FXUS66 KSTO 100945
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
245 AM PDT Sat Jun 10 2023
SYNOPSIS...
Afternoon and evening thunderstorms through at least mid week.
Sunday storms will be most numerous possibly into many valley
locations. Temperatures will stay remain below normal then start
increasing to near to slightly above normal by end of next week.
.DISCUSSION
...
Partly to mostly cloudy skies are spreading across the region
early this morning as the offshore closed low continues to drift
to the southeast toward the central California coast. Radar shows
some light showers east of the Sierra crest near Lake Tahoe
moving slowly to the northwest. Onshore surface pressure gradient
is beginning to increase with winds gusting to around 30 mph
currently at Travis AFB. Profiler data show the marine layer
around 2.5-3k ft deep, so perhaps some stratus will develop in the
Sacramento region early this morning, but it`s not certain.
Current temperatures are mainly in the upper 40s to mid 50s in the
mountains, and in the 50s to mid 60s across the Central Valley
(slightly cooler in the valley and slightly warmer in the
mountains compared to 24 hours ago).
Active convective weather pattern returns this weekend into early
next week with more numerous showers and thunderstorms expected as
the closed low camps out near the central California coast with
east to southeast flow developing over NorCal. Most of the storms
will be over higher terrain, but a few may drift into the northern
Sacramento Valley by this evening. Stronger easterly flow is
forecast on Sunday which will lead to a better chance for storms
moving down into the Central Valley by Sunday evening and
overnight.
Moisture increases this weekend with around 1-1.25 inch TPW
forecast by Sunday. Heavy rain and hail are the primary threats
with stronger storms in the mountains, and HREF probability of
exceeding 1 inch/hr rates is only around 20-30 percent today
across the northern Sierra. Similar to earlier in the week and
last weekend, decent storm motion should limit the overall flash
flood threat.
Unsettled weather will continue early next week, but the
shower/thunderstorm threat is forecast to retreat to mainly the
Sierra and Cascades by Tuesday as the low shifts east.
Temperatures will remain below average.
.EXTENDED DISCUSSION
(Wednesday THROUGH Saturday)...
Model ensembles and clusters continue to show an upper
low/shortwave trough off the Southern California Coast mid to
late week. This leaves area under a weak upper trough with
westerly flow. Temperatures trend warmer from mid to late week,
with near normal highs Wednesday and Thursday and then above
normal for the weekend. NBM shows highs in the mid to upper 80s
with some lower 90s north Sacramento Valley by Friday. The weekend
could see temperatures in the low to mid 90s, but uncertainty in
the exact pattern makes the spread in temperatures still fairly
wide. There is the slight potential for mountain thunderstorms
with the weak westerly flow and the weak upper trough around...but
should be mainly south of I-80 along the Sierra Crest.
|
|
