MESOSCALE PRECIPITATION DISCUSSION 0646
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
822 PM EDT TUE SEP 06 2016
 
AREAS AFFECTED...FAR NORTHEAST IA...FAR SOUTHEAST
MN...CENTRAL/SOUTHERN WI 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 070020Z - 070600Z
 
SUMMARY...INCREASED ORGANIZATION OF THUNDERSTORMS WITH HEAVY
RAINFALL MAY RESULT IN SOME FLASH FLOODING THIS EVENING.

DISCUSSION...SEVERAL CLUSTERS OF THUNDERSTORMS EXTENDING FROM FAR
NORTHEAST IA...INTO FAR SOUTHEAST MN AND ACROSS CENTRAL WI ARE
SHOWING SIGNS OF GRADUALLY GETTING BETTER ORGANIZED AS A WEAK AREA
OF LOW PRESSURE MOVES NORTHEAST ALONG A FRONTAL ZONE. THE ACTIVITY
IS BEST FOCUSED ALONG AN AXIS OF ENHANCED MOISTURE FLUX
CONVERGENCE...AND IS BEING AIDED BY A WELL-ESTABLISHED SW WARM
ADVECTION PATTERN WITH PLENTY OF INSTABILITY POOLING ALONG AND
AHEAD OF THE FRONT.

IN FACT...SW 850 MB FLOW OF NEAR 30 KTS IS SEEN IN THE LATEST AREA
VWP DATA AT KDMX...KDVN AND KARX...AND THE LATEST RAP ANALYSIS
DEPICTS A POOL OF 2 INCH PWATS AND MLCAPE VALUES OF 2000 TO 2500
J/KG NEAR THE WAVE OF LOW PRESSURE AND EXTENDING EAST ACROSS
SOUTH-CENTRAL WI WHERE THERE IS ALSO PROXIMITY OF AN OUTFLOW
BOUNDARY.

THIS OUTFLOW BOUNDARY IS TENDING TO INTERCEPT SOME OF THE
FAVORABLE THERMODYNAMIC BOUNDARY LAYER TRANSPORT INTO THE REGION
WHICH EXPLAINS SOME OF THE CLUSTERS OF THUNDERSTORMS WELL
SOUTHEAST OF THE FRONTAL ZONE.

THE ENVIRONMENT OVER THE NEXT FEW HOURS WILL BE CHARACTERIZED BY
SOME INCREASE IN SOUTHWEST LOW LEVEL JET ENERGY...WITH THE RAP
FORECASTING THE NOSE OF A 40 TO 45 KT JET AIMING INTO SOUTHWEST
AND CENTRAL WI. MEANWHILE...SOME INCREASING LARGE SCALE ASCENT
FROM 250 MB RIGHT-ENTRANCE REGION JET DYNAMICS IS EXPECTED AHEAD
OF THE UPPER TROUGH MOVING INTO THE NORTHERN HIGH PLAINS.

THIS SHOULD SUPPORT SOME UPTICK IN CONVECTIVE ORGANIZATION WITH
HEAVY RAINFALL RATES THAT MAY EXCEED 2 INCHES/HR GIVEN THE HIGH
PWAT ENVIRONMENT. MEANWHILE...THE DEEP LAYER WIND FIELDS WILL BE
INCREASINGLY PARALLEL TO THE FRONT. THUS EXPECT AN INCREASED
THREAT FOR CELL-TRAINING THROUGH THE EVENING HOURS.

RAINFALL AMOUNTS THROUGH 06Z OF 3 TO 5 INCHES WILL BE POSSIBLE
THROUGH MIDNIGHT...AND WITH SOME AREAS SEEING HEAVY RAINFALL
EARLIER...IT IS EXPECTED THAT SOME RUNOFF/FLASH FLOODING MAY OCCUR.

ORRISON

ATTN...WFO...ARX...GRB...MKX...MPX...

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

LAT...LON   44858992 44778926 44478817 44238766 43648751 
            43108781 42878892 42839039 42849129 43009238 
            43639268 44369214 44789110