858
AWUS01 KWNH 140302
FFGMPD
TNZ000-MSZ000-ARZ000-140900-

Mesoscale Precipitation Discussion 0430
NWS Weather Prediction Center College Park MD
1101 PM EDT Fri Jun 13 2025

Areas affected...Central AR into northwest MS and southwest TN

Concerning...Heavy rainfall...Flash flooding likely

Valid 140300Z - 140900Z

Summary...Localized hourly totals of 1-2" expected to continue
through the overnight hours, and training/repeating elements may
lead to additional localized totals of 2-4" (on top of areas that
have already seen as much as 2-4" in recent hours). Isolated to
scattered instances of flash flooding are likely.

Discussion...A deep layer (sfc-250 mb) cyclone is nearly
stationary this evening over MO/IL, with deep layer cyclonic flow
organizing bands of showers and thunderstorms along the southern
periphery of the circulation. While heavy rainfall has generally
been progressive within 20-30 kts of steering flow (850-300 mb),
recent convective initiation to the southwest and south of the low
center (concentrated mostly across northwestern and central AR) is
allowing for localized elements of west-to-east training. This is
resulting in localized hourly totals of up to 1-2" (with the
highest totals confined just to the southwest of Memphis at the
time of writing), per MRMS estimates. Low-level moisture transport
is already on the rise in this area (mainly at 850 mb from the
WSW), and should only become more robust closer to the surface
over the next 3-6 hours (with strengthening isentropic upglide
anticipated along the 300K surface as winds near 925 mb veer to
the WSW and increase from 10-20 kts to 20-25 kts). In addition,
the mesoscale environment is characterized by precipitable water
values of 1.6-1.8" (and expected to increase to 2.0"+, between the
90th percentile and max moving average per LZK sounding
climatology), ML CAPE of 1000-2000 J/kg, and effective bulk shear
of 25-35 kts.

While the steering flow should continue to favor localized
training and repeating of convection, upwind propagation vectors
are also weak and variable in the vicinity of east-central AR into
northwest MS and southwest TN. This is precisely where localized
Flash Flood Guidance (FFG) exceedance is most likely to occur, as
3-6 hour FFGs are as low as 1.5-2.5" (and in reality are likely
even lower now, as this guidance applies to 00z and localized 2-4"
totals have occurred since then with some local FLASH CREST unit
streamflow response suggesting some minor flood impacts already
ongoing). Looking ahead to the next 3-6 hours, additional heavy
rainfall is expected along the base of the aforementioned deep
low, with impacts most likely from Little Rock to Memphis and
surroundings. Recent HRRR runs are in good agreement with this
corridor, suggesting additional localized totals of 2-4" are
possible (with continued potential for hourly totals up to 1-2").
Isolated to scattered instances of flash flooding are likely.

Churchill

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...LZK...MEG...

ATTN...RFC...ORN...TUA...NWC...

LAT...LON   35608908 34848878 34278981 34429176 35039300
            35379313 35579255 35499078