Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Feb 16 2023 12:07:57 FOUS30 KWBC 161207 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 704 AM EST Thu Feb 16 2023 Day 1 Valid 12Z Thu Feb 16 2023 - 12Z Fri Feb 17 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF TENNESSEE, KENTUCKY, MISSISSIPPI INTO THE SOUTHERN APPALACHIANS... 12z Update: Observational trends warranted a westward expansion to the Slight risk this morning into much of the rest of TN and KY. The 00z CAMs have struggled with the convective evolution thus far today, however recent HRRR runs appear to be catching on. 850mb southwesterly winds are around 55 kts across the area, with 0-6km winds around 50 kts and aligned with the low level flow. This is a favorable wind pattern for backbuilding and training convective cells...and we have seen this already this morning over portions of western TN. The threat will likely continue across portions of western TN into southwest to south central KY until the cold front clears the region later this morning into the afternoon hours. With multiple flash flood warnings already in effect and continued rainfall likely as the front approaches, FFG exceedance may start to approach the higher end of the Slight risk range (15-40%) in spots as the morning progresses. -Chenard ....Previous Discussion... There is good model agreement on the eastward push of strong height falls from the Central to Southern Plains into the Mid to Lower MS Valley, OH Valley and TN Valley day 1. Strong south southwesterly low level flow off the western Gulf will continue to transport much above average PW values, 2 to 3 standard deviations above the mean, northeastward ahead of these height falls and the associated cold front. In the wake of the initial surge of heavy rains pushing northeast early this morning from the Lower MS Valley through the TN Valley, an organized frontal or pre-frontal squall line likely to push eastward through the Lower MS Valley into the TN Valley region Thursday into Thursday evening in what will be an overall very favorable pattern for an organized convective line along and ahead of the eastward moving front, with strong frontal convergence expected in the axis of anomalous PW values and Mu-Cape values 500-1000+ j/kg. Areas that receive heavy rains from the initial surge of precip prior to 12Z Thursday will likely receive additional heavy rains as the frontal/pre-frontal squall line pushes eastward later Thursday.=20 This may be especially so from central TN northeast into central to eastern KY. Across these areas HREF neighborhood probabilities for 2"+ amounts after 1200 UTC Thursday are high, 50-90%, and 20-50% for 3"+ amounts. The convective squall line is also expected to be well defined southward from northern-central AL/north GA into southeast MS. The slight risk was drawn farther south from the previous outlook to cover the model consensus for heavy rains across northern to central AL, and far north GA that also overlap some of the lower FFG values.=20 Oravec Day 2 Valid 12Z Fri Feb 17 2023 - 12Z Sat Feb 18 2023 The probablity of rainfall exceeding flash flood guidance is less than 5 percent. Oravec Day 3 Valid 12Z Sat Feb 18 2023 - 12Z Sun Feb 19 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Oravec Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!80O8WCiW8P7Y2OlqS-aNDWs_ift7sw84Tg3UlcqtqeeS= IXK7gXu8O9rvtx2EjdEFf98jouers5lWQ8zaFD7U-_-CeMk$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!80O8WCiW8P7Y2OlqS-aNDWs_ift7sw84Tg3UlcqtqeeS= IXK7gXu8O9rvtx2EjdEFf98jouers5lWQ8zaFD7U-9TQI7s$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!80O8WCiW8P7Y2OlqS-aNDWs_ift7sw84Tg3UlcqtqeeS= IXK7gXu8O9rvtx2EjdEFf98jouers5lWQ8zaFD7UwqaxN3g$=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) .