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000
FXUS66 KSTO 232125
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
225 PM PDT Wed Apr 23 2014

.Synopsis...
Milder temperatures are forecast into Thursday, then another weather
system will bring a chance of widespread precipitation along with
cooler temperatures late Thursday into early Saturday. Thunderstorms
are possible Friday.

&&

.Discussion...
Weak upper ridging moving into the Great Basin as upstream Pacific
storm system approaches. Some overrunning WAA precip showing up radar
along the NW coast attm could spread into portions of the Coastal
and Shasta mountains overnight into Thursday. Associated cold
front then brings more widespread precip over the CWA Thursday
night into Friday. Significantly colder and unstable air is
ushered into the area Friday for the threat of showers and
thunderstorms. Cold pool aloft (5H temps around -28 to -30 deg C)
moves over Interior NorCal Friday...steepening lapse rates and
providing potential for thunderstorms, possibly with hail.
Isolated severe thunderstorms cant be ruled out, although shear
profiles don`t look real favorable. Snow levels will lower from
6000 to 7000 feet late Thursday to 4500 to 5500 feet Friday and
down to 3500 to 4500 feet Friday night into Saturday morning.
Models continuing to show significant differences in QPF,
especially in the Eastern Shasta, Western Plumas and Northern
Sierra Nevada mountains. Oper GFS nearly double the QPF of the NAM
in the NE mountains and almost three times compared to the ECMWF-
HiRes. Both the GFS/NAM are about double the amount of the Euro in
the Northern Sierra Nevada. QPF values in the Central Valley
generally about half an inch or less with the GFS showing high
amounts towards the eastern foothills. Potential for winter
weather advisory criteria in the higher Trans-Sierra, but given
differences in model QPFs, will issue an SPS for now. Potential
exist though for up to a foot or more of snow in the higher
mountain terrain. High temperatures on Friday likely to be 10 to
20 degrees lower than Thursday with upper 50s to lower 60s in the
Central Valley and upper 30s to 50s for the mountains and foothills.

Lingering showers may be possible over the mountains through the
weekend but in general weak short wave ridging progged over Interior
NorCal. AMS warms slightly with high temps returning to near normal
by Sunday.

PCH

&&

.Extended Discussion (Sunday through Wednesday)

A weak wave moves through the Pacific Northwest on Sunday for
possible showers...especially over the mountains. Temperatures on
Sunday are expected to be in the upper 60s to low 70s in the
Valley and 40s and 50s in the mountains which is a few degrees
below normal for this time of year. Temperatures will warm up to
near to above normal with dry weather Monday into Wednesday with
the ridge building over the area. Temperatures on Tuesday
expected to be in the low to mid 80s in the valley and upper 50s
to low 70s in the mountains, which is a few degrees above normal
for this time of year. The GFS has the ridge shifting to the east
with a trough moving into the Pacific Northwest on Wednesday which
could bring a little precipitation to the far north and a little
cooling. The ECMWF keeps the ridge over the area on Wednesday.
The forecast leans toward the ECMWF with a dry forecast and
similar temperatures on Wednesday.


&&

.Aviation...

VFR conditions continue for the next 24 hours. Winds generally
light up to 12 kts. Some moderate gusts in the KSCK-KMOD vicinity
up to 20 kts between now and 03z.  JBB


&&

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

$$









000
FXUS66 KSTO 231610
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
910 AM PDT Wed Apr 23 2014

.Synopsis...
Milder temperatures are forecast today and Thursday, then another
weather system will bring a chance of precipitation along with
cooler temperatures later Thursday into Saturday. Thunderstorms
are possible on Friday.

&&

.Discussion...
Weak upper ridging progged to move over the forecast area today
with drier and milder conditions for Interior NorCal. Highs today
expected in the lower 70s for the Central Valley. Increasing
moisture spilling through the ridge along with some warm advection
ahead of the next system may bring some showers to the far northern
portion of the forecast area tonight.

Upstream Pacific frontal system continues to slowly progress towards
NorCal Thursday with a continued threat of showers over the coastal
range and mountains of Western Shasta county. Associated cold front
then begins to spread more area wide precip over the CWA Thursday
night into Friday morning. Significantly colder and unstable air is
ushered into the area Friday for the threat of showers and
thunderstorms. Cold pool aloft (5H temps around -28 to -30 deg C)
moves over Interior NorCal Friday...steepening lapse rates and
providing potential for thunderstorms, possibly with hail. Isolated
severe thunderstorms cant be ruled out, although shear profiles
don`t look real favorable. Snow levels will lower Friday from 4500
to 5500 feet down to 3500 to 4500 feet by Saturday morning. Up to a
foot or more of snow is possible over portions of the higher
mountain terrain where winter weather advisories may be needed. High
temperatures on Friday likely to be 10 to 20 degrees lower than
Thursday.

Lingering showers may continue over Western Plumas and Northern
Sierra Nevada mountains Saturday but in general weak short wave
ridging progged over Interior NorCal. AMS warms slightly but
continued below normal temperatures with highs in the mid 60s for
the Central Valley with mainly 40s to 50s for the mountains and
foothills.

PCH


&&

.Extended Discussion (Sunday through Wednesday)...
Models showing decreasing threat of showers on Sunday with a
weakening wave moving through the Pac NW. A lingering threat still
exists mainly over the mountains. High temperatures will increase
over Saturday, but still expected to continue slightly below
normal.

