MESOSCALE PRECIPITATION DISCUSSION 0164
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 AM EDT FRI MAY 18 2018

AREAS AFFECTED...FAR NORTHEAST CO...PANHANDLE OF NE...CENTRAL NE

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 180540Z - 180940Z

SUMMARY...VERY HEAVY RAINFALL IS EXPECTED WITH SLOW-MOVING AND
BACKBUILDING SHOWERS AND THUNDERSTORMS.

DISCUSSION...THE LATEST GOES-16 CLEAN IR SATELLITE LOOP SHOWS
IMPRESSIVELY COLD CONVECTIVE CLOUD CANOPY WITH SEVERAL
OVERSHOOTING TOPS IMPACTING PORTIONS OF THE THE NEBRASKA PANHANDLE
WITH CONVECTION SEEN BACKBUILDING AND REPEATING OVER THE SAME
AREA. THE CONVECTIVE AXIS IS BECOMING INCREASINGLY ORIENTED IN A
W/E AXIS AND IS BEGINNING TO STRETCH OUT TO THE EAST TOWARD
CENTRAL NEBRASKA.

THIS FOCUSED AREA OF CONVECTION IS SITUATED ALONG THE SOUTHERN
FLANK OF A SEVERE QLCS GOING ACROSS THE NORTH-CENTRAL PLAINS...AND
IS BEING NOTABLY AIDED BY SOUTHERLY LOW LEVEL JET OF 40 TO 50
KTS...AND A N/S AXIS OF MODERATE INSTABILITY CHARACTERIZED BY
MUCAPE VALUES OF OVER 2000 J/KG. THE OVERALL UPPER FLOW PATTERN IS
ALSO QUITE DIFFLUENT GIVEN THE PROXIMITY OF A DEEP UPPER TROUGH
OVER THE SOUTHWEST.

THE 00Z HIRES ARW/NMMB SOLUTIONS ARE NOT DOING A PARTICULARLY GOOD
JOB IN HANDLING THE FOCUSED NATURE OF THIS CONVECTION...AND THE
HRRR GUIDANCE IS DOING EVEN WORSE WITH VERY LITTLE CONVECTIVE
SIGNAL EVIDENT.

BASED ON THE DEGREE OF LOW LEVEL JET ENERGY AND AVAILABLE
INSTABILITY...THE CONVECTION SHOULD BE SUSTAINABLE ACROSS THIS
REGION FOR AT LEAST A FEW MORE HOURS...WITH A GENERAL PROPAGATION
OFF TO EAST AND IN TIME TO THE SOUTHEAST AS COLD POOL GENERATION
BECOMES BETTER ESTABLISHED. EXPECT RAINFALL RATES OF AS MUCH AS 2
INCHES/HR GIVEN THE OVERSHOOTING TOP ACTIVITY...WITH LOCALIZED
STORM TOTALS OF AS MUCH AS 4 TO 5 INCHES POSSIBLE GIVEN THE SLOW
MOVEMENT AND BACKBUILDING NATURE OF THE ACTIVITY. FLASH FLOODING
IS POSSIBLE.

ORRISON

ATTN...WFO...BOU...CYS...LBF...

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

LAT...LON   41800236 41700134 41280038 40740053 40550155
            40570249 40630324 40800386 41050409 41410391
            41720285