Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Apr 13 2024 00:31:58 FOUS30 KWBC 130031 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 831 PM EDT Fri Apr 12 2024 Day 1 Valid 01Z Sat Apr 13 2024 - 12Z Sat Apr 13 2024 The probability of rainfall exceeding flash flood guidance is less than five percent. Pereira Day 2 Valid 12Z Sat Apr 13 2024 - 12Z Sun Apr 14 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ALONG THE CENTRAL CALIFORNIA COAST AND INTO THE UPSLOPE OF THE NORTHERN TO CENTRAL SIERRA... 21Z Update: No significant changes needed for the Marginal Risk area with relatively good model agreement and run to run consistency for widespread precipitation beginning late tonight/early Saturday morning. An axis of higher PWs / modest IVT values (400-500 kg/m/s) will bring some locally heavier rain to mainly the coastal central California areas but also extending into the foothills of the Sierra of the central/northern Sierra. Taylor ---previous discussion--- There is good model agreement of the southeastward movement of the strong closed low off the Pac NW coast to a position off the northern California coast by the end of the day 1 period and then an eastward inland movement day 2 across central California. A well defined area of precip expected along the slowly southeastward moving frontal boundary. PW values along and ahead of this slow moving front will rise to 1 to 2 standard deviations above the mean along with 850-700 mb moisture flux anomalies of 2 to 4+ standard deviations above the mean. The anomalous moisture flux values will impact the central California coast range from Santa Cruz southward to the western portions of the Transverse Range and the upslope regions of the northern to central Sierra. Across these areas max rainfall totals of 1 to 1.5"+ are possible. No significant changes made to the marginal risk along the central California coast, with a marginal risk introduced for the upslope area of the northern to central Sierra. Oravec Day 3 Valid 12Z Sun Apr 14 2024 - 12Z Mon Apr 15 2024 ....THERE IS A MARGINAL RISK FOR PORTIONS OF SOUTHERN CALIFORNIA... The closed upper level low is expected to slowly move south/east across coastal California during the period with a secondary/embedded vort max pivoting through southern California during the late morning and afternoon hours Sunday. With the lower heights aloft and potential for an axis of instability to develop across this region, some intense rain showers will be possible across the Transverse Range. QPF signal is for an additional 1-2" in spots and this could lead to localized/isolated instances of flash flooding, especially for the terrain areas, so a Marginal Risk was introduced for this area. Taylor Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8XgQNE1wspmBLh7XG_5a6qtxd3UdI0YQQuekRjUYKRDg= WVAiEHvVcsB3G_l0MoSOBhAHKKK7SIGkDkNzSUZLMcgEgIg$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8XgQNE1wspmBLh7XG_5a6qtxd3UdI0YQQuekRjUYKRDg= WVAiEHvVcsB3G_l0MoSOBhAHKKK7SIGkDkNzSUZLWdfMopc$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8XgQNE1wspmBLh7XG_5a6qtxd3UdI0YQQuekRjUYKRDg= WVAiEHvVcsB3G_l0MoSOBhAHKKK7SIGkDkNzSUZLFgEaD-U$=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .