Area forecast discussion
National Weather Service San Francisco Bay area
923 am PDT Thursday may 23 2013
Discussion...as of 9:00 am PDT Thursday...partly cloudy to mostly
cloudy skies were present through parts of the southern half of
the region. Moderate north to northwest winds were present over
the area overnight...with wind gusts to 20 miles per hour common.
Otherwise...with mostly clear skies and a cool mass...overnight low
temperatures fell into the upper 30s to 40s...around 5 degrees
below normal for the end of may. A few spots in southern Monterey
and San Benito counties actually cooled to near freezing...with
Fort Hunter ligget in southern Monterey County dipping to 33
degrees.
Otherwise...current forecast looks right on track. The main focus
of the forecast will continue to be the possibility of rain for
the area on Memorial Day.
Previous discussion...as of 2:38 am PDT Thursday...as previously
stated a low pressure system is centered over the Pacific
northwest this morning. Another low pressure system is apparent on
the current satellite water vapour image entering the Bering Sea.
Both the 0000z GFS and European model (ecmwf) have initialized well with these
features pushing the Pacific northwest low northeast into Canada
Saturday. Both models continue to depict a cool troughy pattern
over our forecast area through the weekend. Both models then
introduce a new trough of low pressure moving towards the West
Coast Monday bringing a possibility of rain to northern portions
of the forecast area by late Monday morning. At this point it
looks like rain will arrive to the North Bay area late Monday
morning spreading south to San Francisco by late afternoon and
Monterey by early evening. Keep in mind that this forecast is
still several days out and the timing of the rain may change by
Monday. By middle week the forecast models are depicting a dirty
ridge scenario which will result in cool onshore flow and possibly
a shower or two through the end of the work week.
&&
Aviation...as of 4:44 am PDT Thursday...for 12z tafs. Gusty west
winds to continue to impact most terminals again today but overall
wind speeds forecast to be lighter than previous days. Early
morning satellite shows low clouds impacting Monterey Bay region
and the San Mateo coast as well as the East Bay/Santa Clara Valley
hills. Low clouds are piling up along the hills in brisk onshore
flow. Good news is there is no well defined inversion layer and
not expecting ceilings to impact Bay area terminals with any ceilings
banked up against the hills expected to mix out quickly this
morning. Low clouds over kmry and ksns early this morning will mix
out by 16z.
Vicinity of ksfo...few-sct clouds nearby early this morning but
not expected to impact terminal. Gusty west winds currently
gusting to 30 knots will subside for a time this morning before
increasing again this afternoon.
Ksfo bridge approach...VFR...a few clouds may pass over the
approach but no ceilings expected. Similar to ksfo but lighter winds.
Monterey Bay area terminals...sct-bkn ceilings at 1500-2000 feet
through 16z Thursday...then clearing. Gusty west winds this
afternoon and evening.
&&
Mtr watches/warnings/advisories...
... Arena to pt Reyes 0-10 nm
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm
Small Craft Advisory...pt Arena to Pigeon pt 10-60 nm
Small Craft Advisory...Pigeon pt to pt Piedras Blancas 10-60 nm
Small Craft Advisory...sf Bay from 1 PM
Small Craft Advisory...mry Bay from 1 PM
&&
$$
Public forecast: Riley/Larry
aviation/marine: rww
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