Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Feb 02 2025 19:37:00 AWUS01 KWNH 021936 FFGMPD CAZ000-030700- Mesoscale Precipitation Discussion 0013 NWS Weather Prediction Center College Park MD 236 PM EST Sun Feb 02 2025 Areas affected...northern California Concerning...Heavy rainfall Valid 021935Z - 030700Z SUMMARY...Moderate to Heavy rain will continue over the northern Sierra Nevada throughout the next 6-12 hours while a second round of moderate to locally heavy rain develops for the northern Coastal Ranges this evening. While locally higher totals will be possible on an isolated basis, additional rainfall totals of 3 to 5 inches are expected for the northern Sierra Nevada into the southern Cascades and an additional 1 to 2 inches for the northern Coastal Ranges through 07Z. DISCUSSION...Eastern Pacific view of total precipitable water (PW) showed a relatively narrow axis of values greater than 1 inch extending from near the triple point of an occluded cyclone 36N 138W (which showed up well in visible satellite imagery), ENE to the northern CA coast. Gauge observations have shown peak hourly rainfall totals in the 18Z hour of 0.1 to 0.2 inches for the northern Coastal Ranges and 0.25 to locally in excess of 0.5 in/hr for the northern Sierra Nevada. 24 hour totals near 9 inches have been reported just east of Chico in the Sierra Nevada with up to roughly 4 inches for the northern Coastal Ranges. Reports of flooding thus far have been limited and primarily focused across southern portions of the region on either side of I-80 in the Sierra Nevada and between San Pablo Bay and Santa Rosa via local storm reports. Confluent mid-level flow between a mid-level low over southwestern Canada and a low amplitude longwave trough centered near 145W along with a ridge over the Baja Peninsula will keep zonal flow focused from the northern CA and OR coastline, eastward into the central U.S. through the overnight. At the surface, a shallow but well-defined stationary front, co-located with the moisture axis, will essentially remain in the same place over the next 6-12 hours (slow northward drift), with low level winds varying within the plume between 40-50 kt in the 850-700 mb layer. Some subtle strengthening of 850 mb winds will be possible toward 00Z ahead of the leading edge of a weak mid-level shortwave expected to near the West Coast at 00Z, but IVT values are forecast to remain in the 400-600 kg/m/s range through 06Z Monday across northern CA. No significant changes to peak rainfall rates are expected for northern CA through 06Z, but additional light to moderate rainfall (perhaps locally heavy) is expected into the northern Coastal Ranges later this evening with the approach of the offshore mid-level impulse. Additional peak rainfall totals of 1-2 inches for the Coastal Ranges and 3-5 inches for the northern Sierra Nevada are likely over the next 12 hours but given rainfall rates will remain somewhat modest, it is the long duration of this rainfall event that will be noteworthy. At least through 06Z tonight, additional flooding impacts are expected to remain isolated with rainfall rates remaining under more critical thresholds. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4n3AZcPfTSdqmNWbK_ffJ6tUgbACVgJ7QSgoq4mOymxc8QfMd6TnHX7t1gN3EeZjfQhd= wbRivGG_nTd2zxNA-mPbQZ4$ for graphic product... ATTN...WFO...EKA...MFR...MTR...REV...STO... ATTN...RFC...CNRFC...NWC... LAT...LON 41932111 41782055 41352037 41122043 40772058=20 40382047 39872026 39282015 38942034 38772068=20 38712095 38892118 39192143 39482163 39782182=20 40032213 40082244 39972271 39512264 39282247=20 38962222 38592215 38302216 38122234 38132269=20 38222311 38502358 38832386 39182406 39592417=20 40192451 40602421 40832377 40892338 40932300=20 41122267 41302234 41712170=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) .