Graphic for MPD #0339

MESOSCALE PRECIPITATION DISCUSSION 0339
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 PM EDT SUN JUN 18 2017

AREAS AFFECTED...EASTERN AR, SOUTHWEST TN, & NORTHWEST MS

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

VALID 181759Z - 182359Z

SUMMARY...THUNDERSTORMS WITH HEAVY RAIN  SHOULD SPREAD EAST AND
SOUTHEAST WITH TIME.  HOURLY RAIN RATES TO 2.5" AND LOCAL AMOUNTS
TO 5" ARE ANTICIPATED.

DISCUSSION...THUNDERSTORMS ARE BEGINNING TO TRAIN ACROSS NORTHEAST
AR IN A WARM ADVECTION PATTERN AHEAD OF A MESOSCALE WAVE IN
NORTHEAST AR, WHICH ARE BEGINNING TO SPREAD EAST AND ATTEMPT TO
LINK WITH A LINE ACROSS SOUTHWEST TN.  THE DIVERGENCE SEEN IN THE
1000-500 HPA THICKNESS PATTERN IMPLIES THAT THIS IS A GOOD SPOT
SYNOPTICALLY FOR A CONVECTIVE COMPLEX.  PRECIPITABLE WATER VALUES
ARE ~2".  INFLOW AT 850 HPA IS CONVERGENT OUT OF THE WEST AT ~20
KTS.  EFFECTIVE BULK SHEAR IS JUST UNDER 25 KTS.  MLCAPE VALUES
ARE 2000-3000 J/KG.

THE MESOSCALE GUIDANCE SHOWS A GROWING SIGNAL FOR LOCAL AMOUNTS IN
THE 3-5" RANGE OVER THE NEXT TWO HOURS.  CONVECTIVE CLUSTERS
SHOULD MOVE EAST INITIALLY, THOUGH AS INSTABILITY ERODES, COULD
TRACK MORE SOUTHEAST AT 15-20 KTS WITH TIME.  RAP MASS FIELDS SHOW
A PAIR OF BOUNDARIES (THE SECOND ONE THE ACTUAL COLD FRONT) MOVING
THROUGH THE REGION TO THE NORTH OF A SIGNIFICANT INSTABILITY POOL,
IMPLYING THAT THERE COULD BE MORE THAN ONE ROUND OF THUNDERSTORMS
BETWEEN NOW AND 00Z.  THE FLOW IS FAIRLY UNIDIRECTIONAL UP TO 600
HPA, IMPLYING THAT CELL TRAINING IS A VALID CONCERN THROUGH THE
PERIOD.  HOURLY RAIN RATES UP TO 2.5" WITH LOCAL AMOUNTS TO 5"
COULD CAUSE ISSUES IN THIS REGION.

ROTH

ATTN...WFO...JAN...LZK...MEG...

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

LAT...LON   36218907 35968840 35168816 34308855 33948996
            34129113 34469197 35319185 35709134 36208981
           


Last Updated: 159 PM EDT SUN JUN 18 2017