Radar — KNKX
Surface Analysis — Western U.S. (South)
Satellite
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Nearest monitored road: West Broadway (Secondary)
Below average temperatures will continue through friday. Conditions will warm over the weekend, with a brief cooling trend early in the week. Conditions will warm for the middle of next week, returning to around average by next wednesday. Night and morning low clouds and fog will reach well into the valley again tonight into thursday, becoming shallower over the weekend.
For extreme southwestern california including orange... San diego...western riverside and southwestern san bernardino counties...
The marine layer was around 3500 ft deep this morning, with low clouds filling in the coastal basin. Visible satellite from this morning even showed low clouds through the cajon pass. At 11 AM, satellite was still showing patchy low clouds along the coast and portions of the western valleys. The marine layer is expected to stay a similar depth tonight, with similar inland extent expected. The marine layer will become shallower for friday into the weekend with night and morning coastal low clouds not spreading inland past the far western valleys.
Weak troughing will gradually move east into the great basin by this weekend. That will result in below cooler conditions through thursday, with a gradual warming friday through sunday as weak transient ridging builds over the west coast. The warming will be most noticeable for inland locations. Even with the warming daytime highs, overnight lows will continue to cool off helping overnight relief from the heat.
Another trough of low pressure is expected to move west across southern california monday which will bring a few degrees of cooling and deepen the marine layer again. By the middle of next week, there starts to be some spread in the upper level pattern. Nbm guidance has an 8 degree difference between the 75th (warmer end of solutions) and 25th (cooler end of solutions) percentile temperatures for the inland valleys. The current forecast follows the nbm which has temperatures within a few degrees of average for most locations.
161745Z...coast/valleys...sct-bkn clouds 3000-4500 ft msl will continue to scatter out of coastal/W valley areas through about 20Z this morning. Low clouds around 2500-3000 feet msl will move ashore after 02Z and again fill most of the coastal basin overnight into thursday morning. These will again generally rise above 3000 ft msl towards 16-17Z, then scatter out 17-20Z thu.
Mountains/deserts...mostly clear and VFR conditions today and tonight.
No hazardous marine conditions are expected through sunday.
Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions.