Graphic for MPD #0253

MESOSCALE PRECIPITATION DISCUSSION 0253
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
119 PM EDT SUN MAY 21 2017

AREAS AFFECTED...SOUTHWEST TO SOUTH-CENTRAL TX

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

VALID 211715Z - 212315Z

SUMMARY...THUNDERSTORMS ARE EXPECTED TO EXPAND IN COVERAGE AND
BECOME MORE ORGANIZED THIS AFTERNOON. VERY HEAVY RAINFALL RATES UP
TO 2.5 INCHES/HR ARE EXPECTED...AND SOME FLASH FLOODING WILL BE
POSSIBLE.

DISCUSSION...THE LATEST EXPERIMENTAL GOES-16 VIS/IR SATELLITE DATA
SHOWS A GRADUALLY EXPANDING CLUSTER OF STRONG THUNDERSTORMS OVER
PARTS OF SOUTHWEST TX AND NORTHERN MEXICO INVOLVING THE NORTHERN
STATE OF COAHUILA. ALREADY NOTING SEVERAL OVERSHOOTING TOPS AND
THE GLD-360 LIGHTNING DENSITY PRODUCT IS SHOWING A NOTABLE UPTICK
IN STRIKE ACTIVITY NEAR THE RIO GRANDE RIVER AND DOWN OVER THE
MEXICAN STATE OF COAHUILA WEST AND SOUTHWEST OF DEL RIO.

THE CONVECTION IS DEVELOPING IN RESPONSE TO A STRONG SHORTWAVE
TROUGH IN THE SUBTROPICAL STREAM ADVANCING EAST ACROSS NORTHERN
MEXICO WHILE INTERACTING WITH A CONVERGENT AND MOIST/UNSTABLE
BOUNDARY LAYER THAT HAS POOLED UP WEST ACROSS THE LOWER AND MIDDLE
RIO GRANDE VALLEY ALONG WITH ADJACENT AREAS OF SOUTH-CENTRAL TX.
THE 12Z DEL RIO RAOB CONFIRMED AN ALREADY MOIST AND UNSTABLE
COLUMN WITH A PWAT OF 1.71...LI OF -8 AS AIDED BY STEEP MID LEVEL
LAPSE RATES...AND AN IMPRESSIVELY HIGH K-INDEX OF 42.

THE UPSTREAM CONVECTIVE ACTIVITY WILL ADVANCE EAST THIS AFTERNOON
INTO THIS FAVORABLY MOIST/UNSTABLE DOWNSTREAM ENVIRONMENT AND
COUPLED WITH RATHER STRONG DEEP LAYER SHEAR PROFILES SHOULD ALLOW
THE CONVECTION TO EXPAND IN COVERAGE AND GROW UPSCALE IN TERMS OF
ORGANIZATION.

RAINFALL RATES THIS AFTERNOON WILL BE VERY HIGH...LIKELY UPWARDS
OF 2.5 INCHES/HR...OWING TO THE MORE CONCENTRATED AND DEEPER LEVEL
OF MOISTURE AS THE CIRA-LPW DATA IS CONFIRMING IN THE 300/500MB
AND 500/700MB LAYERS.

THE LAST FEW RUNS OF THE HRRR HAVE SUGGESTED AS MUCH AS 3 TO 5
INCHES WITH ISOLATED AMOUNTS OVER 5 INCHES CLOSE TO THE RIO GRANDE
RIVER THROUGH THE AFTERNOON. EXPECT THERE TO BE SOME CONCERNS FOR
FLASH FLOODING AS A RESULT.

ORRISON

ATTN...WFO...CRP...EWX...MAF...SJT...

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

LAT...LON   31720180 31400060 31130005 30659941 30109882
            29519815 28909716 28439706 27919753 27449847
            27329930 27609982 28300036 28930070 29170089
            29400118 29580157 29780197 30400251 31270283
            31690258


Last Updated: 119 PM EDT SUN MAY 21 2017