Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 17 2023 07:43:31 FOUS30 KWBC 170743 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 342 AM EDT Mon Jul 17 2023 Day 1 Valid 12Z Mon Jul 17 2023 - 12Z Tue Jul 18 2023 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE EASTERN GREAT LAKES, THROUGH THE OHIO VALLEY AND PORTIONS OF THE LOWER TO MIDDLE MISSOURI VALLEY, AS WELL AS THE EAST CENTRAL FLORIDA COAST, SOUTHERN LOUISIANA, AND SOUTHEAST ARIZONA... ....Eastern Lakes, Ohio Valley into southern Missouri, southeast Kansas and far northeast Oklahoma... A broad marginal risk area was maintained for the upcoming day 1 period along and ahead of the next frontal boundary pushing through the eastern Great Lakes and toward the Ohio Valley. The latest simulated hi res radars depict potential for scattered convection across these regions where PW values are near seasonal norms and instability will range from 1000-200 j/kg through the Ohio Valley and values 3000+ j/kg from eastern Kansas/far northeast Oklahoma into southern Missouri. The previous marginal risk was extended westward across southern Missouri into southeast Kansas/far northeast Oklahoma to capture model heavy qpf potential in the max instability axis. The marginal risk area coincides well with the higher HREF neighborhood probabilities for 1"+ amounts, peaking at 50-80% across the marginal risk area. At the moment, convection should be fairly progressive limiting the upside potential for heavier totals. This is reflected in much low HREF probabilities for 2"+ amounts. ....Middle Missouri Valley... The front dropping south from the Northern Plains into the Central Plains/Mid Missouri Valley will become nearly stationary Monday afternoon from the Central Plains, east southeast into the Mid Mississippi Valley. Strengthening southeasterly to southerly inflow into this front will support potential for organized convection to press east southeast along and north of the front late Monday afternoon into the early hours of Tuesday. There is general model agreement on heavy rainfall potential as this convection presses southeastward, but not very good agreement on placement of max amounts. This is reflected in very low EAS probabilities for 1"+ amounts, maxing out at 5% over southern SD into far north central NE, while HREF neighborhood probabilities for 1"+ amounts are higher 40-50%+ across this area. Risk level kept at marginal given this spread. ....East central Florida coastal area... An axis of above average PW values expected to persist day 1 across much of central FL, with anomalies 2 to 3 standard deviations above the mean. With the low level flow expected to remain westerly, convection that does fire will likely progress eastward and maximize somewhere along the east central Florida coast Monday afternoon. HREF probabilities reflect this with the highest 2"+ probabilities, 50-80%, along the east central FL coast from approximately Melbourne to Miami. This is also where the Ensemble Agreement Scale (EAS) shows the highest probabilities for 1 and 2"+ amounts. For these reasons, the previous broader marginal risk area across FL was decreased in size and concentrated along the east central FL coast where the aforementioned higher probabilities coincide with the more urbanized regions. ....Southern Louisiana... Only some slight changes to the previous marginal risk outlook with the northern edge trimmed south by approximately 50 miles to fit the latest model qpf output. At the moment, the model max axis of additional precip is across far southeast LA just to the south of the urban areas from New Orleans to Baton Rouge and Lafayette, but can not rule out convection still affecting the urban areas where there will be the greatest runoff risk day 1 from isolated rainfall amounts of 1-2 inches Monday afternoon. ....Southeast Arizona... The latest model consensus is for any monsoonal showers to remain primarily across southeast Arizona and southward into northwestern Mexico. This is reflected in the latest HREF probabilities that show any probabilities greater than 25% for 1"+ amounts centered close to the border over south central Arizona. Activity over the past 24 hours was mostly south of the southern AZ border with this trend again likely for day 1. While there may be some scattered convection north into the Mogollon Rim area, moisture is limited here and should preclude any runoff issue threat. The previous marginal risk area was trimmed on the north and northeast side from southwest New Mexico into central AZ. Oravec Day 2 The Day 2 outlook will be updated by 0830Z. 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!7rycYHkI7ZcfQ56F9qvyizdqTiU_Fw339gY3ccuS05cd= tXxdheRthJlyDjk2fQeON0gUqwPfh3wLVkJa9bd_BkJbK50$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7rycYHkI7ZcfQ56F9qvyizdqTiU_Fw339gY3ccuS05cd= tXxdheRthJlyDjk2fQeON0gUqwPfh3wLVkJa9bd_Tg_F_Ig$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7rycYHkI7ZcfQ56F9qvyizdqTiU_Fw339gY3ccuS05cd= tXxdheRthJlyDjk2fQeON0gUqwPfh3wLVkJa9bd_eivO4N8$=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) .