Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jul 15 2023 08:20:59 FOUS30 KWBC 150820 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 419 AM EDT Sat Jul 15 2023 Day 1 Valid 12Z Sat Jul 15 2023 - 12Z Sun Jul 16 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF NORTHEAST NEW MEXICO, THE TEXAS PANHANDLE, CENTRAL APPALACHIANS, THE UPPER SUSQUEHANNA RIVER BASIN, AND NORTHERN NEW JERSEY... ....Eastern Half of the Country... A digging upper level low starting out the day today over northern Manitoba will dig southward, reaching the US/Canadian border in MN late tonight. An upper level wave rotating around that low and its associated cold front will sweep eastward across the Midwest today. The convection ongoing from MI southwest to IL is occurring partially because of that upper level forcing. It is expected to sweep eastward along with its forcing across the Midwest and into the Mid-Atlantic tonight. PWATs ahead of this convection will advect northward out of the Southeast, rising to between 1.5 and 1.75 inches broadly across the Northeast. This will provide plenty of moisture and instability for the storms as they cross the Midwest. Fortunately, as has been the case in recent days, the guidance remains consistent that the storms will be quite progressive, so no one area is expected to see excessive amounts of rain. Thus, the large Marginal Risk area across almost the entire half of the country east of the Mississippi remains in place. After sunset this evening, the storms will be into the Mid-Atlantic, but weakening due to the loss of solar heating. However, the upper level flow will favor more northward movement of the storms with a slowing eastward progression. This will result in a larger area of light to moderate rainfall to develop into PA and NY, resulting in a longer-duration but lighter intensity of rain. This too will favor generally low chances of flash flooding. The two Slight Risks generally over the Virginias and again over PA/NY are largely in place owing to the much lower FFGs in those areas, as the areal rainfall totals will be similar to areas outside the Slight Risk areas. Across the Southeast, the MCS starting out the day over MS will devolve into a broken line of widely scattered storms, which with plenty of available atmospheric moisture will support continued convective development both ahead of and behind that line of storms, as the real air mass change largely stays north from the TN Valley north. As there's little indication that the storms will be able to organize today, largely due to lack of forcing, the Marginal Risk area remains across the Southeast. Somewhat heavier rains are possible across the FL Panhandle today, where sea breeze convection may merge with advancing storms from the north, resulting in locally heavier rainfall totals. As FFGs are also quite high here, especially over the eastern Panhandle, which guidance is in good agreement will see the bulk of the heaviest rainfall today, a high-end Marginal remains in place, which may need to be upgraded to a localized Slight with future forecast updates. ....Southern High Plains... Storms ongoing as of the time of this writing over much of the Slight Risk area from northeastern NM into northwest TX are helping prime the soils and lower FFGs to increase the flash flooding risk when an MCS develops this afternoon into this evening across this region. A complex of storms will develop over northeast NM, then turn eastward as it moves over the southern TX Panhandle, following the upper Red River basin on the TX side of the river overnight tonight. The guidance has shifted south and west with the axis of heaviest rain associated with this MCS, which is in keeping with typical MCS behavior where the south and western sides of the MCS are more likely to get held up and move more slowly than the rest of the complex of storms. The Slight Risk area was shifted south and west, removing all of OK and much of the northeastern TX Panhandle from the Slight with this update. Wegman 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!98BFhRAEl4DNHqNDo3elBGAaLrSqJhEHvlOwn-zNqS4l= 5TPN6eruQXMXEzwHW5Ib47bLgcZJzpGbXkFtUzXf__K9C-8$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!98BFhRAEl4DNHqNDo3elBGAaLrSqJhEHvlOwn-zNqS4l= 5TPN6eruQXMXEzwHW5Ib47bLgcZJzpGbXkFtUzXf0iEePY4$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!98BFhRAEl4DNHqNDo3elBGAaLrSqJhEHvlOwn-zNqS4l= 5TPN6eruQXMXEzwHW5Ib47bLgcZJzpGbXkFtUzXfur-Oj9o$=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) .