Models agree in amplifying a ridge over Interior NorCal Monday
into Wednesday with significant warming and lowering humidity.
High temperatures Tuesday and Wednesday expected in the upper 80s
to low 90s for the Central Valley with 60s to 80s for the
mountains and foothills. JClapp

&&

.Aviation...
NWly flow alf ovr Intr NorCal with VFR conds for the nxt 24 hrs exc
isold MVFR poss ovr Shasta mtns tngt into Thu. Lcl Wly sfc wnd gsts
up to 30 kts poss this aftn/eve ovr hyr mtn trrn.

&&

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

&&

$$








000
FXUS66 KSTO 231040
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
340 AM PDT Wed Apr 23 2014

.Synopsis...
Milder temperatures are forecast today and Thursday, then another
weather system will bring a chance of precipitation along with
cooler temperatures later Thursday into Saturday. Thunderstorms
are possible on Friday.

&&

.Discussion...
Yesterday`s weather system is moving out across the Rockies early
this morning with drier NWly flow on the backside of the trough
across NorCal. Embedded weak short-waves in the flow are
resulting in a few showers across far NW CA while skies are mostly
clear inland. Temperatures are considerably cooler this morning
compared to 24 hours ago and range from the 40s to lower 50s in
the valley and in the upper 20s and 30s in the mountains.

Short-wave ridging will provide dry and milder conditions across
the interior of NorCal today. Increasing moisture spilling through
the ridge along with some warm advection ahead of the next system
may bring some showers to the far northern portion of the forecast
area tonight.

Little change is expected Thursday with the threat of precip
limited to the far northern portions. The cold front finally moves
south Thursday night and early Friday bringing an increasing
chance of precipitation to the entire region along with lowering
snow levels and colder temps. Friday looks like it could be an
active day for showers and thunderstorms in the unstable airmass
behind the front with the deep trough moving overhead. Showers
decrease Friday night, but potential for more showers continues
Saturday especially over the mountains in NWly flow behind the
deep trough.

&&

.Extended Discussion (Sunday through Wednesday)...
Models showing decreasing threat of showers on Sunday with a
weakening wave moving through the Pac NW. A lingering threat still
exists mainly over the mountains. High temperatures will increase
over Saturday, but still expected to continue slightly below
normal.

Models agree in amplifying a ridge over Interior NorCal Monday
into Wednesday with significant warming and lowering humidity.
High temperatures Tuesday and Wednesday expected in the upper 80s
to low 90s for the Central Valley with 60s to 80s for the
mountains and foothills. JClapp

&&

.Aviation...
VFR conditions expected the next 24 hours. Onshore pressure
gradients will generate SW to W winds over the Sierra-Cascades
today. JClapp

&&

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

&&

$$






000
FXUS66 KSTO 230400
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
900 PM PDT Tue Apr 22 2014

.Synopsis...
Milder temperatures are forecast Wednesday and Thursday, then
another weather system will bring a chance of precipitation along
with cooler temperatures later Thursday into Saturday.
Thunderstorms are possible on Friday.

&&

.Discussion...
Showers are tapering off in the Sierra this evening. A very weak
wave is moving inland along the northwest coast but is forecast to
dissipate as it tries to move inland overnight. On Wednesday a
system will spread rain into Oregon with the tail bringing some
precipitation to the northwest coast. As it spreads inland
Wednesday night some showers or light rain may occur over the southern
Cascades and maybe into the far north end of the valley. On
Thursday the cold front will approach the northwest coast. A few
showers may occur over the far northern interior ahead of the
front. The front looks like it will move through Thursday night
into early Friday morning. Snow levels will lower overnight to
around 5000 feet and continue to lower Friday morning to around
4000 feet. Friday looks like to could be an active day for
Thunderstorms and showers post frontal. At this point there is the
potential for up to a foot of snow over the higher elevations and
around half a foot or so near pass levels. Temperatures this week
will remain cool to near normal or below normal at times.


.Extended Discussion (Saturday through Tuesday)

Models showing decreasing threat of showers on Saturday with a
lingering threat over the mountains and far Northern Sacramento
Valley. Low POPs continue Sunday, again mainly over the mountains,
as a weaker Pacific short wave trough moves through in Northwest
flow aloft. High temperatures over the weekend expected to
continue slightly below normal.

Progs similar in building ridge over Interior NorCal early next
week with dry weather and significant warming. High temperatures
by Tuesday expected in the mid 80s for the Central Valley with 60s
to 70s for the mountains and foothills.


&&

.Aviation...

Generally VFR conditions expected the next 24 hours. Local
Northwest to Southwest winds 10-15 kt across Valley TAF sites
will gradually weaken tonight.

Dang


&&

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

$$









000
FXUS66 KSTO 222152 AAA
AFDSTO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SACRAMENTO CA
252 PM PDT Tue Apr 22 2014

.Synopsis...
A quick moving weather system bringing cooler temperatures and showers
this afternoon and early evening...mainly over the mountains.
Milder temperatures are forecast Wednesday and Thursday, then another
weather system will bring a chance of precipitation along with
cooler temperatures later Thursday into Saturday. Thunderstorms
are possible on Friday.

