Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Mar 16 2025 20:43:33 AWUS01 KWNH 162043 FFGMPD CAZ000-ORZ000-170730- Mesoscale Precipitation Discussion 0073 NWS Weather Prediction Center College Park MD 442 PM EDT Sun Mar 16 2025 Areas affected...Southwest Oregon...Northern California... Concerning...Heavy rainfall Valid 162045Z - 170730Z SUMMARY...Flooding risk reducing as cyclone makes landfall and warm conveyor belt presses quickly southward to intersect coastal range and northern Sierra Nevada Foothills with heavy rainfall. DISCUSSION...Southwest Oregon has been experiencing prolonged moderate rainfall for over 24hrs at this point with large areas of 4"+ totals across much of the area of Coos, Douglas, Josephine and northern Jackson counties and spots in the boreal rain forests of Curry county in the 8-10" ranges. Longer duration flooding has been going in atypical locations with the prolonged heavy rainfall. The strong onshore moisture flux will be ending in the next hour or so, but a strong surface wave can be seen with a secondary one further west along an old occluded front. Steeper lapse rates due to CAA aloft and some modest retention of moisture along the boundary may allow for some scattered shower activity to cross SW OR along the occluded front into the stationary front that crosses into central OR. Rates up to .25-.33"/hr are possible but will be more scattered in nature and may result in those ranges of totals in a sub-hourly manner. This is not likely to further contribute to enhanced flooding, but will slow its ending for a few more hours.=20=20 Further south...GOES-W Visible imagery shows the cold front and more directed atmospheric river/warm conveyor belt has started a southward progression. The core of .75-.9" total PWat continues to be advected from strong 40-50kt 850mb winds allowing for IVT values to remain at 650-700 kg/m/s near the triple point that is near the OR/CA coastline and southeastward. Upper-level height-falls will continue to support increasing south and eastward propagation of the cold front and therefore onshore/upslope moisture flux. Occasional rates of .33-.5"/hr are possible especially along the steepest inclines of the northern Sierra Nevada foothills, but duration of moderate rainfall is likely to be limited to a few hours and likely only result in spotty totals of 1.5-3" in traditional locations in Butte, Tamaha and Yuba counties. Coastal Ranges are more likely to see 1.5-2.5", reducing to .75-1.5" by the time the plume further weakens (wind speeds down to below 35kts) and IVT values fall below 400 kg/m/s...nearing the mouth of San Francisco Bay between 03-06z. A secondary weaker band of scattered showers will wrap around the surface low as it translates east and affects the NW California after 00z as well, adding another .5-.75" for the totals. Bringing the overall event to close in the early morning hours tonight. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5nnx9kBXfO4owThSuTG3TcFLcpoLPpnuE59scDkR7fjNIfb7IZmLoD24j9WynYUVfjKv= xqr-e-TbeJ15Le6vVwyrdY8$ for graphic product... ATTN...WFO...EKA...MFR...MTR...STO... ATTN...RFC...CNRFC...NWRFC...NWC... LAT...LON 43762376 43402333 42922284 42092262 41122202=20 39922140 39382078 38672050 38392087 38572132=20 39852189 40562243 39762260 38632211 38022277=20 38442338 39022398 39812419 40592462 41122434=20 41812430 42392466 42882466 43412443 43742423=20 =20=20=20=20=20=20=20=20=20=20=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .