Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Diego California
250 am PST Tuesday Dec 10 2013
strong offshore pressure gradients will continue to bring gusty east
to northeast winds through and below passes and canyons this
morning. The winds will weaken by late morning...but locally gusty
offshore winds will continue at times through Thursday. The
cold...dry air will result in overnight temperatures near freezing in
wind sheltered portions of the valleys...lower deserts...and even
near the coast. Variable high clouds moving in from the southwest
will continue into Wednesday morning. There will be a warming
trend through Thursday...then a little cooler on Friday...followed
by more warming for the weekend into early next week.
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Surface pressure gradients gradients remain strongly offshore this
morning with -10.8 mb san-tph and -4.7 mb san-trm. This continues
to bring strong and gusty NE to east winds in the mountains...inland
valleys and portions of Orange County. Many locations are
reporting win gusts in the 30-40 miles per hour range and one location
continues to report gusts near 60 miles per hour. Satellite imagery shows
high clouds moving across the region from the SW...associated with
an upper level closed low about 550 miles to the SW. The presence
of the high clouds along with the gusty winds are likely
responsible for temperatures in some areas being several degrees higher
than this time Monday morning. This could result in fewer areas of
frost west of the mountains this morning.
Offshore pressure gradients will begin to weaken this afternoon
and continue to do so through Thursday as the surface high over the Great
Basin weakens and retreats to the north. As a result...the
offshore winds will decrease later today through Thursday.
However...periods of locally gusty NE to east winds will continue. At
the same time...the closed low to our SW will open up and be
pulled into the prevailing westerly flow as a vigorous trough
moves into the Pacific northwest...breaking down the upper ridge to our northwest. As
the cold...dry airmass slowly modifies and winds weaken...areas of
frost will be possible west of the mountains again early this morning
and Wednesday morning. Daytime temperatures will also gradually increase
through Thursday. The upper trough moving inland to the NE will bring
weak onshore flow and somewhat lower temperatures on Friday.
For the weekend through early next week...daytime temperatures again
increase and offshore flow returns as the upper trough moves
east...an upper ridge builds in from the west and another surface
high moves into the Great Basin.
101000z...sct-bkn clouds at or above 15000 feet above sea level and unrestricted visible
will continue through tonight. Areas of northeast winds 15-25 kts
with local gusts to 45 kts in foothills with moderate-strong uddfs/low level wind shear over
the mountains and adjacent coastal foothills this morning...weakening
during the day.
widespread low humidities and gusty offshore winds will continue
this morning...but recent rainfall and low temperatures will limit
the wildfire threat. For Wednesday through Friday...humidities
will increase a little and the offshore winds will weaken then
turn onshore briefly on Friday. Periods of gusty offshore winds
will return for the weekend into early next week.
California...Wind Advisory until 10 am PST this morning for the Coachella
Valley...Riverside County mountains.
High Wind Warning until 10 am PST this morning for the Orange
County coastal areas...San Bernardino County mountains...
San Bernardino and Riverside County valleys-the inland
Empire...San Diego County mountains...San Diego County
valleys...Santa Ana Mountains and foothills.
Frost advisory until 9 am PST this morning for the Coachella
Valley...San Bernardino and Riverside County valleys-the
inland Empire...San Diego County coastal areas...San Diego
County deserts...San Diego County valleys.