Apr 23, 2015 0600 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  

   NWS STORM PREDICTION CENTER NORMAN OK
   1249 AM CDT THU APR 23 2015

   VALID 231200Z - 241200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM MIDDAY INTO THE AFTERNOON
   ACROSS PARTS OF SOUTHERN LOUISIANA...

   ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING
   ACROSS PARTS OF NORTHWEST TEXAS AND ADJACENT SOUTHWESTERN
   OKLAHOMA...SOUTHWARD ACROSS THE EDWARDS PLATEAU INTO ADJACENT AREAS
   OF THE RIO GRANDE VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLIGHT RISK
   AREAS....ACROSS THE CENTRAL PLAINS AND SOUTHERN PLAINS INTO THE
   CENTRAL GULF COAST...

   ...THERE IS A MRGL RISK OF SVR TSTMS THIS AFTERNOON ACROSS SOUTHEAST
   FLORIDA COASTAL AREAS...

   ...SUMMARY...
   SCATTERED STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE TODAY ACROSS
   THE CENTRAL HIGH PLAINS...THE SOUTHERN PLAINS...THE CENTRAL GULF
   COAST REGION...AND SOUTHEAST FLORIDA COASTAL AREAS.

   ...SYNOPSIS...
   WITHIN THE NORTHERN BRANCH OF SPLIT WESTERLIES EMANATING FROM THE
   MID-LATITUDE PACIFIC...MODELS INDICATE THAT THE CENTER OF A
   LARGE...COLD MID/UPPER LOW WILL REDEVELOP EASTWARD DURING THIS
   PERIOD...FROM EASTERN ONTARIO INTO NORTHERN NEW ENGLAND BY 12Z
   FRIDAY.  AS THIS OCCURS...AND AN UPSTREAM CLOSED LOW GRADUALLY
   MIGRATES INLAND ACROSS THE SOUTHERN BRITISH COLUMBIA/WASHINGTON
   COAST...UPPER TROUGHING WITHIN THE SOUTHERN BRANCH...IN PHASE WITH
   THE SUBTROPICAL STREAM...IS FORECAST TO DEVELOP EAST NORTHEASTWARD
   TOWARD THE CENTRAL AND SOUTHERN ROCKIES.  AS THE MOST PROMINENT
   SHORT WAVE IMPULSE WITHIN THIS LATTER FEATURE SLOWLY PIVOTS ACROSS
   BAJA AND THE GULF OF CALIFORNIA...BEFORE ACCELERATING NORTHEASTWARD
   TOWARD THE SOUTHERN ROCKIES...DOWNSTREAM SHORT WAVE RIDGING APPEARS
   LIKELY TO AMPLIFY ACROSS PARTS OF THE CENTRAL/SOUTHERN PLAINS
   THROUGH MID/LOWER MISSISSIPPI VALLEY.

   IN LOWER LEVELS...FURTHER SOUTHWARD ADVANCEMENT OF A COLD FRONT
   THROUGH THE SOUTH ATLANTIC /EASTERN GULF COAST STATES IS EXPECTED. 
   THE TRAILING WESTERN FLANK OF THIS FRONT PROBABLY WILL REMAIN
   STALLED NEAR/NORTH OF THE SOUTHERN PLAINS RED RIVER VALLEY THROUGH
   THE DAY...BEFORE REDEVELOPING NORTHWARD INTO THE CENTRAL PLAINS
   TONIGHT.  AT THE SAME TIME...SURFACE TROUGHING SHOULD BEGIN TO
   GRADUALLY DEEPEN ACROSS THE HIGH PLAINS.  SEASONABLY MOIST AIR WILL
   REMAIN CONFINED TO AREAS ALONG AND SOUTH OF THE FRONT...BUT SOME
   INCREASE IN MOISTURE IS ALSO EXPECTED AS SOUTHEASTERLY/SOUTHERLY
   LOW-LEVEL FLOW STRENGTHENS ACROSS THE HIGH PLAINS.

