####018000595#### PENA01 KWNH 181200 @UHPISF000CN MPDSUM@V2.0@0101700060@12180625@@0NMCGPHMPDgP@!' `' ` @ & B7)p&PNAM02@@|NO MDs ARE CURRENTLY IN EFFECT @@d&MESOSCALE DISCUSSION SUMMARY GRAPHIC @@d& OF ALL VALID MESOSCALE DISCUSSIONS AT @@d& TIME OF PRODUCT CREATION:@@d& ISSUED 06/18/2025 0615Z @@ dNOAA/NWS/NCEP@@d WEATHER PREDICTION CENTER @@d FOR COLOR VERSION SEE: @@d WWW.WPC.NCEP.NOAA.GOV @####018004056#### AWUS01 KWNH 180618 FFGMPD MOZ000-ARZ000-OKZ000-KSZ000-181115- Mesoscale Precipitation Discussion 0476 NWS Weather Prediction Center College Park MD 217 AM EDT Wed Jun 18 2025 Areas affected...much of OK into adjacent portions of far southeast KS, southwest MO, and northwest AR Concerning...Heavy rainfall...Flash flooding possible Valid 180615Z - 181115Z Summary...Backbuilding convection may continue to train from west-to-east with localized hourly accumulations of 1.5-2.5". Isolated to scattered instances of flash flooding are possible. Discussion...A mature mesoscale convective system (MCS) with an impressive bow echo has made rapid eastward progress across northern OK over the past several hours, and more recently (over the past couple of hours) elevated convection rapidly initiated and proliferated in the vicinity of the rear inflow jet (RIJ). The west-east orientation of the elevated convection neatly resembles a "bow and arrow" mesoscale convective structure, as a strong low-level jet (LLJ) from the south is resulting in strong moisture transport/isentropic upglide (most prominently around the 925 mb isobaric surface and the 305K isentropic surface) over prominent cold pool resulting from the MCS (and aided by low-level frontogenesis with the close proximity of a front). The "bow and arrow" conceptual model favors an increasing flash flood threat, given the tendency with the lagging "arrow" convection to train from west-to-east (as convection is nearly parallel to both the 850-300 mb mean flow, as well as the forward propagating Corfidi vectors). Should convection continue to backbuild, this could present a significant flash flood risk (with training cells producing localized hourly accumulations of 1.5-2.5", per MRMS estimates). Over the past hour or so, trailing convection has started to show a tendency of southward propagation (upwind into the LLJ, matching the associated Corfidi vectors quite closely), which may limit the flash flood threat somewhat (though this will eventually bring the trailing convection into the more populated OKC metro, additional backbuilding and a cessation of upwind propagation could ultimately be more problematic with regard to impactful flash flooding). In addition, convection may locally have a tendency to train along the north bookend vortex of the bow (near the OK/KS/MO border region), which has recently result in hourly totals to 2.0". Hi-res models have underestimated the intensity and scale of the backbuilding convection (as they tend to do with convection that is elevated in nature) across the 00z HREF suite, and hourly runs of the HRRR and experimental RRFS have not done much better. The HREF PMM QPF indicates the potential for localized 2-4" over east-central OK, and it seems reasonable to shift these totals and resulting post-processed exceedance probabilities (15-25% for 3" exceedance per 40-km neighborhood method) westward (based on the aforementioned observational trends). Convection may continue to backbuild for longer than expected in this environment with a large reservoir of 2000-3000 J/kg of MUCAPE (max 2-6 km AGL layer lapse rates of 8.0-8.5 degC/km) and impressive deep layer (0-6 km) shear of 40-50 kts. Precipitable water values are indicated to be 1.7-2.0 inches (near the max moving average/record levels, per OUN sounding climatology). Isolated to scattered instances of flash flooding are considered possible (and may locally be significant, particularly if storms backbuild and train across the more populated core of central OK). Churchill ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...ICT...OUN...SGF...TSA... ATTN...RFC...KRF...ORN...TUA...NWC... LAT...LON 37739456 37259388 36609363 35939372 35149440 34859536 34809712 35059853 35919931 36329939 36479892 36569838 36519649 36889576 37539542 ####018000733#### PENA01 KWNH 181200 @UHPISF000CN MPDSUM@V2.0@0101700060@12180625@@0NMCGPHMPDgP@!' `' ` @ & B7)p&PNAM02@@?,܄}}}{{{z{z{{{|||}~~~@@,܀@@,܀@@0476 @@d&MESOSCALE DISCUSSION SUMMARY GRAPHIC @@d& OF ALL VALID MESOSCALE DISCUSSIONS AT @@d& TIME OF PRODUCT CREATION:@@d& ISSUED 06/18/2025 0618Z @@ dNOAA/NWS/NCEP@@d WEATHER PREDICTION CENTER @@d FOR COLOR VERSION SEE: @@d WWW.WPC.NCEP.NOAA.GOV @