Scattered showers will continue today, becoming less widespread and weaker in the afternoon. A weaker storm will move through the area Monday afternoon into Wednesday morning, bringing another chance of rain showers and mountain snow. An additional storm system will approach the region by next Thursday and Friday, but forecast details remain uncertain.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Scattered showers continue across the region this morning. For the most part rainfall rates are below 0.15"/hr, but isolated heavier showers have been producing rates closer to 0.30-0.50"/hr. Expect this activity to continue through early this afternoon, then becoming more isolated and weaker for the remainder of the afternoon into tonight. Latest hi-res models aren't showing much of a break in these isolated showers before the next system moves in, but given how isolated they are, most places should have at least a several hour break in precipitation. Additional precipitation through Monday morning will range from around 0.10-0.50" for the coasts/valleys, 0.20-0.80" in the mountains, and 0.10" or less in the deserts. Snow levels will fall to around 6500 ft this morning, though less than an inch of snow is expected at those elevations. Snow levels rise back to around 7000 ft during the afternoon. Otherwise chilly today with high temperatures around 10-20 degrees below normal and breezy southwest to west winds in the mountains and deserts.
While ensembles are in generally good agreement with the progression of the next closed upper low, small deviations in the track are resulting in continued spread in rainfall amounts. The NBM 48 hr totals (4 AM Mon-4 AM Wed) still has a difference of around 0.6-0.8 inch between the 25th percentile and 75th percentile. Mean totals for this 48 hour period are around 0.60-1" for the coasts and valleys, and around 1-1.25" in the mountains, though it is notoriously underdone for orographic precipitation. Current forecast is close to the NBM mean, though with amounts closer to 1.5-1.8" along the coastal mountain slopes. Totals in the high desert are around 0.15-0.40", and around 0.10-0.30" in the low deserts. This storm will have far less moisture associated with it (PW peaking around 1" and IVT near 250 kg/m/s), so rainfall rates will be lower, reducing the threat of flash floods and debris flows. Street flooding will be an issue once again. Precipitation will taper off through the day Wednesday. Snow levels will be much lower with this storm, falling as low as 5000-5500 ft Tuesday morning and only rising slightly to 5500-6000 ft during the day. Around 1-2" of snow is possible at the 6000-6500 ft level, 2-4" at 6500-7500 ft level, and as much as 10-12" on the highest peaks of the San Bernardino Mountains (above 9000 ft).
Another brief dry period occurs Wednesday evening through Thursday morning. Ensemble solutions for the next closed low late in the week vary wildly. Around 22% of the members track the low too far north and east to bring any precipitation here, another 23% swing the low way off the coast, delaying the onset of precipitation until later Friday into Saturday, and the remainder falling somewhere in between. The current resultant range in storm totals is anywhere from 0 to almost an inch. The track of the low will also have implications on snow levels. Will have to wait and see how the details shake out, but there is at least a 40% chance for precipitation sometime late in the week.
161030z, Scattered -SHRA/SHRA currently moving over the region west of the mountains from the southwest to northeast will continue through most of the period. SCT-BKN clouds 3000-5000 ft MSL form the prevailing CIG tonight, but bases will lower to 1500-2500 ft MSL under SHRA along with VIS to 2-5 SM. Some terrain obscurations with VIS 0-3 SM where clouds intersect terrain along the coastal foothills. After 20Z, -SHRA becomes more isolated, though continuing through the evening.
Scattered showers over the waters will occasionally bring winds to 15-20 kts and locally choppy seas through early morning. Northwest winds strengthen again Monday afternoon ahead of the next storm system, possibly bringing gusts to 20-25 knots through Tuesday morning, along with another round of precipitation.
An incoming storm system will lead to elevated surf late Monday into Tuesday, likely to 4 to 6 feet with local sets to 7 feet.
Ca, None. PZ, None.
