Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Sacramento California
331 PM PDT Wed Apr 16 2014

Synopsis...
breezy northerly winds will decrease in the valley this evening. A slight
chance of showers over the mountains Thursday afternoon into
Friday and possibly over the northern Sacramento Valley Thursday
evening. Temperatures above normal through Sunday then may cool to
near normal to below normal early next week due to an unsettled
weather pattern moving over the region. The best chance of showers over
interior northern California looks like Monday night into Tuesday
night along with a slight chance of thunderstorms in the valley
Tuesday.

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Short term discussion...
ridge of high pressure over the area today with mostly sunny
skies and continued above normal temperatures. Locally breezy and
gusty northerly winds will decrease this evening as the surface
pressure gradient weakens. Winds will turn southerly tonight with
an approaching trough. Temperatures this afternoon warmed up into
the low 80s in the valley and 60s to 70s in the mountains so far which
is about 10 to 15 degrees above normal for mid April.

The ridge of high pressure shifts to the east tonight and an upper
level trough approaches and then moves through Thursday afternoon
into Friday. This will bring cooler temperatures Thursday and
Friday with highs in the upper 70s to low 80s in the valley and
50s and 60s in the mountains. Precipitable water increases to
around an inch Thursday afternoon into Friday indicating some
moisture with this system. There is a slight chance to chance of
showers over the mountains and possibly the northern Sacramento
Valley Thursday afternoon into early Friday. Showers and
thunderstorms possible over the Sierra on Friday as the trough
moves to the southeast. Snow levels are expected to be around
9000 ft. Precipitation amounts are generally expected to be less
than a tenth of an inch. The instability moves to the southeast of
the area on Saturday but may still see some cumulus development in
alpine and Tuolumne counties. Another trough may move onshore into
the Pacific northwest on Saturday but it looks like it will stay
far enough north that northern California will stay dry.
Temperatures on Saturday should be around 80 in the valley and mid
50s to low 70s in the mountains.

Extended discussion (sunday through wednesday)

All models showing a large upper level low dropping southward
from the Gulf of Alaska towards the West Coast in the extended
forecast. Details of this system are not consistent across the
models, but a pattern change is expected. Sunday should remain
fairly dry and warm, but wetter and cooler conditions are expected
to arrive by Monday. The low could start bringing light
precipitation to coastal & northern mountains late Sunday. Showers
will then spread southward across our County Warning Area Monday into Tuesday.
Have raised precip chances and introduced slight thunderstorm
chances Tuesday as forecast instability appears favorable. Valley
highs in the low 80s on Sunday cooling to mid-upper 70s on Monday
and upper 60s-low 70s by Tuesday.

&&

Aviation...

General VFR conditions for valley taf sites next 24 hours. North
winds are decreasing, but gusts to around 20 kt continue to be
possible until around 00z. Winds will become north around 10 kt
for the northern Sacramento overnight, light elsewhere. Onshore
winds expected by Thursday afternoon, locally gusting to 20 kt in
the Delta and remaining generally 10 kt or less elsewhere. Broken
high clouds this afternoon will give way to mostly clear by late
afternoon and overnight. Ek



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Sto watches/warnings/advisories...
none.
&&

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