Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Dec 28 2022 08:30:30 FOUS30 KWBC 280830 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 329 AM EST Wed Dec 28 2022 Day 1 Valid 12Z Wed Dec 28 2022 - 12Z Thu Dec 29 2022 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF ARIZONA... The flash flooding threat today will remain temporally confined to the morning hours over portions of central and southern Arizona, as remnant moisture from the coastal atmospheric river event pushes through the Southwest along a staunch cold front. PWATs may hover around an inch with anomalies between +2 to +3 standard deviations in southern/central Arizona this morning before quickly advecting southward and diminishing. The marginal risk area is cutoff on the northeastern edge along the Mogollon Rim and White Mountains, where light to moderate snowfall is expected. Kebede Day 2 Valid 12Z Thu Dec 29 2022 - 12Z Fri Dec 30 2022 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE COASTAL RANGES OF SOUTHERN OREGON, NORTHERN CALIFORNIA AND PORTIONS OF THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY... ....West... Flash flooding concerns return to the West Coast as a pair of low pressure systems arrive on Thursday. The first system will bring a round of rainfall to the coasts of the Pacific Northwest and northern/central California early Thursday morning. Rain rates should be between 0.1-0.25in/hr across the region with PWATs remaining modest at well below an inch. Forcing provided by a weak surface cold front won't help to enhance amounts, but higher totals will still be possible at higher elevations. The second round of precipitation will arrive with the entrance of another system later Thursday afternoon. Rain rates will be more substantial at around 0.5-1in/hr. PWATs between 0.75-1 inch should cause some flash flooding concerns over already well saturated soils, burn scars and in urban areas. ....Lower Mississippi Valley... An upper trough will move into the Great Plains on Wednesday leading to height falls and the return of southerly flow over the Gulf of Mexico and Mississippi Valley. Moist air advection will ensue with PWATs of between 1-1.5 inches flowing from the central Gulf coast up through the Mississippi Valley and into the Midwest. This moist/unstable airmass, overrunning a coastal warm front, a dry line and cold front to the west, will support convective initiation over the Gulf coast and inland areas, where rain rates may range between 0.25-1in/hr with locally higher amounts. The latest 00z guidance has come into better agreement with respect to the orientation and magnitude of the axis of greatest QPF in the Lower Mississippi Valley/Southern Plains. The latest QPF signal is a slightly more progressive one, which is reflected in the current slight risk area. The 00z NAM and UKMET appear to be the only outliers as the NAM is farther to the west with its axis and the UKMET is more progressive and wet than the deterministic and ensemble mean consensus. Kebede 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!52FA69hftYcLyF2LfWhOdOEdAUYSuYKasuKl6-NteHP2= Xl13vIMIpnLzClEvbMWuU75betbwl1S7jb54TGjNVHsfXwM$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!52FA69hftYcLyF2LfWhOdOEdAUYSuYKasuKl6-NteHP2= Xl13vIMIpnLzClEvbMWuU75betbwl1S7jb54TGjNwbLpopc$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!52FA69hftYcLyF2LfWhOdOEdAUYSuYKasuKl6-NteHP2= Xl13vIMIpnLzClEvbMWuU75betbwl1S7jb54TGjNup_O9nk$=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) .