Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Nov 05 2022 00:51:45 FOUS30 KWBC 050051 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 850 PM EDT Fri Nov 04 2022 Day 1 Valid 01Z Sat Nov 05 2022 - 12Z Sat Nov 05 2022 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE PACIFIC NORTHWEST AND FROM THE ARKLATEX INTO SOUTHERN MISSOURI... ....Pacific Northwest... Did not make any large-scale changes for the 01Z update, just minor adjustments based on recent hi-res guidance and observation trends. The ongoing atmospheric river event will continue, with the axis of heaviest precipitation shifting south through the overnight. A well-defined shortwave west of British Columbia will continue to dig southeast, shifting the axis of strongest onshore flow/moisture advection farther south across the Pacific Northwest. This will drive the heaviest precipitation from western Washington and northwestern Oregon into southwestern Oregon by early tomorrow. HREF guidance indicates that additional amounts of 2-3 inches are likely for portions of the region, especially in the southern Washington to Oregon Cascades, as well as the Oregon coastal ranges.=20 ....Southern Plains/Lower Mississippi Valley to the Upper Great Lakes... For the 01Z update, made some smaller-scale adjustments based on observation trends and the latest hi-res guidance, but the overall outlook remains the same. The greatest threat for heavy to excessive rainfall through the remainder of the evening into the overnight period is expected to center from the ArkLaTex region northward into southern Missouri. Deep southerly flow ahead of a highly-amplified trough will continue to usher ample moisture across the region. Recent runs of the RAP show 1.75-2 inch PWs coincident with a 50+ kt low level jet edging eastward across the region. This along with large-scale ascent afforded in part by strong upper forcing will help to support the continuation of south-to-north training storms and the threat for heavy accumulations. Neighborhood probabilities from the 18Z HREF indicate that localized additional amounts of 2-3 inches are likely within this area this evening into the overnight. The heavy rainfall threat is forecast to wane as the line of convection starts to become more progressive during the early morning hours. Pereira Day 2 Valid 12Z Sat Nov 05 2022 - 12Z Sun Nov 06 2022 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF THE LOWER MISSISSIPPI/TENNESSEE VALLEY... Convection ongoing at the start of the period will gradually move eastward across portions of the Lower Mississippi River Valley. The forcing associated with the storm system is expected to weaken during the period as the surface low lifts into the Great Lakes and the system is blocked by ridging off the Southeast. The diminishing forcing, lack of deep instability, and overall dry antecedent conditions will limit the potential flash flooding to areas mainly along the coast, perhaps northward into central MS/AL. Isolated rain rates over 1"/hr will be possible with a localized flash flood risk possible through about 18Z. Wegman/Taylor Day 3 Valid 12Z Sun Nov 06 2022 - 12Z Mon Nov 07 2022 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS COASTAL OREGON AND NORTHWESTERN CALIFORNIA... ....Coastal Oregon and Northwest California... A vertically stacked low sliding down the coast will bring another round of heavy rainfall to coastal OR and northwest CA on Sunday. The rainfall will be supported by a very active shortwave moving across the region in the upper levels. Further, the cold air behind the front will draw a large thermal gradient across the front, supporting greater low level lift. Since these areas have been catching the tail-end weakening phase of the atmospheric rivers hitting areas harder further north, this area should be able to handle the 1-3" of rain expected on Sunday, despite the recent wetter conditions. Snow levels will be dropping from 3,500 ft early in the day to near 2,000 feet Sunday night. The Marginal Risk was maintained for the coastal areas where isolated flooding issues may develop with this next atmospheric river event. Wegman/Taylor Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_MpZ4lXIUFNMBWjfytgaZ1kkBa3CaZh57VIMbvWMlVHD= x04JvaQP39Ig8fTILtcBxTQU7BYz_HAfq09klnH2CrStVS4$=20=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_MpZ4lXIUFNMBWjfytgaZ1kkBa3CaZh57VIMbvWMlVHD= x04JvaQP39Ig8fTILtcBxTQU7BYz_HAfq09klnH2uR10RYw$=20=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_MpZ4lXIUFNMBWjfytgaZ1kkBa3CaZh57VIMbvWMlVHD= x04JvaQP39Ig8fTILtcBxTQU7BYz_HAfq09klnH23nQonwI$=20=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) .