May 26, 2015 0600 UTC Day 1 Convective Outlook

DAY 1 CONVECTIVE OUTLOOK  

   NWS STORM PREDICTION CENTER NORMAN OK
   1252 AM CDT TUE MAY 26 2015

   VALID 261200Z - 271200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS PARTS OF THE GREAT
   LAKES REGION AND OHIO VALLEY...

   ...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING
   ACROSS PARTS OF THE SOUTH CENTRAL PLAINS....

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE
   GREAT LAKES...OHIO VALLEY AND PLAINS...AS WELL AS PORTIONS OF THE
   GULF COAST REGION...

   ...SUMMARY...
   SCATTERED SEVERE STORMS ARE POSSIBLE TODAY ACROSS PARTS OF THE GREAT
   LAKES REGION AND OHIO VALLEY.  ADDITIONAL SEVERE STORMS ARE POSSIBLE
   LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF THE SOUTH CENTRAL
   PLAINS.

   ...SYNOPSIS...
   MODELS ARE SUGGESTIVE THAT MID/UPPER FLOW MAY TREND A BIT MORE ZONAL
   ACROSS MUCH OF THE U.S. DURING THIS PERIOD.  THE SUBTROPICAL HIGH
   CENTERED NEAR THE SOUTH ATLANTIC COAST MAY WEAKEN SOME...BUT A RIDGE
   AXIS EXTENDING NORTHEASTWARD INTO AREAS JUST EAST OF SOUTHERN NEW
   ENGLAND COAST IS EXPECTED TO HOLD FIRM.  AT THE SAME TIME RIDGING IS
   EXPECTED TO BUILD WESTWARD ACROSS CENTRAL MEXICO INTO THE
   SUBTROPICAL EASTERN PACIFIC.  WHILE A SHORT WAVE TROUGH ON THE
   NORTHERN PERIPHERY OF THIS LATTER FEATURE APPROACHES BAJA...SHORT
   WAVE RIDGING IS FORECAST TO BUILD ACROSS MUCH OF THE SOUTHERN
   ROCKIES AND SOUTHERN PLAINS...IN THE WAKE OF THE SHORT WAVE IMPULSE
   NOW PIVOTING NORTHEAST OF THE CENTRAL PLAINS.

   THIS LEAD IMPULSE APPEARS TO BE IN THE PROCESS OF MERGING WITH THE
   REMNANTS OF A MID-LEVEL LOW...WITHIN A BELT OF WESTERLIES TO THE
   NORTH...NOW SHIFTING EAST NORTHEASTWARD THROUGH THE NORTH CENTRAL
   PLAINS...AHEAD OF ANOTHER BROAD LOW DIGGING INTO THE NORTHERN
   INTERMOUNTAIN REGION.  AS THIS CONTINUES...THE CONSOLIDATING IMPULSE
   IS FORECAST TO ACCELERATE NORTHEASTWARD TOWARD THE UPPER GREAT LAKES
   REGION...WHERE AT LEAST MODEST DEEPENING OF A SURFACE CYCLONE
   APPEARS POSSIBLE BY LATE THIS AFTERNOON.

   A TRAILING SURFACE FRONT MAY ADVANCE SOUTHWARD THROUGH MUCH OF THE
   UPPER MIDWEST...MIDDLE MISSISSIPPI VALLEY AND CENTRAL PLAINS BY LATE
   TONIGHT.  HOWEVER...THIS FRONT MAY NOT BE PARTICULARLY
   WELL-DEFINED...DUE TO CONSIDERABLE CONVECTIVELY PROCESSED AIR TO ITS
   SOUTHEAST.  PERHAPS MOST PROMINENT IS THE CONGLOMERATE SURFACE COLD
   POOL ACCOMPANYING THE EXTENSIVE WEAKENING SQUALL LINE NOW ADVANCING
   THROUGH THE WESTERN GULF COAST AND LOWER MISSISSIPPI VALLEY REGION. 
   ALTHOUGH A SOUTHERLY RETURN FLOW SHOULD CONTINUE AROUND THE EASTERN
   PERIPHERY OF WESTERN ATLANTIC/SOUTHEASTERN U.S. SURFACE
   RIDGING...MOISTURE ADVECTION OFF THE GULF OF MEXICO MAY BE
   DISRUPTED...AND THE STABILIZING INFLUENCE OF THIS AIR MASS ON MUCH
   OF THE SOUTHEASTERN PLAINS AND LOWER MISSISSIPPI VALLEY MAY BE
   CONSIDERABLE THROUGH THIS PERIOD.

