Graphic for MPD #0721

MESOSCALE PRECIPITATION DISCUSSION 0721
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
314 AM EDT FRI AUG 25 2017

AREAS AFFECTED...NERN NE INTO FAR SERN SD/NWRN IA/SWRN MN

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

VALID 250713Z - 251230Z

SUMMARY...POCKETS OF SLOW MOVING CONVECTION ARE EXPECTED TO
PERSIST TOWARD SUNRISE LEADING TO A SCATTERED FLASH FLOOD THREAT
IMPACTING PORTIONS OF NERN NE INTO FAR SERN SD/NWRN IA/SWRN MN.
LOCALIZED RAINFALL TOTALS OF 2-4 INCHES CAN BE EXPECTED.

DISCUSSION...RECENT RADAR IMAGERY FROM KOAX HAS SHOWN AN INCREASE
IN SMALL SCALE ELEVATED THUNDERSTORM ACTIVITY ACROSS ERN NE. CELLS
HAVE BEEN SLOW MOVING...SOMEWHAT SIMILAR TO EARLIER CONVECTION
OBSERVED IN THE SAND HILLS OF CNTRL NE PRIOR TO 06Z. THIS ACTIVITY
IS OCCURRING NEAR A WEAK STATIONARY FRONT/TROUGH AXIS EXTENDING
ROUGHLY WEST TO EAST ACROSS NE. IT IS ALSO IN BETWEEN TWO FEATURES
AT 700 MB...AN EWD MOVING SHORTWAVE TROUGH CURRENTLY OVER THE NE
PANHANDLE AND SOUTH OF A 700 MB LOW OVER NERN SD...VISIBLE IN
EXPERIMENTAL GOES 16 INFRARED IMAGERY AND 700 MB VAD WIND PLOTS.
THERE IS ENHANCED LOW LEVEL FLOW BETWEEN THESE TWO FEATURES
CAUSING A WARM ADVECTION PATTERN WITH SWLY 850-700 MB FLOW SIMILAR
TO AREA LFC-EL MEAN WINDS.

ELEVATED INSTABILITY HAS BEEN INCREASING OVER THE ERN SD/NE BORDER
PER THE SPC MESOANALYSIS PAGE AND IS CURRENTLY 500-1000 J/KG WITH
HIGHER INSTABILITY ESTIMATED OVER THE SOURCE REGION OF CNTRL NE.
WHILE 00Z CAM GUIDANCE AND RECENT RUNS OF THE HRRR HAVE STRUGGLED
TO CAPTURE THE ONGOING ACTIVITY IN ERN NE AND DO NOT SUGGEST MUCH
IN THE WAY OF RAINFALL THROUGH THE MORNING OVER THE
REGION...OBSERVATIONAL TRENDS SUGGEST OTHERWISE. PRECIPITABLE
WATER VALUES ARE SOMEWHAT LACKING FOR VERY HEAVY RAINFALL...NEAR
1.1 TO 1.2 INCHES PER 00Z SOUNDINGS FROM LBF AND OAX AND FROM MORE
RECENT GPS SITE OBSERVATIONS...BUT THE SLOW MOVEMENT OF CONVECTION
HAS ALREADY LED TO RADAR ESTIMATED RAINFALL RATES OVER 2 IN/HR IN
BURT COUNTY NE. ADDITIONAL POCKETS OF HEAVY RAIN ARE EXPECTED
THROUGH SUNRISE FROM ERN NE...POSSIBLY SPREADING NORTHEAST INTO
SERN SD AND FAR NWRN IA WITH 2-4 INCH TOTALS BY 12Z OR 13Z. POOR
UPPER LEVEL JET SUPPORT AND A LACK OF BETTER INSTABILITY TO THE
EAST SHOULD LIMIT THE AREA OF FLASH FLOOD IMPACTS.

OTTO

ATTN...WFO...DMX...FSD...GID...LBF...OAX...

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

LAT...LON   43729641 43509564 42889539 41619573 41319633
            41189723 41609925 42079947 42799870 43349764
            43669705


Last Updated: 314 AM EDT FRI AUG 25 2017