Apr 24, 2015 0600 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  

   NWS STORM PREDICTION CENTER NORMAN OK
   1253 AM CDT FRI APR 24 2015

   VALID 241200Z - 251200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS THIS AFTERNOON AND EVENING
   ACROSS PARTS OF CENTRAL AND EASTERN KANSAS...

   ...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF NORTH CENTRAL
   AND NORTHEAST TEXAS INTO ADJACENT PORTIONS OF SOUTHERN OKLAHOMA AND
   THE ARKLATEX...

   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENH RISK
   AREAS...ACROSS MUCH OF THE CENTRAL AND SOUTHERN PLAINS INTO WESTERN
   GULF COASTAL AREAS AND THE LOWER MISSISSIPPI VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS AS FAR NORTH AS PORTIONS OF THE
   NORTHERN PLAINS...AND AS FAR EAST AS THE CENTRAL GULF STATES...

   ...SUMMARY...
   SEVERE THUNDERSTORMS ARE LIKELY THIS AFTERNOON INTO TONIGHT ACROSS
   THE CENTRAL AND SOUTHERN PLAINS.  THIS WILL INCLUDE THE RISK FOR
   SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL AND PERHAPS A FEW
   STRONG TORNADOES...MAINLY ACROSS PARTS OF CENTRAL KANSAS...AS WELL
   AS PARTS OF NORTHEAST TEXAS INTO ADJACENT PORTIONS OF SOUTHERN
   OKLAHOMA AND THE ARKLATEX REGION.

   ...SYNOPSIS...
   A PAIR OF CLOSED LOWS WITHIN THE NORTHERN BRANCH OF SPLIT WESTERLIES
   EMANATING FROM THE MID-LATITUDE PACIFIC MAY ONLY SHIFT SLOWLY
   EASTWARD OR SOUTHEASTWARD TODAY...ONE OFF THE NEW ENGLAND
   COAST...THE OTHER INTO SOUTHERN BRITISH COLUMBIA AND THE PACIFIC
   NORTHWEST.  BETWEEN THESE TWO FEATURES...THOUGH...WITHIN THE
   SOUTHERN BRANCH...A VIGOROUS SHORT WAVE IMPULSE IS FORECAST TO
   ACCELERATE EAST NORTHEASTWARD OUT OF THE SOUTHWESTERN STATES...IN
   PHASE WITH THE SUBTROPICAL STREAM.  ASSOCIATED FORCING FOR UPWARD
   VERTICAL MOTION APPEARS LIKELY TO CONTRIBUTE TO SIGNIFICANT SURFACE
   CYCLOGENESIS TO THE LEE OF THE CENTRAL ROCKIES BY LATE THIS
   AFTERNOON...BEFORE CONTINUING EAST NORTHEASTWARD INTO THE MID/LOWER
   MISSOURI VALLEY BY LATE TONIGHT.

   IN THE WAKE OF DRY/POTENTIALLY COLD AIR ASSOCIATED WITH THE EASTERN
   CLOSED LOW...WHICH IS STILL SETTLING INTO THE SOUTHEASTERN U.S...A
   WEDGE OF LOW-LEVEL MOISTURE RETURN INTO THE SOUTHERN PLAINS MAY
   CONTINUE TO SLOWLY ADVECT NORTHWARD TOWARD THE CENTRAL
   PLAINS...GRADUALLY WRAPPING INTO THE VICINITY OF THE DEEPENING LOW
   CENTER.  THIS MOISTURE...COUPLED WITH INCREASING LARGE-SCALE ASCENT
   IS EXPECTED TO SUPPORT CONSIDERABLE THUNDERSTORM ACTIVITY ACROSS THE
   PLAINS AND MISSISSIPPI VALLEY REGION.  SOME OF THIS ACTIVITY IS
   EXPECTED TO BE SEVERE...ACCOMPANIED BY THE RISK FOR LARGE
   HAIL...DAMAGING WIND GUSTS...AND A FEW TORNADOES.

   OTHERWISE...SCATTERED AFTERNOON AND EVENING THUNDERSTORMS ARE AGAIN
   EXPECTED ACROSS PARTS OF THE INTERMOUNTAIN WEST AND ROCKIES...AND
   PARTS OF SOUTHERN FLORIDA.

