Mesoscale Precip Discussion from NWS Weather Prediction Center:
MESOSCALE PRECIPITATION DISCUSSION 0226
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
319 PM EDT TUE JUN 16 2015
AREAS AFFECTED...WESTERN GULF COAST...SOUTHEAST TX...
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 161918Z - 170018Z
SUMMARY...STRONG CONVECTIVE INNER/OUTER BANDS ARE CURRENTLY MOVING
INTO SOUTHEAST TX. HOURLY RAINFALL RATES OF 1 TO 2 INCHES ARE
SUGGESTED BY LOCAL RADARS. PERSISTENT HEAVY RAINFALL IN THESE
BANDS WILL RAISE THE RISK FOR FLASH FLOODING...PARTICULARLY IN
MORE URBANIZED LOCATIONS.
DISCUSSION...TROPICAL STORM BILL IS SLOWLY WORKING ITS WAY INLAND
ALONG THE TX COAST. THE BLENDED-TPW PRODUCT PORTRAYS A SIGNIFICANT
SLUG OF MOISTURE LIFTING OUT OF THE WESTERN GULF OF MX. THE 17Z
GPS SOUNDER DATA INDICATES NEARLY 2.50 INCH PWATS IN THE VICINITY
OF GALVESTON BAY WITH STANDARDIZED ANOMALIES LOCALLY EXCEEDING 3
SIGMAS. IN ADDITION TO THE IMPRESSIVE MOISTURE IN PLACE...12Z
RAOBS OVER THE REGION INDICATE NEARLY UNIDIRECTIONAL
SOUTH-SOUTHEASTERLY FLOW ANCHORING THE LOWEST 3 KM OF THE
TROPOSPHERE. MESOSCALE BANDS ALIGNING ALONG THIS MOISTURE AXIS
WILL LEAD TO TRAINING/REPEAT CONVECTION WHICH ALREADY APPEARS
UNDERWAY IN SOUTHEAST TX. A SATURATED ATMOSPHERE WITH FREEZING
LEVELS UP AROUND 15 TO 16 KFT PER 12Z RAOBS FROM CRP/LCH INDICATE
WARM RAIN PROCESSES WITH VERY EFFICIENT RAINFALL PRODUCTION IS
LIKELY.
WHILE CURRENT 1-HOUR RAINFALL TOTALS HAVE GENERALLY NOT
EXCEEDED THE 0.75 TO 1 INCH RANGE...EXPECT THESE VALUES TO COME UP
AS THE BANDING BECOMES BETTER ORGANIZED.
HIGH-RESOLUTION MODELS ARE QUITE SUPPORTIVE OF VERY HEAVY RAINFALL
WITH 3 TO 5 INCHES LIKELY THROUGH 00Z. SUCH CONDITIONS SHOULD
CONTINUE INTO THE OVERNIGHT HOURS WITH THE CONVECTION SLOWLY
EXPANDING INLAND.