799
FXUS66 KSGX 261629
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
929 AM PDT Thu Sep 26 2024

.SYNOPSIS...
There will be slow warming through Saturday, slight cooling on
Sunday, then warming for Monday and Tuesday followed by gradual
cooling for the latter half of next week. Saturday is expected to
be the warmest day for the deserts with Tuesday of next week the
warmest day for the coast and valleys. Night and morning coastal
low clouds will continue to spread inland into portions of the
western valleys late each night. A cooling trend is expected for
the latter half of next week.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

.Morning Update...
Clear skies were seen this morning for much of the Inland Empire
into the mountains and deserts. Low clouds covered the western
valleys and coastal areas, with partial clearing over the water.
We`re practically going to rinse and repeat from yesterday`s
weather to today. Temperatures will be a touch warmer as high
pressure centered over New Mexico pushes slightly westward, with
another hot day in the Coachella Valley as temperatures climb near
110 degrees. As the high moves closer to our region, the marine
layer will thin a bit leading to a greater chance for fog
development across coastal valleys Friday and Saturday mornings.
Otherwise, no major forecast changes with warmer temperatures by
early next week with subtle cooling thereafter.

.Previous Discussion (343 AM Thursday)...

.SHORT TERM (Today through Saturday)...
There will be a warming trend through Saturday with the greater
warming for the coast and valleys today and with the warming for
the mountains and deserts mostly on Friday and Saturday. With the
warming, high temperatures on Saturday will range from a few
degrees below average near the coast to 10 to 15 degrees above
average, mostly in the 90s for the inland valleys and 108 to 114
for the lower deserts.

The Excessive Heat Warning will continue for the lower deserts
for Friday and Saturday. Night and morning coastal low clouds will
continue to spread into the western valleys late each night.
Through Saturday, high temperatures for a few locations each day
could be near record levels for the lower deserts. Yesterday, Palm
Springs tied the existing record high temperature of 114 set in
1947 with that high of 114 exceeding the 99th percentile of the
NBM.

&&

.LONG TERM (Sunday through Wednesday)...
A weak low pressure system is expected to move to near the
California coast on Sunday with not much change in high temperatures
for the coast and western valleys with the mountains and deserts a
few degrees cooler. Low pressure will weaken across southern
California on Monday and Tuesday with a warming trend with high
temperatures on Tuesday ranging from a few degrees above average
near the coast to 12 to 18 degrees above average for the mountains
and deserts. High temperatures on Tuesday will range from the mid
70s near the coast to the mid 90s to 102 for the inland valleys with
108 to 114 for the lower deserts.

By Friday of next week, there are large differences among the
deterministic runs of the ECMWF, GFS, and Canadian models with
the placement and amplitude of a low pressure system across the
eastern Pacific and West Coast, however with cluster analysis
showing a similar distribution of solutions for the ensemble
members of each ensemble system. While a cooling trend is expected
for the latter half of next week, there is greater spread with
the timing and amount of the cooling.

&&

.AVIATION...
260930Z...Coasts/Valleys...Low clouds have made their way into
western inland valleys this morning, with bases at 800-1200 ft MSL
and tops to 1300-1600 ft MSL. Isold vis reduced 0-5SM on higher
coastal terrain and in valleys. Scatter out through 19Z this morning
with improving vis, but with only partial or intermittent clearing
at the immediate coast in San Diego County. Low clouds will
redevelop and push inland after 00Z in San Diego County and after
06Z in Orange County tonight, extending not as far into valleys
overnight into Friday. Bases/vis will be slightly lower, scattering
out again 17-19Z Fri.

Mountains/Deserts...Clear today and tonight.

&&

.MARINE...No hazardous marine conditions are expected through
Monday.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning from 10 AM Friday to 8 PM PDT Saturday
     for Coachella Valley-San Diego County Deserts.

PZ...None.

&&

$$

PUBLIC...APR/17
AVIATION/MARINE...CSP/MM