WPC Met Watch |
|
Mesoscale Precipitation Discussion: #0672 (2018) |
(Issued at 209 AM EDT Thu Aug 16 2018
) |
|
MPD Selection |
|
|
|
Mesoscale Precipitation Discussion 0672
NWS Weather Prediction Center College Park MD
209 AM EDT Thu Aug 16 2018
Areas affected...N AR, SE MO, far NW TN, far W KY, far S IL
Concerning...Heavy rainfall...Flash flooding possible
Valid 160608Z - 161200Z
Summary...Thunderstorms were beginning to develop in greater
numbers after Midnight over northern Arkansas, and repeatedly
affecting similar areas. This may continue through the early
morning hours, and the persistent thunderstorm activity could
produce locally heavy rainfall and flash flooding. Rain rates may
exceed 2 in/hr.
Discussion...Regional radars from the Ozarks into the
Mid-Mississippi River Valley have been showing scattered
convection gradually developing in northern Arkansas over the past
several hours. The convection, previously sporadic and relatively
un-focused, was becoming increasingly organized in a WSW-ENE
fashion parallel to the deep layer mean flow. Overlaying the radar
positions of the broken lines of thunderstorms over the past
several hours shows little latitudinal movement, with a gradual
building to the east. Meanwhile, the developing convection was
situated within a confluent ribbon of enhanced low-level flow, and
precipitable water values around or in excess of 2 inches. This
should favor a continued gradual increase and focusing of
thunderstorms near the eastern portion of the AR-MO border, with
potential for training cells and locally heavy rainfall. An axis
of higher MLCAPE values (1500-2000 j/kg with limited CINH per RAP
analysis) to the south and west of developing convection, combined
with the WSW nature of the low-level inflow could favor new cell
growth upstream of ongoing convection, which may enhance the
training pattern across the region. With moderate instability and
abundant moisture, 2+ in/hr rain rates appear achievable, and if
training patterns can sustain this for longer than an hour, then
flash flooding would probably result. Some of the hi-res models,
notably quite a few runs of the HRRR, show localized rainfall
totals by 12Z in excess of 5 inches in a narrow focused band. This
also appears possible wherever training convection most favorably
sets up, as the expected rain rates could produce totals like that
in a few hours.
Lamers
ATTN...WFO...LSX...LZK...MEG...PAH...SGF...
ATTN...RFC...ABRFC...LMRFC...OHRFC...
LAT...LON 37448881 37108835 36438866 35738982 35329179
35669335 36489266 37089069
Last Updated: 209 AM EDT Thu Aug 16 2018
|