Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Sacramento California
402 PM PDT Tuesday Jun 2 2015
isolated shower and thunderstorm chances will persist through
Wednesday over the northern mountains. Better chances for showers
and thunderstorms will develop Thursday into the weekend as a
storm lingers over California.
temperatures running about 1-6 degrees warmer than 24 hours ago
with ample sunshine over much of norcal. Similar conditions
expected tomorrow with the possibility of some patchy morning low
clouds in the Delta into the SAC metropolitan region. There could also be a
few isolated showers/thunderstorms over the mountains north of
Interstate 80 during afternoon/evening hours.
Expect bigger changes Thursday Onward. An upper level low will
drop southward into norcal by early Thursday morning. By Thursday
afternoon it will strengthen and form a closed low over central
California. The atmosphere will become increasingly unstable Thursday
through the weekend. Best chances for showers/thunderstorms on
Thursday and Friday will be over the mountains and in portions of
the northern Sacramento Valley. Jbb
Extended discussion (saturday through tuesday)...
the closed low will linger over central/Southern California on Saturday
and start to drift northeastward on Sunday. This will maintain
instability over our County Warning Area across the mountains and into the valley.
GFS ensembles still show precipitable water in excess of 0.75-1 inch
the highest chances of showers/thunderstorms look to be across
the mountains, but portions of the valley look to be in play as
the low center remains south and east of interior norcal.
Confidence in this occurring has been increasing, but the
trajectory of this type of cutoff low is difficult. Temperatures
will cool a few degrees over the weekend and hinge on resulting
cloud and precipitation coverage, but will generally be close to normal.
VFR conditions expected for most of the period. Periods of
MVFR ceilings in the Delta and southern SAC valley (mainly ksac/kmhr)
Wednesday morning between 14-18z. Generally light winds with
onshore flow...up to 12 kts. Jbb