&&

.Discussion...
Upper level trough moving east through Northern California this
afternoon and evening. This is bringing cooler temperatures along with
some cumulus clouds over interior Northern California and isolated
showers over the mountains. Temperatures are about 5 to 15 degrees cooler
this afternoon compared to yesterday with the most cooling in the
mountains and the Northern San Joaquin Valley. Warmer temperatures
tomorrow afternoon and mainly dry on Wednesday with weak ridging over the
area. Slight chance of showers over the coastal range and over
Shasta County.  Temperatures should be in the upper 60s to low 70s
on Wednesday which is near normal for most locations this time of year.

An upper level trough deepens off the west coast on Thursday and
moves inland on Friday. This system will bring gusty southwesterly
winds and a chance of showers by Thursday evening...mainly north
of Interstate 80 and spreading south overnight. Temperatures will
be colder on Friday with highs expected to be in the low to mid
60s in the valley and 30s and 40s in the mountains. Showers and
Isolated thunderstorms are also possible with this system on
Friday. Snow levels are expected to be around 7000 ft Thursday and
drop to around 4500 ft on Friday. Several inches of snow are
possible over the higher peaks of the Sierra.


.Extended Discussion (Saturday through Tuesday)

Models showing decreasing threat of showers on Saturday with a
lingering threat over the mountains and far Northern Sacramento
Valley. Low POPs continue Sunday, again mainly over the mountains,
as a weaker Pacific short wave trough moves through in Northwest
flow aloft. High temperatures over the weekend expected to
continue slightly below normal.

Progs similar in building ridge over Interior NorCal early next
week with dry weather and significant warming. High temperatures
by Tuesday expected in the mid 80s for the Central Valley with 60s
to 70s for the mountains and foothills.


&&

.Aviation...

Upper trough is moving through interior Northern California.
Generally VFR conditions expected the next 24 hours, except local
MVFR/IFR conditions in showers over the mountains through this
afternoon. Local Northwest to Southwest winds 10-15 kt with gusts
to 25 kt will be possible through early this evening, then will
become light overnight.

Dang


&&

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

$$









000
FXUS66 KSTO 222146
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
246 PM PDT Tue Apr 22 2014

.Synopsis...
A quick moving weather system bringing cooler temperatures and showers
this afternoon and early evening...mainly over the mountains.
Milder temperatures are forecast Wednesday and Thursday, then another
weather system will bring a chance of precipitation along with
cooler temperatures later Thursday into Saturday. Thunderstorms
are possible on Friday.

&&

.Discussion...
Upper level trough moving east through Northern California this
afternoon and evening. This is bringing cooler temperatures along with
some cumulus clouds over interior Northern California and isolated
showers over the mountains. Temperatures are about 5 to 15 degrees cooler
this afternoon compared to yesterday with the most cooling in the
mountains and the Northern San Joaquin Valley. Warmer temperatures
tomorrow afternoon and mainly dry on Wednesday with weak ridging over the
area. Slight chance of showers over the coastal range and over
Shasta County.  Temperatures should be in the upper 60s to low 70s
on Wednesday which is near normal for most locations this time of year.

An upper level trough deepens off the west coast on Thursday and
moves inland on Friday. This system will bring gusty southwesterly
winds and a chance of showers by Thursday evening...mainly north
of Interstate 80 and spreading south overnight. Temperatures will
be colder on Friday with highs expected to be in the low to mid
60s in the valley and 30s and 40s in the mountains. Showers and
Isolated thunderstorms are also possible with this system on
Friday. Snow levels are expected to be around 7000 ft Thursday and
drop to around 4500 ft on Friday. Several inches of snow are
possible over the higher peaks of the Sierra.


.Extended Discussion (Saturday through Tuesday)

Models showing decreasing threat of showers on Saturday with a
lingering threat over the mountains and far Northern Sacramento
Valley. Low POPs continue Sunday, again mainly over the mountains,
as a weaker Pacific short wave trough moves through in Northwest
flow aloft. High temperatures over the weekend expected to
continue slightly below normal.

Progs similar in building ridge over Interior NorCal early next
week with dry weather and significant warming. High temperatures
by Tuesday expected in the mid 80s for the Central Valley with 60s
to 70s for the mountains and foothills.


&&

.Aviation...

Upr trof movg thru Intr NorCal attm wl push E into Grt Basin this
aftn then EPAC upr rdg blds inld Wed. Genly VFR conds nxt 24 hrs
exc lcl MVFR/IFR or isold LIFR poss omtns thru 03z Wed. Lcl SW-
NW sfc wnd gsts to 30 kts poss omtns til 03z Wed.


&&

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

$$









000
FXUS66 KSTO 221645
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
945 AM PDT Tue Apr 22 2014

.Synopsis...
A quick moving weather system will bring some showers to mainly
the Sierra today, otherwise cooler temperatures along with breezy
conditions are expected. Milder temperatures are forecast through
mid-week, then another weather system will bring a chance of
precipitation along with cooler temperatures later in the week.

