Monday, May 16, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 161942
SWODY1
SPC AC 161941

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0241 PM CDT MON MAY 16 2011

VALID 162000Z - 171200Z

...NO SVR TSTM AREAS FORECAST...

--- UPDATES ---

...MID-ATLANTIC REGION...
REF SPC MESOSCALE DISCUSSION 795 FOR SHORT-TERM SVR POTENTIAL ALONG
ERN PORTIONS OUTER BANKS.

...GA...
EXPANDED GEN THUNDER LINES TO ACCOMMODATE RELATIVELY LOW-TOPPED
CONVECTION OVER GA...BENEATH COLD-CORE REGION OF MID-UPPER CYCLONE.
MODIFIED RAOBS AND RUC SOUNDINGS EACH INDICATE 250-500 J/KG MLCAPE
CONTINUING THROUGH ABOUT 23Z. INSTABILITY AND TSTM COVERAGE EACH
SHOULD DIMINISH THEREAFTER AS COMBINATION OF OUTFLOW AND DIABATIC
COOLING STABILIZE PROGRESSIVELY LARGER HORIZONTAL EXTENT OF BOUNDARY
LAYER. MEANWHILE...ISOLATED SMALL HAIL IS POSSIBLE...THOUGH
UNCONDITIONAL SVR HAIL RISK APPEARS PRECLUDED BY LACK OF MORE ROBUST
BUOYANCY AND SHEAR.

...SW TX...
A FEW HIGH-BASED TSTMS MAY DEVELOP THROUGH REMAINDER AFTERNOON OVER
DAVIS MOUNTAINS/BIG BEND REGION OF SW TX...AMIDST STG HEATING OF
HIGHER TERRAIN WITH SFC DEW POINTS 40S F...AS WELL AS OVER SERRANIAS
DEL BURRO RANGE IN NRN COAHUILA. TCU ALREADY ARE EVIDENT IN VIS
IMAGERY OVER BOTH AREAS. MEX CONVECTION SHOULD REMAIN SW OF RIO
GRANDE.

..EDWARDS.. 05/16/2011

.PREV DISCUSSION... /ISSUED 1108 AM CDT MON MAY 16 2011/

LARGE SCALE BLOCKING IS IN PLACE ACROSS NORTH AMERICA...WITH ANCHOR
CYCLONIC CENTERS OVER THE ERN AND WRN US AND RIDGE ACROSS THE
PLAINS. A STRONG UPPER LOW ROTATES ACROSS SERN STATES TODAY UNDER
ERN LOBE OF BLOCK WHILE IN THE W ONE VIGOROUS IMPULSE ROTATES NWD
FROM NRN ROCKIES INTO CANADA AND ANOTHER MOVES ONSHORE NRN CA.

...MID ATLANTIC STATES...

LOW LEVEL FLOW IN THE NORTHEAST QUADRANT OF THE SYSTEM MOVING ACROSS
GA WILL MAINTAIN A MOIST AND MARGINALLY UNSTABLE AIR MASS OVER MUCH
OF THE MID ATLANTIC STATES. GOOD SFC HEATING TAKING PLACE THIS AM
FROM SC/NC INTO THE DELMARVA...WHICH WILL LIKELY RESULT IN SCATTERED
AFTERNOON THUNDERSTORM DEVELOPMENT. FORECAST SOUNDINGS SHOW WEAK
LOW LEVEL FLOW...BUT SUFFICIENT DEEP LAYER EFFECTIVE SHEAR FOR A FEW
MULTICELL STORMS CAPABLE OF GUSTY WINDS. HOWEVER NO WIDESPREAD
SEVERE THREAT IS EXPECTED TO DEVELOP.

...CENTRAL/NRN HIGH PLAINS...

HAVE REMOVED THE LOW PROBS OF SEVERE NRN/CENTRAL HIGH PLAINS AS THE
AIR MASS APPEARS TO BE TOO DRY TO SUPPORT DEEP CONVECTION ALONG THE
NARROW AXIS OF MARGINAL INSTABILITY THAT WILL DEVELOP LATER TODAY.
A FEW HIGH BASED THUNDERSTORMS ARE LIKELY ALONG AND JUST E OF A VERY
SLOWLY MOVING COLD FRONT FROM SERN MT SWD THRU ERN WY. ANY WIND
THREAT BY THIS CONVECTION SHOULD BE MINOR GIVEN THE CURRENT GRADIENT
THAT IS PRODUCING GUSTS TO NEAR SEVERE LEVELS ANYWAY.

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