MESOSCALE PRECIPITATION DISCUSSION 0058
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
500 AM EST WED MAR 09 2016
 
AREAS AFFECTED...EASTERN TX...NORTHWEST LA....EXTREME SOUTHEAST
OK...SOUTHERN AR...EXTREME WESTERN MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 091000Z - 091600Z
 
SUMMARY...VERY HEAVY RAINS WILL CAUSE SEVERE AND POTENTIALLY
LIFE-THREATENING FLASH FLOODING THIS MORNING ACROSS EASTERN TX AND
NORTHWEST LA.

DISCUSSION...CONDITIONS ARE BECOMING CONDUCIVE FOR AN EXTENSIVE
AREA OF EXTREMELY HEAVY RAINFALL THIS MORNING ACROSS PORTIONS OF
EASTERN TX AND NORTHWEST LA. WV IMAGERY SHOWS AN ANOMALOUSLY DEEP
UPPER LOW OVER NORTHERN MEXICO...WITH SHORTWAVE IMPULSES EJECTING
OUT OF THE BASE OF IT AND LIFTING NORTHEAST UP ACROSS EASTERN TX
AND INTO THE LOWER MS VALLEY.

THE UPPER LEVEL FLOW AROUND NORTHEAST FLANK OF THE UPPER LOW IS
VERY DIFFLUENT WHICH IS BEING AIDED BY EACH SHORTWAVE IMPULSE THAT
LIFTS ACROSS THE REGION. STRONG LARGE SCALE ASCENT WILL BE
INTERACTING WITH A VERY MOIST AND MODESTLY UNSTABLE AIRMASS
THROUGH THE MORNING. THIS WILL BE CHARACTERIZED BY AN AXIS OF 1.75
INCH PWATS...AIDED BY A DUAL SUBTROPICAL MOISTURE FEED INVOLVING
THE EASTERN TROPICAL PACIFIC OCEAN AND THE SOUTHERN GULF OF
MEXICO...ALONG WITH 1000 TO 2000 J/KG OF MUCAPE. THE LATEST KHGX
VWP DATA SHOWS A SOUTHERLY LOW LEVEL JET OF 50 KTS WHICH IS
FOSTERING 850 MB MOISTURE FLUX ANOMALIES INTO THE UPPER TX COAST
THAT ARE 4 TO 4.5 STANDARD DEVIATIONS ABOVE NORMAL.

ONGOING CONVECTION OVER CENTRAL AND NORTHEAST TX IS EXPECTED TO
GRADUALLY BECOME MORE FOCUSED AND ORGANIZED A BIT FARTHER EAST
OVER THE SOUTHEAST TX COASTAL PLAIN AND GRADUALLY THE UPPER TX
COAST WHERE STRONGER THERMODYNAMICS WILL BE IN PLACE AFTER 12Z.
HOWEVER...THIS CONVECTIVE AXIS WILL CONTINUE TO LIFT NORTHEAST AND
WILL STILL BE IMPACTING THE ARKLATEX REGION WHERE A STATIONARY
FRONT CONTINUES TO FOCUS EXTREMELY HEAVY RAINS. PARTS OF NORTHWEST
LA HAVE ALREADY SEEN CLOSE TO 10 INCHES OF RAIN AND MUCH MORE IS
ON THE WAY.

HIRES GUIDANCE LED BY THE 00Z ARW/00Z NSSL-WRF AND RECENT RUNS OF
THE HRRR SUGGEST A SSW/NNE AXIS OF VERY HEAVY RAINFALL BETWEEN 12Z
AND 18Z...WITH ADDITIONAL AMOUNTS OF 3 TO 6 INCHES...WITH ISOLATED
HEAVIER AMOUNTS OF 8 INCHES POSSIBLE. UNIDIRECTIONAL DEEP LAYER
SOUTHERLY FLOW WILL BE IN PLACE THIS MORNING AND WILL FAVOR A
STRONG TRAINING CONVECTION SET-UP...AND WITH RAINFALL RATES
EXCEEDING 2"/HR...IT IS POSSIBLE THE HIRES GUIDANCE MAY LOCALLY BE
UNDERDONE WITH THE RAINFALL AMOUNTS.

EXPECT THESE RAINS TO RESULT IN SEVERE AND LIFE-THREATENING FLASH
FLOODING. THE HARDEST IMPACTED AREAS WILL BE FAR NORTHEAST TX AND
NORTHWEST LA WHERE LOCAL STORM TOTALS IN EXCESS OF 1 FOOT OF RAIN
WILL BE EXPECTED BY MIDDAY.

ORRISON

ATTN...WFO...CRP...EWX...FWD...HGX...JAN...LCH...LZK...MEG...
SHV...

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

LAT...LON   34529155 34289072 33569033 32909047 31829179 
            31309264 30479343 29739399 29029501 28599583 
            28139694 27529816 27949860 29409807 30419793 
            32239715 33249615 34179436 34519297