Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 072034

Area Forecast Discussion
National Weather Service San Diego CA
134 PM PDT Tue Apr 7 2020

A low pressure system southwest of Point Conception will move
slowly toward the southeast and east, finally moving eastward and
out of the area on Saturday. Periods of showers will continue
into Friday with a slight chance of thunderstorms this afternoon
and again Wednesday afternoon. Saturday through Monday will be
mostly dry and a little warmer.



Showers are becoming more widespread this afternoon as a weak wave
lifts north ahead of the upper level low, which is currently
centered off Point Conception. Rainfall rates are still low,
generally less than 0.10 in/hr, locally up to around 0.15 in/hr.
Weak instability developing later this afternoon will help
generate locally heavier showers. A slight chance of
thunderstorms remains in the forecast for this afternoon, though
no lightning has been detected yet.

Showers should decrease in coverage and intensity for most of the
forecast area tonight as instability decreases. However, a band of
moderate precipitation is forecast to develop over the deserts
tonight into Wednesday morning. 12Z models trended slightly
southwestward with this feature, moving it into our forecast area,
so confidence has increased that we will see widespread rain in
the deserts tonight.

The upper level low finally moves over the area on Wednesday. The
colder air near the center of the storm will bring snow levels
down to 4500-5000 ft. Greater instability is expected, especially
during the afternoon, increasing the threat of thunderstorms and
isolated heavy showers. Moisture decreases significantly which
will help limit rainfall rates.

This low pressure system will remain centered over the
southwestern states for Thursday and Friday before weakening and
moving off to the east on Saturday. Wrap around moisture could
bring another period of moderate rain and snow to portions of San
Bernardino County on Thursday, with generally light to moderate
showers elsewhere. Showers will decrease on Friday, ending by
Saturday as the low finally moves east.

The lowest high temperatures are expected on Wednesday and
Thursday with high temperatures for some inland areas 20 to 25
degrees below average. There will be a warming trend for Friday
through Monday but with high temperatures remaining below average.


071530Z...Coast/Valleys/Mountains...Occasional -SHRA will continue
today and tonight with variable cigs 1000-3500 feet MSL, occasional
vis 1-4SM with higher terrain obscured at times. Lowest cigs/vis
during SHRA or +RA, as well as during isolated brief TSRA during the
afternoon. -SHSN will occur in the mountains mainly above 5500 feet
MSL. The rainy and snowy pattern will continue into tomorrow.

Deserts...BKN skies around 5000-1000 FT MSL with areas of -SHRA at
times. Best chances this afternoon and tonight where some ceilings
could fall to below 4000 feet MSL, and local vis could fall to 3-


There is a slight chance of thunderstorms, mainly during this
afternoon and Wednesday afternoon. Otherwise, no hazardous marine
weather is expected through Saturday.




Through Friday, additional rainfall is expected to range from
around 0.60-1.25 inches near the immediate coast to 1-1.5 inches
in the valleys, locally up to 2 inches near the foothills of the
San Bernardino Mountains. 1.5 to 3.5 inches is forecast for the
mountains, 1 to 1.5 inches across the high deserts, and one half
to one inch in the lower deserts. There is also a slight chance of
thunderstorms this afternoon and Wednesday afternoon.

A snow level near 6000 to 6500 feet this afternoon will lower to
4500 to 5000 feet for late tonight through Thursday morning, then
rise to 5000 to 5500 feet Thursday afternoon. In the mountains of
San Bernardino and Riverside Counties, additional snowfall of 3
to 6 inches is expected from 4500 to 5500 feet, 6 to 12 inches
from 5500 to 6500 feet, 12 to 24 inches from 6500 to 7500 feet,
with greater than 24 inches on the highest peaks. In San Diego
County, 3 to 6 inches is possible above 5500 ft, and 1-3 inches
at 5000 ft.


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


CA...Flash Flood Watch through Wednesday evening for Apple and
     Lucerne Valleys-Coachella Valley-Orange County Coastal
     Areas-Orange County Inland Areas-Riverside County Mountains-
     San Bernardino County Mountains-San Bernardino and
     Riverside County Valleys-The Inland Empire-San Diego County
     Coastal Areas-San Diego County Deserts-San Diego County
     Mountains-San Diego County Valleys-San Gorgonio Pass Near
     Banning-Santa Ana Mountains and Foothills.

     Winter Storm Warning until 5 AM PDT Friday for Riverside County
     Mountains-San Bernardino County Mountains.



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