&&

.Discussion...
Upper level trough moving through Northern California this
morning which brought some showers overnight into this
morning...mainly over the mountains. Mostly clear skies and cooler
temperatures over the valley this morning with some clouds over
the mountains and showers lingering over the Sierra foothills and
mountains. Showers will continue over the Sierra into this
afternoon as the system shifts to the east. Snow levels around
5000 feet with a couple inches of snow possible today.
High temperatures this afternoon will only be in the mid to upper 60s
in the valley and 30s and 40s in the mountains which is about 5 to
10 degrees below normal for this time of year. Warmer and mainly
dry on Wednesday with weak ridging over the area. Temperatures
should be in the upper 60s to low 70s on Wednesday which is near
normal for most locations.

An upper level trough deepens off the west coast on Thursday and
moves inland on Friday. This system will bring another chance of
showers by Thursday evening...mainly north of Interstate 80 and
spreading south overnight. Temperatures will be colder of Friday
with highs expected to be in the low to mid 60s in the valley and
30s and 40s in the mountains. Isolated thunderstorms are also
possible with this system on Friday.


.Extended Discussion (Saturday through Tuesday)

Shower threat decreases Saturday with some lingering activity
possible over the mountain and northern Sacramento Valley. Weaker
Pacific short wave trough moves onshore Sunday under straight-
line northwesterly flow aloft, but the weak dynamics don`t amount
to much. Ridging set to increase Monday and Tuesday for much warmer
and drier weather.  JClapp

&&

.Aviation...

Upr trof movg thru Intr NorCal attm wl push E into Grt Basin this
aftn then EPAC upr rdg blds inld Wed. Genly VFR conds nxt 24 hrs
exc lcl MVFR/IFR or isold LIFR poss omtns thru 03z Wed. Lcl SW-
NW sfc wnd gsts to 30 kts poss omtns til 03z Wed.


&&

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

$$









000
FXUS66 KSTO 221155
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
454 AM PDT Tue Apr 22 2014

.Synopsis...
A quick moving weather system will bring some showers to mainly
the northern Sierra today, otherwise cooler temperatures along
with breezy conditions are expected. Milder temperatures are
forecast through mid-week, then another weather system will bring
a chance of precipitation along with cooler temperatures later in
the week.

&&

.Discussion...
Pacific frontal system moving quickly through the region early
this morning. A few showers across the northern mountains,
northern Sacramento Valley and northern Sierra while the remainder
of the forecast area has been dry. Satellite imagery indicates the
upper trough nearing the coast which will move inland today
resulting in some showers over mainly the foothills and mountains.
Valley expected to be mainly dry, but cooler and breezy.

Short-wave ridging returns Wednesday for milder and mainly dry
weather. Next upstream trough approaches Thursday resulting in an
increasing chance of showers across the northern half of the
forecast area. Trough moves inland Friday for a better chance of
showers and thunderstorms throughout interior NorCal.

&&

.Extended Discussion (Saturday through Tuesday)...
Shower threat decreases Saturday with some lingering activity
possible over the mountain and northern Sacramento Valley. Weaker
Pacific short wave trough moves onshore Sunday under straight-line
northwesterly flow aloft, but the weak dynamics don`t amount to
much. Ridging set to increase Monday and Tuesday for much warmer
and drier weather. JClapp

&&

.Update Aviation...
Some areas of MVFR/IFR cigs in southern Sac/northern San Joaquin
Valley early this morning as frontal band moves through. The lower
cigs may erode shortly after sunrise. Periods of IFR conditions
possible over the western portion of the Coastal Range and Sierra
this morning. Local SW to NW Central Valley wind gusts up to 30 kts
from Glenn to Stanislaus county through this evening. Cross winds
could be more of a concern today than usual within the Sacramento
Valley.   JClapp

&&

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

&&

$$








000
FXUS66 KSTO 221030
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
330 AM PDT Tue Apr 22 2014

.Synopsis...
A quick moving weather system will bring some showers to mainly
the northern Sierra today, otherwise cooler temperatures along
with breezy conditions are expected. Milder temperatures are
forecast through mid-week, then another weather system will bring
a chance of precipitation along with cooler temperatures later in
the week.

&&

.Discussion...
Pacific frontal system moving quickly through the region early
this morning. A few showers across the northern mountains,
northern Sacramento Valley and northern Sierra while the remainder
of the forecast area has been dry. Satellite imagery indicates the
upper trough nearing the coast which will move inland today
resulting in some showers over mainly the foothills and mountains.
Valley expected to be mainly dry, but cooler and breezy.

Short-wave ridging returns Wednesday for milder and mainly dry
weather. Next upstream trough approaches Thursday resulting in an
increasing chance of showers across the northern half of the
forecast area. Trough moves inland Friday for a better chance of
showers and thunderstorms throughout interior NorCal.

&&

.Extended Discussion (Saturday through Tuesday)...
Shower threat decreases Saturday with some lingering activity
possible over the mountain and northern Sacramento Valley. Weaker
Pacific short wave trough moves onshore Sunday under straight-line
northwesterly flow aloft, but the weak dynamics don`t amount to
much. Ridging set to increase Monday and Tuesday for much warmer
and drier weather. JClapp

&&

.Aviation...
Some areas of MVFR cigs in southern Sac Valley early this morning
as frontal band moves through. The lower cigs may reach into KEDU,
but erode by sunrise. Valley TAF sites expected to remain
primarily VFR, with periods of MVFR conditions possible over the
western portion of the Coastal Range and Sierra. Local SW to NW
Central Valley wind gusts up to 30 kts from Glenn to Stanislaus
county through this evening. Cross winds could be more of a
concern today than usual within the Sacramento Valley. JClapp

&&

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

&&

$$






000
FXUS66 KSTO 220456
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
955 PM PDT Mon Apr 21 2014

.Synopsis...
A weather system will move through the area tonight and Tuesday
bringing cooler temperatures and a chance of showers and higher
elevation snow to the region. Thunderstorms in the Valley could
develop after midnight, and continue through mid day Tuesday. After
drier and warmer conditions mid week...another weather system will
bring cool and wet conditions later in the week...with accumulating
mountain snow possible...especially Friday and Saturday.

