MESOSCALE PRECIPITATION DISCUSSION 0484
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
426 PM EDT FRI JUL 22 2016
 
AREAS AFFECTED...NORTHERN AND EASTERN IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 222026Z - 230026Z
 
SUMMARY...SLOW MOVING HIGHLY EFFICIENT RAINFALL ACROSS WET
ANTECEDENT CONDITIONS YIELD POTENTIAL FOR FLASH FLOODING
CONDITIONS THROUGH THE EARLY EVENING.

DISCUSSION...GOES-E AND RADAR MOSAIC INDICATE VIGOROUS DEVELOPMENT
WITH NUMEROUS E-W CU BANDS DENOTING A WELL DEFINED LOW LEVEL
BOUNDARY.  POOL OF GREATER THAN 2.0" TPWS EXISTS ALONG ACROSS NE
IA WHILE SLIGHTLY DRIER MID-LEVEL PROFILES SUPPORT EXTREME
INSTABILITY VALUES IN EXCESS OF 7000 J/KG (SBCAPE) OVER NW IA. 
850MB FLOW ACROSS THE BOUNDARY THOUGH WEAK CURRENTLY ALONG WITH
ERODING CINH HAS BEEN SUFFICIENT FOR THIS DEVELOPMENT.  CONVECTION
IS DEVELOPING ALONG A FAIRLY TIGHT UPPER LEVEL FLOW GRADIENT AS
WELL...WHICH SUPPORTS LESS THAN 5 KTS OF CELL MOTIONS THROUGH THE
CLOUD BEARING LAYER.

VIS/WV LOOP SHOWS RETURN ANTICYCLONIC FLOW FROM THIS MORNING'S
DYING MCS THAT PROVIDES SOME LOCALIZED HIGHER DIVERGENCE FOR CELL
EVACUATION AS WELL.  CONCURRENTLY THIS MESOSCALE MODERATED FLOW
SUPPORTS  BROADENING OF THICKNESS FIELDS INDICATIVE OF WEAK
PROPAGATION VECTORS.  THE CURRENT ENVIRONMENT SUPPORTS AN
EXPANSION OF THE LINE INTO A SMALL COMPLEX THAT WILL PRODUCE
HIGHLY EFFICIENT RAINFALL PRODUCTION WITH RATES IN EXCESS OF
2"/HR. WITH LIMITED CELL MOTIONS THIS WILL COMPOUND TO LOCAL FLASH
FLOOD THREAT ACROSS N CENT IA IN THE NEXT FEW HOURS.  AN EVENTUAL
COLD POOL SHOULD DEVELOP ALLOWING FOR SOME FORWARD PROPAGATION SSE
INTO CENTRAL AND EASTERN IA AS SUPPORTED BY RECENT RUNS OF THE
HRRR VER. 2 AND ESRL HRRR VER. 3.  

THERE STILL REMAINS SOME QUESTION OF MAINTAINED INFLOW TO THE
CELLS PARTICULARLY IN THE NEAR TERM POTENTIALLY PRIOR TO COLD POOL
GENERATION...LIMITING THE EXPECTED LONGEVITY OF THE COMPLEX
THROUGH FORWARD PROPAGATION.  STILL...WET SOIL CONDITIONS AND SLOW
CELL MOTIONS SHOULD POSE ENOUGH OF LOCALIZED FLASH FLOOD THREAT
THROUGH THE EVENING HOURS ACROSS N AND E IA. 


GALLINA

ATTN...WFO...ARX...DMX...DVN...FSD...

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

LAT...LON   43269484 43269413 43109288 42479077 41299074 
            40759161 41799330 42179440 42589482 42899497