Mesoscale Precipitation Discussion 1179
NWS Weather Prediction Center College Park MD
1050 PM EST Tue Dec 17 2024

Areas affected...Southeast OK...South-central MO...Far Northeast
TX...Arkansas...

Concerning...Heavy rainfall...Flash flooding possible

Valid 180350Z - 180920Z

SUMMARY...Another round of elevated occasionally training
showers/thunderstorms with capability of 1.5"/hr and localized
totals of 2-3".  Intersection with recently saturated increasingly
dormant soil conditions may result in increased localized run-off
and low-end flash flooding potential overnight.

DISCUSSION...03z surface analysis depicts an older polar boundary
draped across the Red River Valley, S Arkansas into the TN River
Valley. CIRA sfc to 850 LPW shows return moisture from the western
Gulf of Mexico streamed northward across central TX, then angling
northwest across much of AR while ascending across/above the
boundary into the 850-700mb layer. Total PWat values are in the
1.25 range, but sharpening upper-level polar trough across the
Central High Plains is increasing flow through the layers into the
30-40kt range through 700mb while sharpening the isentropic
boundary as the northern stream cold front presses further south
and east over the next few hours.  Modest, mid-level drying and
lingering steeper lapse rates along with the near surface
moisture/heating is providing solid MUCAPE over the boundary with
values of 1500-2000 J/kg spreading across SE OK.  Additionally to
the strengthening low level convergence/isentropic ascent; the
right entrance of the 100 kt jet is dropping southeast providing
solid divergence and evacuation to developing elevated convection
(while also moving into broadly diffluent region across S MO/AR
into the MS Valley).

Current GOES-E 10.3um and regional RADAR mosaic depict numerous
narrow core cells breaking out in two SW to NE orientated bands
across E OK and north-central AR.  Coverage will increase and
updrafts will broaden to support 1.25-1.5"/hr rates occasionally
increasing to 2"/hr randomly and widely scattered in nature.  Deep
layer flow while not ideally unidirectional, will support cross
track/repeating particularly over the first 2-4 hours before the
stronger flow/height-falls aloft increase forward cell motions and
increase southeastward cell propagation.  This should allow for a
few scattered incidents of 2-3" totals across E OK/W AR and
perhaps even further downstream; which is likely to align with
areas that missed out on the moderate/heavy rainfall a few days
ago; but FFG values of 1.5"/hr and 2-3"/3hrs are well within
range.  Still there are some overlaps along the edges of
south-central MO and eventually SW AR to south-central AR...that
may be more susceptible given soil saturation values per NASA
SPoRT at or above 65-70% in the 0-40cm layer.   Also considered,
flash flooding is possible, but given rates and totals are at the
thresholds...any flash flooding is likely to be on the lower end
and scattered in nature with highest potential in urban locales.

Gallina

ATTN...WFO...FWD...LZK...OUN...SGF...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON   36789162 36309120 35499120 34769177 33929358
            33409564 33519674 34139694 34849641 36019480
            36739300