MESOSCALE PRECIPITATION DISCUSSION 0028
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
854 AM EST THU FEB 22 2018
AREAS AFFECTED...NORTHERN LA....WEST-CENTRAL AND NORTHERN
MS...NORTHWEST AL
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 221353Z - 221830Z
SUMMARY...VERY HEAVY RAINFALL WITH ADDITIONAL TRAINING OF SHOWERS
AND THUNDERSTORMS CAN BE EXPECTED OVER THE NEXT SEVERAL HOURS WITH
FLASH FLOODING LIKELY.
DISCUSSION....THE LATEST GOES-16 IR SATELLITE IMAGERY SHOWS AN
AXIS OF COLD-TOPPED CONVECTION REDEVELOPING OVER AREAS OF NORTHERN
LA AND EXTENDING NORTHEAST UP ACROSS WEST-CENTRAL AND NORTHERN MS.
THE CONVECTION IS DEVELOPING WITHIN A CORRIDOR OF FOCUSED MOISTURE
CONVERGENCE ALONG A QUASI-STATIONARY FRONT. INSTABILITY PARAMETERS
ARE MODEST WITH ONLY 500 TO 750 J/KG OF MUCAPE...BUT THE
CONVECTION IS BEING AIDED BY AT LEAST SOME WEAK RIGHT-ENTRANCE
REGION JET FORCING.
LOCALLY THE ANTECEDENT CONDITIONS ARE QUITE WET WITH SOIL
CONDITIONS SATURATED AND SO ANY ADDITIONAL RAINFALL...AND
ESPECIALLY ACROSS NORTHERN LA AND PARTS OF WEST-CENTRAL MS WILL BE
PARTICULARLY PRONE TO RUNOFF AND FLASH FLOODING CONCERNS.
PWATS ACROSS THE REGION NEAR THE FRONT ARE AS MUCH AS 1.5 TO 1.7
INCHES. THIS IS SUPPORTING RAINFALL RATES AS HIGH AS 1.5
INCHES/HR...AND WITH A RELATIVELY UNIDIRECTIONAL FLOW PATTERN
ACROSS THE REGION INVOLVING THE SURFACE FRONT...THE ENVIRONMENT
WILL REMAIN CONDUCIVE FOR TRAINING CONVECTION.
THE LATEST CAM GUIDANCE IS DOING A VERY POOR JOB IN HANDLING THE
ONGOING CONVECTIVE AXIS BUT AN EXTRAPOLATION OF ONGOING AND
PRESUMABLY SUSTAINABLE CONVECTION OVER THE NEXT FEW HOURS SUPPORTS
THE IDEA OF AS MUCH AS AN ADDITIONAL 2 TO 3 INCHES OF RAIN WITH
ISOLATED HEAVIER AMOUNTS. THIS WILL ENHANCE THE THREAT OF
ADDITIONAL FLASH FLOODING GOING THROUGH MIDDAY.
ORRISON
ATTN...WFO...BMX...HUN...JAN...MEG...OHX...SHV...
ATTN...RFC...LMRFC...SERFC...WGRFC...
LAT...LON 35018727 34748697 34388709 33818782 33158880
32518994 31949117 31659240 31589290 31689349
31809373 32099373 32399336 32769207 33609079
34418963 34918833
Last Updated: 1009 AM EST THU FEB 22 2018