MESOSCALE PRECIPITATION DISCUSSION 0408
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
154 AM EDT THU JUN 29 2017

AREAS AFFECTED...NORTHERN MO

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

VALID 290600Z - 291000Z

SUMMARY...CONVECTION TRAINING ALONG THE WESTERN EDGE OF AN
ESTABLISHED COLD POOL WILL FEED ON INSTABILITY AND MOISTURE ON A
LOW LEVEL FLOW...WHICH COULD RESULT IN FLASH FLOOD THROUGH THE
EARLY MORNING HOURS.

DISCUSSION...THE LATEST EXPERIMENTAL GOES-16 CLEAN IR IMAGES
SHOWED BURSTS OF COLD TOPS ON THEW WESTERN EDGE OF A WELL
ESTABLISHED COOL POOL EXTENDING FROM NORTHWEST INTO CENTRAL MO.
THE BURSTS OF CONVECTION ARE FORMING ON THE NOSE OF A 30 TO 40
KNOT LOW LEVEL SOUTHWEST FLOW (PER RECENT REGIONAL VWP)...AS THE
LOW LEVEL JET FEEDS 1000-1500 J/KG OF MLCAPE INTO FAR NORTHWEST
MO.

THE CONVECTION IS ALSO FEEDING ON AN AXIS OF 1.80 INCH
PRECIPITABLE WATER (PER THE LATEST BLENDED TPW IMAGES). THE KEAX
RADAR SHOWED HOURLY RAINFALL RATES NEAR 2.00 INCHES OVER PORTIONS
OF NODAWAY COUNTY IN NORTHWEST MO...BUT DRY AIR AHEAD OF A WEAK
SHORT WAVE OVER NORTHWEST IA (AS WELL AS STEEPENING MID LEVEL
LAPSE RATES) COULD BE FOSTERING HAIL GROWTH. THE HAIL SIGNATURE
(CLEARLY SEEN ON THE KEAX HCA PRODUCT) COULD BE INFLATING THE
HOURLY RAINFALL RATES.

WHILE THE PROPAGATION VECTORS SUGGEST THAT THE EASTERN PORTION OF
THE COLD POOL SHOULD CONTINUE TO MOVE SOUTHEAST ACROSS NORTHERN
MO...THE WESTERN EDGE OF THE COLD POOL IS EXPECTED TO MOVE MUCH
MORE SLOWLY. CONVECTION FORMING ON THE WESTERN EDGE OF THE COLD
POOL IS EXPECTED TO TRAIN OVER PORTIONS OF NORTHERN MO THROUGH
ABOUT 10Z.

THERE WAS A DECENT SIGNAL IN THE HIGH RESOLUTION GUIDANCE FOR
LOCAL 2-4 INCH RAINFALL AMOUNTS OVER NORTHERN MO...AND THESE
AMOUNTS SEEM PLAUSIBLE WHERE TRAINING OCCURS. AS THE LOW LEVEL JET
WEAKENS TOWARD 10Z...THE THREAT FOR FLASH FLOODING IS EXPECTED TO
WANE OVER NORTHERN MO.

HAYES

ATTN...WFO...EAX...LSX...

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

LAT...LON   40469384 39989170 39479160 39509271 39699397
            39929478 40359496