Scientific Forecaster Discussion
Area forecast discussion
National Weather Service San Francisco Bay area
301 am PDT Monday Mar 10 2014
Synopsis...a weak cold front will spread light rain across the
North Bay this morning and down to portions of the San Francisco
Bay region. After it passes, dry weather will return for the rest
of the week. Daytime temperatures will slowly warm starting
tomorrow with much above Norma reading slated for the weekend.
Discussion...as of 3:00 am PDT Monday...kmux radar has indicated
minor echos tonight across parts of the North Bay, however to
this point virtually none of it is reaching the ground. In fact,
Bodega Bay is the only spot with measurable rainfall in our County Warning Area --
just 0.02". Latest sweeps do show an increase in returns off the coast,
so still fee fairly confident that at least the North Bay will end
up seeing rainfall into the morning hours as a cold front races
across our area.
Bigger question is whether or not the rain will make it as far
south as sf Bay and the city of San Francisco or if this will end
up being a North Bay event. Latest NAM guidance has trended a bit
drier and more to the north, and based on the limited returns so
far the morning forecast reflects less rainfall for all areas with
mostly dry conditions now anticipated south of San Mateo County.
Not out of the question that the city or parts of the East Bay
could pick up a stray shower today, so decided to leave a chance
of rain for that area through the morning hours. Quantitative precipitation forecast was scaled
back for all spots, so only 1/3" at the most is forecast for North
Bay mountains, with generally 1/10"-1/4" possible for North Bay
communities. For locations to the south less than a few hundredths
can be expected. Only commuting issues would likely be for roads
through the North Bay for those with early morning drives.
Just as quickly as the storm arrives, it will exit our area and
head off to the east by this evening. Behind it a surface ridge
of high pressure will build in from the north helping to boost
offshore winds. Higher elevation spots for the north and East Bay
could easily see gusts in the 20-30 miles per hour which will lead to
elevated fire weather concerns. The winds will slowly dissipate on
Tuesday as the gradient weakens.
Temperatures will slowly increase through the week to the first
part of next week as an upper level ridge of high pressure will
move back to our area while 850 mb temperatures jump back to the 16-18c
range (which would put them in the 95-99th percentile for march).
This will lead to very nice conditions for next weekend --
possibly a few records could be set on Sunday. Case in point is
Pinnacles which has a record high of 91 for the date. If the European model (ecmwf)
verifies, we will be close to that value.
Dry weather will hold through at least the first half of next
week. The ridge is forecast to start to break down by the middle
of next week which could finally allow a system to work its way
into our area as we approach the last full week of March.
Aviation...as of 10:30 PM PDT Sunday...front is moving very
slowly as there is still no sign of low clouds. When the front
finally does arrive there should be low level moisture associated
with it producing MVFR ceilings. Any rain will be spotty and confined
to a sfo-Oak line north.
Vicinity of ksfo...MVFR after 12z with some light rain possible.
Ksfo bridge approach...same as sfo.
Monterey Bay area terminals...MVFR ceilings after 12z clearing 17-18z.
... Arena to pt Reyes 0-10 nm from 9 am
Small Craft Advisory...pt Reyes to Pigeon pt 0-10 nm from 9 am
Small Craft Advisory...Pigeon pt to pt pinos 0-10 nm from 9 am
Small Craft Advisory...pt pinos to pt Piedras Blancas 0-10 nm from 9 am
Small Craft Advisory...Pigeon pt to pt pinos 10-60 nm from 9 am
Small Craft Advisory...pt pinos to pt Piedras Blancas 10-60 nm from 9 am
Small Craft Advisory...pt Arena to pt Reyes 10-60 nm from 9 am
Small Craft Advisory...pt Reyes to Pigeon pt 10-60 nm from 9 am
Public forecast: Bell
aviation: west pi
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