MESOSCALE PRECIPITATION DISCUSSION 0322
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
355 PM EDT TUE AUG 26 2014
 
AREAS AFFECTED...EASTERN CO 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 261955Z - 270155Z
 
SUMMARY...PULSE CONVECTION IS EXPECTED TO PRODUCE HOURLY RAIN
RATES UP TO 2", WHICH SHOULD CAUSE FLASH FLOODING IN AREAS OF
WHICH RECEIVED HEAVY RAINFALL LATE YESTERDAY.

DISCUSSION...THE SURFACE FEATURES AT PLAY IN THIS REGION ARE A
WEAK LOW PRESSURE AREA IN NORTH-CENTRAL CO AND A STATIONARY FRONT
ACROSS EASTERN CO.  MIXED LAYER CAPE -- PER THE SPC MESOANALYSIS
-- ARE 1000-2000 J/KG.  DAYTIME HEATING IS STARTING TO BREAK A
WEAK LOW- TO MID-LEVEL CAP, INDICATED BY THE EXTENT OF THE 12C 700
HPA ISOTHERM.  PRECIPITABLE WATER VALUES IN THE REGION ARE 1-1.5",
WHICH ARE SLOWLY INCREASING DUE TO SOUTHERLY LOW-LEVEL FLOW. 
COMBINED WITH DIVERGENCE ALOFT AHEAD OF THE WESTERN TROUGH, THE
ENVIRONMENT IS CONDUCIVE FOR SINGLE CELL/PULSE CONVECTION.

PRECIPITABLE WATER ANOMALIES RISE FROM 1.5 TO OVER 2.5 STANDARD
DEVIATIONS ABOVE NORMAL PER THE 12Z NAM, PAST THE 90TH PERCENTILE
FOR LATE AUGUST.  THE 850-400 HPA MEAN FLOW IN THE REGION IS
EXPECTED TO BE AROUND 15 KTS TO THE NORTHEAST, WHICH SHOULD
EXPLAIN THUNDERSTORM MOTION THIS AFTERNOON.  LATER ON, PAST 00Z,
850 HPA INFLOW INCREASES OVER THE FRONTAL BOUNDARY IN EASTERN CO,
WHICH COULD LEAD TO MORE ORGANIZED CONVECTION THIS EVENING. 
THUNDERSTORMS WITH HOURLY RAIN RATES UP TO 2" AN HOUR -- NEARLY
DOUBLE THE THREE HOUR FLASH FLOOD GUIDANCE -- WHICH SHOULD LEAD TO
FLASH FLOODING.

ROTH

ATTN...WFO...LBF...DDC...GLD...AMA...PUB...BOU...CYS...ABQ...

ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...

LAT...LON   36840410 37290492 38100516 38950536 39770556 40370519
            41060446 41360347 41230191 40200132 38640173 37700219
            36980298 36840410