MESOSCALE PRECIPITATION DISCUSSION 0324
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1029 PM EDT WED JUN 08 2016
 
AREAS AFFECTED...SOUTHERN MN & NORTHEAST IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 090228Z - 090758Z
 
SUMMARY...A SLOW UPTICK IN CELL TRAINING AND CONVECTIVE STRENGTH
COULD LEAD TO HOURLY RAIN RATES UP TO 1.75".  FLASH FLOODING IS
POSSIBLE.

DISCUSSION...A BATCH OF ELEVATED SCATTERED THUNDERSTORMS CAUSED BY
WARM AIR ADVECTION APPEARS TO BE CONSOLIDATING OVER A RELATIVELY
STATIONARY FRONT.  THE STORMS HAVE EXHIBITED COOLING CLOUD TOPS IN
MN AS A WEAK SHORTWAVE MOVES THROUGH SOUTHERN MANITOBA/SOUTHWEST
ONTARIO TOWARDS NORTHERN MN.  AHEAD OF THE SHORTWAVE, CONVECTION
HAS BEEN FORMING DOWNSTREAM OF A WEAK FRONTAL WAVE ACROSS EASTERN
SD, INITIATING NEAR THE 9C ISOTHERM AT 700 HPA ACROSS SOUTHWEST MN
 WHICH APPEARS TO BE ACTING AS THE EDGE OF A CAPPING INVERSION
ACROSS THE CENTRAL PLAINS AT THIS TIME.  PRECIPITABLE WATER VALUES
OF 1.2-1.4" LIE IN THE AREA PER GPS DATA.  INFLOW AT 850 HPA IS
SOUTH-SOUTHWEST AT 30 KTS, DRAWING IN MUCAPES IN THE 1000-2000
J/KG RANGE PER SPC MESOANALYSES.

AS THE CONVECTION IS ELEVATED, IT SHOULD TEND TO REINFORCE THE
FRONTAL POSITION OVERNIGHT ACROSS EASTERN SD/SOUTHWEST MN/WESTERN
IA.  IT SHOULD CONTINUE TO ATTEMPT TO TRAIN IN A NORTH-NORTHWEST
TO SOUTH-SOUTHEAST ORIENTATION PER A COMPROMISE OF THE FORWARD
PROPAGATING CONVECTIVE VECTORS AND THE 1000-500 HPA THICKNESS
PATTERN.  RECENT RAP RUNS SUGGEST SOME SLIGHT NORTHEAST
PROGRESSION IN THE SURFACE BOUNDARY OVERNIGHT AT 5-10 KTS, WHICH
COULD BE OVERDONE.  PERSISTENT WARM AIR ADVECTION THUNDERSTORM
BANDS ARE TRICKY, AS CHANGES FROM HOUR TO HOUR CAN BE SUBTLE WHICH
MAKES TIMING THE TRANSITION OF A LONGER DURATION RAIN EVENT TO A
SHORTER DURATION FLASH FLOOD EVENT DIFFICULT.  THE MESOSCALE/CAM
GUIDANCE APPEARS LOW ON THE RAINFALL POTENTIAL, ONLY ADVERTISING
LOCAL AMOUNTS OF 1-2".  FLASH FLOOD GUIDANCE ACROSS THE REGION IS
NOT OVERLY HIGH, AND LOCAL AMOUNTS OF 1-2" HAVE ALREADY OCCURRED
PER RADAR ESTIMATES, WHICH SHOULD BE SLOWLY SATURATING AREA SOILS.
 HOURLY RAIN RATES UP TO 1.75" SHOULD BE POSSIBLE IN THIS REGIME,
WHICH COULD LEAD TO LOCAL AMOUNTS IN THE 2-4" RANGE.  DESPITE THE
INHERENT UNCERTAINTY, FLASH FLOODING IS POSSIBLE.

ROTH

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

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

LAT...LON   45459472 45059295 43939224 42269170 41209196 
            41989309 43279425 45039582