Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jan 14 2023 22:37:59 AWUS01 KWNH 142237 FFGMPD CAZ000-ORZ000-151035- Mesoscale Precipitation Discussion 0043 NWS Weather Prediction Center College Park MD 536 PM EST Sat Jan 14 2023 Areas affected...Southwest OR and Northwest CA Concerning...Heavy rainfall Valid 142235Z - 151035Z SUMMARY...Heavy showers will persist through this evening and into the overnight hours for the coastal ranges of southwest OR and northwest CA. DISCUSSION...While the main core of the latest West Coast atmospheric river will continue to advance well to the south and east over the next several hours, there will continue to be areas of heavy showers impacting the coastal ranges of southwest OR and northwest CA. The key driver of this will be the strong and deep area of low pressure offshore that will slowly move east-northeast through tonight. A strong west-southwest low-level jet of 40 to 50 kts will persist around the southern flank of this low center, and this coupled with relatively steep mid-level lapse rates associated with the nearby larger scale upper-level trough/closed low will promote persistent shower activity. The low-level flow will be largely orthogonal to the terrain, and this will promote enhanced orographic ascent over the coastal ranges that will further support heavy rainfall rates. In fact, the 12Z/18Z HREF and multiple runs of the HRRR continue to suggest elevated probabilities of seeing the rain rates approach and occasionally exceed a 0.50"/hour within the belt of strongest onshore flow. The persistence of this tonight is expected to yield some additional rainfall amounts of 2 to 4 inches with a few higher amounts close to 5 inches possible. While these coastal ranges are well known for their ability to efficiently handle large quantities of rainfall, the fact that streamflows are already elevated suggests that these additional totals may foster at least some localized runoff problems and areas of flooding. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4UqWueu224TuTrkEuD-PRH7L_Cc8nb7DsAWOCJOaGAWmdRTrtIHfcIPwDeRQSPQeFCxn= qyeLdVKM2dOVLuWaPaDnmBM$ for graphic product... ATTN...WFO...EKA...MFR... ATTN...RFC...CNRFC...NWRFC...NWC... LAT...LON 43132444 43082396 42642364 42222361 41722350=20 41272361 40942378 41092421 41582426 41882441=20 42662462=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) .