Area forecast discussion
National Weather Service San Francisco Bay area
158 PM PDT Thursday may 23 2013
Discussion...as of 1:58 PM PDT Thursday...breezy northwest winds
and slightly below normal temperatures were present across the
region this afternoon...as an upper level storm system remains
nearly stagnant over the Pacific northwest coast. Northerly wind
gusts around 20 miles per hour were common across the area...especially over
the higher elevations...as onshore gradients tightened.
Temperatures rose into the upper 50s to low 60s along the
coast...to the low 60s to 70 degrees inland. These temperatures
are similar to those observed yesterday at this time and about 5
degrees below normal for the end of may.
For tonight...temperatures are forecast to dip into the 40s.
Patchy stratus may develop along the Monterey Bay and San Mateo
coastline...however confidence is low and was left out of the
forecast. The short term models continue to indicate abundant
stratus tonight...but have missed the mark big time recently with
over forecasting clouds.
Otherwise...no major changes in the weather pattern through at
least Sunday afternoon...before the upper low over the Pacific
northwest finally moves slowly to the east. A storm
system...currently off the northern Aleutian Islands in Alaska...is
forecast to move southeast toward the Pacific northwest coast
Sunday night into Monday. This storm will bring a chance for rain
to the North Bay beginning Monday morning...with rain chances
increasing southward toward the Monterey Bay by the afternoon
hours. The medium range models have been in good agreement the
past 48 hours that the region will at least see some rain with
this storm...but have varied with the timing significantly. For
example...both the GFS and European model (ecmwf) indicated during the 12z model
runs yesterday...that the rain was going to primarily fall in the
North Bay on Tuesday. Now...those models show rain for the entire
area by Monday evening. If rain does impact the region...only
light accumulation...between a few hundredths to a couple of
tenths of accumulation is expected.
Please continue to monitor the forecast for the latest detailed
information about both timing and amount of rain associated with
this storm. As Memorial Day nears...confidence will
increase...especially with regards to timing.
Otherwise...unsettled weather will remain in the region through at
least Wednesday...before upper level zonal flow returns to the region.
&&
Aviation...as of 11:15 am PDT Thursday...interesting satellite
image with mostly clear skies at the coast and pockets of clouds
inland. Northerly gradient still twice the westerly values so
would expect dissipation to continue with VFR conditions this
afternoon and early evening in all spots. Still breezy this
afternoon with gusts over 25 knots possible in spots. For tonight the
big question is will clouds roll in and drop most places down to
MVFR levels. Models are split on the return to clouds and northerly
flow is still expected to be stronger than the flow from the west.
For now...will hedge toward climatology and bring in ceilings tonight.
Moderate confidence.
Vicinity of ksfo...gusty west to northwest winds through the day
with speeds up to 30 knots possible. 50-50 chance of clouds returning
tonight bringing ceilings down to MVFR levels. Moderate confidence.
Few-scattered 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...similar to ksfo but lighter winds.
Monterey Bay area terminals...clouds very slow to burn but should
go VFR for most of the afternoon into the early evening. MVFR ceilings
expected to return tonight. Westerly winds through the period with
gusts to 20 knots during the afternoon and early evening. Moderate
confidence.
&&
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 until 11 PM
Small Craft Advisory...mry Bay until 11 PM
&&
$$
Public forecast: Riley
aviation/marine: Bell
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