Flash Flood Guidance
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Issued by NWS
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994 AWUS01 KWNH 271631 FFGMPD OKZ000-KSZ000-272100- Mesoscale Precipitation Discussion 0182 NWS Weather Prediction Center College Park MD 1231 PM EDT Sat Apr 27 2024 Areas affected...Northwest Oklahoma...South-central Kansas... Concerning...Heavy rainfall...Flash flooding possible Valid 271630Z - 272100Z SUMMARY...A few observations suggest higher rainfall efficiency, rates over 2-2.5"/hr and increasingly favorable orientation for possible repeating pose at least an isolated or widely scattered risk of flash flooding through early afternoon. DISCUSSION...GOES-E Visible/10.3um EIR loops depict strong destabilization ongoing across northwest OK from Roger Mills to E Major, entering Grant county... with further weaker cells nearing the KS border in Kay county. Please refer to SPC MCD 538-539 for additional details about unfolding severe weather hazards. Recent 16z surface analysis denotes a strong dryline extending southward from surface wave near DDC with a slightly bowed segment in proximity to I-40/Wheeler county TX. RAP analysis and VWP depict some solid confluence along this bow enhancing moisture flux convergence while expanding orientation toward the east. Cells further eastward toward Major county appear to have developed at the nose of an enhanced moisture feature through 925-850mb that orients northeastward into south-central KS. The convergence along the axis has provided additional orthogonal convergence flux into the developing storms and have increased rainfall efficiency in the lowest profile with a few observations noting 1.5"/45 min near NW Blaine county and 1.75" in SW Roger Mills county, not within the greatest reflectivity/KDP alignment of heavy rainfall that was further east in the county where there is a lack of observations. The area has been in a significant drought and FFG values are near the extremes of 3"/hr and 4-5"/3hrs...but in driest conditions, extreme rates and hard grounds are difficult for much infiltration and increased run-off so spots of flash flooding could be possible with totals over 2-3" in 1-2hrs. Of concern, further duration of heavy rainfall with training/repeating profiles may also be starting to evolve as the upper-level jet streak is starting to come over-top the region as steering flow appears to be oriented just north of parallel to the convective line`s orientation. Combined this with 500-1000 thickness divergence across NW OK into south-central KS should aid in slowing forward propagation/Corfidi vectors, allowing for increased duration. Lastly, cells are strongly rotating and have shown some signs of southward deflection and slowing as Bunker`s vectors appear to be reducing and orienting favorably to the convective line as well. So while there are increasing signals toward favorable spots of 2-4" of rain over the next few hours; many factors have to align to overcome the dry ground conditions and therefore flash flooding is only considered possible and to be isolated or widely scattered in nature for portions of Northwest OK into south-central KS into early afternoon. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...DDC...ICT...OUN... ATTN...RFC...ABRFC...NWC... LAT...LON 38159741 38099664 37629639 36749702 35249931 35119992 35619998 36529948 37639841