FOUS30 KWBC 030014 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 714 PM EST Fri Jan 2 2026 Day 1 Valid 01Z Sat Jan 03 2026 - 12Z Sat Jan 03 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL CALIFORNIA COAST NORTHWARD INTO NORTHERN CALIFORNIA... 01Z Update... The 18Z HREF guidance supports the idea that few changes...if any...are needed to the Marginal Risk area for the central California coast northward. The upper trough/front...shown by satellite imagery to still be offshore this evening...has gotten close enough to bring the first showers to northern California. Increasing coverage of rainfall and an increase in rainfall rates is expcted this evening and tonight as the trough/front continues moving eastward. Some localized runoff issues will be possible overnight and early Saturday morning given moderate to locally heavy rainfall rates (isolated 0.50+"/hour) and the moist/wet antecedent conditions. Bann 0830Z Excessive Rainfall Discussion... No major model disagreements with the eastward push of the strong mid to upper level low off the northern California coast day 1. The low level southerly flow will strengthen Friday along and ahead of the associated frontal boundary pushing toward the central to northern California coast. While PW values are only 1 to 1.5 standard deviations above the mean, the 850-700 mb moisture flux values are more anomalous, 2-3+ standard deviations above the mean. Precip should increase in intensity along the northern CA coast after 0000 UTC Sat, and spread south into coastal central CA in the 0600-1200 UTC time frame. The frontal boundary is expected to be fairly progressive, limiting very heavy rainfall totals. HREF and RRFS neighborhood probabilities for .50"+ hourly amounts are generally less than 30%, with a few localized 60%+ probabilities along the central CA coast range to the south of Monterey, and across the northern Sierra. Areal average 1 to 1.5" amounts expected along the central to northern CA coast and 1.5-2" in the northern Sierra with isolated heavier totals of 2.5-3"+ possible. No significant changes made to the previous marginal risk, with localized runoff issues possible where soils remain fairly saturated from recent rains, especially across northern CA. Oravec Day 2 Valid 12Z Sat Jan 03 2026 - 12Z Sun Jan 04 2026 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE NORTHERN SIERRA AND SOUTHERN CALIFORNIA... 19z Update: Only minor changes made with this update. The 12z high res models continue to depict a band of heavy rainfall moving southward across the Transverse Range between 12z Sat and 00z Sun. Most high res members depict localized hourly rainfall upwards of 0.5"-1", which should be enough to result in isolated to scattered flash flooding. Chenard ...Previous Discussion... The axis of anomalous 850-700 mb moisture flux values...2 to 4 standard deviations above the mean...along and ahead of the inland moving frontal boundary at the end of the day 1 period will impact the upslope areas of the northern Sierra and spread through the Transverse Ranges of Southern California day 2. The primary change from the previous outlook was to add a small slight risk area in the upslope area of the Northern Sierra. HREF neighborhood probabilities for .50"+ hourly rainfall amounts are fairly high...50%+ at the beginning of the day 2 period and again in the 2100 UTC Sat to 0000 UTC Sun period. This will result in day 2 rainfall totals of 2-4"+ in a region of fairly saturated soils from recent heavy rains. No changes of note made to the previous slight risk area over Southern CA in the vicinity of the Transverse Range. The south southwesterly low level flow will have a significant upslope component into the Transverse Ranges during the first half of day 2. This is reflected in both the HREF and RRFS .50"+ hourly probabilities which are high, 50-80%+ during this period. Localized runoff issues are possible where soils remain fairly saturated from recent heavy rains. Oravec Day 3 Valid 12Z Sun Jan 04 2026 - 12Z Mon Jan 05 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ALONG THE CALIFORNIA COAST AND IN THE UPSLOPE OF THE SIERRA... 19z Update: Minimal changes needed to the inherited Marginal risk. Gave some consideration to carrying over the the day 2 Northern Sierra Slight risk into day 3 as periods of heavy rainfall will continue into Sunday. However, snow levels will drop a bit and thus at this point any Slight risk area would probably be too narrow to depict. Either way, some flood impacts are likely to continue into Sunday across the Marginal risk area. Chenard ...Previous Discussion... Additional shortwave energy expected to rotate through the mean trof position along the West coast and inland across California day 3. This will support a continued wet showery pattern with additional moderate to locally heavy precip totals along much of the California coast Ranges and into the upslope of the Sierra. A broad marginal risk area was maintained from the previous outlook this period with changes mostly to better fit the latest model and WPC qpf. The slight risk area over Southern California in the vicinity of the Transverse Range was removed given consensus of additional moderate totals. Oravec Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt