MESOSCALE PRECIPITATION DISCUSSION 0055
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
842 PM EST TUE MAR 08 2016
 
AREAS AFFECTED...CENTRAL/SOUTHERN TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 090130Z - 090600Z
 
SUMMARY...EXPANDING CONVECTION OVER THE TX HILL COUNTRY WILL
FOSTER ADDITIONAL CONCERNS FOR FLASH FLOODING GIVEN EARLIER HEAVY
RAINS.

DISCUSSION...AN UPPER LOW CONTINUES TO DIG ACROSS NORTHERN MEXICO
THIS EVENING WITH A VERY DIFFLUENT UPPER LEVEL FLOW STRUCTURE
FOCUSED NORTH OF THE RIO GRANDE VALLEY UP ACROSS THE TX HILL
COUNTRY. WV IMAGERY SUGGESTS ADDITIONAL VORT ENERGY LIFTING NORTH
AROUND THE NORTHEAST FLANK OF THE UPPER LOW...AND THIS ENERGY IS
INTERACTING WITH A MODERATE TO STRONG INSTABILITY WITH MLCAPE
VALUES OF 2000 TO 3000 J/KG TO FOSTER REDEVELOPMENT OF NUMEROUS
HEAVY SHOWERS AND THUNDERSTORMS.

PWATS ARE ON THE ORDER OF 1 TO 1.2 INCHES FROM THE LOWER RIO
GRANDE VALLEY UP ACROSS MUCH OF CENTRAL TX...AND SOME OF THIS
MOISTURE IS BEING TRANSPORTED BACK TO THE NORTHWEST WITH A MODEST
LOW LEVEL SOUTHEAST FETCH. THE GLOBAL MODELS INDICATE SOME
INCREASE IN THIS SOUTHEASTERLY FETCH OVERNIGHT...AND THIS WILL
ALLOW FOR SOME SPEED CONVERGENCE THAT COUPLED WITH THE LARGER
SCALE ASCENT AND THERMODYNAMIC ENVIRONMENT SHOULD ALLOW ONGOING
CONVECTION TO ADVANCE EAST AND POTENTIALLY BECOME MORE ORGANIZED
IN NATURE THROUGH 06Z. ADDITIONALLY...THE CONVECTION IS EXPECTED
TO BECOME MORE FOCUSED ALONG A FRONTAL ZONE AND ASSOCIATED WAVE OF
LOW PRESSURE...WITH CONVECTION TENDING TO BE RATHER SLOW-MOVING.

THE HIRES GUIDANCE IS PREFERRED AT THIS POINT AS THE 12Z ARW AND
12Z NMMB HAVE A VERY POOR HANDLE ON THE ONGOING ACTIVITY. THE HRRR
SUGGESTS ADDITIONAL RAINFALL AMOUNTS OF 2 TO 4 INCHES ACROSS THE
MPD OUTLOOK AREA THROUGH 06Z WITH ISOLATED HEAVIER AMOUNTS.
RAINFALL RATES OF 1 TO 1.5 INCHES/HR ARE POSSIBLE...AND ESPECIALLY
WHERE CELL MERGERS OCCUR WHICH RADAR IMAGERY SUGGESTS IS POSSIBLE
LOCALLY.

GIVEN THE RECENT HEAVY RAINS LOCALLY FROM EARLIER TODAY...FFG
VALUES IN SOME AREAS HAVE LOWER SIGNIFICANTLY..AND THE ADDITIONAL
RAINS OVERNIGHT WILL ENHANCE THE THREAT FOR ADDITIONAL FLASH
FLOODING.

ORRISON

ATTN...WFO...CRP...EWX...FWD...LUB...MAF...SJT...

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

LAT...LON   33099967 32559859 32369735 32089620 31219589 
            30669753 30129844 29199882 28349933 28069992 
            28840047 30130025 31290035 31740080 32400123 
            32990086