Strengthening high pressure aloft will bring a warming trend with a long-duration heat wave likely for this weekend through much of next week into the following weekend. The highest HeatRisk is expected for the coast and valleys with widespread Moderate or greater HeatRisk for the coast and valleys for Friday through next week with widespread Major to Extreme HeatRisk for the weekend into next week for inland coastal areas into the western valleys.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Tonight through Thursday,
A ridge is building back in over the region as the upper level low that was positioned over Arizona continues to propagate eastward. This is going to allow for the positively-tilted ridge to continue to expand back towards the northeast. This will result in temperatures gradually increasing through Thursday. Gusty northerly winds will continue to diminish as the low pulls away, but remain gusty each afternoon through tomorrow, especially within the San Gorgonio Pass. For tonight, there will be a little better onshore flow this evening, which will allow for the marine layer to likely set in a little sooner and also fill in better into the inland areas. Ceilings will begin to lower a bit throughout the night, and there may also be some areas of patchy fog along the I-15 corridor again, as there was this morning. For tomorrow, highs will be around 10 to 15 degrees above the seasonal average, and relative humidities will still be relatively higher at night, and therefore nights will still be close to average.
Friday through Wednesday,
By Friday, the ridge is going to continue to strengthen to heights of 590 dm over the region, which is going to cause temperatures to max out generally around 15 to 20 degrees above the seasonal average. This, in combination with increasing RH values, which will not allow for radiational cooling to cool temperatures as much, will produce conditions that may be impactful for those sensitive to those vulnerable to heat, especially for those along the coastal areas that do not have AC units. For this reason, an Extreme Heat Watch has been issued for the coastal and inland valleys from Friday through the mid part of next week. Temperatures are going to become even hotter for this upcoming weekend, and on Sunday there will be easterly winds as the position of the high slides further south over the desert southwest by Sunday. These offshore winds will likely result in highs being even further warmer to the coast. These gusty easterly downsloping winds will also reduce RH values down into the 15-25% range for the inland areas and elevate fire concerns. As the ridge remains locked in place going into the mid part of next week, so will the heat, and there will not be much relief from this looking into the foreseeable future until the
301800z, Coast/western valleys: SKC and VFR through this afternoon. Patchy low clouds based 700-1200 ft MSL return to coastal areas starting 01-02z Thu. Clouds become more uniform in coverage after 06z and push 10-15 miles inland overnight. Areas of minor vis reductions (1-5SM) expected for elevated coastal terrain and western valleys (I-15 corridor). Clouds scatter back toward the coast 15-16z.
Otherwise, clear skies today and tonight.
No hazardous marine conditions are expected through Sunday.
High tides will peak at 6.8-7.1 feet between 11 AM and 1 PM today, leading to minor coastal flooding in low-lying areas and coastal erosion. A Coastal Flood Advisory is in effect through this afternoon.
Please note: mentioned tide predictions in the Advisory have been adjusted to reflect actual measured tide observations.
Ca, Coastal Flood Advisory until 5 PM PDT this afternoon for Orange County Coastal Areas-San Diego County Coastal Areas.
Extreme Heat Watch from Friday morning through Wednesday evening for Orange County Coastal Areas-Orange County Inland Areas- San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Coastal Areas-San Diego County Valleys-Santa Ana Mountains and Foothills.
PZ, None.
