Plaincast

Synopsis

Hotter than normal conditions will continue for the foreseeable future, generally hottest through Sunday. Slightly cooler Monday through Thursday, with heat increasing again Friday and Saturday. The hot daytime and warm night conditions will bring elevated risks of heat-related illness.

Short Term

An influx of mid-to-upper level moisture is pushing into southern California from Mexico. This moisture will bring partly to mostly cloudy conditions at times today to Los Angeles, Ventura, and Santa Barbara Counties. Any time there is an influx like this, the chances for some light showers lifts above 0%. The atmosphere is fairly stable however. There are some mesoscale sources of lift as some weak disturbances rotate through, but they are light. As a result, there is a 5-15% chance for some fat-drop light showers and a remote (0-5%) chance of a mostly dry thunderstorm. These chances peak in the mountains and deserts this afternoon and evening. Will continue to monitor for any changes.

Overall, latest models in good synoptic agreement through the short term period. At upper levels, high pressure centered near the 4 Corners will slowly wobble eastward through the period. At the surface, moderate onshore flow will continue to the east with weak to moderate northwesterly flow at times.

Forecast-wise, main issue in the short term will continue to be the heat. Highs today topped out in the mid 90s to 104 across the valleys and interior sections. Given the synoptic pattern, will expect H5 heights and thicknesses to slowly decrease through Tuesday. So, Sunday will likely be the warmest day with a bit of cooling for most areas Monday and Tuesday. With warm overnight low temperatures, conditions will remain rather uncomfortable. Heat Risk grids indicate moderate to high heat risk will continue through Monday. So, current suite of HEAT ADVISORIES, as well as the EXTREME HEAT WARNING for the Antelope Valley, are looking good through Monday evening.

Secondary concern for the short term will be winds, specifically Sundowner winds across southern Santa Barbara county. Based on high resolution data, northerly offshore pressure gradients peak Sunday evening and again Monday evening (SBA-SMX gradients forecast to be -3.7 mb). So, there will be some gusty northerly winds across the Santa Ynez Range, especially the western half, and Wind Advisories may be needed, beginning tomorrow.

Given the hot temperatures, as well as low surface humidity and gusty winds, there will be elevated to potentially brief critical fire weather conditions across interior sections through the period. Any grass fires will likely spread very quickly. Additionally, mixing heights will be quite high. So, there will be the potential for some significant, plume-dominated, fire behavior if any fires ignite.

Long Term

High pressure aloft will continue to dominate through next weekend. Still expecting the slight drop in temperatures to continue through Thursday as the core of the high settles over New Mexico/Texas. The majority of ensemble projections then have the high strengthening some while sliding back towards California Friday through Saturday. Temperatures will likely creep back up 3 to 5 degrees overall. Heat Advisories are not out of the question, but also not a given based on the under performance of the current heat event. That warming will be focused mainly over the coastal areas as the onshore pressure gradients will likely change little.