Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Apr 20 2025 08:29:23 FOUS30 KWBC 200829 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 429 AM EDT Sun Apr 20 2025 Day 1 Valid 12Z Sun Apr 20 2025 - 12Z Mon Apr 21 2025 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE CENTRAL US TODAY INTO TONIGHT... Introduced a Slight Risk area for the potential of excessive rainfall from parts of Texas into the Upper Midwest/Northern Plains. It is really a composite of multiple reasons to warrant a=20 Slight Risk area in different geographical areas. The northern=20 portion of the Slight Risk area covers the growing model signal for 2-3+ inches of rain due to a combination of deformation=20 zone/surface low and good divergence aloft from the highly curved=20 anticyclonic upper level jet all becoming more or less collocated. Rainfall amounts in the central part of the US are forecast to be=20 less than areas to the north...but the Slight Risk area was more=20 targeted for overlap between future rainfall on top of what MRMS=20 has shown for the past 24-36 hrs in anticipation of how the FFG=20 values will change. Lastly...kept some parts of the Southern Plains in an outlook area based on short term radar/satellite trends.=20 While rates have come down as the plume of highest equivalent=20 potential temperature has narrowed overnight...suspect that the=20 potential for at least some excessive rainfall will persist beyond=20 the start of Day 1 period at 20/12Z. Those areas can be removed in=20 the mid- morning Day 1 ERO assuming that trends continue downward.=20 Bann Day 2 Valid 12Z Mon Apr 21 2025 - 12Z Tue Apr 22 2025 The probability of rainfall exceeding Flash Flood Guidance is less than 5 percent. Bann Day 3 Valid 12Z Tue Apr 22 2025 - 12Z Wed Apr 23 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS=20 OF TEXAS AND/OR THE ADJACENT SOUTHERN PLAINS... Largely maintained a Marginal Risk area over portions of the=20 Southern Plains from Tuesday into early Wednesday morning due to the suite of 00Z numerical guidance continuing to show the=20 potential for repeat/training of cells during the day and with=20 overnight activity within an emerging moist and unstable return=20 flow into and over several frontal boundaries. With the models struggling to latch onto a coherent signal...as shown by some guidance focusing heaviest QPF near the Gulf coast in proximity to a weakening cold front and other guidance developing the threat=20 closer to the Red River in response to the approach of a mid-level wave...have opted to highlight concern for excessive rainfall in=20 broad and rather unfocused Marginal Risk area close to a consensus=20 placement of the precipitable water axis. With PW values generally=20 being 1.25 inches or less...would not be expected numerous=20 torrential downpours. The cumulative effect of what has already=20 fallen from this weekends event and what falls on Tuesday/early=20 Wednesday needs to be watched. Bann Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8Mr6FwZYlfhiAPPt-i7JnTkuyKaWwg8I7xNHHixkpszB= 1uvGDEsX-Y4VixVe60TcjORAjajqb5hY-Y3ynuDRoToLyjE$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8Mr6FwZYlfhiAPPt-i7JnTkuyKaWwg8I7xNHHixkpszB= 1uvGDEsX-Y4VixVe60TcjORAjajqb5hY-Y3ynuDRd-e1Tek$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8Mr6FwZYlfhiAPPt-i7JnTkuyKaWwg8I7xNHHixkpszB= 1uvGDEsX-Y4VixVe60TcjORAjajqb5hY-Y3ynuDR1Wb-RQ4$=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) .