MESOSCALE PRECIPITATION DISCUSSION 0054
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1132 PM EST WED FEB 28 2018

AREAS AFFECTED...ARKLATEX, AR, NORTHERN MS, & TN

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 010431Z - 010901Z

SUMMARY...A BAND OF HEAVY RAIN IS EXPECTED TO IMPACT THE REGION
INTO THE EARLY MORNING HOURS.  LOCAL AMOUNTS OF 3-4" OVER
SATURATED SOILS IS EXPECTED TO LEAD TO AND/OR PROLONG FLASH
FLOODING.

DISCUSSION...A BROAD OVERRUNNING PATTERN HAS SET UP FROM NORTHEAST
TX ACROSS AR AND EXTENDING INTO TN WITHIN A REGION OF OVERLAPPING
850 HPA, 750 HPA, AND 650 FRONTOGENESIS PER THE 18Z GFS GUIDANCE. 
PRECIPITABLE WATER VALUES OF 1.5-1.7" ARE SEEN HERE PER GPS
VALUES.  THE ATMOSPHERE IS SATURATED AS THE MID- AND UPPER-LEVEL
FLOW HAS A FETCH FROM OFFSHORE BAJA CALIFORNIA WHILE THE LOW-LEVEL
INFLOW IS OFF OF THE GULF OF MEXICO.  THE WIND FLOW IS FAIRLY
UNIDIRECTIONAL WITH HEIGHT OUT OF THE WEST-SOUTHWEST ABOVE 2,000
FEET PER THE LITTLE ROCK AR VAD WIND PROFILE.

WHILE MUCAPE VALUES OF 500+ J/KG ARE SEEN ACROSS NORTHEAST TX,
PLACES FARTHER AFIELD ACROSS AR AND NORTHERN MS HAVE VALUES OF
100-200 J/KG PER SPC MESOANALYSES.  WHILE THESE VALUES ARE MEAGER,
SOIL CONDITIONS OVER A VAST PORTION OF THE AREA ARE SATURATED DUE
TO RAINFALL BEING 300-700% OF NORMAL OVER THE PAST COUPLE WEEKS,
WITH THE LARGEST DEPARTURES ACROSS CENTRAL AR, PATCHES OF
NORTHEAST TX AND SOUTHEAST OK.  EVEN WITH THIS LITTLE INSTABILITY,
HOURLY RAIN RATES OF 0.5" ARE POSSIBLE WHICH WOULD COMPROMISE
SATURATED SOILS.  THREE HOURLY FLASH FLOOD GUIDANCE VALUES ARE
PRACTICALLY ZERO ACROSS SOUTH-CENTRAL AR AND ARE LOW FROM THE
ARKLATEX ACROSS MUCH OF TN.  THE MESOSCALE GUIDANCE ADVERTISES
LOCAL AMOUNTS IN THE 3-4" OVER THE MOST SENSITIVE AREA IN AR WITH
LOWER, THOUGH STILL THREATENING, AMOUNTS EXTENDING INTO CENTRAL
TN.  FLASH FLOODING IS CONSIDERED LIKELY.

ROTH

ATTN...WFO...FWD...HUN...JAN...LZK...MEG...OHX...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...OHRFC...SERFC...WGRFC...

LAT...LON   36348580 35318588 34788753 33799102 32919389
            32479595 32699740 34309466 36018946