DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 221250
SWODY1
SPC AC 221248

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0748 AM CDT FRI JUN 22 2012

VALID 221300Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE
MID-ATLANTIC AND NEW ENGLAND...

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CNTRL PLAINS...

...SYNOPSIS...
A RELATIVELY WELL-AMPLIFIED MID/UPPER LEVEL FLOW PATTERN WILL EXIST
ACROSS THE NRN CONUS THIS PERIOD. A STRONG PACIFIC TROUGH WILL SHED
SMALLER SCALE DISTURBANCES THAT WILL TRACK DOWNSTREAM FROM THE
ROCKIES TO THE CNTRL PLAINS. A MORE PROGRESSIVE LARGE SCALE TROUGH
WILL SPREAD EAST FROM THE GREAT LAKES TO THE MID ATLANTIC AND
NORTHEAST TODAY. IN BETWEEN THE TROUGHS...A MID LEVEL
RIDGE...CURRENTLY ACROSS THE SOUTHWEST AND ROCKIES...WILL BUILD
ACROSS THE SCNTRL PLAINS THROUGH THE WEEKEND.

...MID ATLANTIC/NORTHEAST...
A BREAK FROM THE RECENT HEAT IN THE EAST WILL EVENTUALLY COME IN THE
FORM OF A WEAK COLD FRONT THAT WILL CROSS THE APPALACHIANS TODAY AND
MOVE OFF THE MID ATLANTIC SEABOARD BY EARLY SATURDAY. A VERY MOIST
AND INCREASINGLY UNSTABLE AIR MASS WILL PRECEDE THE FRONT THIS
AFTERNOON WITH SBCAPE LIKELY TO EXCEED 2000 J/KG FROM NC TO NYC.
TSTMS SHOULD BECOME MORE COMMON AS CONVECTIVE TEMPERATURES ARE
BREACHED EARLY AND LIFT WITH THE FRONT AND UPPER TROUGH SPREADS EAST
ACROSS THE SPINE OF THE APPALACHIANS.

EFFECTIVE SHEAR MAGNITUDES COINCIDENT WITH THE DEVELOPING CONVECTION
ARE FORECAST TO REMAIN GENERALLY UNDER 30KT. THUS...EXPECT
MULTICELLULAR STORMS WITH UPDRAFTS OCCASIONALLY BECOMING BETTER
ORGANIZED OR PERSISTING IN THE PRESENCE OF POCKETS OF STRONGER
INSTABILITY AND/OR POSITIVE STORM/BOUNDARY INTERACTIONS. BRIEF
EXTREME RAINFALL AND WET MICROBURSTS WITH SCATTERED DAMAGING WINDS
SHOULD BE THE PRIMARY HAZARDS FROM THIS ACTIVITY...MOST OF WHICH
SHOULD SUBSIDE CONSIDERABLY WITHIN A FEW HOURS AFTER SUNSET AND/OR
FRONTAL PASSAGE.

...MAINE...
SOME MODELS DEPICT THE DEVELOPMENT OF STRONG INSTABILITY ACROSS
MAINE THIS AFTERNOON WHERE DEEP-LAYER FLOW WITH THE ADVANCING TROUGH
IS A BIT STRONGER THAN AREAS TO THE SOUTH. AFTER REVIEWING THE
FORECAST GUIDANCE IT APPEARS THAT MOST SIMULATIONS ARE
OVERESTIMATING SFC DEWPOINTS IN MAINE THIS MORNING. WHILE STRONG TO
ISOLATED SEVERE STORMS WITH WIND AND SMALL HAIL ARE STILL
LIKELY...THE DEGREE OF DESTABILIZATION EXPECTED DOES NOT CURRENTLY
WARRANT AN INTRODUCTION OF SLGT RISK PROBABILITIES. THIS SITUATION
CAN BE REASSESSED WITH THE NEXT OUTLOOK.