   ...GREAT LAKES/OHIO VALLEY REGION...
   ALTHOUGH SUBSTANTIVE STEEPENING OF MID-LEVEL LAPSE RATES APPEARS
   UNLIKELY...DAYTIME HEATING OF A MOISTENING BOUNDARY LAYER /AHEAD OF
   THE AFOREMENTIONED OUTFLOW BOUNDARY...NORTHWESTWARD INTO THE WARM
   SECTOR OF THE DEEPENING SURFACE CYCLONE/ PROBABLY WILL BE SUFFICIENT
   TO SUPPORT WEAK TO MODEST MIXED LAYER CAPE BY THIS AFTERNOON.  THIS
   INSTABILITY...COINCIDENT WITH STRENGTHENING OF SOUTHERLY TO
   SOUTHWESTERLY LOWER/MID TROPOSPHERIC WIND FIELDS TO 30-50 KT...IS
   EXPECTED TO BE SUFFICIENT TO SUPPORT A MIXTURE OF ORGANIZED
   CONVECTIVE CLUSTERS AND PERHAPS WIDELY SCATTERED DISCRETE
   SUPERCELLS.  STRONGEST ACTIVITY MAY BE CAPABLE OF PRODUCING ISOLATED
   TORNADOES...IN ADDITION TO THE RISK FOR DAMAGING WIND GUSTS...AS IT
   SPREADS NORTHEASTWARD ACROSS THE REGION DURING THE AFTERNOON AND
   EARLY EVENING HOURS.

   ...SOUTHERN PLAINS...
   CONVECTIVE POTENTIAL REMAINS A BIT UNCLEAR.  MOST OF THE REGION MAY
   BE UNDER THE INFLUENCE OF BROADER SCALE MID-LEVEL HEIGHT RISES...BUT
   WEAK UPPER TROUGHING MAY PERSIST ACROSS THE TEXAS/ OKLAHOMA
   PANHANDLE THROUGH AT LEAST LATE AFTERNOON.  BENEATH A RESIDUAL
   POCKET OF STEEP MID-LEVEL LAPSE RATES...A ZONE OF STRONGER
   DIFFERENTIAL HEATING ACROSS THE EASTERN TEXAS PANHANDLE AND WESTERN
   OKLAHOMA INTO NORTHWEST TEXAS SEEMS LIKELY TO PROVIDE THE PRIMARY
   FOCUS FOR VIGOROUS CONVECTIVE DEVELOPMENT.  MODELS ARE SUGGESTIVE
   THAT MOISTURE RETURN WILL BE SUFFICIENT TO CONTRIBUTE TO LARGE MIXED
   LAYER CAPE BY LATE AFTERNOON.  AS INHIBITION ERODES DURING PEAK
   HEATING...THE INITIATION OF ISOLATED TO WIDELY SCATTERED STORMS IS
   EXPECTED...IN THE PRESENCE OF SUFFICIENT SHEAR FOR SUPERCELLS.  THIS
   MAY INCLUDE THE RISK FOR TORNADOES...PARTICULARLY AS THE LOW-LEVEL
   SHEAR INCREASES WITH BOUNDARY LAYER DECOUPLING THIS EVENING.  AIDED
   BY ASCENT ASSOCIATED WITH LOW-LEVEL WARM ADVECTION...A SMALL BUT
   ORGANIZED CONVECTIVE CLUSTER MAY EVENTUALLY EVOLVE OVER PARTS OF
   NORTHWEST TEXAS...BEFORE ACTIVITY WEAKENS OVERNIGHT.