&&

.Discussion...
Frontal band beginning to move onshore with the main area of showers
and isolated thunderstorms...still just west of our CWA. Very little
precip forecast by the high resolution HRRR-3km in the valley with
the QPF "skipping" over the valley and into the foothills by
morning. Ahead of it...clouds and sprinkles occurred throughout the
day...with some areas mainly in zone 68...the Nrn Sierra and Lassen
Park zone getting some measurable precip. C-G strikes noted this
evening along the tri-county border (Trinity/Shasta/Siskiyou county
border) in the indirect circulation of the upper jet and in area of
elevated instability and terrain forcing. This elevated instability
should work its way Ewd tonite and into the Siernev before morning.
It may linger over the Siernev into Tue afternoon...until the upper
trof axis passes...but most of the convective activity should be in
NV later in the day. The I-80 corridor looks to be on the Srn end of
the area of elevated instability...but it may sag Swd over the high
Siernev on Tue.

The post-frontal/post upper trof forecast Bufkit hodographs show
mostly straight-line hodographs in the valley Tue afternoon which
suggests more multicellular convection than supercellular if any
convection develops at all. By then however...the elevated
instability threat will decrease with terrain forcing...mid-level
CAA and boundary layer instability becoming the main threat for
convection. This would put the best thunder threat from the Nrn
Motherlode...Nwd to Lassen Park...generally....Auburn...Nevada
City...Grass Valley Nwd as the seemingly the best location.

Onshore flow continues overnite...but should weaken on Tue and then
shift to NWly during the afternoon...not a favorable wind flow for
valley thunder. It does however provide some upslope flow for the W
slope Siernev. Satellite indicates good clearing behind the frontal
band with an unimpressive open cellular cumulus field over the
ocean. So after front and trof passage...there should be clearing
with cumulus developing in the valley during the day. Thus...there
may be some decent heating on the edge of the cloud deck over the
Siernev during the afternoon to generate convection due to
solenoidal circulations.     JHM


.Previous Discussion...
The main precipitation will be Tuesday morning, with and just behind
the cold front as it passes through. Since the moisture plume with
this system is fairly limited, rainfall amounts are not expected to
be generally very high, several hundredths to a tenth of an inch for
the Valley and maybe around a third to half of an inch for the
foothills and mountains. Higher amounts are possible locally with
thunderstorms and heavy convective showers.

Timing is off for a strong convective event. There is a slight
chance of thunderstorms tonight, mainly after midnight, starting
around the northern Sacramento Valley. These storms are not expected
to be strong. Low level instability will be better behind the front,
during the daylight hours, so stronger storms are possible in the
morning with models showing some decent CAPE. Without a strong cold
core aloft, though, conditions are not that favorable for severe
storms. Soundings show a cap developing from subsidence and drier
air arriving in the afternoon, so convective activity should weaken
by shortly after noon. Late morning would be the most likely time to
see some isolated stronger thunderstorms. Small hail would probably
be the main issue.

Around 1-3 inches of snow could fall over the Sierra mountain
passes, mainly Tuesday morning, potentially causing some minor travel
issues. Motorists should be prepared for slow downs and are
advised to carry chains in case they are needed. Lingering snow
showers are possible into Tuesday evening, with little additional
accumulation. Isolated thunderstorms in the foothills and heavier
showers during the day could cause local travel difficulties from
hail and brief heavy rain.

Ridging on Wednesday should bring a generally drier and slightly
warmer day, with a weak wave bringing a slight chance of showers
to the mountains of northern Shasta County. Another system arrives
late Thursday with, precipitation spreading into the mountains and
northern Sacramento Valley. &&

.Extended Discussion (Friday through Monday)

Medium range models differ on depth of system to impact the area
Friday with Oper GFS/GEM showing a deeper closed system than the
ECMWF-HiRes. Either solution points to a wetter colder system
Friday than the one to impact the area Tuesday. Snow levels look
lower (lowering to around 4000 to 5000 feet overnight Friday into
early Saturday). Also potential for Central Valley thunderstorms,
possibly with hail, looks better Friday with 5h temps progged
near -30 deg C and large area of moderate CAPE progged over
Interior NorCal. Shower threat decreases Saturday with some
lingering activity possible over the Sierra Nevada. Weaker Pacific
short wave trough moves onshore Sunday but models differ on
strength of this. ECMWF-HiRes brings some precip over the area
Sunday while the GFS maintains stronger ridging and shows a much
weaker wave. GEM is between the two and have leaned towards this
solution for now, however would not be surprised to see future
model runs trend drier. Ridging looks to increase Monday for
warmer and drier weather.

&&

.Aviation...

