MESOSCALE PRECIPITATION DISCUSSION 0604
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1238 PM EDT FRI OCT 23 2015
 
AREAS AFFECTED...EASTERN TEXAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 231636Z - 232236Z
 
SUMMARY...INCREASING TRAINING CONVECTION TO CONTINUE FLASH FLOOD
THREAT INTO THIS AFTERNOON. 


DISCUSSION...CONVECTION CONTINUES ACROSS EASTERN TEXAS THIS
MORNING...WITH MULTIPLE FACTORS AT PLAY IN CREATING THE CONTINUED
HEAVY RAINFALL THREAT. SOUTHERLY LOW LEVEL FLOW AROUND 30 KTS
CONTINUES TO ADVECT ANOMALOUS MOISTURE NORTHWARD...WITH
PRECIPITABLE WATER VALUES GENERALLY BETWEEN 1.75-2.25" ACROSS
SOUTHEAST TEXAS PER GPS...WHICH ARE AT OR NEAR RECORD LEVELS FOR
THIS TIME OF YEAR. ISENTROPIC LIFT CREATED BY THE STRONG SOUTHERLY
FLOW...AND A DIVERGENT PATTERN ALOFT ON THE OUTSKIRTS OF HURRICANE
PATRICIA AND THE RIGHT ENTRANCE REGION OF AN UPPER JET ACROSS THE
SOUTHERN/CENTRAL PLAINS...ARE PROVIDING THE ASCENT NEEDED FOR
CONTINUED REDEVELOPMENT.

TOUGH TO REALLY FIND AT THE SURFACE...BUT A LOW LEVEL BOUNDARY
DOES APPEAR TO EXTEND FROM THE LOW ACROSS SOUTH DAKOTA...SOUTH
THROUGH THE MISSISSIPPI VALLEY...BEFORE BECOMING ORIENTED MORE
SOUTHWEST TO NORTHEAST ACROSS NORTH TEXAS. THIS SOUTHWARD MOVING
BOUNDARY IS EXPECTED TO BECOME NEARLY STATIONARY ACROSS TEXAS AS
IT ENCOUNTERS THE STRONG 30 KT SOUTHERLY FLOW. THIS MOIST INFLOW
RUNNING OVER THE BOUNDARY SHOULD SUPPORT CONTINUED CONVECTIVE
DEVELOPMENT ACROSS NORTHEAST TEXAS INTO THE AFTERNOON. THIS
CONVECTION SHOULD HELP REINFORCE THE BOUNDARY...ENHANCING
CONVERGENCE EVEN MORE.

HIGH RES GUIDANCE DIFFER ON THE EXACT LOCATION OF THIS BOUNDARY
AND THUS WHERE THE GREATEST TRAINING AND HIGHEST QPF WILL OCCUR.
BASED ON RADAR TRENDS WOULD APPEAR THE 0Z NMMB IS TOO FAR
NORTHWEST...WITH THE 12Z GEM REG AND 14Z HRRR FOCUSING CONVECTION
TOO FAR SOUTHEAST. INSTEAD PREFER A COMPROMISE OF THE 12Z NAM
CONUS NEST...0Z ARW AND 13Z EXPERIMENTAL HRRR QPF AXIS...WHERE THE
EASTWARD MOVING COMPLEX INTERSECTS THE NORTHWARD MOVING
CONVECTION. EXPECT THIS NORTHWARD PROGRESSION TO EVENTUALLY STOP
AS THE BOUNDARY BECOMES REINFORCED...FOCUSING THE HEAVY RAINFALL
THREAT FROM NEAR/SOUTH OF DALLAS INTO THE REST OF NORTHEAST TEXAS.
THROUGH 22Z GUIDANCE SUGGEST AN ADDITIONAL 2-5"...WHICH SEEMS
VALID GIVEN THE TRAINING POTENTIAL AND CURRENT OBSERVED RATES AS
HIGH AS 1-2" AN HOUR. LATEST RADAR/SATELLITE APPEARS TO BE SHOWING
THE FIRST SIGNS OF THIS EAST/WEST TRAINING BEGINNING TO OCCUR FROM
AROUND CORSICANA TO NEAR TYLER TEXAS.

FURTHER SOUTH...SATELLITE SHOWS A TROPICAL CONNECTION FROM THE
WESTERN GULF NORTH INTO COASTAL TEXAS...WITH CONVECTION CONTINUING
TO STREAM NORTH. THIS MOISTURE WILL MERGE WITH THE FRONT TO THE
NORTH AND ENHANCE THE HEAVY RAINFALL THREAT THERE...BUT WILL ALSO
PRODUCE LOCALLY HEAVY RAINFALL ACROSS SOUTHERN TEXAS AS IT MOVES
NORTH THROUGH THE AFTERNOON. THIS AXIS APPEARS TO BE SETTING UP
FROM JUST WEST OF VICTORIA NORTH TO NEAR AUSTIN ALIGNED WITH THE
UNIDIRECTIONAL LOW LEVEL FLOW. THE FLASH FLOOD THREAT APPEARS MORE
ISOLATED IN THIS AREA GIVEN THE HIGHER FFG AND FAST CONVECTIVE
MOVEMENT. BUT STILL SEEING SOME TOTALS OF AROUND 2" AN
HOUR...WHICH COMBINED WITH REPEATING CELLS...MAY EVENTUALLY RESULT
IN A FLASH FLOOD THREAT INTO THIS AFTERNOON.

CHENARD

ATTN...WFO...CRP...EWX...FWD...HGX...OUN...SHV...

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

LAT...LON   33809586 33709452 33659439 33069383 32179369 
            31779432 31729550 31219618 30759635 29809631 
            28679642 27989669 27969756 28689801 29939840 
            30249849 31689820 32489791 33639741