MESOSCALE PRECIPITATION DISCUSSION 0024...CORRECTION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1024 AM EDT WED MAY 01 2013
 
AREAS AFFECTED...SOUTHWEST AL AND CENTRAL MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 011403Z - 011903Z
 
SUMMARY...A BAND OF CONVECTION ACROSS SOUTHWEST AL AND CENTRAL MS
IS EXPECTED TO PERSIST THROUGH THE MORNING HOURS, WHICH COULD LEAD
TO FLASH FLOODING.

DISCUSSION...A QUASI-STATIONARY BAND OF THUNDERSTORMS WITH HEAVY
RAINFALL HAS BEGUN TRAINING ACROSS SOUTHWEST ALABAMA INTO CENTRAL
MISSISSIPPI.  A BAND OF PRECIPITABLE WATER (PW) VALUES IN EXCESS
OF 1.5 INCHES, WHICH IS ABOVE THE 75TH PERCENTILE FOR THE AREA FOR
MAY 1.  THE BAND OF BEST 850 HPA INFLOW IS EXPECTED TO REMAIN
QUASI-STATIONARY ACROSS WESTERN AL AND CENTRAL MS INTO THE EARLY
AFTERNOON, WHICH COULD CONTINUE CELL TRAINING OVER THE NEXT
SEVERAL HOURS.  CORFIDI/PROPAGATION VECTORS ARE OPPOSITE TO THE
LOW-LEVEL INFLOW, WHICH IS HELPING TO KEEP ONGOING CONVECTIVE
AREAS QUASI-STATIONARY.  THE AREA IS WITHIN A REGION OF
SIGNIFICANT DIVERGENCE ALOFT AHEAD OF A SLOW-MOVING UPPER LEVEL
LOW, THOUGH THERE IS A CONCERN THAT DRY AIR ALOFT TO THE SOUTH
COULD BE DEPRESSING RAINFALL RATES.  THE 09Z HRR HAS AN INDICATION
OF THIS ACTIVITY ACROSS MISSISSIPPI, WITH THE 11Z RAP SHOWING
PRECIPITATION IN THIS AREA THOUGH AMOUNTS APPEAR QUITE LIGHT.  THE
09Z HRR, 11Z RAP, AND 00Z ARW ARE COMPLETELY MISSING THE ALABAMA
ACTIVITY.  NEW SURFACE-BASED CONVECTION ALONG SEA BREEZE
BOUNDARIES IS EXPECTED TO FIRE ACROSS SOUTHEAST LA AND SOUTHERN MS
THIS AFTERNOON DUE TO A COMBINATION OF DAYTIME HEATING AND COOL
AIR ALOFT, WHICH MIGHT CAUSE THIS NORTHERN AREA IS FADE -- OR DIE
OFF -- EARLY THIS AFTERNOON AS THE 700 HPA LEVEL INFLOW FROM THE
GULF OF MEXICO IS CUT OFF.  LOCAL AMOUNTS OF 3-5 INCHES ARE
POSSIBLE WHERE CELLS TRAIN, WHICH SHOULD FALL WITHIN A FEW HOURS'
TIME.  FLASH FLOOD GUIDANCE IS IN THIS AREA IS 2.5-3 INCHES IN
THREE HOURS, WHICH COMBINED WITH THE LOCALLY HEAVY RAINFALL
POTENTIAL, WOULD LEAD TO FLASH FLOODING IF CELL TRAINING CONTINUES
THROUGH THE REMAINDER OF THE MORNING HOURS.

ROTH


ATTN...WFO...BMX...MOB...MEG...JAN...

LAT...LON   31748780 32818791 33768887 34168992 34059082 33139106
            32479037 31868887 31748780