DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 161953
SWODY1
SPC AC 161951

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0251 PM CDT THU MAY 16 2013

VALID 162000Z - 171200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE CNTRL HIGH
PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE ARKLATEX...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF VA...

SEVERAL MINOR MODIFICATIONS HAVE BEEN APPLIED TO 1630Z
OUTLOOK...NAMELY TO INCREASE SEVERE PROBS ACROSS THE CNTRL HIGH
PLAINS AND TO EXPAND SEVERE THREAT ACROSS PARTS OF NRN LA.
OTHERWISE...SEVERE PROBABILITIES HAVE BEEN ADJUSTED OVER THE MIDDLE
ATLANTIC TO BETTER REFLECT ONGOING THREAT.

...CENTRAL HIGH PLAINS...

CONVECTION HAS RECENTLY INCREASED MARKEDLY IN ASSOCIATION WITH WEAK
MID LEVEL CIRCULATION OVER NERN CO/SWRN NEB. THIS ACTIVITY IS
EVOLVING WITHIN A STEEP LAPSE RATE ENVIRONMENT CHARACTERIZED BY
SFC-6KM SHEAR ON THE ORDER OF 30KT. LATEST WDSS-II HAIL ALGORITHM
SUGGESTS HAIL MAY APPROACH GOLF BALL SIZE...ESPECIALLY WITH
STRONGEST ACTIVITY ACROSS YUMA INTO DUNDY COUNTIES. CURRENT
THINKING IS CONVECTION MAY REMAIN ORGANIZED AS IT SPREADS ALONG THE
NEB/KS BORDER.

...ARKLATEX...

LONG LIVED SHORT LINE SEGMENT CONTINUES ITS SEWD MOVEMENT ACROSS
NERN TX INTO NWRN LA. THIS BAND OF STORMS APPEARS CLOSELY
CORRELATED WITH LARGER CONVECTIVE CIRCULATION THAT IS DRIFTING INTO
SWRN AR. 51KT WIND GUST HAS RECENTLY BEEN RECORDED IN HARRISON
COUNTY TX AND DAMAGING WINDS MAY ACCOMPANY THIS ACTIVITY AS IT
SPREADS ACROSS PARTS OF SHV COUNTY WARNING AREA. 18Z SOUNDING FROM
SHV DEPICTS DEEP LAYER SHEAR MORE THAN ADEQUATE FOR MAINTENANCE OF
ORGANIZED LINE SEGMENT AND FOR THIS REASON HAVE ADJUSTED SEVERE
PROBS ACROSS MUCH OF NRN LA.

...VA...

EARLIER THOUGHTS REGARDING SEVERE ACROSS VA REMAIN. E-W LINE
SEGMENT HAS EVOLVED OVER CNTRL VA WHERE SFC TEMPERATURES HAVE WARMED
INTO THE MID 80S. GUSTY WINDS REMAIN POSSIBLE WITH THIS ACTIVITY AS
IT PROPAGATES SEWD.

..DARROW.. 05/16/2013

.PREV DISCUSSION... /ISSUED 1129 AM CDT THU MAY 16 2013/

...CENTRAL VA/SRN MD...
A PRE-FRONTAL BAND OF CONVECTION/ASSOCIATED CLOUDS EXTENDS FROM
NRN/CENTRAL WV INTO NRN PARTS OF THE DELMARVA REGION. VISIBLE
IMAGERY SHOWS GENERALLY CLEAR SKIES OVER CENTRAL VA AND SRN MD WHERE
STRONG DIABATIC HEATING IS OCCURRING. SURFACE TEMPERATURES ARE
EXPECTED TO WARM INTO THE MID/UPPER 80S THIS AFTERNOON AND WITH DEW
POINTS IN THE LOW/MID 50S...A DEEP SURFACE-BASED MIXED LAYER
/INVERTED-V SOUNDING STRUCTURE/ IS DEVELOPING. CONTINUED HEATING
WILL GRADUALLY WEAKEN THE LIMITED CIN WITH ADDITIONAL THUNDERSTORMS
EXPECTED TO DEVELOP EAST OF THE MOUNTAINS THIS AFTERNOON.
UNIDIRECTIONAL WLY LOW/MID LEVEL WINDS OF 25-35 KT WILL CONTRIBUTE
TO SUFFICIENT VERTICAL SHEAR FOR A FEW ORGANIZED STORM CLUSTERS TO
FORM WITH STRONGER STORMS CAPABLE OF PRODUCING DAMAGING WIND GUSTS.
THE THREAT IS EXPECTED TO DIMINISH BY THIS EVENING AS BOUNDARY LAYER
COOLING/STABILIZATION COMMENCES.

