MESOSCALE PRECIPITATION DISCUSSION 0683
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
354 PM EDT WED SEP 21 2016
 
AREAS AFFECTED...SOUTHERN TO CENTRAL MN/WESTERN WI... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 211953Z - 212353Z
 
SUMMARY...ELEVATED CONVECTION CONTINUES TO FIRE ALONG A 925/850-MB
BOUNDARY WITH THUNDERSTORMS ALIGNING IN A WEST-EAST FASHION. WHILE
NORTH OF WHERE HEAVY RAINFALL FELL DURING THE PAST 24
HOURS...FLASH FLOODING IS STILL POSSIBLE GIVEN THE REPEAT/MERGING
CONVECTION UNFOLDING.

DISCUSSION...A SHARP THERMAL/MOISTURE GRADIENT WAS NOTED IN THE
19Z OBSERVATIONS. SURFACE DEW POINTS WERE IN THE LOW 40S ACROSS
NORTHERN MN WHILE UPPER 60S/LOW 70S WERE COMMONPLACE SOUTH OF THE
BOUNDARY ACROSS SOUTHERN MN. ALONG THE AXIS OF ENHANCED
FRONTOGENESIS...ELEVATED CONVECTION CONTINUES TO ERUPT WITH
ACTIVITY SPREADING FARTHER UPSTREAM. RECENT VISIBLE SATELLITE
IMAGERY INDICATED TOWERING CU AND NUMEROUS CBS ACROSS THE WESTERN
EXTENT OF THE MPD. CURRENT RAP OBJECTIVE ANALYSES AND FORECAST
SOUNDINGS SHOW THE CONVECTION REMAINS ROOTED WELL ABOVE THE
SURFACE. THIS ACTIVITY HAS GENERALLY BEEN FORMING AT 850-MB AND
ABOVE WITHIN A REGION OF STEEP LAPSE RATES. IT IS UNCLEAR HOW
DEVELOPED THE CONVECTION ACROSS WESTERN/CENTRAL MN WILL BECOME.
PERHAPS THE INFLUENCE OF THE UPSTREAM IMPULSE ALONG THE NE/IA
BORDER MAY AID IN ADDITIONAL ASCENT ACROSS WESTERN MN THIS
AFTERNOON/EVENING.

OVERALL...THE RECENT CAMS HAVE NOT BEEN OF SIGNIFICANT HELP THUS
FAR. HOWEVER...SOME OF THE HRRR/EXPERIMENTAL-HRRR RUNS HAVE SHOWN
A PERSISTENT WEST-EAST TRAINING LINE FOR MULTIPLE HOURS MOVING
TOWARD 00Z. DIFFICULT TO SAY HOW LONG THIS WILL PERSIST BUT THE
ENVIRONMENT IS RIPE FOR SUCH AN EVENT TO CONTINUE TO UNFOLD. 


RUBIN-OSTER

ATTN...WFO...ARX...DLH...FSD...GRB...MPX...

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

LAT...LON   45809187 45478984 44828959 44279033 44419239 
            44249459 44619561 45259558 45709386