fxus66 kmtr 241537
afdmtr
area forecast discussion
national weather service san francisco ca
900 am pdt tue jun 24 2003
the warming and drying trend is beginning over the district on or
even a little ahead of schedule. stratus has disappeared from the
coast though there is still some offshore s of mry bay. n to ne
winds are beginning to develop in the e bay hills but speeds are
mostly 20 mph or less below 2500 ft. on the other hand...gusts have
already reached 50 mph atop mt diablo at 3800 ft. surface pressure
gradients at 8 am include 6 mb acv-sfo...1.4 mb sfo-sac...2.3 mb
offshore wmc-sfo...and 0.5 mb s-n smx-sfo. all these gradients are
currently trending more n-s and offshore.
as is usually the case the main forecast challenge the next few days
will be coastal max temps. this is not forecast to be a really
strong offshore event. the new eta forecasts 12z wmc-sfo gradients
to remain moderate...around 8 mb the next 2 days. we need numbers
above 10 mb to really set up a strong offshore event. and the model
develops aftn seabreezes each day...with wed being the weakest with
only 1.4 mb sfo-sac at 00z. the current forecast tops coastal temps
in the 70s while sending inland readings into the 90s and lower 100s
and this looks ok for now.
on the other hand...yda mrngs mesoeta left stratus in along the
coast this mrng...it underestimated the strength and speed of the
development of the offshore flow. if that error continues the coast
could sneak one hot day into this week...probably wed when the
offshore flow is forecast to reach its greatest strength and
southward extent with the mesoeta bringing very dry air to the coast
as far s as pt sal at 15z wed. the current forecast has monterey and
san francisco topping out around 80 on wed but if the eta is
overdoing the aftn seabreeze its not impossible that the actual
observing sites in those two cities...which are both a short distance
inland...could top out at 90.
the hottest air this week will be over the district on thu...but by
that aftn the mesoeta forecasts a much stronger onshore gradient to
develop than on wed aftn and if the model is on the right track
coastal temps should be cooler than on wed due to an earlier...
stronger seabreeze. however...inland sites should be a little
warmer on thu than on wed. after that the models forecast a
pronounced cooling trend...probably beginning with a southerly surge
of stratus up the coast thu night/fri and continuing with an upper
trof replacing the ridge as a strong onshore flow redevelops over
the weekend. by early next week the gfs indicates temps back well
below normal...similar to the past few days. so...it looks like a
dynamic week of weather ahead. pops zero. markkanen
.sfo...tda...glw...pt arena to pigeon pt.
sca...pigeon pt to pt piedras blancas and sfo bay.
$$
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