Mesoscale Precipitation Discussion 0084
NWS Weather Prediction Center College Park MD
1200 AM EDT Sun Mar 15 2020
Areas affected...Northeast TX...Extreme Southeast OK...Southwest
to Central AR
Concerning...Heavy rainfall...Flash flooding possible
Valid 150400Z - 150900Z
SUMMARY...Some isolated flash flooding potential exists overnight
from locally training showers and thunderstorms.
DISCUSSION...The latest GOES-16 satellite imagery is showing an
area of rapid convective cloud top cooling over portions of
northeast TX, generally involving portions of Collin, Hunt and
Delta counties. Showers and thunderstorms have been developing
across this region in response to a notable increase in elevated
instability north of a quasi-stationary front, and within an zone
of favorable right-entrance region jet dynamics. In fact, 3-hour
MUCAPE delta values across much of central to northeast TX, and
across central AR have been on the order of 400 to 500 j/kg.
Already the latest dual-pol radar estimates have shown some peak
rainfall rates of as much as 1.5 inches/hr, and some localized
training of cells that has resulted in storm totals of as much as
2 to 3+ inches.
Over the next few hours, the corridor of stronger jet-aided
forcing aloft should translate downstream across areas of
southwest and central AR, and parallel to the aforementioned
elevated instability axis with overall MUCAPE values of 1000+
j/kg. This coupled with increasingly confluent flow in vicinity of
the 850/925 mb frontal placement should result in an expanding
axis of showers and thunderstorms, with activity likely continuing
to redevelop over areas of northeast Texas, but expanding in
coverage downstream across areas of southwest and central AR.
PWs across the lower MS Valley are on the order of 1.5 to 1.7
inches which are about 2 to 2.5 standard deviations above normal
for this time of the year. Some of the anomalous moisture
contribution is certainly connected to the southwesterly mid-level
(700/500 mb) flow emanating from the eastern tropical Pacific
Ocean, where the latest CIRA-LPW data is showing a well-defined
zone of moisture transport.
Given the anomalously higher PWs and efficient mid-level moisture
transport, the rainfall rates within the deeper convective cores
should remain quite high, with rates that perhaps even locally
approaching 2 inches/hr. This coupled with a fairly decent set-up
for some periodic training of cells should result in a threat of
locally excessive totals. The 00Z HREF suite of guidance favors
some additional storm totals of as much as 3 inches going toward
dawn, which may perhaps be a tad underdone given the instability
and moisture parameters that are in place. As a result, at least
some isolated areas of flash flooding will be possible going
through the remainder of the overnight time-frame.
Orrison
ATTN...WFO...FWD...LZK...OUN...SHV...TSA...