VFR conditions across interior Northern California as a Pacific
low pressure system approaches the region. Showers will gradually
increase in coverage this evening, with most of the showers
occurring tonight through Tuesday morning. Valley TAF sites
expected to remain primarily VFR, with periods of IFR/LIFR
conditions possible over the Sierra. Local south to southwest
wind gusts up to 25 kts across the Central Valley and Delta
through this evening.

Dang


&&

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

$$









000
FXUS66 KSTO 212321
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
421 PM PDT Mon Apr 21 2014

.Synopsis...
A weather system has brought increasing clouds, cooler
temperatures and a chance of showers and higher elevation snow by
tonight and Tuesday. Thunderstorms in the Valley could develop
after midnight, and continue through mid day Tuesday. After drier
and warmer conditions mid week. Another weather system will bring
cool and wet conditions later in the week, with accumulating
mountain snow possible, especially Friday and Saturday.

&&

.Discussion...
An upper level trough is beginning to move into the region with
overcast skies and cooler temperatures than seen in recent days.
Radar and satellite show a weak sw-ne oriented band/surface
boundary moving through the southern Sacramento and northern this
afternoon, and this has had some virga and even a couple lightning
strikes several miles south of Tracy. This band has weakened and
is exiting the area. Current radar shows returns moving into the
Coastal and Shasta mountains, but gages have yet to record any
rain so far. A cold front will spread more significant
precipitation into the coastal mountains by early evening,
spreading showers across the rest of the area by early morning
Tuesday. Elevated convective parameters with the NAM12 show a
decent potential for some embedded thunderstorms overnight.
Southerly winds are also picking up and will be breezy this
evening and into Tuesday.

The main precipitation will be Tuesday morning, with and just
behind the cold front as it passes through. Since the moisture
plume with this system is fairly limited, rainfall amounts are not
expected to be generally very high, several hundredths to a tenth
of an inch for the Valley and maybe around a third to half of an
inch for the foothills and mountains. Higher amounts are possible
locally with thunderstorms and heavy convective showers.

Timing is off for a strong convective event. There is a slight
chance of thunderstorms tonight, mainly after midnight, starting
around the northern Sacramento Valley. These storms are not expected to
be strong. Low level instability will be better behind the front,
during the daylight hours, so stronger storms are possible in the
morning with models showing some decent CAPE. Without a strong cold
core aloft, though, conditions are not that favorable for severe
storms. Soundings show a cap developing from subsidence and drier
air arriving in the afternoon, so convective activity should
weaken by shortly after noon. Late morning would be the most
likely time to see some isolated stronger thunderstorms. Small
hail would probably be the main issue.

Around 1-3 inches of snow could fall over the Sierra mountain
passes, mainly Tuesday morning, potentially causing some minor travel
issues. Motorists should be prepared for slow downs and are
advised to carry chains in case they are needed. Lingering snow
showers are possible into Tuesday evening, with little additional
accumulation. Isolated thunderstorms in the foothills and heavier
showers during the day could cause local travel difficulties from
hail and brief heavy rain.

Ridging on Wednesday should bring a generally drier and slightly
warmer day, with a weak wave bringing a slight chance of showers
to the mountains of northern Shasta County. Another system arrives
late Thursday with, precipitation spreading into the mountains and
northern Sacramento Valley. &&

.Extended Discussion (Friday through Monday)

Medium range models differ on depth of system to impact the area
Friday with Oper GFS/GEM showing a deeper closed system than the
ECMWF-HiRes. Either solution points to a wetter colder system
Friday than the one to impact the area Tuesday. Snow levels look
lower (lowering to around 4000 to 5000 feet overnight Friday into
early Saturday). Also potential for Central Valley thunderstorms,
possibly with hail, looks better Friday with 5h temps progged
near -30 deg C and large area of moderate CAPE progged over
Interior NorCal. Shower threat decreases Saturday with some
lingering activity possible over the Sierra Nevada. Weaker Pacific
short wave trough moves onshore Sunday but models differ on
strength of this. ECMWF-HiRes brings some precip over the area
Sunday while the GFS maintains stronger ridging and shows a much
weaker wave. GEM is between the two and have leaned towards this
solution for now, however would not be surprised to see future
model runs trend drier. Ridging looks to increase Monday for
warmer and drier weather.

&&

.Aviation...

VFR conditions across interior Northern California as a Pacific
low pressure system approaches the region. Showers will gradually
increase in coverage this evening, with most of the showers
occurring tonight through Tuesday morning. Valley TAF sites
expected to remain primarily VFR, with periods of IFR/LIFR
conditions possible over the Sierra. Local south to southwest
wind gusts up to 25 kts across the Central Valley and Delta
through this evening.

Dang


&&

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

$$









000
FXUS66 KSTO 211640
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
940 AM PDT Mon Apr 21 2014

.Synopsis...
A weather system will approach NorCal today bringing increasing
clouds, cooler temperatures and a chance of showers and higher
elevation snow by tonight and Tuesday. Thunderstorms in the Valley
could develop after midnight, and continue through mid day
Tuesday. Another weather system will bring cool and potentially
wet conditions later in the week.

