Area Forecast Discussion
Issued by NWS San Diego, CA
FXUS66 KSGX 041709
Area Forecast Discussion
National Weather Service San Diego CA
908 AM PST Sun Dec 4 2016
Sunny and warmer weather today, will give way to increasing clouds
and cooler conditions on Monday as winds turn back onshore and the
marine layer builds. The moist layer may get deep enough for a few
light showers or some drizzle on Tuesday. Warming begins on
Wednesday and continues through the end of the week as winds turn
back offshore under fair skies.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
It was a clear and chilly morning across SoCal. At 7 AM PST, temps
west of the mts mostly ranged from the mid 30s to the mid 40s. It
was warmer along the coastal foothills, and where moderate NE winds
prevailed. Peak gusts in the 20 MPH range continued in offshore wind-
prone locations. The sfc pressure gradients were considerably weaker
this morning at about 6 MBS from SW NV to KSAN. Our Miramar sounding
had a 17 degree C temp at the top of the inversion near 1700 FT AGL
and moderate NE flow at 10-20 KTS above through 10K FT.
Given the weakening offshore pattern and clear skies, today is
shaping up to be very nice, with afternoon temperatures climbing
into the lower 70s most areas west of the mts/lower deserts, and
into the 60s elsewhere across the high deserts and mts. Not as cold
tonight as dewpoints recover and clouds develop.
The prevailing offshore pattern will be turning around later today
as the broad 1028 MB sfc high over the Great Basin collapses ahead
of a sagging Polar trough over the PacNW. A shortwave embedded in
the trough should guide it east across the Great Plains this week,
but it will be able to maintain onshore flow across SoCal through
Tue before cold sfc high pressure turns our flow back offshore for
the remainder of the week. Dry and mild Thu through Sun.
Clouds/Precip...High res model guidance suggests a return of coastal
low clouds and fog by early Monday morning as a coastal eddy
develops. As the marine layer builds, look for more extensive low
cloud cover, and there may even be a few light showers or some
patchy drizzle west of the mts on Tue/Tue night. At this time,
precip does not look significant.
Wind...The surface high building south over the Rockies is forecast
to reach 1040 MBS or more by 12Z Thu, but the sfc gradient is not
supported aloft. Given the current forecast position of the sfc high
and the lack of upper support, offshore winds do not look to be near
the strength of the event late last week.
Temperatures...Coldest days Tue/Wed this week with max temps from 2
to 8 degrees F below average. Warmest days today and Fri with temps
2 to 6 degrees F above average.
041700Z...Mostly clear skies and unrestricted vis will continue
through late tonight. Stratus/fog could return to the immediate
coast sometime in the 11Z-15Z Mon time frame and could impact KSAN
and KCRQ and possibly KSNA. Timing and heights of stratus are low
confidence, but ceilings could be 600 ft MSL or less before lifting
rapidly by late morning Monday. Visibilities of less than 3 miles
are also possible along the coast early Monday morning, with a
slight chance of dense fog with vis 1/4 mile or less.
No hazardous marine weather is expected through Thursday.
Winds continue to weaken this morning with peak gusts under 30 MPH.
Humidity recovery is poor near the foothills and inland valleys.
Warmer and dry today with widespread humidity in the teens, except
along the coast. However, winds will be much lighter today.
Conditions will improve further Monday and Tuesday as onshore flow
returns. Another round of gusty Northeast to East winds and very dry
conditions will develop late Wednesday morning and continue through
Thursday, weakening friday.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.