MESOSCALE PRECIPITATION DISCUSSION 0194
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1038 PM EDT MON MAY 08 2017

AREAS AFFECTED...NORTHEAST CO...FAR SOUTHWEST NE

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

VALID 090240Z - 090640Z

SUMMARY...TRAINING CONVECTION OVER NORTHEAST CO COULD RESULT IN A
FLASH FLOOD THREAT THROUGH THE LATE EVENING HOURS.

DISCUSSION...REGIONAL RADARS SHOWED CONVECTION ACROSS EASTERN CO
MOVING SLOWLY NORTHEAST WITH THE MID LEVEL FLOW. GOES-16
EXPERIMENTAL IR IMAGES INDICATED SLOWLY COOLING TOPS ACROSS
NORTHEAST CO...WITH CLOUD TOP TEMPERATURES NEAR -68 C. THE
CONVECTION IS TRACKING THROUGH AN AXIS OF 500-1000 J/KG OF
MLCAPE...WHICH IS SUPPORTED BY UPSTREAM 00Z SOUNDINGS.
PRECIPITABLE WATER VALUES IN THIS AXIS WERE GENERALLY NEAR 1.00
INCHES...PER 00Z SOUNDINGS AND THE LATEST BLENDED TPW IMAGERY.

BASED ON THE RADAR TRENDS...THE CONVECTION IS STILL MAINLY OUTFLOW
BASED (WHICH IS NOW SURPRISING...GIVEN THE AMOUNT OF DRY AIR IN
THE MID LEVELS ON LOCAL 00Z SOUNDINGS).

HOWEVER...THE NORTHERN PORTION OF THE LINE APPEARS TO BE
SLOWING...AS THE CONVECTION ACROSS NORTHEAST CO BECOMES BETTER
ALIGNED WITH THE MID LEVEL FLOW. THE KGLD RADAR SHOWED HOURLY
RAINFALL RATES NEAR 1.50 INCHES...BUT BASED ON THE STEEP LAPSE
RATES IN THE MID LEVELS ON THE 00Z SOUNDINGS... AND RECENT SPOTTER
REPORTS... SOME OF THESE AMOUNTS COULD BE HAIL CONTAMINATED.

THE LATEST RAP SHOWED MUCAPE VALUES REMAINING BETWEEN 500-1000
J/KG ACROSS NORTHEAST CO THROUGH ABOUT 06Z...WHICH SHOULD BE
SUFFICIENT TO MAINTAIN THE CURRENT CONVECTION. A LOW LEVEL
EASTERLY INFLOW IS EXPECTED TO CONTINUE THE MOISTURE PLUME INTO
NORTHEAST CO AND FAR SOUTHWEST NE...AND GOOD DIFFLUENCE IS
EXPECTED TO KEEP THE CONVECTION ORGANIZED.

AS THE CONVECTION BECOMES BETTER ALIGNED WITH THE MID LEVEL
FLOW...THE THREAT FOR TRAINING INCREASES. THE LATEST
HRRR/EXPERIMENTAL HRRR/RAP SHOWED THE POTENTIAL FOR LOCAL 2.00
INCH RAINFALL AMOUNTS ACROSS NORTHEAST CO...WHICH LOOKS REASONABLE
WHERE TRAINING OCCURS. THREE HOUR FLASH FLOOD GUIDANCE VALUES ARE
AS LOW AS 1.50 INCHES IN THIS AREA...WHICH SUGGESTS A FLASH FLOOD
THREAT.

INSTABILITY SHOULD START WANING AFTER 06Z...WHICH SHOULD LIMIT THE
FLASH FLOOD THREAT WITH TIME. THIS WAS INDICATED BY MOST HIGH
RESOLUTION MODEL SOLUTIONS.

HAYES

ATTN...WFO...BOU...GLD...LBF...

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

LAT...LON   40990186 40190141 39460224 39130279 39420344
            39680360 40660309