599
AWUS01 KWNH 090452
FFGMPD
ILZ000-MOZ000-IAZ000-NEZ000-091030-
MESOSCALE PRECIPITATION DISCUSSION 1227
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1251 AM EDT WED SEP 09 2026
AREAS AFFECTED...SOUTHEAST NEBRASKA...SOUTHERN IOWA...NORTHWEST
ILLINOIS...
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 090450Z - 091030Z
SUMMARY...LOCALIZED FLASH FLOODING POTENTIAL CONTINUES. NEW
UPSTREAM DEVELOPMENT SHOWS POTENTIAL FOR REPEATING ACROSS AREAS
RECENTLY AFFECTED WITH ADDITIONAL 2-3" TOTALS. LEADING EDGE,
HIGHER RATES MAY STILL POSE LOCALIZED RISK DUE TO HIGHER 2"/HR
RATES.
DISCUSSION...REGIONAL RADAR SHOWS ELONGATED CONVECTIVE COMPLEX
ACROSS MUCH OF IOWA, WITH LEADING BOW ECHO NEAR A MESO-LOW ALONG
THE MISSISSIPPI RIVER SOUTHWEST OF THE QUAD CITIES REMAINS FAIRLY
POTENTIAL WITH STRONG MOISTURE FLUX CONVERGENCE HELPING TO BROADEN
THE WIDTH OF THE BOW FOR INCREASED OVERALL DURATION WHILE IT STILL
REMAINS FORWARD PROPAGATING. HOWEVER, IT IS STARTING TO MOVE INTO
A MORE STABLE REGIME OVER N IL WHERE INFLOW IS LESS HUMID/UNSTABLE
WITH LOWER 60S TDS LIKELY TO BE FED INTO THE COMPLEX. STILL A
HOUR OR SO MORE OF 1.5-2"/HR RATES MAY RESULT IN LOCALIZED URBAN
FLOODING CONCERNS. HOWEVER, THE UPSTREAM ENVIRONMENT REMAINS
CONDITIONALLY UNSTABLE WITH SOLID ISENTROPIC ASCENT PATTERN FOR
CONTINUED DEVELOPMENT.
HOWEVER, MUCH OF THE ENVIRONMENT HAS STABILIZED, THERE DOES REMAIN
SOME INCREASED UNSTABLE AIR BETWEEN FRONTAL ZONES ACROSS SOUTHERN
NEB AND THROUGH IA WHICH IS INTERSECTED BY A NORTH-SOUTH AXIS OF
500-1000 J/KG OF CAPE ACROSS WESTERN MO ALONG AN OLDER FRONTAL
ZONE, WITH TOTAL PWATS OVER 2". CIRA LPW SHOWS MOST OF THIS AREA
AS THE ENHANCED MOISTURE STREAM CONNECTED TO THE PACIFIC
SUB-TROPICS ALONG THE NORTHWEST EDGE OF THE LARGER SCALE RIDGE
WITH VERY HIGH MOISTURE DENOTED IN THE 700-500MB LAYER ALONG WITH
SURFACE TO 850MB SHOWING HIGHER VALUES (TDS IN THE LOW TO MID
70S). HOWEVER, SOUTH OF THE FRONT LOWER TDS AND A WEDGE OF DRIER
AIR CAN BE SEEN THROUGH THE 850-700 AND 700-500MB ACROSS SE KS
THROUGH KC METRO TOWARD N MO; SO THOUGH STRONGER CONFLUENT 850MB
FLOW IS THE DRIVER OF ISENTROPIC ASCENT THERE MAY BE SOME NEGATIVE
DRY AIR ENTRAINMENT INTO THE CELLS. THIS MAY BE THE REASON FOR
THE MORE STRINGY/TENDRIL APPEARANCE TO THE CONVECTIVE CELLS ACROSS
W IA. STILL, THE LENGTH OF THE AXIS WITH EMBEDDED STRONGER CORES
IN AN IDEAL TRAINING (WEST TO EAST) ENVIRONMENT WITH STRONG
SOUTHWEST TO SOUTHERLY DEEP LAYER CONVERGENCE SHOULD STILL
MAINTAIN THE SCATTERED ASCENT PATTERN WITH REPEATING ELEMENTS
ACROSS S IA TO BE EXPECTED. OVERALL RATES GIVEN SOME OF THE DRY
AIR ENTRAINMENT MAY BE A BIT MORE LIMITED THAN SEEN EARLIER WITH
THE INITIAL LINE, BUT SCATTERED 1.25-1.5" STREAKS AND 1-3 HOURS OF
REPEATING ACROSS AREAS HAVING RECEIVED 1-3" MAY START TO EXCEED
THE LONGER 3-6 HR FFG VALUES WHICH ARE 2-3" OR 3-4", RESPECTIVELY.
AS SUCH, LOCALIZED FLASH FLOODING MAY BE POSSIBLE BUT LIKELY
LIMITED IN OVERALL AREAL COVERAGE AND BE MORE WIDELY SCATTERED IN
NATURE THROUGH EARLY MORNING.
GALLINA
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...DMX...DVN...EAX...ILX...OAX...
ATTN...RFC...KRF...MSR...NWC...
LAT...LON 42149161 42089051 41858979 41418965 40998998
40649070 40589212 40599417 40629568 40719654
41069691 41559656 41829554 41929443 42059296
42109232 42109202
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