAND.

IN THE LOW LEVELS...MID-MORNING SFC ANALYSIS REVEALED THE PRESENCE
OF A COUPLE OF SYNOPTIC BOUNDARIES...ONE EXTENDING FROM LOW PRESSURE
OVER THE UPPER-HUDSON VALLEY SWWD THROUGH THE MID-SOUTH INTO SRN
PLAINS. THE OTHER STRETCHED FROM LOW PRESSURE OVER SWRN ONTARIO
WSWWD TO A LEE LOW OVER NERN CO. EXPECT AT LEAST THE ERN EXTENSIONS
OF BOTH BOUNDARIES TO CONTINUE SEWD WITHIN PREVAILING NWLY MIDLEVEL
FLOW REGIME.

...UPPER-OH VALLEY EWD INTO NEW ENGLAND...THE MID-ATLANTIC STATES
AND CAROLINAS THIS AFTERNOON AND EVENING...

12Z OBSERVED SOUNDINGS AND SATELLITE-DERIVED PW IMAGERY INDICATE A
VERY MOIST AIR MASS PRESENT E OF THE APPALACHIANS AND AHEAD OF THE
SYNOPTIC FRONT WITH BOUNDARY-LAYER DEWPOINTS IN THE MID 60S TO
LOW/MID 70S AND PW VALUES OF 1.5-2.0 INCHES. AND WHILE MIDLEVEL
LAPSE RATES WILL REMAIN WEAK...THE PRESENCE OF THIS RICH MOISTURE
ALONG WITH DAYTIME HEATING WILL PROMOTE AFTERNOON MLCAPE VALUES OF
1000-1500 J/KG ACROSS NRN PORTION OF DISCUSSION AREA TO 2000-3000
J/KG OVER PARTS OF THE CNTRL/ERN CAROLINAS.

LOW-LEVEL UPLIFT ALONG THE SYNOPTIC COLD FRONT...LEE TROUGH...AND
FAVORED TERRAIN WILL BE AUGMENTED BY DCVA ATTENDING THE WEAK
IMPULSES ROTATING AROUND THE UPPER LOW TO FOSTER SCATTERED TSTMS
THIS AFTERNOON AND EVENING. UPSCALE GROWTH OF STORMS INTO LINE
SEGMENTS IS POSSIBLE THE GIVEN THE FAVORABLE OVERLAP OF THE
MODERATE-STRONG INSTABILITY AND ABOVE-MENTIONED BELT OF ENHANCED
MIDLEVEL FLOW. WHILE THE THREAT OF DAMAGING WINDS APPEARS TO BE THE
PRIMARY HAZARD...SEVERE HAIL IS ALSO POSSIBLE WITH THE STRONGEST
UPDRAFTS.

...ARKLATEX EWD ACROSS THE GULF COAST STATES THIS AFTERNOON AND
EVENING...

THE LEADING EDGE OF CONVECTIVE OUTFLOW ASSOCIATED WITH A RECENTLY
DECAYED NOCTURNAL MCS IS EXPECTED TO FOCUS RENEWED STORM DEVELOPMENT
THIS AFTERNOON FROM CNTRL PARTS OF MS/AL SEWD TO ONGOING STORMS
ACROSS PARTS OF NRN FL/SRN GA. ABUNDANT SUNSHINE/INSOLATION COUPLED
WITH A VERY MOIST BOUNDARY LAYER /I.E. LOWEST-100-MB MEAN MIXING
RATIOS OF 17-19 G PER KG/ WILL YIELD A STRONGLY UNSTABLE AFTERNOON
AIR MASS WITH MLCAPE VALUES APPROACHING 3000-4000+ J/KG.
MOREOVER...LATEST VAD DATA FROM MEMPHIS TN INDICATES THAT
MCS-ENHANCED MIDLEVEL THERMAL/HEIGHT GRADIENTS HAVE RESULTED IN A
CORRIDOR OF 30-40 KT NWLY WINDS IN THE 3-7-KM AGL LAYER WHICH WILL
ADVANCE SEWD TODAY INCREASING DEEP-LAYER VERTICAL SHEAR. AS
SUCH...THE POTENTIAL WILL EXIST FOR THE EVOLUTION OF A SEWD-MOVING
BOWING MCS CAPABLE OF CORRIDORS OF WIND DAMAGE.

ADDITIONAL STORMS ARE ONGOING IN THE WAKE OF THE NOCTURNAL MCS GUST
FRONT AND NEARER TO THE SYNOPTIC FRONT JUST SW OF MEMPHIS. THOUGH
LATEST MODEL GUIDANCE INDICATES THE TENDENCY FOR WARMING MIDLEVEL
TEMPERATURES TODAY...THE INFLUX OF A HOT...MODERATELY UNSTABLE AIR
MASS FROM THE W/NW MAY SUSTAIN ONGOING STORMS TODAY ACROSS THE MS
DELTA REGION WITH AN ASSOCIATED RISK FOR MAINLY DAMAGING WINDS.

...CNTRL HIGH PLAINS THIS AFTERNOON AND EVENING...

THE PRESENCE OF THE LEE LOW AND WEAKER SECONDARY FRONT WILL ENHANCE
UPSLOPE FLOW FROM THE CHEYENNE RIDGE SWD INTO N-CNTRL/NERN
CO...BENEATH THE WRN FRINGE OF STRONGER NWLY FLOW ALOFT. THOUGH
LARGE-SCALE FORCING FOR ASCENT WILL REMAIN NEGLIGIBLE THROUGH THE
PEAK OF THE DIURNAL HEATING CYCLE...ISOLATED TSTMS ARE EXPECTED TO
FORM OVER THE HIGH TERRAIN AND SUBSEQUENTLY MOVE SEWD. GIVEN STEEP
LAPSE RATES...MLCAPE OF 1000-1500 J/KG...AND MODESTLY STRONG DEEP
NWLY SHEAR...THE SETUP WILL BE SUPPORTIVE OF SUSTAINED/ROTATING
STORMS CAPABLE OF HAIL AND LOCALLY DAMAGING WINDS. EXPECTED STORM
COVERAGE PRECLUDES AN UPGRADE TO SLIGHT RISK AT THIS JUNCTURE.

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