Ation DISCUSSION,
Large-scale, mid-level troughing continues for the western U.S. through much of the work week, leading to afternoon temperatures as much as 10-15 degrees F below daily averages today. This persistent low pressure aloft is also leading to a deep marine cloud layer at 3500-4500 ft MSL. This morning, clouds reached to cover most of the coastal basin. So far (late this morning), clouds have been slow to clear out of coastal and north areas of the region, but this morning's inversion was shallow enough that clouds will clear for the most part for over-land areas.
As the week progresses, high pressure to the southeast will slowly flatten the trough out, leading to gradually warming temperatures through mid-next week. Despite that, temperatures will linger in the below-average range through Friday region-wide, with the deserts warming into the average to slightly above average zone by this weekend while valley regions are still about 5 degrees below average. By mid- next week the whole region will likely be in the typical temperature range (+/- about 5 degrees from average). This includes temperatures reaching around 100 degrees in the high desert and temperatures approaching or just exceeding 110 degrees in the low desert, resulting in moderate HeatRisk (impactful heat for sensitive communities) for the low deserts even with the seasonability of these temperatures.
Building heights overhead will also squish the marine layer down gradually through next week, with clouds lowering from 4000 feet or so tonight to 2000-3000 ft over the weekend, which means that clouds will move less far inland overnight and likely not linger as long in the mornings. Besides marine layer clouds, though, we're likely to see upper to mid level clouds moving into the region over the weekend, generated from moisture moving in from a distant tropical system which will otherwise likely have little effect on our weather locally. A minority of GFS ensemble members have some spotty light precipitation for late in the weekend and parts of next week, but National Blend of Models chances for precipitation (>= 0.01") are less than 5% for each day during the next seven days.
There will be a slow warming trend for the next week. High temperatures near the coast will warm a few degrees and inland areas will warm around 10 degrees over the next week. High temperatures for the deserts will warm to around average during the weekend and around 5 degrees above average for the middle of next week with the valleys still a few to around 5 degrees below average for early next week. The marine layer will gradually decrease in depth with night and morning low clouds not spreading as far into the valleys by next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
, UPDATED AVIATION DISCUSSION,
Large-scale, mid-level troughing continues for the western U.S. Through much of the work week, leading to afternoon temperatures as much as 10-15 degrees F below daily averages today. This persistent low pressure aloft is also leading to a deep marine cloud layer at 3500-4500 ft MSL. This morning, clouds reached to cover most of the coastal basin. So far (late this morning), clouds have been slow to clear out of coastal and north areas of the region, but this morning's inversion was shallow enough that clouds will clear for the most part for over-land areas.
As the week progresses, high pressure to the southeast will slowly flatten the trough out, leading to gradually warming temperatures through mid-next week. Despite that, temperatures will linger in the below-average range through Friday region-wide, with the deserts warming into the average to slightly above average zone by this weekend while valley regions are still about 5 degrees below average. By mid- next week the whole region will likely be in the typical temperature range (+/- about 5 degrees from average). This includes temperatures reaching around 100 degrees in the high desert and temperatures approaching or just exceeding 110 degrees in the low desert, resulting in moderate HeatRisk (impactful heat for sensitive communities) for the low deserts even with the seasonability of these temperatures.
Building heights overhead will also squish the marine layer down gradually through next week, with clouds lowering from 4000 feet or so tonight to 2000-3000 ft over the weekend, which means that clouds will move less far inland overnight and likely not linger as long in the mornings. Besides marine layer clouds, though, we're likely to see upper to mid level clouds moving into the region over the weekend, generated from moisture moving in from a distant tropical system which will otherwise likely have little effect on our weather locally. A minority of GFS ensemble members have some spotty light precipitation for late in the weekend and parts of next week, but National Blend of Models chances for precipitation (>= 0.01") are less than 5% for each day during the next seven days.
020015z. Coast/Valleys/Foothills, Low clouds based 1800-2500 ft MSL are clustered in patches along the North SD County coast. Cloud coverage is expected to increase throughout the SD County coast through 03z, expanding to inland areas and Orange County through 08z and filling into the Inland Empire 08-12z Thu. VIS 4-6SM for eastern Inland Empire valleys and eastern SD County valleys as bases lower down to 1500 ft MSL in spots through the coastal basin overnight. Scatter out to coast 15-18z Thu, then VFR conditions prevail through Thursday afternoon.
.Mountains/Deserts, W/SW winds gusting 20-30 kts along desert slopes this evening with isolated gusts up to 45kts in mountain passes. MOD up/downdrafts and LLWS over and east of the mountains will be possible. Low clouds moving in after 05Z will obscure terrain in clouds/fog on the coastal mountain slopes below 4500 ft MSL through Thursday morning. Otherwise, VFR conditions expected through the period.
No hazardous marine conditions are expected through Monday.
Ca, None. PZ, None.
