Graphic for MPD #0295

MESOSCALE PRECIPITATION DISCUSSION 0295
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
902 AM EDT SUN JUN 04 2017

AREAS AFFECTED...SOUTHEASTERN TX/SOUTHWESTERN LA...

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

VALID 041301Z - 041701Z

SUMMARY...A POTENTIAL FOR FLASH FLOODING EXISTS ACROSS
SOUTHEASTERN TX INTO SOUTHWESTERN LA WHERE DEEP TROPICAL MOISTURE
AND A HIGHLY BUOYANT THERMODYNAMIC ENVIRONMENT ARE IN PLACE.
EXPECTED SLOW CELL MOTIONS WILL FOSTER A THREAT FOR TRAINING
CONVECTION...THUS BOLSTERING THE POTENTIAL FOR SOME HYDROLOGIC
ISSUES.

DISCUSSION...RADAR IMAGERY ACROSS THE UPPER TX COAST INTO THE
LOWER MS VALLEY DEPICTED MULTIPLE CLUSTERS OF SHOWERS AND
THUNDERSTORMS. PER DERIVED INSTABILITY FROM THE RAP OBJECTIVE
ANALYSIS AND RELATED 12Z RAOBS...A MODERATELY UNSTABLE/UNCAPPED
ATMOSPHERE IS IN PLACE WHICH ALLOWED CONVECTION TO THRIVE THIS
MORNING. A NORTHEAST/SOUTHWEST ORIENTED BAND OF CONVECTION WAS
OBSERVED ACROSS THE UPPER TX COAST WHILE SOME INFLOW FEEDER BANDS
WERE DETECTED IN THE EXPERIMENTAL GOES-16 INFRARED IMAGERY. THIS
IS OCCURRING IN THE PRESENCE OF SUFFICIENT LOW-LEVEL CONFLUENCE AS
NOTED IN THE LOCAL VAD-WIND PROFILER DATA. THE 12Z LCH SOUNDING
SAMPLED THE THERMODYNAMIC ENVIRONMENT WELL WITH OVER 2000 J/KG OF
SURFACE-BASED CAPE COUPLED WITH PRECIPITABLE WATER VALUES NEAR 2
INCHES. SUCH TROPOSPHERIC MOISTURE CONTENT IS EASILY ABOVE THE
90TH PERCENTILE FOR EARLY JUNE BASED ON THE SPC SOUNDING
CLIMATOLOGY PAGE. FURTHER...LOW-LEVEL WINDS APPEAR TO BE
EQUAL/OPPOSITE RELATIVE TO THE MEAN-STEERING FLOW SUGGESTING SLOW
CELL MOTIONS...THUS SUPPORTING A FLASH FLOOD THREAT.

HIGH-RESOLUTION MODELS SHOW A SIGNAL OF HEAVY RAINFALL AFFECTING
THIS REGION BUT VARY IN HOW QUICKLY TO USHER THE ACTIVITY
DOWNSTREAM. THE 11Z HRRR/09Z EXPERIMENTAL HRRR BOTH SHOW THE
CONVECTION HANGING UP ACROSS ALONG THE TX/LA BORDER...WITH THE
LATTER A BIT SLOWER IN DEVELOPMENT. THE 06Z NAM CONUS NEST IS A
BIT MORE PROGRESSIVE THAN THE REST OF THE MODEL SUITE. AND A
FURTHER NOTE...THE 08Z TIME-LAGGED HRRR SHOWS FAIRLY HIGH
PROBABILITIES FOR 1 INCH IN AN HOUR FOR MULTIPLE HOURS...POSSIBLY
THROUGH 17Z. THUS...WILL KEEP AN MPD ACTIVE THROUGH THEN AND
RE-ASSESS AFTERWARD.

RUBIN-OSTER

ATTN...WFO...HGX...LCH...SHV...

ATTN...RFC...LMRFC...WGRFC...

LAT...LON   31559338 31489244 30599206 30199209 29759253
            29559312 29339350 28969392 28819454 29299549
            29959524 30859440


Last Updated: 902 AM EDT SUN JUN 04 2017