14/758 PM.
An unusually strong storm system will bring widespread rain to the area through Sunday. The heaviest rain will fall late tonight through early Saturday afternoon. During the peak of the event isolated strong thunderstorms will bring a moderate risk of flash flooding, debris flows, and damaging winds. The stormy pattern will continue and periods of rain are possible through late next week.
(tdy-Mon), 15/906 AM.
***UPDATE***
Significant early season storm will continue to affect much of the region into tonight. Periods of moderate to heavy rain which moved in earlier this morning will continue to affect the area. Widespread urban flooding along with debris flows in and around recent burn areas will persist. A slight chance to chance of thunderstorms is also possible especially this afternoon.
Pay close attention to the latest warnings and statements throughout the day. Easiest way to stay abreast of the situation is to monitor NOAA Weather Radio or go to our web site at www.weather.gov/losangeles.
***From Previous Discussion***
, MODERATE TO HIGH RISK OF DANGEROUS FLASH FLOODING, DEBRIS FLOWS, AND DAMAGING WINDS THROUGH TONIGHT,
The storm has shifted into the 2nd phase as Friday's cold front has exited the area. Phase 2 involves an upper low that is currently 250 miles to the SW of KLAX. A low level jet riding up the east side of the has added plenty of energy and has even produced a baroclinic leaf. PWs in this plume of mositure are near 1.4 inches (about 1 inch greater than normal). Lgt-mdt rain is currently falling over most of the area. this will all change around dawn. A well formed vort lobe with some embedded lightning is riding up the east side of the low. This vort lobe will kick the storm up a couple notches and the rain will become moderate with pockets of heavy rain. There will be enough lift and instability to bring a chc of TSTMs. While there is enough twist in the lower atmosphere to allow any TSTM that forms to produce severe weather or even a weak tornado, the real threat from any convection will be the rainfall rates which will be close to 1 inch per hour. These rainfall rates on top of the already saturated grounds will could well produce flash flooding anywhere. The recent burn areas, of course, will be most vulnerable to flash flooding and debris flows. A flash flood watch is in effect for all of the area.
Areas north of Point Conception will not be immune from this system as the vorticity moves to the NW and into and over the area.
Most mdls show a marked decrease in rainfall this afternoon but a few mdls do not let the rain up and there is a 30 percent chc that moderate rainfall could continue well into the afternoon.
Additional rainfall through this afternoon will likely range from 1.5 to 2 inches for the csts/vlys south of Pt Conception and 2 to 4 locally 5 inches for the coastal slopes. The interior sections and areas north Pt Conception should see around an inch to an inch a quarter. Snow levels will remain above 7500 ft and snow will not be a factor with this storm.
This is a dangerous situation and all residents of LA/VTA and eastern SBA counties are urged to monitor this storm closely and follow the directions of all emergency personnel.
The low will linger in the area overnight. The cold core will bring enough instability to continue the chance of showers and perhaps an isolated TSTM. There will not be that much dynamics so the shower activity will be much less organized. Rainfall amounts will be less homogeneous but will likely range from a quarter inch to an inch. Some showers may have rainfall rates a little over a half inch per hour.
There is a fair amount of disagreement on the evolution of the upper low Sunday with most solutions shoving the upper harmlessly to the east. 30 percent or so of the solutions, however, still show the low close enough to bring some rain. So the Sunday forecast calls for partly to cloudy skies with a 30 to 40 percent chc of rain. This forecast may be a little on the pessimistic side.
Sunday evening and into Monday a colder upper low scoots down the west coast and into the state. A chance of rain will develop across the Central Coast after midnight and the rain will likely sweep over the area during the day. This is a colder system and it will not hold nearly as much water as today's storm. Rainfall totals from early Monday morning through Monday evening will likely range from .75 to 1.5 inches with local 2 inch amounts in the mtns. This is a colder system and snow levels will lower from 7000 ft to 6000 ft by evening.
As with almost all rain events this late in the year max temps across the csts and vlys will be in upper 50s to mid 60s all three days or 6 to 12 degrees blo normal.
(Tue-Fri), 15/256 AM.
