Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Mar 08 2023 08:13:50 FOUS30 KWBC 080813 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 312 AM EST Wed Mar 08 2023 Day 1 Valid 12Z Wed Mar 08 2023 - 12Z Thu Mar 09 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF ARKANSAS, SOUTHEASTERN OKLAHOMA, AND PORTIONS OF NORTH TEXAS... The heavy rainfall threat on Day 1 extends from ongoing convective activity over southeastern OK and AR early this morning that is expected to push southeast before redeveloping showers and storms near the Red River Valley potentially overlap these areas this evening. The excessive rainfall threat to start the period is in response to shortwave energy advancing to the east across the lower/mid Mississippi Valley. Convection should weaken and become less widespread by midday as instability lacks downstream, but may reinforce the stationary boundary draped across the region and aid in forcing later today from northeast TX to southern AR. Overall, a lull in activity is then anticipated until the low-level jet reloads by tonight. Anomalous PWs (above the 90th climatological percentile) will be readily available as convection develops in response to sufficient 850 mb inflow and MUCAPE values upwards of 1000 J/kg. The lingering stationary front will also remain in the area and extend from the lower Mississippi Valley to northern TX. Meanwhile, a stronger shortwave crossing the Four Corners region should eject into the High Plains by Thursday and aid in increasing ascent over the Southern Plains, which will support convective development to the north of the front and spanning from southeast OK to central AR. At the same time, a pivot point in the frontal boundary over parts of southern MS could also be a focus for slow-moving localized convection and intense rainfall rates over 1"/hr. The Slight Risk area incorporates a region where guidance highlights both the greatest chances for additional rainfall amounts in the 1-2" range (locally up to 3") and the potential for 1-1.5" per hour rainfall rates, while also overlapping with saturated ground conditions. 00z HREF neighborhood probabilities of 6 hr QPF exceeding 2" are highest (greater than 30 percent) in the ArkLaTex region through midday. This rainfall, combined with the previous rain, could yield scattered areas of flash flooding. Given the antecedent conditions (AHPS 14 day precip departures are 200-300 percent of normal and NASA SPoRT soil moisture percentiles in the 10-40 cm layer are above 80 percent in areas) over parts of AR and southeast OK, terrain may be more sensitive for ponding of water in low-lying areas and urban flooding. A recent trend in guidance has been to slide the potential for 1-2"/hr rates to the south along with a gradual southward trend in the stationary front. This has led to the heavier rainfall axis forecast to occur the south and not overlapping with even wetter antecedent conditions over central AR, thus a subtle southward shift to the Slight Risk and Marginal Risk. Snell Day 2 The Day 2 outlook will be updated by 0830Z. Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-yuMCIdfl6fypI2pDi4Nxjfh5ZIooU0oGTKQdGmJu3xi= Woeo8w3psXIFCTDfx9LfOZpf4Ym3-PwauO-hQNJYAgK-ihY$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-yuMCIdfl6fypI2pDi4Nxjfh5ZIooU0oGTKQdGmJu3xi= Woeo8w3psXIFCTDfx9LfOZpf4Ym3-PwauO-hQNJY8XqFzaE$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-yuMCIdfl6fypI2pDi4Nxjfh5ZIooU0oGTKQdGmJu3xi= Woeo8w3psXIFCTDfx9LfOZpf4Ym3-PwauO-hQNJYU8i8Udw$=20 $$ =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .