Flash Flood Guidance
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
AWUS01 KWNH 252139
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-260320-

MESOSCALE PRECIPITATION DISCUSSION 0047...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
438 PM EST SUN FEB 25 2018

CORRECTED FOR ADDING MORE MODEL DETAIL

AREAS AFFECTED...SOUTHEAST TX...WEST-CENTRAL TO NORTHEAST
LA...SOUTHWEST TO CENTRAL LA...SOUTHWEST TO CENTRAL MS

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

VALID 252120Z - 260320Z

SUMMARY...SHOWERS AND THUNDERSTORMS GOING INTO THE EVENING HOURS
ARE LIKELY WHICH WILL CONTINUE TO FOSTER A THREAT OF RUNOFF
PROBLEMS AND/OR FLASH FLOODING GIVEN THE WET ANTECEDENT CONDITIONS.

DISCUSSION...RADAR IMAGERY IS SHOWING A RATHER EXPANSIVE AREA OF
SHOWERS AND THUNDERSTORMS EXTENDING FROM AREAS OF SOUTH-CENTRAL TX
NORTHEASTWARD UP ACROSS CENTRAL/NORTHEAST LA AND INTO WEST-CENTRAL
MS. THE CONVECTION IS DEVELOPING WITHIN A FAVORABLE REGION OF THE
UPPER JET WITH WELL-DEFINED 300 MB RIGHT-ENTRANCE REGION JET
DYNAMICS FOSTERING DEEPER LAYER ASCENT. MEANWHILE...A PERSISTENT
WARM AIR/MOISTURE ADVECTION REGIME CONTINUES WITH LOW LEVEL
SOUTHERLY FLOW OVERRUNNING A STATIONARY FRONTAL ZONE SITUATED
ALONG TX COAST AND INLAND ACROSS SOUTH-CENTRAL LA AND INTO
SOUTHERN MS. SURFACE OBSERVATIONS INDICATE MULTIPLE WAVES OF LOW
PRESSURE HAVE ALSO DEVELOPED ALONG THE TX PORTION OF THE BOUNDARY
AND ARE LIFTING NORTHEAST ALONG IT.

THE VERTICAL COLUMN IN VICINITY OF THE FRONT IS QUITE MOIST WITH
PWATS GENERALLY OF 1.5 TO 1.75 INCHES ACROSS THE SOUTHEAST TX
COASTAL PLAIN AND INTO SOUTH-CENTRAL LA. MEANWHILE...INSTABILITY
IS CHARACTERIZED BY A POOL OF 1000 TO 2000 J/KG OF MUCAPE OVER
SOUTH-CENTRAL TX AND THAT IS HAS BEEN INSTRUMENTAL IN ALLOWING
CONVECTION TO REGENERATE OVER THE BROADER SOUTHEAST TX COASTAL
PLAIN.

THE LATEST CAM GUIDANCE LED BY THE HRRR INDICATES THAT THE
AFOREMENTIONED WAVES OF LOW PRESSURE WILL LIFT NORTHEAST ALONG THE
FRONT THIS EVENING AND TEND TO CONSOLIDATE OVER SOUTH-CENTRAL MS.
THE NOSE OF A SOUTHERLY LOW LEVEL JET OF 30 TO 40 KTS CURRENTLY
TRANSPORTING MOISTURE AND INSTABILITY NORTH OVER THE FRONTAL ZONE
WILL BEGIN TO VEER THIS EVENING ACROSS THE WESTERN GULF COAST
REGION AND SHOULD EVENTUALLY BEGIN TO WEAKEN SOME BY LATE EVENING.
NEVERTHELESS...THERE IS EXPECTED TO BE SUFFICIENT LARGE SCALE
ASCENT COUPLED WITH ISENTROPIC LIFT AND ELEVATED INSTABILITY
TRANSPORT AHEAD OF LOW PRESSURE FOR AN AXIS HEAVY SHOWERS AND
THUNDERSTORMS TO IMPACT AREAS OF SOUTHEAST TX AND NORTHEAST ACROSS
MUCH OF WEST-CENTRAL/NORTHEAST LA AND THROUGH
WEST-CENTRAL/SOUTHWEST MS.

RAINFALL RATES OF LOCALLY OVER 1 INCH/HR ARE EXPECTED...WITH
ADDITIONAL TOTALS THROUGH 03Z OF AS MUCH AS 2 TO 3 INCHES WHERE
THE STRONGER CONVECTIVE CORES SET UP AND REPEAT OVER THE SAME
AREA. THIS IS CONSISTENT WITH THE LATEST CONSENSUS OF CAM GUIDANCE
INCLUDING THE LATEST HRRR. THE SOIL CONDITIONS ARE VERY
MOIST...AND SO THESE ADDITIONAL RAINS WILL CONTINUE TO FAVOR
CONCERNS OF EXCESSIVE RUNOFF AND SOME FLASH FLOODING.

ORRISON

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...CRP...EWX...FWD...HGX...JAN...LCH...LIX...SHV...

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

LAT...LON   33308978 33178877 32508846 32038889 31608987
            31299081 30939170 30539269 30159381 29799488
            29349596 28979704 29469761 30229728 30839640
            31459529 31979411 32539273 33049107


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.