   ...CENTRAL/SOUTHERN PLAINS INTO LOWER MISSISSIPPI VALLEY...
   WHILE THE EVOLVING LARGE-SCALE PATTERN COULD SUPPORT EVEN MORE
   SUBSTANTIVE SEVERE WEATHER POTENTIAL THAN CURRENTLY INDICATED...A
   NUMBER OF UNCERTAINTIES DO EXIST WHICH PRECLUDE HIGHER SEVERE
   PROBABILITIES AT THE PRESENT TIME.  THIS INCLUDES THE LIKELIHOOD OF
   CONSIDERABLE EARLY PERIOD MID/UPPER CLOUD COVER ASSOCIATED WITH A
   CIRRUS SHIELD ACCOMPANYING THE SUBTROPICAL JET...AND AREAS OF
   CONVECTIVE DEVELOPMENT WITHIN THE RETURNING MOIST PLUME. 
   THUNDERSTORM ACTIVITY MAY BE ONGOING THIS MORNING ACROSS MUCH OF
   NORTHERN/EASTERN TEXAS...AS WELL AS NEAR MID/UPPER TEXAS GULF
   COASTAL AREAS.  IT IS UNCLEAR WHAT IMPACT THIS WILL HAVE ON
   SUBSEQUENT DEVELOPING WARM SECTOR INSTABILITY...INCLUDING MOISTURE
   RETURN TO THE CENTRAL PLAINS.

   REGARDLESS...FORCING IN THE EXIT REGION OF A 70-80+ KT 500 MB JET
   NOSING INTO THE CENTRAL PLAINS...AND A STRONGLY DIFLUENT UPPER FLOW
   REGIME OVERSPREADING NORTH TEXAS /JUST NORTH OF THE SUBTROPICAL JET
   AXIS...AHEAD OF THE BASE OF THE SHORT WAVE TROUGH ADVANCING INTO THE
   PLAINS/...PROBABLY WILL PROVIDE THE FOCUS FOR THE PRIMARY SEVERE
   WEATHER POTENTIAL LATE THIS AFTERNOON AND EVENING.  MOISTURE WILL BE
   MORE SUBSTANTIVE ACROSS THE SOUTHERN AREA...WHERE MID-LEVEL LAPSE
   RATES MAY BE WEAKER...WHILE STEEPER MID-LEVEL LAPSE RATES ACROSS THE
    NORTHERN AREA MAY COMPENSATE FOR MORE LIMITED LOW-LEVEL MOISTURE
   RETURN.

   BY 21-23Z...THE ENVIRONMENT PROBABLY WILL BE CONDUCIVE TO SUPERCELL
   STORMS ALONG THE DRYLINE...AND NEAR THE WARM FRONT... ACROSS PARTS
   OF CENTRAL KANSAS.  STRONGEST ACTIVITY IS EXPECTED TO BE CAPABLE OF
   PRODUCING VERY LARGE HAIL AND TORNADOES...A COUPLE OF WHICH COULD BE
   STRONG...BEFORE WEAKENING AS IT SPREADS EASTWARD THIS EVENING.

   TIMING IS A BIT MORE UNCERTAIN ACROSS PARTS OF NORTHERN TEXAS... BUT
   IT MAY BE CLOSER TO...OR AFTER...25/00Z...WHEN LARGE-SCALE FORCING
   AND INSTABILITY MAY SUPPORT AN UPSCALE GROWING MESOSCALE CONVECTIVE
   SYSTEM.  VERY LARGE HAIL MAY BE POSSIBLE WITH INITIAL
   ACTIVITY...BEFORE THE RISK OF DAMAGING WIND GUSTS BECOMES MORE
   PROMINENT DURING THE EVENING.  IT IS POSSIBLE THAT THE EVOLVING
   CONVECTIVE SYSTEM COULD BE PRECEDED BY DISCRETE SUPERCELL STORMS
   WHICH COULD POSE A MORE APPRECIABLE RISK FOR
   TORNADOES...PARTICULARLY AS ACTIVITY SPREADS TOWARD THE ARKLATEX
   REGION...COINCIDENT WITH STRENGTHENING OF INITIALLY MODEST SOUTHERLY
   850 MB FLOW FIELDS.