Subj : HVYRAIN: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jul 08 2023 07:46:20 FOUS30 KWBC 080746 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 345 AM EDT Sat Jul 08 2023 Day 1 Valid 01Z Sat Jul 08 2023 - 12Z Sat Jul 08 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE CENTRAL/SOUTHERN PLAINS INTO THE SOUTHERN MID-MISSISSIPPI VALLEY... ....Central High Plains/Oklahoma into Mid-MS Valley... Retrograding ridge into the Southwest continues to slightly amplify across the Rockies in tandem with the base of the larger scale trough over the Northern Plains/Upper MS Valley continuing to carve out cyclonic flow into the Ozarks and Ohio River Valleys. At the start of the forecast period, a mature to weakening MCS will be fading through the Red River Valley, but starting to round through the base of the aforementioned trof into increasingly diffluent flow aloft. The surface boundary will continue to sag southward across the southern Central Plains into S MO and become stationary. Insolation will allow for increased instability above 2000 J/kg by mid-afternoon and utilizing older outflow boundaries, weak convergence should allow for scattered thunderstorm activity to develop/expand though the Delta Region of the Mid-MS Valley with cells utilizing pooled deep layer moisture (in excess of 2" Total PWat) for efficient rainfall production. Loosely organized, training elements across AR/W TN/MS slowly moving into W AL with 00z Hi-Res CAMs and HREF PMM supporting 2-4" totals resulting in possible flash flooding conditions. 00z HREF 2-3"/3hr probabilities range from 40-50% and 25-40%, respectively and the inherited Slight Risk was adjusted slightly to encapsulate those signals. Upstream, as the ridge increases, the southeasterly flow veers a bit more across the upslope region expanding organized thunderstorm activity into E WY; however, best focus again remains along/south of the Lake/Palmer divide in SE Colorado. The strength of return moisture is a bit more limited given the stronger mid-level shortwave is now a bit further east, but the westerly flow over the Rockies remains potent enough for thunderstorms to once again grow upscale into an MCS crossing into NW OK through the central portions of the state, likely to overlap areas recently saturated by prior few days of MCSs. So while the overall rainfall intensity/totals is diminished versus prior waves, a Slight Risk remains in place (a tad south and west of prior tracks) connecting to the broader area in the Mid-MS Valley. ....Central Great Lakes and Ohio Valley... Large scale pattern remains on track with exiting shortwave across the Great Lakes into SE Canada to be replaced by deepening wave that will further carve out broader cyclonic flow further south into the Ohio and Mid-MS Valleys A surface low along the draped central CONUS frontal zone will ride northward across IL/IND today, with an attendant warm front across Ohio moving toward the Lower Great Lakes though the evening. This will increase overall deep layer moisture (1.5" toward pockets of 1.75" TPW) and broader pockets of typical summer instability values (1000 to 2000 J/kg, from Lower MI to SW KY/W TN). Proximity to the frontal zones may allow for increased clustering of stronger, but generally progressive thunderstorms capable of 1.5-2"/hr rates, localized cell training/repeating, with localized pockets of 2-3" totals, inducing isolated to widely scattered flash flooding incidents that seems appropriate for a Marginal Risk category. ....Carolinas, Mid-Atlantic into Northeast... Stubborn ridge over the NW Atlantic and main forcing wave lifted well into Eastern Canada, has left a residual sheared out higher Theta-E/moisture ribbon across central New England. Insolation will support a similar narrow instability axis of 1000-2000 J/kg by mid-afternoon to again initiate thunderstorms through the axis, but today forcing will be weaker and more isolated than prior days; however very weak steering will allow for pulse thunderstorms with high efficient rainfall production for isolated flash flooding risk. Further south, the deeper moisture is broader across Eastern Carolinas, a little more cyclonic curvature and low level convergence should allow for increased converge of thunderstorms with expected scattered shot QPF pattern with scattered to numerous spots of 2"+ with broad area of 3"/24r probabilities of 50-80% in E North Carolina, though over sandy soils and higher FFG a broad Marginal Risk seems appropriate for level of widely scattered flash flooding potential here as well. ....Southern Florida... Flat/broad deep layer westerly flow remains across Peninsular Florida today with anomalous deep layer moisture in the 2-2.25" range which is generally 2-2.5 standard deviations from normal.=20 Near surface flow is backed across Southeast Florida, to increase moisture convergence/anchor expected sea-breeze a bit further south and east than prior days. This results in continued above average QPF signal and 00z HREF probability highlighted greatest near Martin/Palm Beach county, but extending west a bit into the Glades/Lake Okeechobee. As such, maintained the Marginal Risk of Excessive Rainfall across this area again today. Gallina 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!_e5k6trdG92K2pPgHiD29HOvUo3pLkLfcRMiijq-KjIP= kY6jeKpmUWlT66f-F2B58tQZ9PT9nHMCKPfo_cLjanIh8jw$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_e5k6trdG92K2pPgHiD29HOvUo3pLkLfcRMiijq-KjIP= kY6jeKpmUWlT66f-F2B58tQZ9PT9nHMCKPfo_cLjl1x3W3E$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_e5k6trdG92K2pPgHiD29HOvUo3pLkLfcRMiijq-KjIP= kY6jeKpmUWlT66f-F2B58tQZ9PT9nHMCKPfo_cLjmmfL2_s$=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) .