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000
FXUS66 KSTO 202225
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
325 PM PDT Mon Apr 20 2015

.Synopsis...
Threat of afternoon and evening showers and thunderstorms...
mainly over the mountains...will continue through the week with
gradual cooling trend.

&&

.Discussion...
Omega block in place along the West Coast with strong upper ridging
over NorCal and trapped low off the SoCal coast. Instability over
the mountains this afternoon has resulted in scattered showers and
thunderstorms with activity likely to subside after sunset. Delta
breeze will continue moderate to strong tonight with marine layer
currently around 2500 feet. Coastal stratus expected to push back
into the Delta later tonight and enough marine air may advect
into the Southern Sac Valley for some patchy stratus around the
Sacramento area Tuesday morning.

Omega block progresses next 24 hours as elongating upper
troughing in the EPAC approaches the West Coast. Synoptic cooling
will increase Tuesday along with onshore flow resulting in more
substantial drop in max temps across Interior NorCal. Instability
again depicted over the mountains for showers and thunderstorms
tomorrow afternoon. Best instability progged by models over the
mountains from I-80 northward, and also suggest slight chance of
deep moist convection drifting into portions of the Northern/Central
Sacramento valley, given proximity to higher terrain.

Upper trough stretches as it reaches the West Coast with southern
portion forming closed low. Models dig this low south of the
California coast Wed as minor upstream ridging begins to nose
inland over S Oregon. Limited instability still depicted over
portions of the higher terrain Wed, but less extensive than today
or Tuesday. Max temps continue to trend downward slightly Wednesday.

Closed low forecast to track into the desert SW Thursday as
another elongating upper trough approaches the West Coast.
Afternoon instability looks even more limited Thursday with slight
chance of afternoon development confined to the higher terrain of
the eastern mountains of our CWA. High temperatures Thursday
expected to be similar to Wednesday.

PCH


.Extended Discussion (Friday through Monday)

A shortwave trough will have moved into Nevada by Friday with a
flat ridge overhead. However, enough instability and orographic
flow will remain to generate some showers mainly over the
Sierra/Cascades Friday/Saturday. The flat ridge will strengthen a
bit through the weekend, bringing warmer and drier weather.
Previous medium range model runs had hinted at a stronger trough
moving through Northern California early next week. However,
latest runs have kept the bulk of moisture primarily to our north.
We`ve trended down our precipitation forecast chance accordingly.

Dang


&&

.Aviation...

Mainly VFR conditions for the next 24 hours. Isolated
thunderstorms will continue over the Sierra and Coastal Range
through 03z. MVFR stratus may reach Sacramento TAF sites between
10-16z. Across the Valley...south winds will increase to 7-15 kt
this afternoon and tonight. Near the Delta, southwest winds 15-25
kt will continue.

Dang


&&

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

$$









000
FXUS66 KSTO 201645
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
945 AM PDT Mon Apr 20 2015

.Synopsis...
Very warm weather continues across the region today. Isolated to
scattered afternoon/early evening showers and thunderstorms possible
over the mountains today and Tuesday. Another low pressure system
will move into the region by the middle of the week bringing cooler
temperatures and continuing the threat of afternoon showers or
thunderstorms into Friday, mainly over the mountains.

&&

.Discussion...
Omega block in place along the West Coast with strong upper ridging
over NorCal and trapped low off the SoCal coast. Strong subsidence
inversion evident on 12z KOAK sounding with marine layer around 2100
feet deep. Satellite imagery showing extensive stratus along the
coast extending inland into portions of the Delta. Heights and
thicknesses are slightly less today and should equate to a few
degrees of cooling, however delta influenced areas will see greater
cooler as moderate delta breeze persists today. Elevated instability
progs showing potential for afternoon showers/thunderstorms over the
Coastal range, Western Plumas mountains, and Sierra Nevada.