&&

.Discussion...
Increasing high clouds this morning and mid clouds this afternoon
as an upper level trough approaches. This system will move onshore
later today/tonight with a cold front moving through in the early
morning hours. Most of the area will remain dry through the day,
except for maybe the mountains of western Shasta County later this
afternoon. Cooler temperatures will be the main change today, with
highs about ten degrees lower than yesterday. These will still be
above normal, but compared to the recent very warm highs will seem
relatively cool. There will also be increasing southerly winds,
becoming breezy for the afternoon and evening.

The main precipitation will be Tuesday morning, with the cold
front as it passes through. This could touch off a few Valley
thunderstorms after midnight, with some decent mid level
instability. Low level instability will be better behind the front
during the daylight hours, but without a strong cold core aloft
conditions are not that favorable for severe storms. Subsidence
and drier air arriving in the afternoon mean that convective
activity should weaken later in the day, so mid day would be the
most likely time to see some isolated stronger thunderstorms. Small
hail would probably be the main issue.

Around 1-3 inches of snow could fall over the Sierra mountain
passes, mainly Tuesday morning, potentially causing some minor travel
issues. Motorists should be prepared for slow downs and are
advised to carry chains in case they are needed. Lingering snow
showers are possible into Tuesday evening, with little additional
accumulation. Isolated thunderstorms in the foothills and heavier
showers during the day could cause local travel difficulties from
hail and brief heavy rain.

Ridging on Wednesday should bring a drier and slightly warmer day,
before another system arrives Thursday and Friday bringing cooler
and wetter conditions into the weekend. Main issue is weather
drier weather returns on Sunday (GFS) or weather an additional
wave keeps the unsettled pattern going through the weekend. EK

&&

.Extended Discussion (Friday through Monday)

The upper level trough that generated over the Gulf of Alaska
moves inland on Friday, but the trough splits with the most
dynamic portion of the airmass going into the Pacific NW.
Nonetheless, northern CA will experience some showery activity
Friday. Snow levels will likely be around 5500 to 6000 ft Friday
before dropping 1000 ft to 4500-5000 ft into Saturday. Lingering
showers continue through the weekend as another wave comes through
northern CA late Saturday into Sunday. It is a pretty short break
between these systems with little to no ridging, so we have kept
the chance of precipitation going, with the highest probability
over the Sierra. Temperatures will cool down and southerly to
southwesterly winds will increase into the weekend.

Temperatures will rebound nicely Monday as an upper level ridge
builds over the West Coast. The area will increase some 5 to 15 F,
with the higher increases being over the mountains.    JClapp

&&

.Aviation...

VFR conds tda with incrsg clds as Pac fntl sys apchs. Areas
MVFR/IFR with lcl LIFR dvlpg in shwrs aft 06z Tue...mnly omtns.
Incrsg SWly flow alf ovr the nxt 24 hrs with areas SW sfc wnd
gsts to 30 kts or gtr ovr hyr mtn trrn bgng this aftn and contg
into Tue. Lcl S-SW sfc wnd gsts up to 25 kts poss this aftn/eve
thru Delta into Cntrl Vly.

&&

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

$$










000
FXUS66 KSTO 211100
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
400 AM PDT Mon Apr 21 2014

.Synopsis...
A weather system will approach NorCal today bringing increasing
clouds, cooler temperatures and a chance of showers and higher
elevation snow by tonight and Tuesday. Another weather system will
bring unsettled conditions later in the week.

&&

.Discussion...
Skies remain mostly clear across the interior of NorCal early this
morning, however satellite imagery shows clouds associated with
the approaching weather system now spreading into NW CA. Winds are
generally light though a light delta breeze continues through the
Carquinez Strait into the southern Sacramento Valley.

The upper trough over the eastern Pacific will continue to
approach the region today but most of the area will remain dry as
forecast soundings indicate gradual moistening through the day
above about 700-500 mbs while the lower levels remain dry. Appears
that most shower activity will hold off until later this evening
as the main vort and trough axis approach, though there will be
potential for a few showers this afternoon across the mountains of
NW Shasta County.

Mainly light amounts of QPF are expected later tonight and Tuesday
with less than a 1/4 inch in the valley with up to 1/3 to 1/2 inch
in the northern Sierra Nevada. The trough is forecast to split as
it moves onshore with most of the vort energy headed to our south
into Central California and to our north. The main frontal band is
timed to move through between 06Z and 12Z Tuesday, but will have a
tap to TPW of less than 3/4 inch. Looks like the best prospects
for deep convection will be Tuesday morning as the upper trough
swings through - not the most ideal.

Temperatures will decrease about 10 degrees today from Sunday`s
readings and will likely drop about another 10 degrees on Tuesday.
A few inches of accumulating snow will be possible over the higher
elevations Tuesday as snow levels lower.

Short-wave ridging behind the trough will attempt to dry things
out for Wednesday and Thursday, but moisture flowing over the
ridge along with warm advection may continue a few showers across
the far northern portion of the forecast area. Otherwise, a little
drier and milder conditions are expected.

&&

.Extended Discussion (Friday through Monday)...
The upper level trough that generated over the Gulf of Alaska
moves inland on Friday, but the trough splits with the most
dynamic portion of the airmass going into the Pacific NW.
Nonetheless, northern CA will experience some showery activity
Friday. Snow levels will likely be around 5500 to 6000 ft Friday
before dropping 1000 ft to 4500-5000 ft into Saturday. Lingering
showers continue through the weekend as another wave comes through
northern CA late Saturday into Sunday. It is a pretty short break
between these systems with little to no ridging, so we have kept
the chance of precipitation going, with the highest probability
over the Sierra. Temperatures will cool down and southerly to
southwesterly winds will increase into the weekend.

