The Weather Prediction Center is still concerned about some flooding across the southern Louisiana, Mississippi coasts through the next few hours. As the storms continue to train over the same area, places dealing with flooding already as well as flood-prone areas could see an additional few inches of rain before the current batch of storms move out of the area.
The most difficult thing to figure out is when that will happen – and therefore, when the rain will subside – before the next round of rain begins on Friday.
From the WPC:
MESOSCALE PRECIPITATION DISCUSSION 0074
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1129 PM EST THU MAR 10 2016AREAS AFFECTED…SE LOUISIANA…S MISSISSIPPI
CONCERNING…HEAVY RAINFALL…FLASH FLOODING POSSIBLE
VALID 110428Z – 110858Z
SUMMARY…FOCUS IN FORCING IN THE NEAR TERM LEADING TO FRACTURED CONVECTION. HOWEVER ENVIRONMENT FOR REPEAT ISENTROPIC EFFICIENT RAINFALL PRODUCING CONVECTION SUPPORTS CONTINUED THREAT FOR FLOODING ACROSS E LA/S MS.
DISCUSSION…WV LOOP SHOWS NORTHERN S/W IS NOW WELL DISPLACED OUT OF KY INTO WV WITH A WEAK WAVE INDUCED FROM THE CONVECTIVE COMPLEX SHEARING ACROSS N AL AS WELL LEADING TO REDUCED FOCUS EXCEPT FOR THE BROAD AREA OF STRONG SURFACE 25-30 KT FLOW ACROSS THE EASTERN GULF WEST. A BOUNDARY ESTABLISHED BY THE WEAK COLD POOL FROM
CONVECTION THROUGHOUT THE DAY CONTINUES TO FLATTEN E-W FROM DYING CONVECTION ENTERING S AL ACROSS THE COASTAL COUNTIES OF MS INTO EASTERN LA. GIVEN THE ORIENTATION OF THE BOUNDARY AND CONTINUED LARGE SCALE SOUTHERLY FLOW…ILL-FOCUSED/BROAD ISENTROPIC ASCENT REMAINS LEADING TO FRACTURED CONVECTION. GIVEN THE AMPLE MOISTURE
AND SOME SKINNY INSTABILITY PROFILES WITH MUCAPES IN THE 1000-1500 J/KG RANGE ACROSS SE LA THERE IS ENOUGH VIGOR TO KEEP THESE CELLS GOING WITH RATES OF 1.0-1.25″/HR ON AVERAGE AND GIVEN REPEATING NATURE ALONG WITH LITTLE MOVEMENT OF SOUTH…TOTALS HAVE BEEN SUFFICIENT TO KEEP FLOODING A HIGH CONCERN ACROSS THE AREA
HIGHLIGHTED. ADDITIONAL FRACTIONAL COVERAGE ACROSS SE LA MAY INCREASE GIVEN SOME LOW LEVEL CONVERGENCE DUE TO COASTAL FRICTION COMPONENT…POTENTIALLY SHIFTING THE FOCUS SOUTH TOWARD AREAS LESS AFFECTED OVER THE LAST 3-4 HRS…WHICH COULD HELP THE PROLONGED FLOODING SITUATION ALONG THE LA/MS BORDER.FURTHER SOUTH THE ISOLATED CONVECTION CAN BE SEEN BREAKING OUT ALONG N-S COLD FRONTAL BOUNDARY THAT IS JUST A BIT E OF 94W THAT WAS SEEN IN SWIR/IR LOOPS…ADDITIONAL DRYING ALOFT JUST WEST OF THE FRONT IS EVIDENCE OF INCREASING JET STREAK THAT HAS ROUNDED THE BASE TO PROVIDE ADDITIONAL ASCENT OVER THE NORTH WEST CENTRAL
GULF IN THE COMING HOURS. THIS DRY AIR MIXING WILL ALLOW FOR EASTWARD MOVEMENT OF THE BOUNDARY/COLD FRONT BUT THIS SHOULD STRENGTHEN SURFACE CONVERGENCE FIELDS WITH THE 20-30KT SELY THAT REMAINS QUITE MOIST OVER A DEEP LOW LEVEL DEPTH…WITH TPWS STILL AT OR ABOVE 2.0″. BIGGEST QUESTION REMAINS THE TIMING OF THE
ACTIVATION AND APPROACH TO SHORE. THE 12Z ARW HAD BEEN THE BEST PERFORMING HI-RES CAM THROUGH 04Z…BUT ALSO STARTED BREAKING OUT CONVECTION BY THIS TIME AS WELL OVER THE GULF AND WITH RECENT HRRR RUNS BACKING OFF…SLOWING DOWN THERE INCREASING UNCERTAINTY TO THE TIMING.
