Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Nov 12 2023 08:12:41 FOUS30 KWBC 120812 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 312 AM EST Sun Nov 12 2023 Day 1 Valid 12Z Sun Nov 12 2023 - 12Z Mon Nov 13 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHERN TEXAS... Deep southwesterly mid-to-upper level flow ahead of a low/trough moving across northwestern Mexico and the southwestern U.S. will combine with strengthening low level easterly winds to support increasing moisture across Deep South Texas. Model soundings show deep saturation through the column, with PWs climbing to around 2 inches from the lower Texas Coast back into the Rio Grande Valley later today. This moisture interacting with increasing ascent afforded by mid level energy and favorable upper jet forcing will support organized rainfall and the potential for locally heavy accumulations across the region. Models continue to indicate that a lack instability will diminish the potential for heavy rainfall rates. However, a deep warm cloud layer and saturation through the low to mid levels will likely support efficient rates and the potential for runoff concerns, especially in poor drainage and urbanized areas. A Slight Risk was maintained although the area was reduced based on overnight model trends. The general consensus, including the CAMs, indicated a more southerly axis for heavy amounts, therefore both the Marginal and Slight Risk areas were trimmed and confined mostly to Deep South Texas. Expect the greater threat for excessive rain will be largely confined to the immediate coast where instability may be enough to support heavier rainfall rates. Pereira=20 Day 2 Valid 12Z Mon Nov 13 2023 - 12Z Tue Nov 14 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE MIDDLE TEXAS COAST TO SOUTHERN LOUISIANA... As the previously noted mid-to-upper level trough/low continue to move east, models show a surface low developing along a lingering front over the northern Gulf, with the surface wave tracking slowly from the northwestern to the north-central Gulf this period. Deep southerly flow ahead of the wave will direct increasing moisture into an area of large-scale ascent, supporting organized and potentially heavy rainfall from the middle Texas Coast to southern Louisiana. Instability will remain a limiting factor however, with models indicating that the greater instability and threat for heavy rainfall rates will remain mostly out over the Gulf. However, efficient rates supported by deep warm cloud layers and saturation through the low to mid levels may generate some localized runoff concerns, especially if prolonged periods of rain occur over poor drainage and urbanized areas.=20 This supported the continuation of a Marginal Risk area across the region. However, the area was reduced, reflecting model trends.=20 The general consensus of the 00Z guidance continued a southerly shift, confining heavy amounts mostly to the coast, with a decreasing signal for heavy amounts farther to the north into southeastern Texas and central Louisiana. Pereira Day 3 Valid 12Z Tue Nov 14 2023 - 12Z Wed Nov 15 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM SOUTHEASTERN LOUISIANA TO THE FLORIDA PANHANDLE... The threat for heavy rainfall will shift east as the previously noted low continues to track slowly across the northern Gulf.=20 While moisture and lift will remain sufficient for widespread, organized rainfall, limited instability will confine the greater threat for heavy rainfall rates and amounts mostly to the coast.=20 As on Day 2, the consensus of the 00Z models shifted the axis of heavier QPF farther south and therefore the extent of the Marginal Risk was reduced from the previous outlook. Pereira Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!4QNbLrSR9tkAKLVR5HfEiWJo48bXwJGh4hFaNOlE180Q= 6Q4KXuktE_iW97Kre4FEsXs4A4eahezziAPQ_wNQd_qOS68$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4QNbLrSR9tkAKLVR5HfEiWJo48bXwJGh4hFaNOlE180Q= 6Q4KXuktE_iW97Kre4FEsXs4A4eahezziAPQ_wNQjg1ql7c$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4QNbLrSR9tkAKLVR5HfEiWJo48bXwJGh4hFaNOlE180Q= 6Q4KXuktE_iW97Kre4FEsXs4A4eahezziAPQ_wNQ1don8cQ$=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) .