National Weather Service Forecast Discussion

Dicussion provided by the National Weather Service Forecast Office located in San Diego, California

000
FXUS66 KSGX 242044
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
144 PM PDT Thu Sep 24 2020

.SYNOPSIS...
Seasonal weather will continue through Saturday, with areas of
night and morning low clouds along the coast and into some western
valleys. High pressure aloft will strengthen Sunday and continue
most of next week and bring hot weather to the region. On Sunday,
locally gusty northeast to east winds will occur over the
mountains and into some of the valleys, especially in San Diego
and Riverside Counties. Low humidity will continue over inland
areas for at least the next week.

&&

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

At 1 PM, skies were mostly clear across SoCal. Temperatures were
at or near where they were at this time yesterday. Low clouds will
redevelop later this evening and overnight, covering most coastal
areas by daybreak.

Fair weather will continue through Saturday, with temperatures
within a few degrees of normal for Friday and Saturday. A trough
of low pressure to the north will strengthen onshore flow and
deepen the marine layer through Saturday. Low clouds will be
mainly confined to coastal areas, but could reach into portions of
the western valleys. Clouds will become more patchy Sunday
through much of next week as high pressure builds into the region.

The big story for the next week is the upcoming heat and dry
conditions. High pressure will begin to strengthen and expand
across the West on Sunday and continue through at least the middle
part of next week. Northeast to east winds will develop over the
mountains and foothills Sunday through Monday morning, with gusts
of 20 to 30 mph. Some locally higher gusts are possible in the
windiest locations. Relative humidity will plummet in the deserts,
mountains and portions of the inland valleys on Sunday, with
minimum daytime humidity of 10 to 15 percent for much of next
week. The heat will begin to build in on Sunday, peaking Tuesday
and Wednesday, with temperatures 10 to 15 degrees above normal for
most locations away from the coast. Coastal areas will still have
somewhat of a marine influence, but temperatures should be around
5 to 10 degrees above normal.

Some differences exist between models and their ensembles on the
placement and strength of the high for the end of next
week. Temperatures may cool a few degrees late next week,
depending on the placement of the high, but still remaining above
normal through all of next week.


&&

.AVIATION...
242100Z...Coast/Western Valleys...Low clouds to develop after 03z
Fri across southern San Diego County and will spread northward
through coastal Orange County early Friday morning. Bases 500-800 FT
MSL. Patchy dense fog with VIS 1-4 miles where clouds interact with
terrain. Low clouds and fog to dissipate 15-17z Fri.

Elsewhere...Mostly clear tonight and Friday.

&&

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

&&

.FIRE WEATHER...
Lowest daytime humidity in the deserts and the desert mountain
slopes will fall to 10 to 15 percent each day through Saturday.
Combined with the west to southwest winds locally gusting around
25 to 30 mph, there likely will be a few hours of elevated fire
weather conditions in the deserts onto the desert slopes of the
mountains each day from mid afternoon through early evening.

High pressure over the western states will bring significant
warming for Sunday through at least the middle part of next week
with high temperatures 10 to 15 degrees above normal. Humidity
will fall to 10 to 15 percent each day in the mountains, deserts,
parts of the Inland Empire and far inland San Diego County
valleys. Gusty northeast to east winds will occur Sunday through
Monday morning in the mountains and far inland valleys, with
gusts mostly 30 mph or less, but higher gusts are possible in the
windiest locations. The combination of low humidity and gusty
winds will result in near critical fire weather conditions Sunday
and again Monday, mainly in the mountains. Elevated fire weather
conditions will exist for most of next week, due to the hot
temperatures and low relative humidity.

&&

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


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&

$$

PUBLIC/FIRE WEATHER...Connolly
AVIATION/MARINE...PG/Schenk

NWS SGX Office Area Forecast Discussion