Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Feb 15 2024 20:01:13 FOUS30 KWBC 152001 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 300 PM EST Thu Feb 15 2024 Day 1 Valid 16Z Thu Feb 15 2024 - 12Z Fri Feb 16 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. ....16Z Update... The nil D1 ERO was maintained from the previous forecast with very low probability for flash flood concerns focused along the southern Rio Grande, mainly within the confines of the developing surface trough in-of Starr and Hidalgo counties. Recent HREF blended mean did come up within the vicinity of the neighboring county lines with most of the hi-res suite indicating a max within a narrow region of higher theta-E's, likely situated along the developing surface trough this afternoon and evening. 12z BRO sounding was meager with observed MUCAPE, but it was non-zero and is forecast to increase a touch this afternoon over the southern portions of TX thanks to increasing boundary layer moisture and better mid-level moisture advection from a weak disturbance moving into the area out of MX. A low probability of thunder will exist within the zone closest to the surface trough, and considering the near-record airmass (PWATs) for mid-February in place, some modest rainfall over the course of the evening could cause a local flooding risk where heavy rainfall is persistent. As of now, the 1/3/6 hr FFG exceedance probabilities remain at 0% within the 12z HREF fields and are certainly at 0% for the NBM considering a more conservative forecast regarding the respective 1/3/6 hourly totals. In summary...the threat is non-zero but still below the 5% threshold with any flooding likely relegated to a triangulated area between McAllen-Rio Grande City-McCook in Deep South Texas. Kleebauer ....Previous Discussion... Over south TX 1-3" of rain is expected today into tonight. HREF neighborhood probabilities of exceeding 3" are as high as ~40%, suggesting localized 3-5" totals are a possibility. However, limited instability is expected to keep rainfall rates in check...generally peaking at 1"/hr on a localized basis. Dry antecedent conditions is resulting in high FFG over the area...thus despite some of the high QPF coming out of various HREF members...the probability of exceeding 1,3, or 6 hr FFG is 0% in the 00z HREF. Thus while areas of heavy rain are probable, and some localized ponding of water is possible...the chance of flash flooding still appears to be below 5%. Thus will continue with no risk area in the ERO. Chenard Day 2 Valid 12Z Fri Feb 16 2024 - 12Z Sat Feb 17 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Very low probability for flash flooding concerns remains for D2 across southeast TX, but will be monitoring the progression of a cold front interacting with elevated moisture and limited instability fields along coastal TX. GFS/ECMWF are indicating a local maximum near Corpus Christi, but to varying magnitudes with the NAM the most bullish with the areal extent of heavy rainfall approaching 2-3" within the coastal areas north of Brownsville. NBM probability for greater than 2" of precip remains very low with the 12z HREF also signifying a low-end potential for such totals, along with a flat 0% for the 1/3/6 hr FFG exceedance probabilities across the region. This will be mainly beneficial rainfall across the area with more ponding across impervious surfaces. Chenard/Kleebauer 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!8csb2lLG7eahI2fCXQfS9u-gDzasVQMVe9yviWHFwkC7= UihWDY7wndbdOpHB5vZ60nlVrKYiCYqEwLLsJKY9UjXmfvc$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8csb2lLG7eahI2fCXQfS9u-gDzasVQMVe9yviWHFwkC7= UihWDY7wndbdOpHB5vZ60nlVrKYiCYqEwLLsJKY9peH82H4$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8csb2lLG7eahI2fCXQfS9u-gDzasVQMVe9yviWHFwkC7= UihWDY7wndbdOpHB5vZ60nlVrKYiCYqEwLLsJKY9ipqCdUs$=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) .