...CNTRL HIGH PLAINS...
LOW LEVEL MOISTURE RETURN IS UNDERWAY ACROSS THE HIGH PLAINS WITH
SFC DEWPOINTS CLIMBING 1-3F PER HOUR FROM THE TX PNHDL ACROSS ERN CO
PER LATEST SPC MESOANALYSIS DATA. SFC HEATING AND STEEPENING
DEEP-LAYER LAPSE RATES WILL CONTRIBUTE TO A PLUME OF STRONG
INSTABILITY DEVELOPING WITH SBCAPE OF 2000-3000 J/KG EXPECTED ACROSS
ERN CO/WRN KS NWD TO WRN SD BY THIS AFTERNOON. STORM INITIATION IS
MOST LIKELY TO OCCUR WEST OF THE AXIS OF STRONGER INSTABILITY...OVER
THE HIGHER TERRAIN...DURING THE AFTERNOON. OVER THE ADJACENT HIGH
PLAINS THE AIR MASS WILL LIKELY REMAIN CAPPED FOR MOST OF THE DAY
GIVEN VERY WARM 700MB TEMPERATURES.

CAPPING SHOULD EVENTUALLY BE OVERCOME IN SOME AREAS THROUGH A
COMBINATION OF HEATING/OROGRAPHIC INFLUENCES AND LARGER SCALE ASCENT
AS A SHORT WAVE TROUGH SPREADS EAST LATE IN THE AFTERNOON AND ACTS
TO SUPPRESS THE RIDGE AXIS FROM WY TO NWRN KS. AVAILABLE GUIDANCE
PROVIDES MIXED SIGNALS WITH RESPECT TO STORM COVERAGE WITH SOME
INDICATIONS THAT SURFACE-BASED CONVECTION WITHIN THE MOST UNSTABLE
AIR COULD REMAIN ISOLATED TO WIDELY SCATTERED. HOWEVER...ANY STORMS
THAT CAN INITIATE IN THIS REGIME WILL BE CAPABLE OF PRODUCING LARGE
HAIL AND HIGH WINDS AND THE MOST LIKELY CORRIDOR FOR THIS
DEVELOPMENT WILL EXTEND FROM ERN WY ACROSS ADJACENT AREAS OF WRN
NEB/NERN CO AND NWRN KS.

...CNTRL PLAINS...
THE AFOREMENTIONED SHORT WAVE TROUGH WILL SPREAD ACROSS THE PLAINS
COINCIDENT WITH THE ONSET OF THE STRONGER NOCTURNAL LOW LEVEL JET.
THERE IS BETTER CONFIDENCE THAT ELEVATED TSTMS SHOULD ERUPT ON THE
EDGE OF THE CAP...IN AN ARC FROM SD ACROSS ERN NEB. THIS ACTIVITY
COULD SPREAD ACROSS THE MIDDLE MO RIVER VALLEY WITH A THREAT FOR
HAIL INTO EARLY SATURDAY MORNING.

...NRN ROCKIES...
STRONG ASCENT WILL PERSIST OVER THE NRN ROCKIES BENEATH THE
DIFFLUENT EXIT REGION OF AN UPPER JET ASSOCIATED WITH THE DEEP
TROUGH OFF THE PACIFIC COAST. THIS LIFT WILL BE FOCUSED BY TERRAIN
AND FRONTAL FORCING AND...IN CONCERT WITH DIURNAL HEATING...SHOULD
RESULT IN AN INCREASE IN TSTMS THROUGH LATE TODAY FROM THE
CONTINENTAL DIVIDE ESEWD ACROSS CNTRL AND SRN MT. WHILE LOW LEVEL
ELY FLOW WILL REMAIN STRONG AND CONTRIBUTE TO BOTH ENHANCED SHEAR
AND WWD TRANSPORT OF RICHER BOUNDARY LAYER MOISTURE...SEVERE
POTENTIAL MAY BE TEMPERED BY LACK OF GREATER DESTABILIZATION WITH
FORECAST MLCAPE AOB 500 J/KG IN AREAS OF EXPECTED CONVECTION.
NONETHELESS...A COUPLE OF SEVERE HAIL/WIND EVENTS CANNOT BE RULED
OUT AND A SLGT RISK AREA MAY BE CONSIDERED IN LATER OUTLOOKS IF
GREATER INSTABILITY CAN BE REALIZED.

..CARBIN/GARNER.. 06/22/2012

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