Omega block progresses Tuesday as elonngated upper troughing in the
EPAC approaches. Synoptic cooling and increased onshore flow will
result in more substantial drop in max temps across Interior NorCal
Tuesday. Potential exists for some coastal stratus to invade
portions of the Southern Sacramento Valley tomorrow morning.
Afternoon instability again depicted over the mountains with GFS,
more than NAM, supporting slight chance of deep moist convection
over the Northern Sacramento valley, given its proximity to higher
terrain, compared to the rest of the Central Valley.

Upper trough stretches as it reaches the West Coast with southern
portion forming closed low. Models dig this low well to the south of
the CWA Wed as minor upstream ridging begins to nose inland over S
Oregon. Limited instability still depicted over portions of the
higher terrain Wed, but less extensive than today or Tuesday. Max
temps continue to trend downward Wednesday.

Closed low forecast to track inland over far southern portions of CA
Thursday with only weak afternoon instability depicted over southern
portions of the Sierra Nevada.

PCH

&&

.Extended Discussion (Friday through Monday)...
A shortwave trough will have moved into Nevada by Friday with a
flat ridge overhead. However, enough instability and orographic
flow will remain to generate some showers mainly over the Sierra/
Cascades Friday/Saturday. Meanwhile, a deepening longwave trough
remains over the eastern Pacific and moves closer to the West
Coast resulting in an increased potential for showery activity
Sunday/Monday with snow levels generally above pass levels. The
cold frontal boundary may move into northern CA on Monday/Monday
night, lowering snow levels to around 5500-6500 feet. JClapp

&&

.Aviation...
Upr rdg movs E as upr trof in EPAC apchs. VFR conds ovr Intr NorCal
nxt 24 hrs exc lcl MVFR/IFR poss vcnty delta into Srn Sac Vly in ST
btwn 08z-19z Tue. Isold tstms poss ovr Cstl Rnge, Wrn Plumas mtns,
and Siernev btwn 21z-03z. Lcl SWly sfc wnd gsts to 30 kts poss vcnty
delta mnly aftns and eves.


&&

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

&&

$$







000
FXUS66 KSTO 201645
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
945 AM PDT Mon Apr 20 2015

.Synopsis...
Very warm weather continues across the region today. Isolated to
scattered afternoon/early evening showers and thunderstorms possible
over the mountains today and Tuesday. Another low pressure system
will move into the region by the middle of the week bringing cooler
temperatures and continuing the threat of afternoon showers or
thunderstorms into Friday, mainly over the mountains.

&&

.Discussion...
Omega block in place along the West Coast with strong upper ridging
over NorCal and trapped low off the SoCal coast. Strong subsidence
inversion evident on 12z KOAK sounding with marine layer around 2100
feet deep. Satellite imagery showing extensive stratus along the
coast extending inland into portions of the Delta. Heights and
thicknesses are slightly less today and should equate to a few
degrees of cooling, however delta influenced areas will see greater
cooler as moderate delta breeze persists today. Elevated instability
progs showing potential for afternoon showers/thunderstorms over the
Coastal range, Western Plumas mountains, and Sierra Nevada.

Omega block progresses Tuesday as elonngated upper troughing in the
EPAC approaches. Synoptic cooling and increased onshore flow will
result in more substantial drop in max temps across Interior NorCal
Tuesday. Potential exists for some coastal stratus to invade
portions of the Southern Sacramento Valley tomorrow morning.
Afternoon instability again depicted over the mountains with GFS,
more than NAM, supporting slight chance of deep moist convection
over the Northern Sacramento valley, given its proximity to higher
terrain, compared to the rest of the Central Valley.

Upper trough stretches as it reaches the West Coast with southern
portion forming closed low. Models dig this low well to the south of
the CWA Wed as minor upstream ridging begins to nose inland over S
Oregon. Limited instability still depicted over portions of the
higher terrain Wed, but less extensive than today or Tuesday. Max
temps continue to trend downward Wednesday.

Closed low forecast to track inland over far southern portions of CA
Thursday with only weak afternoon instability depicted over southern
portions of the Sierra Nevada.

