Severe Thunderstorm Warning 123, NWS New Orleans, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
312 PM CDT WED JUL 11 2007

.SHORT TERM...

A VERY DYNAMIC PATTERN WILL CONTINUE ACROSS THE EASTERN TWO THIRDS
OF THE NATION THROUGH THE SHORT TERM...AS A DEEP TROUGH OF LOW
PRESSURE OVER THE HUDSON BAY CONTINUES TO TAKE ON A NEGATIVE TILT
IN RESPONSE TO A JET STREAK DIVING DOWN THE CANADIAN PLAINS. A
COLD FRONT RACING THROUGH THE SOUTHEAST WILL STALL OVER THE CWA
TONIGHT. HOWEVER...STRONG NEGATIVE VORTICITY ADVECTION IN THE WAKE
OF THE UPPER LEVEL TROUGH AXIS WILL LIMIT ANY CONVECTIVE
DEVELOPMENT OVERNIGHT INTO TOMORROW MORNING. LOW LEVEL MOISTURE
WILL REMAIN HIGH...SO TEMPERATURES ARE NOT EXPECTED TO FALL MUCH
BEHIND THE FRONT. IN FACT...THE MAIN EFFECT FROM THE FRONT WILL BE
A DRYING OF THE MID AND UPPER LEVEL LAYERS. GOING INTO
TOMORROW...STRONG SUBSIDENCE ALOFT AND THE WEAK FRONTAL BOUNDARY OVER THE
REGION WILL WORK AGAINST EACH OTHER...THUS LIMITING OVERALL
CONVECTION. HAVE DECIDED TO GO WITH ISOLATED TO LOW END CHANCE
POPS ACROSS THE CWA AS RESULT. THE DRIER AIRMASS ALOFT COMBINED
WITH STRONG SUBSIDENCE...AND MORE SOLAR HEATING WILL ALLOW
TEMPERATURES TO CLIMB INTO THE MIDDLE TO UPPER 90S ACROSS THE
REGION TOMORROW. THIS TREND WILL CONTINUE INTO FRIDAY AS A DRY
UPPER LEVEL AIRMASS REMAINS IN PLACE. WITH DEWPOINTS REMAINING IN
THE LOWER TO MIDDLE 70S...HEAT INDICES SHOULD RISE INTO THE
105-110 RANGE TOMORROW AFTERNOON. HOWEVER...ADDITIONAL CLOUD COVER
ON FRIDAY WILL ALLOW HEAT INDICES TO FALL BACK TO AROUND 100. WITH
THIS IN MIND...HAVE HELD ON ISSUING ANY TYPE OF HEAT ADVISORY FOR
THE REGION.

.LONG TERM...

BY FRIDAY NIGHT...THE FULL FORCE A DEEP COLD POOL AND STRONG COLD
FRONT SWINGING DOWN FROM THE NORTHERN PLAINS ON THE BACK SIDE OF
THE DEEP TROUGH OVER THE EASTERN PORTION OF CANADA AND THE GREAT
LAKES WILL BEGIN TO BE FELT IN THE CWA. AT THIS TIME...IT APPEARS
THAT A STRONG MESOSCALE CONVECTIVE SYSTEM MAY FROM OVER OKLAHOMA
AND ARKANSAS AND RACE SOUTHWARD INTO THE LOWER MISSISSIPPI VALLEY
AS IT FOLLOWS THE 850 WINDS AND THETA E AXIS. IF THIS
HAPPENS...THERE COULD BE SOME SEVERE WEATHER TOWARD DAYBREAK ON
SATURDAY. THIS SITUATION WILL HAVE TO BE MONITORED. IN ANY
EVENT...THE MAIN FRONT WILL SWEEP THROUGH THE CWA SATURDAY
AFTERNOON INTO SATURDAY EVENING...WHICH SHOULD SET OFF ANOTHER
LINE OF STRONG TO SEVERE THUNDERSTORMS. IT APPEARS THAT STRONG
WINDS AND HAIL WILL BE THE MAIN THREAT FROM THESE THUNDERSTORMS
BASED OFF MODEL SOUNDINGS.

UNFORTUNATELY...IT ALSO APPEARS THAT JUST AS THE FRONT GETS INTO
OUR FORECAST AREA...IT WILL BEGIN TO LOSE ANY DYNAMIC FORCING AS
THE UPPER LEVEL TROUGH AXIS PULLS NORTHEASTWARD. THUS...THE FRONT
WILL SLAM INTO THE DEEP RIDGE AXIS OVER THE GULF AND FLORIDA AND
STALL ON TOP OF OUR AREA ON SUNDAY. SOUTHERLY FLOW WILL REDEVELOP
ACROSS THE AREA AS THE UPPER LEVEL RIDGE IN THE WESTERN ATLANTIC
PUSHES WESTWARD...WHICH WILL INTERACT WITH THE FRONTAL BOUNDARY IN
PLACE. AS A RESULT...PERIODS OF SHOWERS AND THUNDERSTORMS ARE
EXPECTED SUNDAY INTO MONDAY. ON TOP OF THIS...DEEP TROPICAL
MOISTURE SHOULD ALSO OVERSPREAD THE REGION MONDAY INTO
TUESDAY...AS A WEAK TROPICAL WAVE MOVES UP FROM THE YUCATAN. THIS
DEEP TROPICAL MOISTURE...COMBINED WITH THE SURFACE BOUNDARY SHOULD
ALLOW FOR SOME VERY HEAVY RAINFALL OVER THE CWA MONDAY THROUGH
WEDNESDAY. IN FACT...FLOODING MAY BE A CONCERN BY THE MIDDLE OF
NEXT WEEK GIVEN THE PATTERN EXPECTED.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  74  95  73  94 /  10  30  20  30
BTR  76  96  75  96 /  10  30  20  30
MSY  77  94  77  95 /  10  20  20  30
GPT  75  95  75  95 /  10  20  20  30

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...NONE.
MS...NONE.
GM...NONE.
&&

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