Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 221658
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
900 AM PST Wed Nov 22 2017

.SYNOPSIS...
High pressure aloft near the West Coast combined with weak
offshore lower level flow will bring record setting heat through
Thanksgiving. High pressure aloft will begin to weaken on Friday
with cooling beginning to spread inland. Onshore lower level flow
will strengthen for Sunday and Monday with greater cooling and
stronger and gusty west winds in the mountains and deserts.
Moderate strength Santa Ana winds and warming may follow for next
Tuesday.

&&

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

The forecast for record heat is on track today record highs in many
areas. 8 AM temperatures were running several degrees higher than 24
hour ago, especially where the offshore winds were keeping the
atmosphere well mixed. Campo was 76 degrees with east winds 21G31
mph. Miramar was 82(!) with east winds at 5 mph. The warmth reached
all the way to the coast where some sites were exceptionally warm
including La Jolla Scripps with a report of 76F and northeast winds
at 3 mph.

Pressure gradients were more strongly offshore this morning (-12.0)
compared to yesterday (-9.7), resulting in stronger northeast winds
in the mountains and passes. Sill Hill, typically the windiest
location in the county, peaked at 58 mph at 7:30 AM. Fremont
Canyon hit 50 mph and Pleasants Peak reached 47 mph.

*From Previous Discussion*

High pressure aloft anchored along the West Coast will begin to
slowly weaken on Thanksgiving and Friday. That high pressure aloft
combined with weak offshore lower level will bring well above
average high temperatures with high temperatures in the deserts
around 15 degrees above average today with high temperatures for
inland coastal and western valley areas around 25 degrees above
average today. This will push high temperatures for some inland
coastal and western valley areas to around 95 and locally into the
upper 90s with high temperatures a few degrees cooler towards the
coast on Thanksgiving. Slow cooling will begin to spread inland on
Friday.

&&

.LONG TERM (Saturday through Tuesday)...
High pressure aloft will continue to weaken during the weekend
with onshore lower level flow strengthening for Sunday and Monday.
This will bring greater cooling for Sunday and Monday with
stronger and gusty southwest to west winds for the mountains and
deserts.

As the low pressure system continues to move inland...high
pressure aloft will strengthen along the West Coast and surface
high pressure over the Great Basin will strengthen. Warming
combined with a very dry air mass will bring much lower inland
humidities. The surface high pressure over the Great Basin could
bring more widespread moderate strength Santa Ana winds with
critical fire weather conditions for Tuesday into Wednesday though
with weaker winds on Wednesday.

&&

.AVIATION...
221605Z...NE to E winds through mountain passes/canyons and into the
coastal foothills/slopes gusting to 25-35 kt will create areas of
moderate-strong uddfs/llws over and W/SW of the mountains through
2100 UTC. However, llws not expected at any TAF sites. Winds will
weaken for late today through Thursday morning. Otherwise, FEW
clouds AOA 20000 ft MSL and P6SM vis through Thursday morning.

&&

.MARINE...
No hazardous marine weather is expected through Sunday.

&&

.FIRE WEATHER...
Elevated Fire Weather concerns today and tomorrow in the mountains
and passes with northeast winds 15 to 25 mph gusting to 50 mph and
low inland humidities of 8 to 12 percent. Continued very warm on
Thanksgiving Day with lowest humidities of 10 to 15 percent with
winds from 10 to 20 mph with gusts to 40 mph.

Stronger Santa Ana winds and lower inland humidities are possible
for Tuesday of next week with more widespread critical fire weather
conditions possible.

&&

.CLIMATE...
Forecast high temperatures that could be near or exceed existing
record high temperatures through Thanksgiving...

For today...
Location       Forecast       Current Record
Newport Beach     81              81 in 2002
San Diego         88              84 in 2015
Vista             93              86 in 2015
Chula Vista       95              88 in 2015
Riverside         95              90 in 1924
Escondido         96              91 in 1950
El Cajon          98              92 in 2002
Ramona            92              85 in 2015
Alpine            89              88 in 2005
Big Bear Lake     69              65 in 1995
Idyllwild         78              73 in 2002
Palomar Mountain  78              74 in 2007
Campo             84              84 in 2002
Palm Springs      92              93 in 1933
Thermal           92              93 in 1950
Borrego Springs   90              87 in 2002


For Thanksgiving...
Location       Forecast       Current Record
San Diego         85              86 in 1950
Vista             88              83 in 1975
Chula Vista       90              87 in 1924
Riverside         92              91 in 1995
Escondido         92              90 in 1949
El Cajon          94              86 in 1995
Ramona            92              89 in 1995
Alpine            89              86 in 1995
Big Bear Lake     69              68 in 1981
Idyllwild         75              75 in 1954
Palomar Mountain  76              75 in 1954
Campo             87              82 in 1995
Palm Springs      92              94 in 1950
Thermal           90              93 in 1950
Borrego Springs   89              88 in 1989

There will likely also be some record warm minimum temperature
records set...and a few additional high temperature records tied
or broken on Friday.

&&

.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/CLIMATE...Moede/17
AVIATION/MARINE...Harrison


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