MESOSCALE PRECIPITATION DISCUSSION 0111
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
618 PM EDT WED JUN 19 2013
 
AREAS AFFECTED...WRN TO N-CNTRL MT 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 192217Z - 200317Z
 
SUMMARY...INCREASING COVERAGE OF CONVECTION WILL HEIGHTEN FLASH
FLOOD RISK AS RAINFALL MOVES OVER WET ANTECEDENT CONDITIONS.

RECENT RADAR IMAGERY HAS SHOWN A RAPID EXPANSION OF THUNDERSTORM
COVERAGE OVER THE PAST HOUR ACROSS MUCH OF CNTRL AND WRN
MONTANA...OUT AHEAD OF A NEGATIVELY TILTED SHORTWAVE ROTATING IN
FROM SRN IDAHO. IR SATELLITE IMAGERY HAS SHOWN AN INCREASING TREND
IN OVERSHOOTING TOPS...INDICATING A TREND TOWARD MORE INTENSE
UPDRAFTS AND STRENGTH OF CONVECTION. 

AT 22Z...A WARM FRONT WAS ANALYZED NEAR THE MONTANA/WYOMING BORDER
WITH A DEEP AXIS OF MOISTURE EXTENDING AHEAD OF THE BOUNDARY FROM
ERN MONTANA BACK INTO NWRN PORTIONS OF THE STATE. STANDARDIZED
PRECIPITABLE WATER ANOMALIES OF +1 TO +3 COINCIDE WITHIN THIS
MOISTURE AXIS AND OVERLAP WITH LOWERED FLASH FLOOD GUIDANCE VALUES
OF 0.5 TO 1.0 IN/HR AND .75 TO 1.5 IN / 3 HR DUE TO ANTECEDENT
RAINFALL.

AS HEIGHT FALLS TIED TO THE ADVANCING SHORTWAVE MOVE INTO CNTRL
AND WRN MONTANA OVER THE NEXT FEW HOURS...THE COVERAGE OF STORMS
IS LIKELY TO INCREASE ALONG WITH CELL MERGERS OCCURRING WHILE CELL
MOVEMENT GENERALLY TRACKS FROM SSE TO NNW. TRENDS AND CONVECTIVE
DEVELOMENT WILL BE MONITORED FOR LOCATIONS EAST OF MPD #0111 FOR A
POSSIBLE FLASH FLOOD THREAT INTO THE OVERNIGHT HOURS.
 
OTTO

ATTN...WFO...TFX...MSO...

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

LAT...LON   46161112 45781249 46361358 47171435 48081478 48881479
            49241407 49411200 49311041 48620979 47710982 46941020
            46161112