MESOSCALE PRECIPITATION DISCUSSION 0335
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
924 PM EDT SAT JUN 17 2017

AREAS AFFECTED...NORTHEAST MO, CENTRAL IL

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

VALID 180122Z - 180522Z

SUMMARY...THUNDERSTORMS WILL CONTINUE TO GROW UPSCALE ACROSS THE
REGION THIS EVENING AND WILL HAVE THE POTENTIAL FOR HOURLY RAIN
RATES NEAR 2 INCHES.

DISCUSSION...MESOANALYSIS TRENDS CONTINUE TO SHOW STRONG
DEEP-LAYER INSTABILITY POOLED INTO THE AREA AHEAD OF A SAGGING
FRONTAL SYSTEM...WITH MUCAPES AVERAGING 2000-3000 J/KG.
MEANWHILE...THE CAP CENTERED AROUND 850-800 MB CONTINUES TO WEAKEN
PER THE OBSERVED 00Z RAOBS... PARTICULARLY WHEN COMPARED TO THE
2100Z RAOB AT KTOP. THIS AS THE UPPER SHORTWAVE CURRENTLY OVER SD
PER THE LATEST SATELLITE WV IMAGERY WILL CONTINUE ON A
SOUTHEASTERLY TRAJECTORY INTO NORTHERN IA BY 0600 UTC. THE
INCREASE IN BROAD-SCALE UPPER DIVERGENCE/DEEP LAYER ASCENT AHEAD
OF THIS WAVE...CONCURRENT WITH AN UPTICK IN LOW LEVEL
FRONTOGENESIS...WILL CONTINUE TO ALLOW THE CONVECTION TO BECOME
BETTER ORGANIZED AND GROW UPSCALE THIS EVENING.

AS THE LOW-LEVEL INFLOW INCREASES TO 30+ KTS AND VEERS MORE
WESTERLY WITH TIME THIS EVENING (FROM SW TO WSW OR MORE PARALLEL
TO THE SURFACE BOUNDARY)...CELL TRAINING WILL BECOME MORE LIKELY
AFTER 03Z. DURING THAT TIME THE LOW-LEVEL INFLOW BECOMES MORE
PARALLEL TO (WHILE EXCEEDING THE MAGNITUDE OF) THE MEAN 850-300 MB
FLOW. FORECAST CORFIDI VECTORS RESPOND BY DECREASING TO 10 KTS OR
LESS. DUE IN LARGE PART BECAUSE OF THE INCREASED POTENTIAL FOR
UPWIND PROPAGATION AND CELL TRAINING...MUCH OF THE MESOSCALE
GUIDANCE (INCLUDING THE NSSL-WRF...WRF-ARW...AND NAM CONUS NEST)
SHOW POCKETS OF 4-6" TOTALS WITHIN THE MPD AREA. FLASH FLOODING
WILL THEREFORE BECOME MORE OF A CONCERN TOWARD MIDNIGHT...
ESPECIALLY IN URBAN AREAS.

HURLEY

ATTN...WFO...DVN...EAX...ILX...LOT...LSX...

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

LAT...LON   41088912 40878804 40368768 39638820 39048895
            38439025 38379198 38759293 39559293 40249224
            40779093