Graphic for MPD #0015

MESOSCALE PRECIPITATION DISCUSSION 0015
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
858 AM EST SUN FEB 11 2018

AREAS AFFECTED...FL PANHANDLE...SW GA...S AL...COASTAL MS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 111357Z - 111957Z

SUMMARY...PERSISTENT THUNDERSTORM ACTIVITY THROUGH THE MORNING AND
INTO THE EARLY AFTERNOON MAY PRODUCE HEAVY RAIN RATES UP TO 2
IN/HR AND LOCALIZED FLASH FLOODING. FLOODING ISSUES WILL BE MOST
LIKELY IN URBAN AREAS OF THE FLORIDA PANHANDLE.

DISCUSSION...REGIONAL RADARS SHOWED AN EXTENSIVE SQUALL LINE IN A
LINE ECHO WAVE PATTERN (LEWP) EXTENDING FROM NEAR LAKE
SEMINOLE...TO NEAR DESTIN...AND THEN SOUTHWEST OVER THE GULF OF
MEXICO TO A POINT AROUND 100 MILES SW OF THE MOUTH OF THE
MISSISSIPPI RIVER. THE VIGOROUS CONVECTION WAS LARGELY CONTAINED
WITHIN THE AXIS OF HIGHEST PRECIPITABLE WATER AND THE
SOUTHWESTERLY LOW-LEVEL JET. ELEMENTS WITHIN THE SQUALL LINE WERE
GENERALLY MOVING TO THE NORTHEAST...HOWEVER DISTINCT MESOVORTICES
(SUCH AS ONE ABOUT 20 MILES OFFSHORE OF OKALOOSA COUNTY AT 1345Z)
WERE SHOWING A GREATER EASTERLY COMPONENT TO THEIR MOTION. CORFIDI
VECTORS DO IMPLY A GRADUAL EASTWARD DRIFT OF THE LINE THIS
MORNING...BUT THESE BOWING LINE SEGMENTS MAY ACCELERATE PORTIONS
OF THE LINE FASTER TO THE EAST AT TIMES. CORFIDI VECTORS
EVENTUALLY BACK AROUND TO A MORE SW DIRECTION THIS
AFTERNOON...RAISING THE POSSIBILITY THAT OFFSHORE CONVECTION WILL
EVENTUALLY BEGIN TO BUILD BACK INTO AREAS THAT HAVE ALREADY
RECEIVED RAINFALL.

HI-RES MODELS ARE STRUGGLING WITH THEIR DEPICTION OF THE ONGOING
SCENARIO ACROSS THE CENTRAL AND EASTERN GULF COAST.
FUNDAMENTALLY...THERE IS A GREATER CHANCE FOR BUILDING INSTABILITY
JUST AHEAD OF THE SQUALL LINE OVER THE CENTRAL AND EASTERN FLORIDA
PANHANDLE. GOES-16 VISIBLE SATELLITE ALREADY SHOWED SOME FILTERED
SUNSHINE...WHILE DEEPER CLOUD COVER EXISTED IN THE IMMEDIATE
VICINITY OF THE SQUALL LINE AND BACK TO THE WEST AND NORTHWEST.
THE STRONGER INSTABILITY...COMBINED WITH GREATER LOW-LEVEL FORCING
ALONG THE GUST FRONT...SUGGEST THAT THE MOST ORGANIZED CONVECTION
AND STRONGER RAIN RATES ARE LIKELY TO PERSIST IN THE FLORIDA
PANHANDLE. HOWEVER...PWATS BEGIN TO DECREASE EAST OF THE
APALACHICOLA RIVER...SO THERE IS A SMALLER AREA THAT IS LIKELY TO
BE MOST FAVORABLE FOR FLASH FLOODING THIS MORNING AND EARLY THIS
AFTERNOON. RAIN RATES OF UP TO 2 IN/HR WILL BE POSSIBLE...AND SOME
LOCALIZED TOTALS COULD EXCEED 5 INCHES.

HOWEVER...THERE IS ALSO THE POTENTIAL FOR RENEWED DEVELOPMENT AND
BACKBUILDING FURTHER TO THE WEST ALONG THE GULF COAST.
PRECIPITABLE WATER VALUES IN EXCESS OF 1.5 INCHES SHOULD STRETCH
AS FAR WEST AS THE CENTRAL LOUISIANA COAST...WITH LOW-LEVEL INFLOW
FROM THE SW OR WSW ALONG THE ENTIRE GULF COAST. ADDITIONALLY...THE
RIGHT ENTRANCE REGION OF A 80+ KNOT UPPER LEVEL JET STREAK SHOULD
BE FAVORABLY ALIGNED WITH SE LA...SRN MS...AND SRN AL OVER THE
NEXT 6 HOURS. REGIONAL RADARS ALREADY SHOW SOME SCATTERED
CONVECTION ACROSS THE SAME AREA BEHIND THE PRIMARY SQUALL
LINE...BUT OBSERVED RAIN RATES WERE LOWER THAN WHAT WAS BEING
EXPERIENCED WITH THAT SQUALL LINE. GIVEN THE MORE EXTENSIVE CLOUD
COVER...THERE IS A BETTER CHANCE THAT INSTABILITY WILL CONTINUE TO
BE RESTRICTED FROM COASTAL MISSISSIPPI INTO SOUTHERN ALABAMA...AND
THUS RAIN RATES MAY CONTINUE TO BE LIMITED. HOWEVER...IF A MORE
COHERENT FOCUSING MECHANISM CAN FAVORABLY ALIGN WITH LOW-LEVEL
INFLOW AND POCKETS OF GREATER INSTABILITY CAN DEVELOP...LOCALIZED
FLASH FLOODING COULD OCCUR WITH TRAINING BANDS OF RAIN OVER
ALREADY SATURATED GROUND. THIS WOULD BE MOST LIKELY WITHIN 20
MILES OF THE IMMEDIATE COAST WHERE INSTABILITY SHOULD BE HIGHEST.

LAMERS

ATTN...WFO...BMX...FFC...LIX...MOB...TAE...

ATTN...RFC...LMRFC...SERFC...

LAT...LON   31968407 31358388 30648422 29918475 29638543
            30168654 30088818 30198898 30238922 30838912
            31448759 31698652 31928548


Last Updated: 858 AM EST SUN FEB 11 2018