Subj : HVYRAIN: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jul 07 2023 07:33:57 FOUS30 KWBC 070733 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 333 AM EDT Fri Jul 07 2023 Day 1 Valid 01Z Fri Jul 07 2023 - 12Z Fri Jul 07 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE CENTRAL/SOUTHERN PLAINS AND MID-ATLANTIC INTO NORTHERN NEW ENGLAND... ....Mid-Atlantic through Northern New England... Upper-level pattern denotes a sheared shortwave along the southeast portion of the global-scale Canadian closed low, continuing to lift into a stubborn shortwave ridge along the New England Coastline. Deep layer moisture transport continues to be favorable from the SSW with above average moisture values of 1.75" as far north as the Rooftop of Maine, with 2"+ from Baltimore south. Early morning heating will allow for 1000-1500 J/kg of CAPE and within modest but sufficient convergence should spark numerous thunderstorms across the Mid-Atlantic through northern New England. Slow cell motions and storm outflow collisions will support localized very intense rainfall rates with 2"/hr probabilities well above normal (20-40% per HREF) and 2"/3hr probabilities nearing 50-60% by 21z across much of N PA to NW ME.=20 Cells should be a bit more scattered to isolated across the Mid-Atlantic into the Northern Carolinas, respectively; however, the risk remains for scattered incidents of flash flooding, which may be of greatest concern over the lower FFG of urban centers from DC to Philly and again through Upstate New York and Burlington. As such, small adjustments were made to include all of N ME and broadening the Slight Risk across central MD. The Marginal Risk was also brought further south across central and E VA including Richmond, Newport News/Norfolk. While clustering/most intense rainfall appears to be over higher FFG east of I-95 in N NC, lower FFG along the I-85 corridor, allowed for some broadening of the Marginal across this region for today as well. ....Central Plains and northern Southern Plains... With the southern Ridge retrograding toward the west and the strong Canadian global-scale closed low anchored across the north-central portion of North America; the persistent parade of convective complexes developing in the lee of the Rockies with upslope and strengthening of the LLJ at nightfall will continue through much of the short-term period. Again tonight, an MCS is developing and is expected to be ongoing across SW KS into NW OK toward the start of the forecast period (08.12z). Pooled moisture up to 2" with stronger LLJ (given stronger shortwave emerging from WY/SD) will enhanced moisture flux convergence along the leading edge supporting a warm advection wing along/downstream of the MCV, weakening should be taking place by 18z resulting in an enhanced boundary across S KS, while the main squall line races out toward AR. By evening, instability will have built up again with maturing thunderstorms breaking out across SE CO/NE NM once again congealing/growing upscale into a MCS. However, as the northern stream shortwave is sliding east, the LLJ will be broader and likely to converge orthogonally across the lingering boundary in S KS/N OK. As a result additional thunderstorms are expected with slow motions. Global models have been supporting at a broad area of 3-6" across this area, with a continued trend southward into NE OK. Hi-Res CAMs have been much less aggressive with the WAA wing with exception of the more synoptically forced guidance such as the FV3, CMC_regional, and Nam-Nest...which even hint toward some higher totals. The ARWs and HRRR solutions are more focused on more intense rainfall totals/rates near the surface-based intersection with the squall line/bow echo expected over central to southern OK. All in all, there is a very solid signal for maintaining the high-end Slight Risk with very small adjustments, totals upstream into SE CO will be less than further east, but the overlap with multiple days of heavy rainfall support maintaining the extension of the Slight Risk further west, but the coverage/intensity is more on the low-end to average Slight Risk compared to further east. ....Mid-Missouri/Mid-Mississippi Valley toward Chicago... A shortwave trough is exiting from Wyoming into the northern Central Plains at the base of the global scale trough anchored in north-central Canada. Favorable cyclonic curvature and divergence aloft has been feeding ongoing convection across W SD that will further feed back in maturing the cyclone. Ongoing thunderstorms and showers are likely to be ongoing through th Missouri Valley but should be generally down-trending and fairly progressive.=20 Some training near along/downstream of the shortwave center may help increase rainfall totals, but rates may be a limiting factor. The NAM/NAM-Nest are quite aggressive with the totals in the deformation zone so a low-end, longer duration flooding condition or two may occur. Residual boundaries along/ahead of the wave will build up insolation to destabilize the environment along the southeast quadrant across MO/IL by late evening. Modest moisture (1.50-1.75") and instability to 1500 J/kg along with favorable height-falls/low-level convergence should spark some stronger thunderstorms, that may maintain through evening, perhaps encroaching on the Chicagoland area toward the end of the forecast period. Spots of enhanced rainfall totals supports a broad Marginal across the area for isolated flash flooding incidents.=20 In the wake of the wave as it shifts east, a stronger northern stream cold front will be dropping southward across the Red River Valley into the Mid-Missouri Valley helping to the residual moisture (and with some clearing) instability across the area.=20 Slow moving scattered thunderstorms across E SDAK into MN may have strong enough rates for an isolated flash flood condition as well. ....East Coast of Florida... Deep layer moisture plume remains draped across much of the FL peninsula within the tail end of the exiting shortwave trough.=20 Confluent mid-level westerly flow should allow for slower moving/anchored convection along the eastern Florida sea-breeze with 00z Hi-Res CAMs depicting an above average coverage of intense rainfall totals, likely due to the deeper available moisture and warm cloud layer with highest probabilities of 2"+ between 20-01z around 50% per 00z HREF. Given multiple days of scattered heavy rainfall and proximity to urban corridor from I-95 ear the Space Coast and south, a Marginal Risk remains in place 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!_OyhtdH_0wtyksiVLyCdbRX7w_wr38K_sOMC_gs_g2nY= b24T_t4bWfjWwEGbcku8WgYfgh5t4uoAXAxE8H4lF3_M9N0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_OyhtdH_0wtyksiVLyCdbRX7w_wr38K_sOMC_gs_g2nY= b24T_t4bWfjWwEGbcku8WgYfgh5t4uoAXAxE8H4lw0Rmi3M$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_OyhtdH_0wtyksiVLyCdbRX7w_wr38K_sOMC_gs_g2nY= b24T_t4bWfjWwEGbcku8WgYfgh5t4uoAXAxE8H4ln3YEZuE$=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) .