MESOSCALE PRECIPITATION DISCUSSION 0331
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
751 PM EDT SAT JUN 11 2016
 
AREAS AFFECTED...EASTERN MT 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 112345Z - 120545Z
 
SUMMARY...EXPANDING CONVECTION THIS EVENING WITH INTENSE RAINFALL
RATES MAY RESULT IN SOME POSSIBLE FLASH FLOODING.

DISCUSSION...LATE-AFTERNOON VIS/IR IMAGERY SHOWS AN IMPRESSIVE
CLUSTER OF DEEP CONVECTION WITH A FEW OVERSHOOTING TOPS OVER
SOUTHEAST MT THAT IS EXPANDING IN COVERAGE IN RESPONSE TO AN
APPROACHING SHORTWAVE TROUGH SEEN LIFTING NORTHEAST OUT OF
NORTHERN UT AND INTO SOUTHEAST ID AND WESTERN WY. 

IMPROVING FORCING/ASCENT ASSOCIATED WITH DEVELOPING RIGHT-ENTRANCE
REGION JET DYNAMICS OVER NORTHERN WY AND SOUTHEAST MT IS
INTERACTING WITH A VERY MOIST AND UNSTABLE BOUNDARY LAYER AIDED BY
THE PERSISTENT S/SE LOW LEVEL FETCH UP THROUGH THE HIGH PLAINS.
THE LOW LEVEL THERMODYNAMIC ENVIRONMENT OVER SOUTHEAST MT IS
CHARACTERIZED BY LI/S IN THE -6 TO -8 RANGE...AND MLCAPE VALUES OF
3000 TO 3500 J/KG. PWATS OVER THE REGION ARE SEEN IN GOES-SOUNDER
IMAGERY AS HIGH AS 1.25 INCHES...WHICH IS 2 TO 3 SIGMAS ABOVE THE
MEAN FOR THIS TIME OF THE YEAR.

THE ENVIRONMENT IS CONDUCIVE FOR WIDESPREAD AND STRONG CONVECTION
THIS EVENING WITH VERY HEAVY RAINFALL RATES THAT MAY APPROACH 2
INCHES/HR...AND ESPECIALLY GIVEN THE ANOMALOUSLY MOIST COLUMN AND
STRENGTHENING DEEP LAYER ASCENT AHEAD OF THE APPROACHING
SHORTWAVE. SURFACE LOW PRESSURE ALREADY NEAR THE MT/WY BORDER WILL
LIFT N/NEWD THIS EVENING ACROSS SOUTHEAST MT AND WITH A SOUTHERLY
LOW LEVEL JET INCREASING TO 40 TO 50 KTS. THUS...EXPECT AN
EXPANSION OF ORGANIZED CONVECTION OVER THE NEXT SEVERAL HOURS.

EXPECT AS MUCH AS 3 TO 4 INCHES OF RAIN OVER EASTERN MT THROUGH
06Z WITH ISOLATED HEAVIER AMOUNTS WHERE CELL-MERGERS AND
OVERSHOOTING TOPS OCCUR. SOME FLASH FLOODING WILL BE POSSIBLE AS
FFG VALUES MAY BE EXCEEDED BY THE HIGH RAINFALL RATES.

ORRISON

ATTN...WFO...BYZ...GGW...

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

LAT...LON   48960495 48630425 47400413 46090436 45150512 
            44960627 45110686 45810734 47130719 48240662 
            48880593