Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Mar 19 2023 20:25:12 FOUS30 KWBC 192025 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 424 PM EDT Sun Mar 19 2023 Day 1 Valid 16Z Sun Mar 19 2023 - 12Z Mon Mar 20 2023 ....16Z Update... The probability of rainfall exceeding flash flood guidance is less than 5 percent. However, an area of interest today turns once again to California... A widespread area of rain is ongoing across nearly all of California this morning. A cold front associated with a low tracking north up the coast is spreading the rain across the state. So far anyway, the storm is all bark and no bite. While the radar shows rain ongoing across the whole state, those radar returns are resulting in very light rainfall totals. As of the time of this writing, the highest 24-hour rainfall total thus far is less than 0.2 inches anywhere in the state. Meanwhile, IR satellite shows an area of much drier air approaching the northern half of the state. The drier air will help cut off what light rain is ongoing in that area, further reducing any flash flooding risk. Just like the most recent atmospheric river (A.R.) event, the drier air associated with the leading edge of a 130 kt jet will rapidly advect inland, pushing the area of rainfall ahead of it. This will ensure a progressive evolution to the rainfall, preventing it from hanging up in any one area of CA before pushing east. Snow levels remain lower with this event than the last A.R., which means the colder temperatures will allow a greater percentage of the expected QPF to fall as snow in the mountains. The primary factor favorable for flash flooding are the antecedent conditions. Soils remain fully saturated over nearly the entire state from previous A.R. events. However, once again the fast duration and very light rainfall rates over most of the state should make any flash flooding isolated, and most likely to occur near burn scars, urbanized areas, and where any locally heavy rain occurs over other particularly flood-sensitive areas.=20 Wegman Day 2 Valid 12Z Mon Mar 20 2023 - 12Z Tue Mar 21 2023 ....2030Z Update... The probability of rainfall exceeding flash flood guidance is less than 5 percent. Wegman Day 3 The Day 3 outlook will be updated by 2030Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6aKsSM2mxwgLAsoxf90OWfwQEDxy1PJn0KiFyd_VhnGZ= 2FXUTaL1y6AoP7i5TO2OFLEv30OCUezjImcRoKy0jumfbQw$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6aKsSM2mxwgLAsoxf90OWfwQEDxy1PJn0KiFyd_VhnGZ= 2FXUTaL1y6AoP7i5TO2OFLEv30OCUezjImcRoKy0FKH7ND0$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6aKsSM2mxwgLAsoxf90OWfwQEDxy1PJn0KiFyd_VhnGZ= 2FXUTaL1y6AoP7i5TO2OFLEv30OCUezjImcRoKy0VMW2dL0$=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) .