MESOSCALE PRECIPITATION DISCUSSION 0056
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
356 PM EDT WED MAY 06 2015
 
AREAS AFFECTED...NORTH-CENTRAL KS AND SOUTHEAST NE 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 062000Z - 070200Z
 
SUMMARY...AN INVADING WARM FRONT IS EXPECTED TO ACT AS THE INITIAL
FOCUS FOR ORGANIZED CONVECTION NEAR THE KS/NE BORDER.  CONVECTION
SHOULD MOVE EAST-NORTHEAST WITH TIME.  WITH HOURLY RAIN RATES UP
TO 1.75" EXPECTED, FLASH FLOODING IS CONSIDERED POSSIBLE.

DISCUSSION...SCATTERED THUNDERSTORMS HAVE BEGUN TO DEVELOP ACROSS
NORTH-CENTRAL KS IN RESPONSE TO AN UPPER LOW IN THE VICINITY AND A
DEVELOPING WARM FRONT BEING FORCED BY THE CLOUD COVER ACROSS THE
AREA.  INFLOW AT 850 HPA OF 45-50 KTS HAS BEEN OBSERVED BY RECENT
VAD WIND PROFILES, WHICH EXCEEDS THE 850-400 HPA MEAN WIND IN THIS
REGION BY 15-20 KTS.  WHEN SUBTRACTING OUT THE SURFACE WIND, THIS
YIELDS ~35 KTS OF CLOUD BASE INFLOW.  RECENT SPC MESOANALYSES
INDICATE MIXED LAYER CAPE VALUES OF 1000+ J/KG ACROSS PORTIONS OF
CENTRAL KS, MOVING INTO THE REGION ON THE HEELS OF THE WEAK WARM
FRONT.

PRECIPITABLE WATER VALUES (PWS) ARE CURRENTLY SHY OF 1.25" PER
SATELLITE-BASED GPS VALUES.  HOWEVER, RAP GUIDANCE HAS BEEN
INDICATING AN INCREASE IN PWS TO 1.25-1.50" ACROSS THE REGION. 
THUNDERSTORMS TODAY HAVE SHOWN A TENDENCY TO FORWARD PROPAGATE,
INDICATING THAT THE PRIMARY FLASH FLOOD RISK IS CELL TRAINING. 
HOWEVER, A COLD POOL IS LIKELY TO FORM DUE TO EXPECTED CONVECTION,
WHICH COULD STOP THE FORWARD PROGRESSION OF THE WEAK WARM FRONT
AND CAUSE BACKBUILDING ACROSS NORTH-CENTRAL KS LATER THIS
AFTERNOON INTO THIS EVENING.  AS THE UPPER LOW PULLS AWAY, DEEP
LAYER WIND SHEAR INCREASES SETTING THE STAGE FOR SUPERCELLS, PER
SPC.  PROPAGATION/ CORFIDI VECTORS ALONG WITH THE MEAN WIND VECTOR
INDICATE NORTHEAST MOTION TO CONVECTION.  HOWEVER, THE EXPECTED
COLD POOL SHOULD CAUSE A DEVIATION TO THE EAST-NORTHEAST WITH
TIME, ROUGHLY PARALLEL TO THE ORIENTATION OF THE 1000-500
THICKNESS LINES IN THE REGION.  THE 12Z MESOSCALE GUIDANCE IS
UNANIMOUS IN THE POSITION OF THE HEAVY RAIN THREAT, WITH AT LEAST
3-5" LOCAL AMOUNTS ADVERTISED.  USED THE RAP MASS FIELDS (1.25"+
PWS, PROXIMITY OF 1000+ J/KG CAPE AND CAPE GRADIENT, STRONG 850
HPA INFLOW) TO TRY TO REFINE THE THREAT AREA.  FLASH FLOODING IS
CONSIDERED POSSIBLE.

ROTH

ATTN...WFO...DDC...EAX...GID...GLD...ICT...OAX...TOP...

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

LAT...LON   40979700 40729536 39899520 39269687 39089752 
            38879863 38799908 38689965 39099966 39549982 
            40059988 40439937 40739860