Graphic for MPD #0467

MESOSCALE PRECIPITATION DISCUSSION 0467
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
934 PM EDT TUE JUL 11 2017

AREAS AFFECTED...NORTHEAST IA & SOUTHWEST WI

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

VALID 120133Z - 120633Z

SUMMARY...THUNDERSTORMS ARE EXPANDING IN COVERAGE ACROSS NORTHEAST
IA, ELEVATED OVER THE WARM FRONT.  HOURLY RAIN RATES UP TO 2" WITH
LOCAL AMOUNTS TO 4" ARE POSSIBLE.

DISCUSSION...CIN IS BEGINNING TO SET IN TO THE REGION, WHICH IN
ADDITION TO A JET STREAK MOVING THROUGH ALOFT IS ALLOWING ELEVATED
CONVECTION TO FORM WITHIN THE MU CAPE GRADIENT ACROSS NORTHEAST
IA, WHERE MU CAPE VALUES ARE ~3000 J/KG.  STORMS ARE MOVING EAST
AT ~20 KTS AT THE MOMENT, BUT ARE DEVELOPING A WEST-NORTHWEST/
EAST-SOUTHEAST ORIENTATION, WITH BOTH BACKBUILDING AND TRAINING
BEGINNING TO BE NOTED IN RADAR IMAGERY.  PRECIPITABLE WATER VALUES
ARE 1.5-1.75".  EFFECTIVE BULK SHEAR IS ~45 KTS PER SPC
MESOANALYSES. INFLOW AT 850 HPA IS WEST-SOUTHWEST AT 25-30 KTS,
SLIGHTLY EXCEEDING THE MEAN 850-400 HPA WIND.

LOW-LEVEL INFLOW IS EXPECTED TO RAMP UP FOR ANOTHER FEW HOURS,
WHICH SHOULD CONTINUE TO PROMOTE BACKBUILDING WHILE CONVECTION ON
THE EASTERN END MOVES ROUGHLY EASTWARD AT 20 KTS.  MESOCYCLONES
ARE POSSIBLE WITH THE AMOUNT OF BULK SHEAR PRESENT, WHICH WOULD
LEAD TO HEAVY RAINFALL.  FORWARD PROPAGATING CONVECTIVE VECTORS
SUPPORT A NORTH OF EAST MOTION WHILE A FORMING COLD POOL COULD
DIRECT THE CONVECTION ON A SLIGHTLY MORE SOUTHERLY TRAJECTORY. 
THE MESOSCALE GUIDANCE IS NOT HANDLING THIS ACTIVITY WELL, WITH
THE 12Z ARW, 12Z NMMB, AND 12Z/18Z GFS HAVING A CLUE IN THIS
REGION.  AVAILABLE MOISTURE AND INSTABILITY SUPPORT HOURLY RAIN
RATES TO 2" WITH LOCAL AMOUNTS TO 4".

ROTH

ATTN...WFO...ARX...DVN...LOT...MKX...

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

LAT...LON   43379020 43068899 42258915 42619125 43049184
            43309122


Last Updated: 934 PM EDT TUE JUL 11 2017