Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Dec 17 2023 08:29:02 FOUS30 KWBC 170828 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 328 AM EST Sun Dec 17 2023 Day 1 Valid 12Z Sun Dec 17 2023 - 12Z Mon Dec 18 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE EASTERN U.S. FROM THE CAROLINAS TO THE NORTHERN MID-ATLANTIC REGION AND SOUTHERN NEW YORK/NEW ENGLAND... ....Southeast US into the Mid Atlantic Region... Longitudinal differences in where the axis of heavy rainfall occurs does linger in the higher resolution guidance from the Carolinas into the Mid-Atlantic. The differences were continuing to revolve around the slightly faster solutions...and for a secondary northern shortwave into pivot into the deepening trof farther north and west. This draws higher moisture from the increasingly distant warm conveyor belt back west into the foothills of the Appalachians and western Piedmont regions of the Carolinas and dries out the Coastal Plains. The 17/00Z run of the HREF supported this idea...showing a potential for 2 inch and 3 inch per hour rainfall rate over portions of the Carolina coastal plains during the morning before rates decrease to around an inch per hour in southeast Virginia as instability tapers off. Given the nature of the coastal plains to be difficult to flood combined with 30 day rainfall amounts being so minimal...think this will be a high-end Slight Risk although some hydrologic concerns beyond urban and small stream flooding could occur in areas should some of the higher amounts from the models materializes. ....Northeast/Northern Mid-Atlantic... Moderate to occasionally heavy rainfall is expected over parts of the Northeast and northern Mid-Atlantic region given widespread synoptic scale forcing with embedded higher amounts due to mesoscale enhancements from frontogenesis/TROWAL ahead of the deepening mid-level cyclone. As was the case farther to the south...increasing distance from the core of the higher theta-E air and reduced instability relative to the core of the digging upper-low to the south should limit rates. But However, favorable orographic enhancement along terrain of eastern Pennsylvania/New Jersey as well as southern New York very late will allow for some 2.5 to 3.5 inch amounts mainly in that favored southeast exposed terrain. So little adjustments were required at this time. ....Northwest California... Removed the Marginal Risk area across northern California given an overall slowing of the system. Areal average deterministic rainfall amounts are generally at or below an inch and the latest HREF guidance shows any risk of 0.5 inch of rainfall in an hour now remaining off-shore through 12Z Monday.=20 Bann 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!7L0xBTFY2PYTmXOcf6JQCein5lKNs_dzTCF-Ac0BLg5l= pIoQnRM4BLfrkdd9zrbqSBJWjrj_Xp4Kaa_pJLDYBT4RJU8$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7L0xBTFY2PYTmXOcf6JQCein5lKNs_dzTCF-Ac0BLg5l= pIoQnRM4BLfrkdd9zrbqSBJWjrj_Xp4Kaa_pJLDYuiv0FVA$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7L0xBTFY2PYTmXOcf6JQCein5lKNs_dzTCF-Ac0BLg5l= pIoQnRM4BLfrkdd9zrbqSBJWjrj_Xp4Kaa_pJLDYZqkL2vs$=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) .