AIR POLLUTION
CONTROL DISTRICT

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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.

April 28 2016
Be Advised
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
BRIEF DISCUSSION FROM THE PHOENIX OFFICE
Very transient pattern still in place over the entire CONUS with upper level features only staying in residence across the West for 1-2 days before shifting East of the region. This goes for both positive and negative height anomalies shortwave ridges and troughing. Shower and thunderstorm activity is continuing across Southern NV and portions of Northern AZ this early morning enhances along the latest VORT max intrusion and ML OMEGA pocket traveling along with an UL low anchored over the Sierra/Eastern NV. Skies across much of the CWA were clear at time of writing with some CU fields along the Northern CWA boundary and over the higher terrain East of Phoenix. Initial UL jet intrusion and vort lobe passage through late morning may support some light shower activity across Northern portions of La Paz and Maricopa counties with even some ACCAS and VIRGA/sprinkles over the Phoenix metro in the am. Hi-res models support the idea of light showers and maybe an isolated thundershower in the early AM before the main vort band and jet streak begin to sink South of the area by the afternoon. Breezy conditions from the West will return today but not to the tune of speeds we saw earlier in the week. Cooler temperatures will result again after yesterday's 80s with high temperatures cooling 5 to 10 degrees or so. Main CIRC center will clear into the four corners overnight with a few trailing short waves that could gen up an additional round of CU/light showers/sprinkles by the late afternoon/evening across Central AZ. Rainfall amounts throughout our CWA will be on the light side generally less than 0.05 inches. Friday will find the forecast area under subsident Northwesterly flow as the latest low exits into the plains with another system quick on its heels for Saturday.

SYNOPSIS FROM THE PHOENIX OFFICE
Another area of low pressure will dip into the area today with more breezy conditions and a slight chance of showers and a few thunderstorms most significant over the higher terrain North and East of Phoenix this afternoon. More seasonably warm weather will return for Saturday before yet another weather disturbance impacts the region Saturday night into Sunday. High pressure will return by the middle of next week supporting warming temperatures and clearing skies.

BRIEF DISCUSSION FROM THE SAN DIEGO OFFICE
A low pressure trough has dropped into Southern California this morning. Lots of showers have developed in San Bernardino County, including the high desert, mountains, and even Northern Inland Empire. Amounts are generally less than a tenth inch, but a couple gages have shown heavier. Elsewhere: Isolated trace amount in sprinkles or light showers. We expect the showers to take a somewhat inland track during the day most likely in the mountains and coastal foothills. Just enough instability develops this afternoon for a slight chance of thunderstorms, but just barely. Winds have been strong with gusts exceeding 45 mph at several stations along the mountain/desert transition zone in Riverside and San Diego county. The winds will decrease this morning, but hang on rather brisk, although not advisory strength, through the evening. Snow will stay above about 6500 feet and will not amount to much. The trough moves out tonight. Friday and Saturday will feature a deep marine layer propped up by a coastal eddy with some clouds in the coastal basin during the nights and mornings. The next low pressure trough drops down from the north Saturday. This one has limited moisture like our current system. There are lots of similarities with the precip chance, amount, and distribution. Most places will record none, but some convective showers could produce briefly heavy rain and there is a slight chance of thunderstorms Saturday afternoon. That trough slowly moves out on Sunday. A ridge of high pressure builds Monday and Tuesday ahead of a digging trough over the ocean. That will bring much warmer weather and above average temps. Confidence is still low, but growing, that the Pacific trough will grab some moisture from the South and move showers into Southern California around Thursday and Friday.

SYNOPSIS FROM THE SAN DIEGO OFFICE
Low pressure aloft will bring some showers and a slight chance of thunderstorms to the region today, most likely in and near the mountains. Strong gusty winds in the mountains and deserts will decrease today. Fair weather will return Friday before another system from the North Saturday brings a slight chance of showers or thunderstorms Saturday afternoon through Sunday afternoon. Fair and warmer weather will arrive Monday and Tuesday under high pressure
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