MESOSCALE PRECIPITATION DISCUSSION 0151
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1103 PM EDT FRI APR 28 2017

AREAS AFFECTED...FAR NORTHEAST OK...SOUTHERN MO...NORTHWEST AR

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

VALID 290300Z - 290900Z

SUMMARY...TRAINING SHOWERS AND THUNDERSTORMS WITH INTENSE RAINFALL
RATES OF OVER 2 INCHES/HR ARE EXPECTED TO DEVELOP OVERNIGHT. FLASH
FLOODING IS POSSIBLE.

DISCUSSION...EXPERIMENTAL GOES-16 IR IMAGERY CONFIRMS THAT
CONVECTIVE INITIATION IS UNDERWAY IN AN ELEVATED FASHION ACROSS
AREAS OF SOUTHERN MO...FAR NORTHWEST AR AND PARTS OF EASTERN OK. A
STRENGTHENING AND VERY MOIST LOW LEVEL JET COUPLED WITH GRADUALLY
IMPROVING RIGHT-ENTRANCE REGION JET DYNAMICS IN VICINITY OF A
WELL-DEFINED QUASI-STATIONARY FRONTAL ZONE SHOULD FACILITATE A
SW/NE AXIS OF STRONG THUNDERSTORMS WITH INTENSE RAINFALL RATES
OVER THE NEXT FEW HOURS.

A VERY UNSTABLE AIRMASS IS POOLED SOUTH OF THE FRONTAL ZONE...WITH
MUCAPE VALUES AS HIGH AS 3000 TO 4000 J/KG. MEANWHILE AREAS VWP
DATA IS INDICATING A 40 TO 50 KT S/SW LOW LEVEL JET OVERRUNNING
THE FRONT ALONG WITH A SUBSTANTIAL AMOUNT OF SPEED CONVERGENCE
OVER NORTHERN AR AND SOUTHERN MO. A NOSE OF PWATS TO NEAR 1.5
INCHES HAVE EMERGED UP ACROSS THE AR/MO BORDER...WITH NOTABLY
HIGHER PWATS AND A VERY MOIST BOUNDARY LAYER WITH 70+ DEWPOINTS
POOLED SOUTH OF THE FRONT.

OVER THE NEXT FEW HOURS...ELEVATED CONVECTION SHOULD CONTINUE TO
DEVELOP AND EXPAND IN COVERAGE WHILE ATTAINING BETTER ORGANIZATION
GIVEN THE EXPECTATION OF SOME FURTHER UPTICK IN THE LOW LEVEL JET.
VERY STRONG WARM ADVECTION OVER THE FRONT AND IMPROVING JET
DYNAMICS AHEAD OF THE DEEP UPPER TROUGH OVER THE FOUR CORNERS
REGION WILL ALSO FOSTER ENHANCED LARGER SCALE ASCENT FOR
CONVECTIVE ORGANIZATION.

CONVECTIVE CELL MOTION WILL BE GENERALLY ORIENTED IN A SW/NE
FASHION...WITH A HIGHLY FAVORABLE ENVIRONMENT FOR CELL-TRAINING.
THE INCREASING MOISTURE TRANSPORT AND STRONG FORCING WILL FAVOR
INTENSE RAINFALL RATES OVER 2 INCHES/HR. ADJUSTING FOR WHERE
CONVECTIVE INITIATION IS UNDERWAY...HIRES MODEL SIGNALS SUGGEST AS
MUCH AS 3 TO 5 INCHES RAIN WILL BE POSSIBLE THROUGH 09Z. GIVEN THE
RELATIVELY WET ANTECEDENT CONDITIONS...ESPECIALLY OVER SOUTHERN
MO...FLASH FLOODING IS LIKELY.

ORRISON

ATTN...WFO...LSX...LZK...MEG...PAH...SGF...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...

LAT...LON   38149011 37748939 37208942 36878985 36699038
            36219241 35799428 36189494 36969458 37539351
            37869245 38109135