FXUS66 KHNX 262255
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
355 PM PDT Thu Apr 26 2018
A chance of afternoon showers and thunderstorms across the Sierra
Nevada due to an approaching upper level weather disturbance.
Expect cooler and breezy conditions on Friday and into the
weekend, and then another chance for mainly mountain showers and
thunderstorms during early next week.
Skies still relatively clear this mid-day as isolated cumulus was
start to develop over the Sierra Nevada. Based on upper level
dynamics and instability parameters, confidence is still high for
afternoon convection over the Sierra Nevada. Therefore, will
expect convection to start closer to 3 PM PDT and fire-up until
near sunset this evening. In addition, the marine layer, as seen
on the Fort Ord wind profiler, has been at around the 2500 foot
MSL level with some possible filtering of cooler air into the San
Joaquin Valley. As of this afternoon, temperatures have been
running cooler by 3 to 5 degrees. While widespread temperatures
this afternoon are likely to reach in the 80s, it is very unlikely
that they will reach the 90 degree mark under a changing air-
mass. Furthermore, surface frontal analysis has a cold front just
off the West Coast that is progged to push through California on
Friday, lowering temperatures even further and increasing surface
winds that will last into the weekend.
While models show the bulk of the upper level dynamic lift pushing
mostly into Northern California, the southern edge will skirt the
Southern Sierra Nevada and raise the potential for afternoon
convection. In addition to the vort-lobe energy, some difluence
flow along with reasonable CAPE and LI values will tip the scales
toward the possibility of Thunderstorms. Therefore, will keep a
mention of mostly isolated convection until sunset. By Friday
afternoon, models show the cold front pushing into Eastern
California and shifting the convective potential further eastward.
While the convective threat will become minimal over the
district, the colder air will help tighten the surface pressure
from KSFO to KLAS as winds over the Kern County Mountains and
Deserts reach wind advisory criteria (gusting to 45 mph). In
addition, the cold front will usher in lower freezing levels as
the Yosemite Valley could see overnight lows in the upper 30s
during the weekend.
By the end of the weekend models swings piece of vort max energy
through Central California and maintain a chance of possible
mountain precipitation. Moreover, the northerly flow aloft will
push additional cold air into the region to maintain cooler
temperatures. Afterward, model uncertainty increases, but models
are trending toward the continuation of a cyclonic flow pattern
through early next week. Going into the middle of next week,
models then show a ridge pattern developing with high uncertainty
in its timing. Will opt for the slower ECMWF solution and wait
until the end of the forecast cycle before starting another
warming and drying trend.
Isolated showers and thunderstorms along the Sierra through 03z
Friday. Otherwise VFR conditions will prevail across the Central CA
Interior during the next 24 hours.
.AIR QUALITY ISSUES...
The level of certainty for days 1 and 2 is high.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.
Wind Advisory from 2 PM Friday to 5 AM PDT Sunday CAZ095-098-099.
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