Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jun 04 2023 08:01:53 FOUS30 KWBC 040801 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Sun Jun 04 2023 Day 1 Valid 12Z Sun Jun 04 2023 - 12Z Mon Jun 05 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHERN HIGH PLAINS... ....Southern to Central Plains into the Central to Northern Rockies... No significant changes anticipate to the blocking pattern across much of the nation during the day 1 period. A closed upper high will remain centered across the Northern Plains with an elongated area of troffing extending northwest to southeast on the western side of this ridge from the Northern Rockies into the Central to Southern High Plains. PW values in this elongated trof axis will remain above average, especially from northeast Colorado into Montana where PW anomalies will run 2+ standard deviations above the mean. Weak vorts in the high PW axis will again support another day of widespread scattered convection stretching from the Southern to Central Plains into the Central to Northern Rockies. This entire region has seen much above average precip over the past few weeks, with many areas having observed values 300 to 600% of normal. This will continue the risk of isolated flash flooding where any additional day 1 rains fall across areas that have received recent heavy amounts. With confidence low with respect to where any heavy day 1 totals will occur, much of this region was kept in marginal risk. The one exception continues over the Southern High Plains from far northeast New Mexico, across the Texas/Oklahoma Panhandle region and southwest Oklahoma, where a slight risk area was maintained. This region has seen heavy rains over the past two days in the general same region and has a larger region of high 1"+ HREF probabilities for the upcoming day 1 period. ....Florida... The remnants of Arlene expected to pass to the south of South Florida early Sunday with any associated heavy rains on the north side likely having already pushed to the southeast of the southern portion of the peninsula by the beginning of the day 1 period.=20=20=20 In its wake, another day of scattered to widespread afternoon thunderstorms is likely across the southern half of the Florida Peninsula as the upper trof that the remnants of Arlene have been rotating through pushes across the Florida peninsula. HREF probabilities are high across the southern half of the Florida peninsula for 1 and 2"+ amounts. This may lead to isolated flash flooding, especially in urbanized areas where hourly rate of 1 to 2" are possible. Oravec Day 2 Valid 12Z Mon Jun 05 2023 - 12Z Tue Jun 06 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHERN HIGH PLAINS... ....Southern Plains through the Northern Rockies... With little in the way any significant changes to the overall large scale flow across the central portion of the nation day 2, the day 2 Excessive Rainfall Outlook is very similar to the day 1 outlook. PW values are forecast to remain above average from the Southern to Central Plains through the Central to Northern Rockies. Similar to the day 1 period, shortwave energy embedded in this high PW axis will support another day of widespread scattered convection across these areas. A slight risk area was continued from northeast New Mexico into the Texas/Oklahoma Panhandle region. There continues to be somewhat better agreement that this area will see a better chance of organized heavy precip than other areas in the high PW axis. As stated in the day 1 discussion, isolated flash flooding is possible across the entire area given recent rainfall amounts that have been as much as 400-600% of normal.=20 ....Sierra Nevada... One of the biggest changes to the large scale flow across the U.S. during the day 2 period will be the closed mid to upper level low approaching the central to southern California coastal region.=20 Increasing upper difluence Monday afternoon to the north and northeast of this closed low will support scattered convection through the Sierra, northern California and portions of the Northern Great Basin. With PW anomalies rising to 1 to 2+ standard deviations above the mean in this upper difluent region, locally heavy rainfall amounts of up to an inch possible. With stream flows remaining much above average through the Sierra, isolated flash flooding is possible Monday afternoon into Monday evening. Oravec 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!9rGu3a5oEY3Lna7G6gqaoCOQszJRtTH5i_RP_mOPNlXP= QLesuO_ZbRkVKjG8mBGRmoZuzA80NbGXV4OfjSEB2M0MDJ0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!9rGu3a5oEY3Lna7G6gqaoCOQszJRtTH5i_RP_mOPNlXP= QLesuO_ZbRkVKjG8mBGRmoZuzA80NbGXV4OfjSEB9MzhnRk$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!9rGu3a5oEY3Lna7G6gqaoCOQszJRtTH5i_RP_mOPNlXP= QLesuO_ZbRkVKjG8mBGRmoZuzA80NbGXV4OfjSEBsK-nA4Y$=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) .