MESOSCALE PRECIPITATION DISCUSSION 0658
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
137 PM EDT FRI SEP 09 2016
 
AREAS AFFECTED...EASTERN NE...WESTERN IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 091736Z - 092300Z
 
SUMMARY...INCREASED CONVECTIVE COVERAGE AND SOME TRAINING OF CELLS
MAY RESULT IN ISOLATED FLASH FLOODING THOURGH THE AFTERNOON. 

DISCUSSION...CONVECTION WAS BUILDING ACROSS PORTIONS OF EASTERN
NEB IN A NORTHEAST TO SOUTHWEST LINE.  THE SYNOPTIC SCALE FLOW
ALOFT IS DIFLUENT WHILE A SUBTLE SHORTWAVE WAS MAKING ITS WAY
EASTWARD OVER EASTERN NEBRASKA...AND CONVECTION WAS MOST ACTIVE
ALONG A GRADIENT OF LOW LEVEL THETAE.  12Z SOUNDINGS INDICATED
THAT THE AXIS OF MOST UNSTABLE AIR WAS ALREADY IN PLACE WITH THE
SHORT TERM HIGH RESOLUTION AND RAPID REFRESH MODELS INCREASE MU
CAPES TO VALUES IN EXCESS OF 3000 J PER JG BY 21Z.  THIS SHOULD
ALL CONTINUE TO SUPPORT CONVECTION CAPABLE OF PRODUCING VERY HEAVY
RAINFALL RATES ALONG WITH THE POTENTIAL FOR FLASH FLOODING IN
REGIONS WHERE CELLS ARE ABLE TO REPEAT OR TRAIN. 

ONE NEGATIVE AT WORK IS THE FAIRLY HIGH 1 AND 3 HOUR FLASH FLOOD
GUIDANCE OVER MUCH OF THE AREA.  GUIDANCE IS LOWEST OVER THE VERY
FAR NORTHERN PORTION OF THE AREA...ON THE ORDER OF 1.5 INCHES PER
3 HOURS...WHILE FFG VALUES WERE CLOSER TO 3 INCHES OVER THE
CENTRAL AND SOUTHERN PORTION OF THE MPD.  MAXIMUM RAINFALL RATES
FROM KUEX AND KOAX 88DS WERE RUNNING FROM 1 TO 2 INCHES PER HOUR
WITH LOCALIZED AMOUNTS APPROACHING 3 INCHES PER HOUR...SO THE
RAINFALL RATES MAY BE ENOUGH TO OVERCOME THE HIGH FFG. 

MOST OF THE HIGHER RESOLUTION GUIDANCE TENDED TO FAVOR HEAVIEST
RAINFALL AMOUNTS OVER THE NORTHERN PART OF THE MPD LATER THIS
AFTERNOON...WHERE FFG WAS LOWEST...BUT THEY ALL TENDED TO
UNDERSTIMATE RAINFALL RATES IN EASTERN IA IN THE VERY NEAR TERM. 
THE ARW WAS CONSIDERABLY DONE WITH ITS RAFL AMOUNTS. 

BANN

ATTN...WFO...DMX...FSD...GID...OAX...

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

LAT...LON   43389384 42799348 40629563 40339711 41019756 
            41909661 42889538