MESOSCALE PRECIPITATION DISCUSSION 0131...RESENT
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
426 PM EDT TUE JUN 17 2014

RESENT FOR AWIPS
 
AREAS AFFECTED...EASTERN MT AND THE WESTERN DAKOTAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 172018Z - 180058Z
 
SUMMARY...A SECOND BATCH OF THUNDERSTORMS WITH COOLING TOPS HAS
DEVELOPED NEAR AND AHEAD OF A TROWAL ACROSS NORTHEASTERN MT. 
CONSIDERING EARLIER, CURRENT, AND FUTURE ACTIVITY EXPECTED LATER
THIS AFTERNOON, A FEW INSTANCES OF FLASH FLOODING ARE POSSIBLE.

DISCUSSION...A TROWAL EXTENDS NORTHWESTWARD FROM AN AREA OF LOW
PRESSURE ACROSS SOUTHEAST MT.  STORMS HAVE FORMED ALONG IT AND ARE
TRAVELING GENERALLY NORTHEAST AT LESS THAN 10 KTS.  CAPE VALUES UP
TO 3000 J/KG EXIST IN THE REGION, WITH EVEN HIGHER INSTABILITY
UPSTREAM ACROSS THE WESTERN DAKOTAS.  THE DEPTH OF MOISTURE FROM
THE 12Z GREAT FALLS AND GLASGOW MT SOUNDINGS WAS IMPRESSIVE, WITH
THE WET BULB ZERO HEIGHT CLOSE TO 9000 FT ABOVE GROUND LEVEL AT
THE LATTER.  PRECIPITABLE WATER VALUES ARE IN THE 1.25-1.50 RANGE,
WHICH IS NEAR THE 99TH PERCENTILE FOR MID-JUNE.

DO NOT EXPECT MUCH DOWNWIND PROPAGATION HERE DUE TO THE DEPTH OF
WARMTH AND MOISTURE -- CORFIDI VECTORS YIELDS ABOUT 10 KTS OF CELL
MOTION.  THUNDERSTORM INITIATION SHOULD SLOWLY SHIFT EASTWARD WITH
TIME DUE TO THE TROWAL'S FORWARD MOTION. THERE IS A MODERATE
SIGNAL FOR HEAVY RAINFALL IN THE REGION, WITH THE GUIDANCE SHOWING
MAXIMA IN THE 2-3" RANGE.  RAINFALL RATES OF 1.5" AN HOUR ARE
CONSIDERED POSSIBLE, WITH A QUICK 2-3" POSSIBLE IN ISOLATED
LOCATIONS.  CONSIDERING THE LOW FLASH FLOOD GUIDANCE IN THE AREA,
AND THE THERMAL RIDGE'S INFLUENCE ON SLOW CELL MOTION ACROSS THE
REGION, BELIEVE A FEW INSTANCES OF FLASH FLOODING ARE POSSIBLE
THIS AFTERNOON.  THE 12Z ARW HAS THE CAPE VALUES ACROSS THE REGION
FADING BY 01Z, WHICH WAS USED AS THE VALID TIME.

ROTH

ATTN...WFO...BIS...UNR...BYZ...GGW...

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

LAT...LON   48740231 46490244 44650319 45420524 46580652 48100805
            49020814 49070524 49090290 48740231