Temperatures will rebound nicely Monday as an upper level ridge
builds over the West Coast. The area will increase some 5 to 15 F,
with the higher increases being over the mountains. JClapp

&&

.Aviation...
VFR conditions will continue through this afternoon across
interior Northern California. Generally light valley winds will
become southerly 7-15 kt across the valley ahead of a low pressure
system mid to late this afternoon. Look for precipitation to
spread into Northern Interior CA after 06z Tuesday, with IFR/LIFR
conditions possible over the mountains. Delta winds (SFC-020)
breezy tonight into Tuesday as wave moves toward coast. JClapp

&&

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

&&

$$






000
FXUS66 KSTO 210439
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
935 PM PDT Sun Apr 20 2014

.Synopsis...
A Pacific trough will approach the coast Monday bringing
increasing clouds and a chance of rain and higher elevation snow
Monday night and Tuesday. Another trough will bring unsettled
conditions Friday and Saturday.

&&

.Discussion...

Darkening in the water vapor imagery this evening indicative of a
well defined vort max rotating Ewd with the Ern Pac trof. This trof
is tapping into a modest PW plume of about six to seven tenths of an
inch north of 35N...with the higher PWs to the south. Thus...the
potential for a modest precip event will be challenged by the lower
PW air off the coast which the frontal band must navigate on MON
likely eroding the plume to some degree...and the forecast splitting
of the vort max as the trof approaches/nears Norcal. The apparent
timing of the precip seems to indicate that interior Norcal will
remain dry until the late afternoon and evening hours when some
scattered showers should develop...per the WRF.

Most of the rain is likely to hold off until the Mon nite (after
midnite)/Tue morning period...with widespread showers over the
Siernev Tue afternoon...and decreasing activity in the Valley. Looks
as if the WRF indicates (forecasts) a decent band of convective
precip along the I-80/Hwy 50 corridor early Tue afternoon
corresponding to the passage of the upper trof axis.

This weekend`s Bufkit forecast hodographs for the valley on Tue
mainly showed straight line hodographs indicative of more
multicellular convection than supercellular convection. Generally...
some of the storms may contain small hail rather than rotating
updrafts this time around.

A much cooler day on Tue with 850 mbs temps and low to mid level
thicknesses some 13 deg/20 dam lower than Sun. Max temps in the
valley should only reach into the 60s.    JHM

.Previous Discussion...

Upper trough will move east towards the coast late tonight with
increasing clouds after midnight...but no precip. Trough will
deepen as it moves along the coast tomorrow. Scattered showers will
move over the coastal range and northern Shasta county during the
afternoon. High temperatures will cool into the mid to upper
70`s at most valley spots...due to the increased cloud cover.
These readings are still about 5 degrees above normal.

Band of showers with frontal system will move across Norcal after
midnight. Sufficient instability is indicated by modified
totals/totals over the northern and central Sacramento valley for
thunderstorms and decided to add slight thunderstorm chances for
these areas. Lift will also be aided by initial vort lobe swinging
through the area.

Skies will turn partly cloudy Tuesday morning behind leading
moisture band. Models prog best instability over the valley 11am-
4pm Tuesday and showers and isolated thunderstorm should develop
with surface heating. Snow levels will drop to 4500 feet during
the afternoon. Up to 2 inches of snow will be possible at pass
levels during the afternoon and evening. Qpf`s will generally be
light outside of thunderstorms with this system as most valley
locations receive 0.10 inches or less. High temperatures will
cool into the mid and upper 60`s for valleys.

Trough will move into the great basin region on Wednesday...but an
unsettled northwest flow will keep shower chances over the
northern mountains and Shasta county. Temperatures will warm into
low 70`s at most valley locations. Another trough will approach
the area Thursday increasing the shower chances over northern and
western areas.

.Extended Discussion (Thursday through Sunday)

Ridging Thursday will bring a brief return to above normal highs,
before a cool shortwave from the Gulf of Alaska begins edging into
the area late afternoon/evening. Showers will begin to spread into
the northern and Coastal Mountains, then into most of area by
Friday. Peak precipitation over the north is expected Friday
afternoon, over the Sierra Friday evening (snow levels around 6000
ft). Lingering showers continue int Saturday. Precipitation totals
of an inch or possibly 2 possible for the higher mountains.

Another wave may arrive Saturday night/Sunday across most of the
area (ECMWF) or weak ridging with some moisture over the northern
mountains. Will lean towards the wetter ECMWF for now, with the
weekend remaining relatively wet and with below normal
temperatures. EK

&&

.Aviation...

VFR conditions will continue through Monday afternoon across
interior Northern California. Generally light Valley winds will
become southerly 5-15 kt across the Valley ahead of a low pressure
system Monday. Near KRDD-KRBL, south winds 15-20 kt with gusts to 35
kt possible Monday afternoon. Look for precipitation to spread into
Northern Interior CA after 00z Tuesday, with IFR/LIFR conditions
possible over the mountains.

Dang

&&

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

$$







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