494
FXUS66 KSGX 251614
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
914 AM PDT Tue Jun 25 2024

.SYNOPSIS...
High temperatures will be cooler today for the coast and valleys
followed by more gradual cooling through Friday. Otherwise not
much change in high temperatures for the next week except for
Friday being slightly cooler. High temperatures near the coast
will be a few degrees above average to around 5 to 10 degrees
above average for the deserts. Moisture will be slowly drying for
the rest of the week, but there may still be enough residual
moisture for a slight chance of showers and thunderstorms this
afternoon for the San Bernardino Mountains north and northeastward
across the adjacent deserts. Night and morning coastal low clouds
may gradually return during the week.

&&

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

.Morning Update...
High pressure remains centered over the southwestern U.S., which
will lead to another day of southerly flow aloft over our region.
Mid and high level clouds are mostly surrounding our region this
morning from the San Joaquin valley out toward southern Arizona.
There is still plenty of moisture in place, with near 1.70" of
precipitable water via this morning`s weather balloon sounding.
This, along with the position of the high, will allow for one
more day with a notable chance of thunderstorms for the SBD
mountains into the high desert this afternoon and early evening.
As stated below, we will be on the edge of the action today,
though hi-res models do indicate a convergence boundary setting up
across those aforementioned locations leading to isolated storm
chances.

Otherwise, elsewhere looks relatively quiet and warm this week
with minimal day to day changes. The high will weaken slightly
this week, allowing the marine layer to deepen with night and
morning low clouds/fog west of the mountains.

.Previous Discussion (530 AM Tuesday)...

.SHORT TERM (Today through Thursday)...
There will be a gradual cooling trend for the coast and valleys
through Friday with high temperatures falling to around average.
For the deserts, only very slight cooling of high temperatures is
expected with greater cooling of low temperatures for Wednesday
through Saturday as gradual drying occurs.

Moisture is continuing to dry with a decrease in precipitable
water in the NKX sounding from 1.68 inch on early Monday morning
to 1.53 inch late Monday afternoon. There is once again a slight
chance of showers and thunderstorms for this afternoon with the
most likely location similar to Monday afternoon and early
evening, over the San Bernardino Mountains and toward the north
and northeast along a convergence boundary across the adjacent
desert areas.

With the moisture aloft, low clouds have once again been slow to
develop. However there are some areas of low clouds near the coast
of northern Baja with a few patches of low clouds off the San
Diego County coast. Coastal low clouds are expected to gradually
return over the next few nights as drying aloft continues.

&&

.LONG TERM (Friday through Monday)...
The gradual drying will continue into the weekend with NBM showing
the lowest surface dewpoints for the lower deserts this weekend.
While high temperatures for the deserts aren`t expected to change
much, the gradual cooling of very warm nights will slowly reduce
the daily Heat Risk, perhaps just enough to let the Excessive Heat
Warnings for the deserts expire after Thursday. In any event, the
relief from the heat for the deserts for Friday through the
weekend won`t be much. After warming on Sunday, there is growing
spread in the temperature guidance for the early and middle part
of next week for inland areas with the deterministic NBM toward
the warmer end of the guidance spectrum.

&&

.AVIATION...
251600Z...Coast/Valleys...Mostly clear skies with the exception of a
few high clouds will prevail through this afternoon. There`s a 50-60
percent chance of CIGS at the coastal airports after 08Z Wed with
bases around 1000-1500 ft MSL, locally down to 700 feet. Otherwise,
FEW-SCT clouds at/above 15,000 ft MSL and unrestricted VIS through
Wed morning. Any clouds that do develop at coastal TAF sites will
likely clear 16-18Z Wed.

Mountains/Deserts...There is a 15-20 percent chance of TSRA over the
San Bernardino Mountains north into the high desert this afternoon,
with CB bases near 12,000 ft MSL and tops to 25,000 ft MSL. Gusty
outflow winds and reduced VIS VCTY TSRA. Otherwise, FEW-SCT clouds
at/above 15,000 ft MSL and unrestricted VIS through Wed morning.

&&

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

&&

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


&&
.AVIATION...
251600Z...Coast/Valleys...Mostly clear skies with the exception of a
few high clouds will prevail through this afternoon. There`s a 50-60
percent chance of CIGS at the coastal airports after 08Z Wed with
bases around 1000-1500 ft MSL, locally down to 700 feet. Otherwise,
FEW-SCT clouds at/above 15,000 ft MSL and unrestricted VIS through
Wed morning. Any clouds that do develop at coastal TAF sites will
likely clear 16-18Z Wed.

Mountains/Deserts...There is a 15-20 percent chance of TSRA over the
San Bernardino Mountains north into the high desert this afternoon,
with CB bases near 12,000 ft MSL and tops to 25,000 ft MSL. Gusty
outflow winds and reduced VIS VCTY TSRA. Otherwise, FEW-SCT clouds
at/above 15,000 ft MSL and unrestricted VIS through Wed morning.

&&

.MARINE...
No hazardous marine conditions are expected through Saturday.
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Excessive Heat Warning until 8 PM PDT Thursday for Apple and
     Lucerne Valleys-Coachella Valley-San Diego County Deserts-
     San Gorgonio Pass Near Banning.

PZ...None.

&&

$$

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