Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed May 17 2023 08:21:10 FOUS30 KWBC 170821 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 420 AM EDT Wed May 17 2023 Day 1 Valid 12Z Wed May 17 2023 - 12Z Thu May 18 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF THE SOUTHEAST TO THE CENTRAL GULF COAST AND ALONG THE MOGOLLON RIM OF ARIZONA... ....Mogollon Rim of Arizona... Highly anomalous moisture along with weak forcing will be enough to trigger and maintain convection across portions of the Desert Southwest. PW values approaching 1" (+4 sigma), as southerly flow off the Pacific and up the Gulf of California advect into the region. These PWs would be much more common between July and September. As the trough moves east, favorable upper divergence will also remain over much of the Southwest. The Marginal Risk was expanded somewhat to include the broader threat for isolated convection capable of intense rainfall within flood-prone regions. Convection is likely to initiate near the terrain of the Mogollon Rim of Arizona and nearby ranges, but the potential exists for storms to migrate slowly into the lower terrain before rapidly weakening given the dry air infiltration. The flash flooding threat is expected to be on the low-end and highly isolated, thus the Marginal designation. ....Southeast and Central Gulf Coast... The slow-moving frontal boundary draped across the Southeast will continue to have additional rounds of unorganized, impulse convection develop as a steady stream of deep moisture advects northward. The PW values will generally be around 1.5" over this stalled boundary; which should be more than adequate to keep the threat for intense rainfall rates, though the flash flooding threat will be low due to very high FFG and sandy soils. The main flash flooding threat will be in the urban areas of the Marginal Risk, including New Orleans, Gulfport, Mobile, Pensacola, Tallahassee, Valdosta, and Savannah. A small adjustment was made to the northern bounds of the Marginal Risk over central South Carolina. Campbell/Snell 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!9QLrJhG_YiHsodr5snQAaWMlVYPksgLginNhVKw_ZlXe= tr81N2_1FszdBaZHRT8pnKWfnUtFwucEcOBtVU5W2c1RnxQ$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!9QLrJhG_YiHsodr5snQAaWMlVYPksgLginNhVKw_ZlXe= tr81N2_1FszdBaZHRT8pnKWfnUtFwucEcOBtVU5WFHBtwNA$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!9QLrJhG_YiHsodr5snQAaWMlVYPksgLginNhVKw_ZlXe= tr81N2_1FszdBaZHRT8pnKWfnUtFwucEcOBtVU5W9cAjqh4$=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) .