Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri May 19 2023 08:30:04 FOUS30 KWBC 190829 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 429 AM EDT Fri May 19 2023 Day 1 Valid 12Z Fri May 19 2023 - 12Z Sat May 20 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR EASTERN OKLAHOMA INTO WESTERN ARKANSAS... ....Eastern Oklahoma into Western Arkansas... The previous Marginal Risk area has been upgraded to a Slight Risk with this morning's update. A southwesterly low level jet (LLJ) will develop ahead of a southward moving cold front moving down the Plains. This LLJ will increase the available atmospheric moisture with PWATs approaching 1.75 inches, which in addition to MUCAPE values exceeding 2,500 J/kg will provide more than ample moisture and instability for multiple rounds of storms to develop this afternoon through this evening across the Slight Risk area. Corfidi Vectors are very weak, generally 5 kt out of the northwest. This will support training storms as several rounds of storms develop along the front, then push southeast as new storms form behind it. This area has average to above average soil moisture for this time of year. Finally, the Ozarks in the region will further increase flash flooding potential as the rainfall drains into the locally narrow river valleys that criss-cross the region. ....Southern/Central Rockies into Central Arizona... No significant changes noted with the Marginal Risk area here. As with previous days, anomalously high atmospheric moisture in this region, plenty of instability, and a weak upslope flow will all support scattered convection that could locally cause flash flooding, especially along complex terrain, burn scars, slot canyons and dry washes as hourly rates locally exceed 1 inch/hour. Low level easterly flow upsloping into the northern High Plains and the southern Rockies is set to deliver an increase of 850-700mb moisture into southern CO and northern NM. Meanwhile, the upper low over northern Baja will provide sufficient vertical ascent for developing showers and thunderstorms along the mountain ranges. PWs will reach as high as 0.75" and according to NAEFS, PWS throughout the affected regions will easily top the 80th climatological percentile. Storm motions will also be rather slow as 850-300mb wind speeds generally hover around 5 knots or less. Soils throughout the at-risk region are still quite sensitive (0-40cm soil moisture percentiles above the 90th percentile in some cases). ....Coastal North Carolina... Some of the North Carolina beaches; from Cape Fear to the Outer Banks, could see rainfall totals of 4-5" in some spots on Friday as low pressure along the front just off the Southeast coast lifts north. However, storm motions are expected to be more progressive and the beaches there will likely be able to handle the rainfall amounts in the forecasts. No Marginal Risk in place, although some localized street ponding and nuisance flooding cannot be fully ruled out. The primary threat for heavy rains will be over the Outer Banks and the swamps of far eastern NC, where flash flooding risk is negligible. Wegman/Mullinax 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!4GKP-K37EFHFf1Wwn2YSxXE7zcYJ5R4QTd-hVA0Te4VA= Af8VyyPLl5l3gGjMYDsJud29Y1Nz_Stsk9h0lNSVhVi76q8$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4GKP-K37EFHFf1Wwn2YSxXE7zcYJ5R4QTd-hVA0Te4VA= Af8VyyPLl5l3gGjMYDsJud29Y1Nz_Stsk9h0lNSVbdgSayw$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4GKP-K37EFHFf1Wwn2YSxXE7zcYJ5R4QTd-hVA0Te4VA= Af8VyyPLl5l3gGjMYDsJud29Y1Nz_Stsk9h0lNSVDSdsQ_8$=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) .