Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Feb 08 2023 08:25:01 FOUS30 KWBC 080824 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 323 AM EST Wed Feb 08 2023 Day 1 Valid 12Z Wed Feb 08 2023 - 12Z Thu Feb 09 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF ARKANSAS AND SOUTHEASTERN MISSOURI... A Slight Risk area has been maintained for the new Day 1 outlook, primarily encompassing north-central Arkansas and southeastern Missouri (along with some small portions of adjoining states). Showers and thunderstorms are ongoing early this morning in the ArkLaTex region, and the relatively slow forward speed of the main upper trough as it lifts northeastward (and gradually takes on a negative-tilt) is expected to lead towards a distinct QPF maxima (per WPC) of 2-4 inches (centered over northern AR). Deep layer southerly flow ahead of the trough will facilitate these precipitation totals, as tropospheric moisture levels are in the process of broadly increasing across the MS/OH Valleys, which should result in precipitable water values peaking as high as 1.3-1.7 inches (from 1.0-1.4 inches early this morning) across the outlook area. This increased tropospheric moisture, along with strong lift and sufficient instability (MUCAPE of 500-1500 J/kg), will result in multiple rounds of heavy rainfall across the Slight Risk area (with only one distinct round of more progressive convection farther south in LA/MS). NASA SPoRT data shows elevated 0-40 cm relative soil moisture values across portions of the Lower MS Valley (as high as the 80-90th percentile across southern AR), while soil moisture values in the Middle MS and OH Valleys are well below normal (as low as the 10th percentile across portions of southern MO/IL/IN and western KY). These drier soils (along with a lack of instability) will likely preclude meaningful coverage of any flash flooding well north of the AR/MO border, but strong frontogenetic forcing may still allow for an isolated occurrence or two of meaningful runoff into portions of central MO and southern IL. Farther south across LA/MS, any instances of flash flooding should remain rather isolated given the progressive nature of the convection (with 0-6 km shear on the order of 40-60 kts). Churchill Day 2 Valid 12Z Thu Feb 09 2023 - 12Z Fri Feb 10 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS THE WESTERN FLORIDA PANHANDLE, SOUTHERN ALABAMA, AND WESTERN GEORGIA... A Marginal Risk of excessive rainfall has been maintained for the western FL Panhandle, southern AL, and portions of western GA for the new Day 2 outlook, mainly due to a stalling cold front moving into the region. High tropospheric moisture levels are expected ahead of the front, as indicated by HREF mean precipitable water values of 1.3-1.6 inches (well above the 90th percentile per TLH sounding climatology). The presence of sufficient instability (MUCAPE of 250-750 J/kg, per the HREF) will increase the potential for heavy rainfall, with rainfall rates locally approaching 2"/hr at times. The possibility of repeating rounds of heavy rainfall is also expected, increasing the threat of excessive runoff potential (with ECENS probabilities for 2" exceedance as high as 20-30%). However, antecedent soil conditions in the region are quite dry, with NASA SPoRT 0-40 cm soil moisture values indicated to be as low as the 10-20th percentile. This should significantly limit the areal extent of any flash flooding, with poor drainage/urban areas the most at risk of realizing any isolated flooding impacts. Churchill Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7Y3Y5ihe5pMSzTydHoxtcjOyl0dLsN_Tb0YpddTizbqi= b-Gus1XBayVHkvL_HZ6st9HE125joI0Z3qyjHW-iLXFOLe4$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7Y3Y5ihe5pMSzTydHoxtcjOyl0dLsN_Tb0YpddTizbqi= b-Gus1XBayVHkvL_HZ6st9HE125joI0Z3qyjHW-ilkFM1uU$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7Y3Y5ihe5pMSzTydHoxtcjOyl0dLsN_Tb0YpddTizbqi= b-Gus1XBayVHkvL_HZ6st9HE125joI0Z3qyjHW-iPXX-VeE$=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) .