Area Forecast Discussion
Issued by NWS Sacramento, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KSTO 121625
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
925 AM PDT Sat Jul 12 2014

.Synopsis...
Warmer daytime temperatures into Monday then slight cooling back to
near normal by the end of next week. A chance of Sierra crest
thunderstorms returning Monday spreading northward on Tuesday. A
slight chance of thunderstorms over the Shasta county mountains and
Sierra cascade range Wednesday. A diminishing shower threat towards
the end of the week as the upper level flow becomes more westerly.

&&

.Discussion...
A little warmer today across much of the region as upper ridge
builds westward a bit. Delta breeze will moderate warmup a bit in
the south valley. Main convective threat appears will remain north
and east of the area, though the region around Mt. Lassen may see a
few storms pop later this afternoon. Minor updates out shortly.

&&

.Previous Discussion...
Northern California under stable southwest flow between a high
pressure ridge over the Great Basin and a low pressure system over
the eastern Pacific. A weak disturbance moving through this
southwest flow is bringing some high cloudiness to northeast
California this morning. Skies are mainly fair elsewhere except the
delta where some coastal stratus has moved inland. Upper ridge is
forecast to retrograde westward today bringing a warm up in the
general airmass. Should see daytime highs today on the order of 5
degrees warmer than on Friday. Subsidence under the ridge will keep
the CWA under fair skies today while RH values lower under drying
airmass. Airmass continues to warm and dry on Sunday as the upper
ridge amplifies and shifts over the west coast. This will bring
still warmer temperatures and drying. Airmass warms just a bit more
on Monday as the upper ridge axis develops along the coast bringing
what will likely be the warmest temperatures of the week under
minimal onshore flow. Humidity values drop as well with minimum RH
likely in the teens most areas. Subtropical moisture does start to
make its way northward however and may see effects of this moisture
beginning in the afternoon in the form of a Sierra thunderstorm
along the Sierra crest south of Tahoe. Subtropical monsoon moisture
continues to work its way northward on Tuesday. The combination of
cloud cover and a cooler airmass will bring the beginning of a
cooling trend starting Tuesday and lasting through the end of the
week. RH values should begin to creep up while instability progs
indicate the thunderstorm threat will likely start to shift
northward up the Sierra crest.

&&

.Extended Discussion (Wednesday through Saturday)...
Precipitable water forecasts from GFS model show TPW on Wednesday
ranging from a little over an inch to nearly 1.5 inches over NORCAL.
More moderate RH values should result with instability forecasts
showing the best chance of thunderstorms over the Sierra Cascade
range and the Shasta county mountains. Models showing plenty of
moisture and sufficient instability but lack of lift should confine
and thunderstorms to where mountains can provide the lift. Extended
models in fairly good agreement in moving an upper low into the
Pacific Northwest around next Thursday. This will bring a more
westerly flow aloft which will keep any thunderstorm development
limited to the Sierra cascade range. The passage of the upper low to
the north will bring a continue slight cool down as well.
Temperatures continue to cool Friday and Saturday as a trough
develops along the coast. Models vary on strength of this trough but
for the most part forecast area looks to remain under fair skies
with daytime highs dropping to near normal and more moderate
humidity.

&&

.Aviation...
VFR conditions expected to continue for the next 24 hours except for
local areas west of KSUU this morning. Marine stratus nudging into
the western side of the delta will have MVFR ceilings with
BKN010-015 during morning hours. Near the delta...SW winds at 15-25
kt will continue with gusts up to 30 kt. Onshore flow through the
delta will bring south to west winds at 5-15 kt today for the
Sacramento Valley TAF sites. Northern San Joaquin valley will have
west to northwest winds also at 5-15 kt today.  JBB

&&

.STO Watches/Warnings/Advisories...None.

&&

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.