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AWUS01 KWNH 081959

FFGMPD

VAZ000-TNZ000-KYZ000-INZ000-ILZ000-MOZ000-090200-



Mesoscale Precipitation Discussion 0241

NWS Weather Prediction Center College Park MD

358 PM EDT Wed May 08 2024



Areas affected...Lower Ohio Valley and Northern Tennessee

Valley...



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



Valid 082000Z - 090200Z



SUMMARY... Broad area of 2-4" totals with spots of 5+" at areas of

intersecting/repeating across area recovering from this morning's

MCS.  Broad area of flash flooding is likely with embedded spots

of locally significant flooding probable.



DISCUSSION...GOES-E imagery suite denotes much of the area of

concern lies between the remnants of the early morning MCS

crossing the southern Appalachians into the Carolinas, while a

maturing cluster/MCS is developing upstream exiting MO into S IL

over-topping a subtle ridge/split in upper-level flow through the

Central MS Valley into the TN Valley.  19z sfc analysis denotes a

complex pattern in the wake of the MCS with multiple convergence

boundaries to trigger new development. Main synoptic warm front

crosses southern MO and is generally along the Lower Ohio Valley

becoming a bit more diffuse east of OWB, south of which the

outflow boundary is starting to lift northeastward under response

to the synoptic height-falls but also return flow around the

stronger 1012 meso-high in E TN.  Tds of mid 70s are streaming

northward across W and central TN with general confluence east of

the MS River, aligned with the mid-level moisture stream out of

the Gulf resulting in core of 1.75" total PWAT in W KY/TN. A

secondary pocket of enhanced moisture and instability extends

along the synoptic boundary intersecting the return flow in

central KY.



As such, convection is developing in earnest across each boundary,

with increased density further west ahead of the approaching MCS. 

 Ample bulk shear is allowing for more discrete if more densely

scattered narrow updrafts to rotate and locally increase moisture

flux convergence.  In addition, the weak rotation is slowing

eastward propagation allowing for increased duration in any given

location.  Given flux and ample moisture rates of 2"/hr are

probable especially further east, with spots of 2-3" possible in

advance of the approaching MCS.  This is likely to induce

localized scattered incidents of flash flooding initially

especially in the axis affected this morning with 2-4" from

Marshall county in W KY across north-central TN to Roane/Meigs

county in E TN. 



As the afternoon evolves to evening, the MCS will continue to

advance expanding into the highly unstable air east of the

Mississippi and south of the Ohio River and with strong moisture

flux from the south-southwest, total PWATs will rise to 2" and

rainfall efficiency will increase to allow for 2.5-3"/hr rates

along the leading bow. Given forward progress, duration may limit

totals to 2", but in intersecting with the aforementioned areas of

discrete cells and sweeping them up in mergers...a broad swath of

2-4" will result with spots of 5+" probable, maybe resulting in

considerable levels of flash flooding into this evening.  A

potential limiting factor may be upstream development in SW TN,

that may disrupt inflow/flux of higher unstable air and will be

monitored closely for an additional MPD later.



Gallina



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



ATTN...WFO...JKL...LMK...MEG...MRX...OHX...PAH...



ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC...



LAT...LON   38288791 38208658 37948487 37698371 37168324 

            36698341 35438444 35588614 35808741 36278920 

            36848961 37438939 38178877