Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jan 15 2023 08:27:38 FOUS30 KWBC 150827 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 326 AM EST Sun Jan 15 2023 Day 1 Valid 12Z Sun Jan 15 2023 - 12Z Mon Jan 16 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ALONG A MAJORITY OF THE WEST COAST...A PORTION OF THE RANGES IN SOUTHERN CALIFORNIA AND FOR PORTIONS OF CENTRAL AND SOUTHEAST ARIZONA... ....Washington and Oregon coasts... Low pressure off the Oregon coast will continue to move north- and northeastward...allowing for a fetch of moisture to be transported onshore from Oregon into Washington through this evening.=20 Precipitable water values on the order of 0.6 to 0.75 inches will be drawn inland toward the coast and the coastal ranges by low level winds of 20 to 35 kts. The global models show an increasing amount of air with lower precipitable water values getting wrapped around the southern flank of the upper low which should help to lead to decreasing rates. QPF spaghetti plots tend to show 1 to 2 inch amounts clustered along the coastal ranges while the HREF was more aggressive in showing 24-hour probabilities over 70 percent of 2 inches in 24 hours ending at 16/12Z close to the Columbia River Delta. The previous outlook had this covered and few changes were needed here. ....California... There should be a relative break in the rainfall across California during the day as one system pulls away and before the next system makes its appearance. Moisture transport should be ramping up during the late afternoon/early evening prior to the arrival of the surface low and associated upper level trough later in the evening. IVT values increase to around 500 kg/m/s in southern California near the Peninsular Range as the winds become normal to the range axis. Thinking is that rainfall amounts of 1 to 2 inches could occur in the mountains with a few spots in excess of 0.5 inches in the upslope region. The biggest change here was to provide a break in the Marginal Risk area farther north early in the period from the second area of rain and potential excessive amounts farther south. Given uncertainty with the timing and placement...maintained the Marginal Risk from the Bay area southward. ....Arizona... A Marginal Risk area was maintained for portions central and southeastern AZ with this update due to the potential for convection early where a few of the CAMs suggest there may be some convective elements embedded within the atmospheric river as it moves eastward across the state. Areas south of the Mogollon Rim will have the advantage of additional upslope with impressive IVT resulting in PWAT approaching 3/4 inch, which is 3 sigma above normal. Thus, the main factor determining the extent of flooding will be the hourly rainfall rates, which may briefly exceed 0.5 inches/hour, depending on how much convection is embedded within the main line of rain as it moves across the state. 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!4LeJdjIDbE26YBoGZu_KKxmCH-ba06GO6pvlViJKwPAZ= ZRScQrSPnLk_ROuOIzIbSWqMxmaZp1nfB_l4d2ItPha8HGQ$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!4LeJdjIDbE26YBoGZu_KKxmCH-ba06GO6pvlViJKwPAZ= ZRScQrSPnLk_ROuOIzIbSWqMxmaZp1nfB_l4d2ItzQN7sRs$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!4LeJdjIDbE26YBoGZu_KKxmCH-ba06GO6pvlViJKwPAZ= ZRScQrSPnLk_ROuOIzIbSWqMxmaZp1nfB_l4d2ItAiY7s4I$=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) .