MESOSCALE PRECIPITATION DISCUSSION 0049
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
207 PM EST TUE FEB 27 2018

AREAS AFFECTED...NERN TEXAS/SERN OK/SWRN AR/NWRN LA

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

VALID 271905Z - 280100Z

SUMMARY...TRAINING RAINFALL WITH RATES OF 1-2 IN/HR APPEARS LIKELY
FROM NORTHEASTERN TEXAS INTO AND ACROSS THE ARKLATEX. RAINFALL
TOTALS THROUGH 01Z ARE EXPECTED TO RANGE FROM 3-4 INCHES WHERE
IDEAL CELL TRAINING OCCURS WHICH WOULD POSE A FLASH FLOOD THREAT
GIVEN ANTECEDENT RAINFALL.

DISCUSSION...REGIONAL RADAR REFLECTIVITY OVER THE PAST COUPLE OF
HOURS HAS SHOWN A RAPID INCREASE IN THE COVERAGE OF ELEVATED
CONVECTION OVER NORTHEASTERN TEXAS AND OKLAHOMA ENDING 19Z. THIS
ACTIVITY IS OCCURRING NORTH OF A WARM FRONT SEEN RAPIDLY SURGING
NORTH IN VISIBLE SATELLITE IMAGERY OVER SOUTHEASTERN TEXAS.
MOISTURE AS SEEN IN THE BLENDED TPW PRODUCT HAS ALSO SHOWN A RAPID
INCREASE TO THE NORTH ACROSS EASTERN TEXAS INTO OKLAHOMA WITH 1.25
INCHES SEEN AS FAR NORTH AS THE RED RIVER...CONFIRMED WITH GPS
DATA.

THE 3 HOUR CHANGE IN MUCAPE ACROSS NORTHEASTERN TEXAS...COINCIDENT
WITH ONGOING CONVECTION...WAS IN THE 200-400 J/KG RANGE. AS A
SURGE IN THE 850-700 MB FLOW MOVES ACROSS THE ARKLATEX AS FORECAST
BY THE 12Z HI-RES MODEL SUITE AND RECENT RUNS OF THE
RAP/HRRR...CONVECTION IS EXPECTED TO BECOME SLIGHTLY BETTER
ORGANIZED WHILE INCREASING IN COVERAGE. THE 850-700 MB FLOW IS
FORECAST TO REACH 35-45 KT FROM THE SOUTHWEST...WHICH IS OF
SIMILAR DIRECTION AND SLIGHTLY STRONGER THAN ONGOING STORM MOTIONS
OF 30-40 KT. THIS WOULD SUPPORT TRAINING ELEMENTS WITH RAINFALL
RATES OF 1-2+ IN/HR EXPECTED AS MOISTURE CONTINUES TO SURGE
NORTHEASTWARD.

GIVEN EXTREMELY WET CONDITIONS OVER THE PAST 7 DAYS WITH 5-10+
INCHES OF RAIN AS SEEN IN THE STAGE IV DATA IN THE VICINITY OF THE
ARKLATEX...CURRENT AREA FLASH FLOOD GUIDANCE VALUES OF 2-3 INCHES
PER 3 HOURS COULD BE TOO HIGH. FLASH FLOODING APPEARS LIKE A GOOD
POSSIBILITY FROM PARTS OF NORTHEASTERN TEXAS INTO FAR SOUTHEAST
OKLAHOMA...NORTHERN LOUISIANA AND CENTRAL TO SOUTHERN ARKANSAS.

OTTO

ATTN...WFO...FWD...HGX...JAN...LZK...OUN...SHV...TSA...

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

LAT...LON   34809373 34469220 33229156 32089230 31539510
            31839667 32819725 33729676 34409545