Severe Thunderstorm Warning 18, NWS New Orleans, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
335 AM CST SAT MAR 18 2000

WILL GO WITH AVN/ETA SOLUTION THROUGH 48 HOURS ON OVERALL PATTERN
HOWEVER DIFFERENCES ARE SEEN IN 36-48 HOURS WITH 200 MB JET
STRUCTURE AND SURFACE FRONTAL TIMING. FORECAST THROUGH 3/19 00Z
CENTERS ON CONCERNS WITH AREA OF ENHANCEMENT COMING ACROSS N MEXICO
NEAR DEL RIO. AVN AND ETA BOTH SHOW THIS AS AN AREA OF 200 MB
DIVERGENCE ACROSS SE LA AT 18Z. LOOK AT 300K ISENTROPIC SURFACE
SHOWS 30 MB OF LIFT REQUIRED ACROSS CWA OF SE LA WITH SUFFICIENT LOW
LEVEL INFLOW OF 30 KT AT 925-850 MB. WITH THIS ISENTROPIC LIFT
COUPLED WITH UPPER LEVEL SUPPORT WILL LOOK FOR CHANCE CATEGORY OF
POPS TO START THIS AFTERNOON. WILL KEEP SKIES MOSTLY CLOUDY TO
CLOUDY. TEMPS OF MID 70S WILL HOLD CWA WITH STATIONS S OF LAKE
PONTCHARTRAIN BENEFITING FROM FRONT IN COASTAL WATERS RETREATING N
AS A WARM FRONT THIS AFTERNOON.

WILL KEEP CATEGORICAL FORECAST FOR POPS TONIGHT. LOOK AT AVN/ETA
SHOWS IMPRESSIVE 200 MB DIVERGENCE FIELD SWEEPING ACROSS GULF COAST
REGION THROUGH SUN IN CONJUNCTION WITH 500 MB COLD POOL. WITH THESE
DYNAMICS IN MIND WILL MENTION SOME THUNDERSTORMS POSSIBLY SEVERE PER
COORD WITH SPC. WILL ALSO INCLUDE HEAVY RAIN HOWEVER FLASH FLOOD
GUIDANCE VALUES ARE HIGH. PRECIPITABLE WATER CLIMBS INTO 1.8-1.9
INCH BY 06Z WITH LOW LEVEL FEATURES INDICATING A PLUME OF HIGH THETA
E AIR PULLED AHEAD OF FRONT AS IT MOVES OUT OF TEXAS. WILL GO WITH
FRONTAL TIMING CLOSE TO NATIONAL GUIDANCE AND CANADIAN MODEL WHICH
IS A COMPROMISE OF FAST AVN AND SLOWEST ETA. REALIZE THAT DRY SLOT
OF MODELS HAS BEEN A PROBLEM IN CLEARING OF PRECIPITATION WITH LAST
SYSTEMS BUT THIS ONE IS NOT LIFTING AS QUICKLY TO THE NE AS PREVIOUS
AND MAIN DRY SLOT LOOKS TO BE GOING INTO CENTRAL LA AND MS WITH SOME
RESIDUAL MOISTURE LEFT ALONG GULF COAST. FRONTAL TIMING COUPLED WITH
INCREASED SUNSHINE HOURS WARRANT CHANCE POPS IN FOR SUN NIGHT WITH
GOOD CHANCE FOR MS COAST. ONLY PROBLEM WILL BE IF MAIN SQUALL LINE
RACES EAST AND MESO-HIGH DEVELOPS IN ITS WAKE.

MARINE FORECAST HAS EXERCISE CAUTION THIS AFTERNOON BUT SMALL CRAFT
CRITERIA FORECAST FOR TAONIGHT WITH STRONG STORMS CREATING ADDITIONAL
PROBLEMS.

MCB 74/60/69/45 3973  BTR 75/60/69/46 4973
MSY 76/62/70/53 4983  BIX 75/63/72/55 4985

.NEW...NONE.
LA...NONE.
MS...NONE.

13

LAZ034>040-046>050-056>070-MSZ068>071-077-080>082-191000-

THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE NEW ORLEANS LA
1015 AM CST SAT MAR 18 2000

SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL CONTINUE TO
SPREAD ACROSS SOUTHEAST LOUISIANA AND SOUTH MISSISSIPPI THROUGH
TONIGHT. SOME OF THESE THUNDERSTORMS MAY SEVERE WITH BRIEF HEAVY
RAINFALL...GUSTY WIND 40 TO 50 MPH...SMALL HAIL AND FREQUENT
LIGHTNING.

FOR MORE INFORMAT:ION, VISIT OUR WEB SITE AT WWW.SRH.NOAA.GOV/LIX
(ALL LOWER CASE).