MESOSCALE PRECIPITATION DISCUSSION 0171
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
944 PM EDT FRI MAY 18 2018

AREAS AFFECTED...WESTERN KS

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

VALID 190140Z - 190630Z

SUMMARY...HIGHLY ORGANIZED CONVECTION IS EXPECTED TO EVOLVE OVER
THE NEXT SEVERAL HOURS WITH GROWING CONCERNS FOR ENHANCED RAINFALL
RATES AND FLASH FLOODING.

DISCUSSION...RAPIDLY EXPANDING CONVECTION IS SEEN IN GOES-16 CLEAN
IR IMAGERY WITH VERY COLD CLOUD TEMPS...AND NUMEROUS OVERSHOOTING
TOPS OVER WESTERN KS. BROADLY DIFFLUENT ALOFT AHEAD OF A DEEP
LAYER TROUGH/CLOSED LOW OVER THE FOUR CORNERS REGION COUPLED WITH
AN EJECTING SHORTWAVE IS WORKING TANDEM WITH A MODERATE TO
STRONGLY UNSTABLE BOUNDARY LAYER FOR ENHANCED CONVECTIVE
POTENTIAL. ADDITIONALLY...THERE IS A STATIONARY FRONT DRAPED
ACROSS THE REGION WITH MOIST LOW LEVEL EASTERLY FLOW NORTH OF THIS
BOUNDARY AND FOCUSED INTO TOWARD WESTERN KS WHERE AN INVERTED
TROUGH IS SITUATED. THIS RELATIVELY ENHANCED SURFACE-BASED
CONVERGENCE IS HELPING TO PROVIDE ADDITIONAL FORCING.

THE LATEST GOES-16 MID LEVEL WV AND AIRMASS-RGB IMAGERY SUGGESTS A
SHORTWAVE EJECTING OUT ACROSS THE NORTHERN TX/WESTERN OK PANHANDLE
REGION WHICH IS INTERACTING WITH INSTABILITY CHARACTERIZED BY
MLCAPE VALUES OF 2000 TO 2500 J/KG. EFFECTIVE BULK SHEAR VALUES
ARE ON THE ORDER OF 40 KTS AS WELL WHICH COUPLED WITH THE
INSTABILITY IS FOSTERING VERY STRONG UPDRAFTS. PWATS ACROSS
WESTERN KS ARE ON THE ORDER OF 1.1 TO 1.2 INCHES...BUT GIVEN THE
VERY FAVORABLE THERMODYNAMIC ENVIRONMENT CURRENTLY IN
PLACE...RAINFALL RATES OF AS MUCH AS 2.5 INCHES/HR CAN BE
EXPECTED...AND ESPECIALLY WITHIN AREAS OF OVERSHOOTING TOPS.

THE HRRR/HRRRX GUIDANCE SUPPORTS AS MUCH AS 3 TO 5 INCHES OF RAIN
LOCALLY GOING THROUGH 06Z...AND THE CONVECTION IS EXPECTED TO
ORGANIZED INTO A STRONG MCS WITH SUBSEQUENT MOVEMENT OFF TO THE
EAST OR NORTHEAST IN LINE WITH THE DEEP LAYER MEAN FLOW.

GIVEN THE ENHANCED SHORT-TERM RAINFALL RATES AND ORGANIZED NATURE
OF THIS EVOLVING MCS...FLASH FLOODING IS POSSIBLE.

ORRISON

ATTN...WFO...DDC...GID...GLD...

ATTN...RFC...ABRFC...MBRFC...

LAT...LON   40030015 39889954 39479923 38449931 37690021
            37460093 37450162 37800180 38480138 39380129
            39850110