Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Mar 15 2023 08:17:42 FOUS30 KWBC 150817 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 416 AM EDT Wed Mar 15 2023 Day 1 Valid 12Z Wed Mar 15 2023 - 12Z Thu Mar 16 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS ARIZONA... ....Southern California and the Interior Southwest... A shortwave trough and its associated surface low will continue to move across the Intermountain West and Rockies, with a trailing cold front extending back across Southern California this morning. As drier air settles in across Northern to Central California, moderate to potentially heavy rains may continue across portions of Southern California as the front, accompanied by a plume of deep moisture, settles south through the region this morning. PWs of 1-1.25in on the leading edge of 30kt low level inflow, along with favorable mid-to-upper level forcing, and orographics may contribute to additional heavy rain this morning along the coast, before decreasing in coverage and intensity by the afternoon as the axis deeper moisture advection settles farther south. Farther to the east, southwesterly flow ahead of the advancing front will focus deeper moisture across Arizona, southern Nevada, and southern Utah later this morning. PWs of 0.5in or more (3-4 standard deviations above normal) will spread across the region.=20 This moisture, combined with favorable mid-to-upper level forcing, is expected to support widespread precipitation, with locally heavy rain rates possible. Some of the heaviest amounts are expected to focus in the upslope regions along and south of the Mogollon Rim and across portions of northwestern Arizona, where a Slight Risk was introduced with this update. In addition to the heavy rain, melting snow may also contribute to runoff concerns.=20=20 Pereira Day 2 Valid 12Z Thu Mar 16 2023 - 12Z Fri Mar 17 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY... ....Eastern Texas to the lower Mississippi Valley... A shortwave trough moving across Southern California and the Southwest today is forecast to lift northeast and interact with a northern stream trough amplifying over the northern Plains on Thursday. This will support the development of a strong surface low that is forecast to track from the central Plains on Thursday to the Great Lakes by Friday morning. A 40-60kt low level jet will tap a plume of Gulf moisture, drawing it ahead of the low's trailing cold front as it settles southeast across eastern Texas and Oklahoma on Thursday. Guidance shows PWs of 1.5+ inches centered across eastern Texas into western Louisiana and southern Arkansas Thursday afternoon-evening. This moisture interacting with mid level energy moving through the base of the broader scale trough is expected to help initiate convection. Showers and storms are expected to continue into the overnight as southerly to southwesterly winds continue to draw ample moisture along the boundary and mid level energy and right-entrance region upper jet forcing support large scale ascent over the area. As the mean flow become parallel to the boundary, training storms may further raise the threat for heavy accumulations. While model spread continues to limit confidence in the details, there remains a good signal for heavy rainfall and the threat for isolated to scattered flash flooding across the highlighted area. Pereira =20 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!6HHFNxIhaskNxCh2eTcaFr4pdIGs5iC7KCwLBo1Oe90L= DQSJNF_8DXEPjgxxjAPk1481YLMXcwNkW6VmsGzjQv-m_Xw$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6HHFNxIhaskNxCh2eTcaFr4pdIGs5iC7KCwLBo1Oe90L= DQSJNF_8DXEPjgxxjAPk1481YLMXcwNkW6VmsGzjyXefS04$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6HHFNxIhaskNxCh2eTcaFr4pdIGs5iC7KCwLBo1Oe90L= DQSJNF_8DXEPjgxxjAPk1481YLMXcwNkW6VmsGzjkQ7HIHg$=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) .