Old Advisory Events
The information herein is NOT intended for use as a weather forecast. The Air District DOES NOT forecast but solely compiles information from both the Phoenix and San Diego National Weather Offices to relay information concerning potential changes in ambient air concentrations that may impact the public.
| December 22 2016
|High wind levels have the potential to suspend particulate matter into the air. High levels of PM10 may pose an impact to public health. It is recommended that active children and adults, and people with respiratory disease, such as asthma, limit their outdoor activities.
Potential increases in PM10 concentrations may increase to moderate or unhealthy level.
|Imperial County Weather Synopsis
|Winter Storm will impact holiday travel Friday night through Saturday night
SYNOPSIS FROM THE SAN DIEGO OFFICE
An upper level low will move slowly east along the US-Mexico border today. Showers and a few thunderstorms will taper off this afternoon and evening. There will still be a threat of heavy rain this morning. Friday will be a mainly dry day, then a major winter storm will drop into SoCal from the northwest on Friday night with widespread rain, a few thunderstorms, and heavy snow in the mountains. Travel will be hazardous in the mountains on Saturday and Christmas Eve due to slick roads and areas of snow. Christmas Day into early next week is expected to be slightly warmer and dry.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...
The cutoff upper low has begun to accelerate to the east early this morning. Positioned just SW of San Diego ATTM, it will begin to move ENE during the day today near the US-Mexico border. Heavy subtropical moisture (PWAT 1.00-1.25") continues this morning and heavy showers will continue at times, mainly focused over San Diego County. There will also be a slight chance of thunderstorms mainly this morning and early afternoon and mainly in San Diego County which will be closest to the destabilized northern periphery of the upper low track.
Showers will taper off by this evening. On Friday there could be some drizzle west of the mountains due to persistent moisture in the low levels, and mostly cloudy west of the mountains, some filtered sun in the deserts Friday.
Winds will pickup ahead of a strong cold front Friday afternoon. S to SW winds will become strong in the mountains and a bit gusty near the coast too Friday afternoon. The cold front will approach Orange County Friday evening, and sweep across the region through Saturday morning. Very heavy frontal precipitation right along and just behind the front. Strong frontogenetical forcing will bring the risk of isolated thunderstorms Friday night into Saturday morning. Heavy precip short duration will bring a risk of flash flooding in the mountains and urbanized flooding in the lower elevations.
Cold air will arrive immediately behind the front, bringing snow levels crashing from 8000 feet Friday evening down to 4000 to 5000 feet Saturday morning. Precip will turn showery on Saturday and additional vort lobes rotating through the region through Saturday night will continue the shower activity. The snow showers could contain heavy bursts of snow which could drop a quick inch or two of snow, which would have the potential to cause travel havoc on the busy travel corridors. CAA continues through Saturday evening, bringing snow down to the busy pass level, and possibly even a skiff of snow down into the higher terrain of the high desert of San Bernardino around 3000 feet Christmas Eve.
Transitory ridging Sunday into Monday with dry but cool weather conditions. Another cutoff low could form off the Baja coast around Tuesday and Wednesday next week which could bring another round of precipitation and unsettled weather to our region.
SYNOPSIS FROM THE PHOENIX OFFICE
Numerous showers will redevelop through today as a weather system continues moving through the region. A break in the unsettled weather will occur tonight and Friday as the first system moves to the east. A second weather system will move through region Saturday leading to another round of rain, mountain snow, windy conditions, and much cooler temperatures. Conditions will slowly dry by Sunday with temperatures lingering slightly cooler than average early next week.
|Weather Story Phoenix Station
||Weather Story San Diego Station
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