Rain will taper off and end on Tuesday as the upper low pushes off to the south and east. The Central will likely be dry. Any additional rainfall will be light, under a quarter inch. Max temps should rise a few degrees, but will still be below normal with csts and vlys only reaching the mid 60s.
A little pop up ridge should bring one complete day of dry weather on Wednesday. Max temps will rise a few more degrees, but highs will remain many degrees blo normal.
Another system is slated to affect the state on Thursday and Friday. Since the storm is so far out in time, there is considerable disagreement on the exact timing and intensity of this system. Best to wait a little bit before talking about specifics and just realize that it could be wet couple of days.
15/1720z.
At 1700Z at KLAX, there was no marine layer. There was a deep moist layer up to at least 10000 feet.
Overall, low confidence in 18Z TAF package. With periods of moderate to heavy rain through this evening, CIGs and VSBys will bounce from MVFR to LIFR levels at all sites. Overnight, the rain is expected to decrease in intensity, but CIGs and VSBYs will likely remain in the MVFR to IFR levels.
KLAX, Low confidence in 18Z TAF. CIGs and VSBYs will bounce between MVFR and LIFR levels through this evening, and between MVFR and IFR overnight. East-southeast winds around 8 knot are expected to develop in the 21Z-00Z time frame, but there is a 50% chance that winds will not shift to the east to southeast.
KBUR, Low confidence in 18Z TAF. CIGs and VSBYs will bounce between MVFR and LIFR levels through this evening, and between MVFR and IFR overnight.
15/852 AM.
There is a 20-30% chance of thunderstorms across the coastal waters south of Point Conception through tonight. Any thunderstorms that develop will be capable of producing brief heavy rain, small hail, dangerous cloud to surface lightning, gusty and erratic winds, locally rough seas, and possible waterspouts.
For the Outer Waters, moderate confidence in the winds forecast through today, otherwise moderate to high confidence in the forecast. Some Small Craft Advisory (SCA) level seas this morning will slowly subsiding through this afternoon, with a 20% chance of SCA level SW-W winds. On Sunday, winds and seas are expected to be below advisory levels. For Sunday night through Tuesday, high confidence in SCA level seas with a 30-40% chance of SCA level winds. For Wednesday, high confidence in winds and seas remaining below SCA levels.
For the Inner Waters north of Point Sal, seas near SCA levels can be expected thru this afternoon but should remain below these levels. On Sunday, high confidence in winds and seas remaining below SCA levels. For Monday through Tuesday, high confidence in SCA level seas with a 30-40% chance of SCA level winds on Monday. For Tuesday through Wednesday, high confidence in winds and seas remaining below SCA levels.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Conds should be below SCA levels through this evening except for a 30% chance of SCA wind gusts at times this afternoon and early evening. For tonight through Sunday, high confidence in winds and seas remaining below SCA levels. On Monday, there is a 60-80% chance of SCA level winds across all the southern Inner Waters. For Tuesday through Wednesday, high confidence in winds and seas remaining below SCA levels.
15/1213 AM.
A moderately long period west-northwest swell will bring hazardous surf conditions to portions of Southwest California today into at least this afternoon. In addition to the west- northwest swell, a storm system will continue to bring gusty southerly winds which will add a southerly wind swell component to the surf. HIGH SURF ADVISORIES remain in effect for the Central Coast, the Ventura County Beaches, the L.A. County Beaches, as well as a Beach Hazards Statement for the Santa Barbara South Coast. Please refer to the LAXCFWLOX and LAXSRFLOX for details.
There is a 20-30% chance that HIGH SURF ADVISORIES may be needed for the LA county beaches today and tonight.
Additionally, there is a 20-30% chance of thunderstorms across all the beaches at times from late this afternoon through Saturday night. Any thunderstorms that form will be capable of producing locally strong winds, small hail, dangerous lightning, heavy rainfall, and possibly even a weak/brief tornado.
Ca, Flood Watch remains in effect through this evening for zones 87-88-346>358-362-366>383-548>550. (See LAXFFALOX). High Surf Advisory in effect until 3 PM PST this afternoon for zones 340-346-354-362-366. (See LAXCFWLOX). Beach Hazards Statement in effect until 3 PM PST this afternoon for zones 349-350. (See LAXCFWLOX). PZ, NONE.
