Saturday, May 11, 2013

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 112002
SWODY1
SPC AC 112000

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT SAT MAY 11 2013

VALID 112000Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE
MID-ATLANTIC/NORTHEAST STATES...

...MID-ATLANTIC/NORTHEAST STATES...
PRIMARY SHORT-TERM CONCERN IS FOR SEVERE WIND/HAIL ACROSS PORTIONS
OF THE COASTAL NORTHEAST INCLUDING PORTIONS OF FAR SOUTHEAST NY/NYC
METRO AND NJ....WITH SOME CHANGES TO EXISTING SLIGHT RISK IN NYC
VICINITY FOR ONGOING STORMS. SEE MESOSCALE DISCUSSION 633 FOR MORE
DETAILS ON THE SHORT-TERM SCENARIO. OTHER SEVERE TSTMS ARE STILL
POSSIBLE...AND LIKELY TO YET INCREASE...ACROSS ADDITIONAL PARTS OF
THE MID-ATLANTIC/DELMARVA THROUGH LATE AFTERNOON.

...SOUTH TX...
TSTMS MAY STILL DEVELOP/MOVE INTO FAR SOUTH TX LATER TODAY...BUT
CONFIDENCE/NEED FOR A SLIGHT RISK AT 20Z IS STILL LIMITED BASED ON
LATEST SHORT-TERM GUIDANCE/OBSERVATIONS. SEE PRIOR DISCUSSION BELOW
REGARDING SOUTH TX.

...ELSEWHERE...
OTHERWISE...NO APPRECIABLE CHANGES TO PRIOR FORECAST
REASONING...WITH LITTLE/IF ANY CHANGES TO EXISTING GENERAL
TSTM/SEVERE PROBABILITIES. SEE PRIOR OUTLOOK DISCUSSION BELOW.

..GUYER.. 05/11/2013

.PREV DISCUSSION... /ISSUED 1130 AM CDT SAT MAY 11 2013/

...MID ATLANTIC...
SURFACE LOW PRESSURE IN SRN QUEBEC WILL TRACK TOWARD THE MOUTH OF
THE ST. LAWRENCE RIVER WHILE A TRAILING COLD FRONT SWEEPS EAST AND
OFF MOST OF THE ERN SEABOARD THROUGH SUNDAY MORNING. THE FRONT IS
FORECAST TO BECOME A FOCUS FOR STRONG TO SCATTERED SEVERE TSTMS
THROUGH THE AFTERNOON AS LIFT ALONG THE ADVANCING BOUNDARY ACTS ON
POCKETS OF MODEST BUOYANCY FROM NC NWD ACROSS THE DELMARVA TO
NJ/SERN NY. FORECAST THERMODYNAMIC PROFILES WITHIN THE WARM SECTOR
CORRIDOR ARE CHARACTERIZED BY GENERALLY WEAK MID LEVEL LAPSE RATES
BUT SUFFICIENT MOISTURE AND LIMITED INHIBITION TO CONTRIBUTE TO
SUSTAINED STORMS. ACTIVITY MAY CONGEAL INTO A BROKEN LOW-TOPPED
SQUALL LINE WITH STRONGER CORES CAPABLE OF PRODUCING BOTH SMALL HAIL
AND LOCALLY STRONG TO DAMAGING WIND GUSTS. LATEST 12Z 4KM WRF-NMM
AND WRF-ARW MODELS FORECAST THE STRONGEST CONVECTION TO SPREAD EAST
FROM ERN PA ACROSS NJ SOUTHWARD TO NRN VA AND MD ERN SHORE IN THE
18-21Z TIME FRAME.

...FL...
STRONG HEATING AND ABUNDANT MOISTURE WILL CONTRIBUTE TO AREAS OF
STRONG DESTABILIZATION BENEATH DIFLUENT AND MODEST MID/UPPER LEVEL
FLOW. THIS COMBINATION SHOULD SUPPORT ROBUST STORMS DEVELOPING
THROUGH THE AFTERNOON PRIMARILY FROM CNTRL INTO ERN PORTIONS OF THE
PENINSULA. EFFECTIVE SHEAR ON THE ORDER OF 25-30KT SHOULD ALLOW FOR
LOOSELY ORGANIZED MULTICELLULAR STORMS WITH LOCALIZED HAIL AND
DAMAGING WIND POTENTIAL.

...SOUTH TX...
POST FRONTAL UPSLOPE FLOW INTO THE MOUNTAINS OF NRN MEXICO WILL
LIKELY RESULT IN RENEWED DIURNAL CONVECTIVE DEVELOPMENT SOUTH/WEST
OF THE RIO GRANDE THROUGH LATE AFTERNOON. ASCENT ACROSS THE REGION
MAY BE FURTHER ENHANCED LATER TODAY AS DISTURBANCES CONTINUE TO
EJECT FROM THE LOW LATITUDE SHORT WAVE TROUGH/LOW OVER NCNTRL
MEXICO. STRONG SRN STREAM UPPER FLOW PERSISTS AROUND THE ERN
PERIPHERY OF THE DISTURBANCE IN MEXICO AND WILL MAINTAIN SUFFICIENT
DEEP SHEAR ACROSS SRN TX SO THAT ANY CONVECTION MOVING EAST WOULD
REMAIN ORGANIZED. SOME SIGNALS IN LATEST STORM SCALE GUIDANCE
SUGGEST THE DEVELOPMENT OF A SMALL MCS SPREADING EAST ACROSS SOUTH
TX LATER THIS EVENING BUT MODEL CONSISTENCY IN THIS SCENARIO REMAINS
LIMITED. FURTHER REVIEW MAY SUPPORT THE INTRODUCTION OF A SMALL SLGT
RISK AREA WITH HIGHER HAIL/WIND PROBABILITIES IN SUBSEQUENT OUTLOOKS
LATER TODAY.

...HIGH PLAINS...
UPSLOPE FLOW AND STRONG HEATING BEHIND FRONTAL SURGE SHOULD RESULT
IN SOME TSTM DEVELOPMENT WHERE LAPSE RATES ALOFT AND WARM BOUNDARY
LAYER COULD SUPPORT A LOW PROBABILITY AND MARGINAL HAIL/WIND THREAT
LATER TODAY FROM SERN WY INTO NERN CO.

...NERN OK ACROSS THE OZARKS...
LIFT ALONG ADVANCING POLAR FRONT WILL COMBINE WITH STRONG HEATING
AND POCKETS OF GREATER BOUNDARY LAYER MOISTENING TO SUPPORT THE
DEVELOPMENT OF RELATIVELY HIGH-BASED TSTMS LATER THIS AFTERNOON.
SOME SMALL/MARGINAL HAIL AND LOCALLY GUSTY WINDS APPEAR TO BE THE
PRIMARY HAZARDS WITH THIS ACTIVITY.

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