   BENEATH SEASONABLY STEEP MID-LEVEL LAPSE RATES...THIS MOISTURE...
   COUPLED WITH DAYTIME HEATING...WILL CONTRIBUTE TO SCATTERED
   THUNDERSTORM ACTIVITY ACROSS THE HIGH PLAINS...PORTIONS OF THE
   CENTRAL GULF COAST STATES...AND THE FLORIDA ATLANTIC COASTAL AREAS. 
   ADDITIONAL SCATTERED THUNDERSTORM ACTIVITY LIKELY WILL FORM WITH
   DAYTIME HEATING ACROSS PARTS OF THE CENTRAL ROCKIES...THE GREAT
   BASIN...THE SIERRA NEVADA AND ADJACENT INTERIOR VALLEYS OF
   CALIFORNIA...AND THE MOGOLLON RIM AREA OF ARIZONA INTO THE MOUNTAINS
   OF SOUTHWESTERN NEW MEXICO.  WHILE MUCH OF THIS ACTIVITY DIMINISHES
   THIS EVENING...INCREASING LARGE-SCALE ASCENT DOWNSTREAM OF THE
   SOUTHERN BRANCH TROUGHING IS EXPECTED TO PROVIDE THE FORCING/FOCUS
   FOR NEW STORM DEVELOPMENT ACROSS PARTS OF THE CENTRAL AND SOUTHERN
   PLAINS.

   ...TEXAS AND ADJACENT SOUTHERN OKLAHOMA...
   MOISTURE CONTENT IS EXPECTED TO REMAIN SUPPORTIVE OF SIZABLE MIXED
   LAYER CAPE BY LATE AFTERNOON BENEATH RELATIVELY STEEP MID-LEVEL
   LAPSE RATES.  IN THE PRESENCE OF STRONG DEEP LAYER VERTICAL SHEAR
   BENEATH 40-50+ KT SOUTHWESTERLY 500 MB FLOW...THE ENVIRONMENT SHOULD
   BE CONDUCIVE TO SEVERE STORMS...INCLUDING SUPERCELLS...WHERE DEEP
   CONVECTION CAN BE INITIATED AND MAINTAINED.  THE DRYLINE SEEMS TO
   PROVIDE THE MOST LIKELY FOCUS FOR THIS DURING THE LATE AFTERNOON OR
   EARLY EVENING...PARTICULARLY ACROSS PARTS OF NORTHWEST AND WEST
   CENTRAL TEXAS...WHERE IT APPEARS MID-LEVEL HEIGHT RISES COULD BE
   SUPPRESSED/SLOWED BY THE PROGRESSION OF A WEAK MID-LEVEL IMPULSE.

   ...SOUTHERN LOUISIANA...
   GUIDANCE SUGGESTS THAT FORCING ON THE NORTHEASTERN PERIPHERY OF THE
   BUILDING MID-LEVEL RIDGE COULD SUPPORT INCREASING STORM DEVELOPMENT
   BY MIDDAY...IN THE PRESENCE OF WEAK TO MODERATE BOUNDARY LAYER CAPE.
    LOW-LEVEL FLOW WILL BE WEAK...BUT 40-50 KT WEST NORTHWESTERLY 500
   MB FLOW WILL PROVIDE SUFFICIENT VERTICAL SHEAR FOR ORGANIZED STORM
   DEVELOPMENT...INCLUDING SUPERCELLS.

   ...SOUTHEAST FLORIDA...
   OUTPUT FROM THE NCEP SREF AND VARIOUS CONVECTION ALLOWING MODELS
   SUGGEST THE POTENTIAL FOR VIGOROUS STORM DEVELOPMENT THIS
   AFTERNOON...MAINLY NEAR COASTAL AREAS...ALONG THE SEA BREEZE.  IF
   THIS OCCURS...DEEP LAYER SHEAR AND INSTABILITY PROBABLY WILL BE
   SUFFICIENT FOR AN ISOLATED SUPERCELL OR TWO.

   ...CENTRAL HIGH PLAINS...
   A WEAK MID-LEVEL IMPULSE EMERGING FROM THE APPROACHING SOUTHERN
   BRANCH TROUGHING PROBABLY WILL AID CONVECTIVE DEVELOPMENT FROM THE
   FRONT RANGE OF THE ROCKIES NORTHWARD TOWARD THE BLACK HILLS BY LATE
   AFTERNOON.  LOW MOISTURE CONTENT APPEARS THE PRIMARY LIMITING FACTOR
   TO HIGHER SEVERE PROBABILITIES AT THE PRESENT TIME...AS LAPSE RATES
   ARE EXPECTED TO BE STEEP...AND VERTICAL SHEAR SHOULD BE AT LEAST
   MARGINALLY SUFFICIENT FOR ISOLATED SUPERCELLS.