...NERN TX/SRN AR/NRN LA...
UPPER LOW OVER ERN OK IS FORECAST TO CONTINUE MOVING EWD INTO AR
THROUGH TONIGHT AND PROVIDE A FOCUS FOR STRONG/SEVERE THUNDERSTORMS
ALONG THE SRN PERIPHERY OF THE CIRCULATION. STORMS HAVE PERSISTED
THIS MORNING NEAR THE RED RIVER WITHIN A LOW-LEVEL WARM ADVECTION
ZONE ALONG/NORTH OF AN EARLIER OUTFLOW BOUNDARY. THIS ACTIVITY MAY
ALSO BE ENHANCED BY A SMALL VORTICITY CENTER ROTATING CYCLONICALLY
INTO THE SRN SEMI-CIRCLE OF THE UPPER LOW.

VISIBLE IMAGERY SHOWS A CLEAR SLOT PROGRESSING EWD OVER ERN TX WHERE
STRONGER DIABATIC HEATING WILL OCCUR...CONTRIBUTING TO
DESTABILIZATION SPREADING INTO NWRN LA THIS AFTERNOON. STORMS ARE
LIKELY TO INTENSIFY ALONG THE DIFFERENTIAL HEATING ZONE FROM NERN TX
INTO SWRN AR/NWRN LA THIS AFTERNOON AND SPREAD EWD INTO THE EVENING
HOURS. 35-45 KT WLY MID LEVEL WINDS WILL CONTRIBUTE TO SUFFICIENT
DEEP LAYER SHEAR /40-50 KT IN THE LOWEST 6 KM/ TO ENHANCE STORM
ORGANIZATION AND INTENSITY...WITH A THREAT FOR LARGE HAIL...DAMAGING
WIND GUSTS...AND POSSIBLY SEVERAL TORNADOES.

...OH VALLEY INTO WV...

LARGE-SCALE FORCING FOR ASCENT WILL REMAIN NEGLIGIBLE THIS AFTERNOON
IN THE WAKE OF THE MIDLEVEL TROUGH MOVING INTO THE CANADIAN
MARITIMES. THUS...IT APPEARS THAT LOW-LEVEL CONVERGENCE ALONG THE
SURFACE FRONT WILL BE THE PRIMARY MECHANISM FORCING SURFACE-BASED
TSTM DEVELOPMENT. POTENTIAL EXISTS FOR CORRIDORS OF STRONGER
INSTABILITY WITH AFTERNOON MLCAPE APPROACHING 1000-1500 J/KG.
HOWEVER...THE STRONGEST DEEP-LAYER WIND FIELD AND RESULTING VERTICAL
SHEAR WILL REMAIN DISPLACED TO THE NORTH OF THE SURFACE FRONT. THIS
WILL LIMIT THE POTENTIAL FOR AN ORGANIZED SEVERE WEATHER
EPISODE...THOUGH ISOLATED OCCURRENCES OF DAMAGING WINDS AND/OR HAIL
WILL BE POSSIBLE INTO THIS EVENING.

...HIGH PLAINS INTO MID-MO VALLEY...

FORCING FOR ASCENT/DCVA ASSOCIATED WITH A SHORT-WAVE TROUGH EMERGING
FROM THE CNTRL ROCKIES HAS CONTRIBUTED TO ELEVATED TSTMS MOVING
ACROSS CENTRAL NEB WITHIN A MARGINALLY UNSTABLE THERMODYNAMIC
ENVIRONMENT. EXPECT A GRADUAL INCREASE IN TSTM ACTIVITY AHEAD OF
THIS FEATURE THIS AFTERNOON ALONG A NWD-MOVING SURFACE FRONT ACROSS
SD/NEB...WITH ISOLATED TO WIDELY SCATTERED AFTERNOON TSTMS POSSIBLE
WITHIN A WEAKER-FORCED ENVIRONMENT FROM THE VICINITY OF THE LEE LOW
OVER WRN SD SWD ALONG THE LEE TROUGH/DRYLINE.

THE COMBINATION OF MODERATELY STEEP MIDLEVEL LAPSE RATES...A
MOISTENING BOUNDARY...AND DAYTIME HEATING WILL YIELD AFTERNOON
MLCAPE APPROACHING 1000-1500 J/KG. WHEN COUPLED WITH MODEST /30-35
KT/ DEEP-LAYER SHEAR...THE POTENTIAL WILL EXIST FOR ISOLATED SEVERE
STORMS CAPABLE OF HAIL AND DAMAGING WIND GUSTS.

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