Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 241543
Area Forecast Discussion
National Weather Service San Diego CA
742 AM PST Fri Feb 24 2017
Continued dry and cool through Saturday with patchy frost possible
in the valleys again Saturday morning. For Sunday and Monday...
cooler with periods of rain and snow showers as a pair of low
pressure systems moves south along the Coast. High pressure aloft
and weak offshore flow will bring dry and warmer weather again
Wednesday through Friday with periods of weak offshore flow.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Skies were mostly clear across SoCal this morning, except for a few
high clouds. It was a chilly start to the day with little cloud
cover and light winds. Temperatures fell to near freezing in some
valley areas this morning. The Miramar sounding had a 5 degree C
inversion based near 4500 FT MSL and indicated a very dry atmosphere
with a PW of only 0.33 inch. Surface pressure gradients from the
coast to the deserts were nearly neutral at 7 AM PST. This has
resulted in mostly light winds across the forecast area.
Look for a slow increase in high clouds on Saturday, and a few
degrees warmer after a chilly start, with possible frost again in
the valleys. No forecast changes this morning
From previous discussion...
A low pressure system will move southward along the central
California coast on Saturday night and move inland across Southern
California on Sunday. The current forecast leans towards the
ECMWF...but confidence remains low on the timing and amounts of any
precipitation. Based on the ECMWF timing...some lighter
precipitation could reach areas bordering Los Angeles County late
Saturday night with generally light to possibly locally moderate
precipiation moving through southwest California on Sunday. A second
low pressure system moving southward along the West Coast could
bring another round of light to possibly moderate precipitation late
Sunday night into Monday.
Confidence is low with the timing and amounts of any precipitation,
but rainfall could range from around one-quarter inch near the
coast, to one-half to three-quarters of an inch in the mountains
through early Tuesday, with local amounts exceeding one inch on the
south slopes of the San Bernardino County mountains. The most
widespread precipiation is expected for Sunday...and again for late
Sunday night into Monday morning. Snow levels will lower to around
5000 feet on Sunday...and 4000 to 4500 feet on Monday.
In addition to any precipitation...these low pressure systems are
expected to bring cooling with gusty west to northwest winds in
the mountains and deserts. Periods of advisory strength winds are
possible near the mountain ridge tops onto the desert slopes of
the mountains for Saturday night into early Sunday...and again
Sunday night into Monday morning. Some showers could linger into
Slight warming for Tuesday...then greater warming for Wednesday
through Friday with periods of mostly weak offshore flow.
241540Z...P6SM vis through Saturday morning. FEW-SCT clouds AOA
20000 ft msl becoming SCT-BKN by 25/1200 UTC.
Another storm may bring a period of showers and gusty winds sometime
Sunday and Monday, but confidence in timing and expected impacts
remains low at this time.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.