PCH

&&

.Extended Discussion (Friday through Monday)...
A shortwave trough will have moved into Nevada by Friday with a
flat ridge overhead. However, enough instability and orographic
flow will remain to generate some showers mainly over the Sierra/
Cascades Friday/Saturday. Meanwhile, a deepening longwave trough
remains over the eastern Pacific and moves closer to the West
Coast resulting in an increased potential for showery activity
Sunday/Monday with snow levels generally above pass levels. The
cold frontal boundary may move into northern CA on Monday/Monday
night, lowering snow levels to around 5500-6500 feet. JClapp

&&

.Aviation...
Upr rdg movs E as upr trof in EPAC apchs. VFR conds ovr Intr NorCal
nxt 24 hrs exc lcl MVFR/IFR poss vcnty delta into Srn Sac Vly in ST
btwn 08z-19z Tue. Isold tstms poss ovr Cstl Rnge, Wrn Plumas mtns,
and Siernev btwn 21z-03z. Lcl SWly sfc wnd gsts to 30 kts poss vcnty
delta mnly aftns and eves.


&&

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

&&

$$








000
FXUS66 KSTO 201040
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
340 AM PDT Mon Apr 20 2015

.Synopsis...
Very warm weather continues across the region today. Isolated to
scattered late day showers and thunderstorms will be possible over
the mountains. Another low pressure system will move into the
region by the middle of the week bringing cooler temperatures and
continuing the threat of showers or thunderstorms into the end of
the week, mainly over the mountains.

&&

.Discussion...
Clear skies across the interior of NorCal early this morning as
the blow-off from yesterday afternoon`s convection moves off the
coast. Temperatures are a little cooler through much of the valley
early this morning compared to 24 hours ago due to stronger
onshore flow. Redding is considerably cooler than early Sunday due
to lighter northerly winds.

Another warm day is on tap for much of the interior of NorCal
today as the Rex Block moves overhead in response to the approach
of a stronger upstream trough. Most areas expected to see at least
a few degrees of cooling, but Delta Breeze influenced areas of the
valley should be down around 5 degrees or so from Sunday, and may
even see a little stratus in the Sacramento area around sunrise
given the marine layer depth now around 2000 ft and strong
southwest winds gusting through Travis AFB.

Diurnal convection is expected to spread back into the northern
mountains today as a little more moisture feeds up from the south
and soundings are less capped.

More substantial cooling is expected to spread across NorCal
Tuesday as the upstream trough splits as it approaches the west
coast. It is expected to be strong enough to bring stronger
onshore flow to the region along with more widespread mainly
mountain convection, and the northern Sacramento Valley may even
see some activity given its proximity to higher terrain compared
to the rest of the valley.

Southern portion of the splitting trough is forecast to develop a
closed low as it drops south off the coast on Wednesday. Depending
on where the low tracks, the deformation zone may set up favorably
for much of the region to see at least a slight chance of showers
or thunderstorms that day with scattered showers and thunderstorms
continuing over the mountains. Less activity is anticipated by
Thursday as the low moves into the desert southwest and weak
ridging moves into NorCal.

&&

.Extended Discussion (Friday through Monday)...
A shortwave trough will have moved into Nevada by Friday with a
flat ridge overhead. However, enough instability and orographic
flow will remain to generate some showers mainly over the Sierra/
Cascades Friday/Saturday. Meanwhile, a deepening longwave trough
remains over the eastern Pacific and moves closer to the West
Coast resulting in an increased potential for showery activity
Sunday/Monday with snow levels generally above pass levels. The
cold frontal boundary may move into northern CA on Monday/Monday
night, lowering snow levels to around 5500-6500 feet. JClapp

&&

.Aviation...
VFR conditions for the next 24 hours. Delta Breeze with gust 20 to
30kt in southern Solano Co this morning. Stratus filling in west
of KSUU with marine layer around 2000 ft thick. Decent probability
(50%) of some stratus forming over and east of KMHR 12-15Z, and
potentially a brief impact at KSAC. Isolated thunderstorms likely
over Sierra and Coastal Range this afternoon/early evening. JClapp

&&

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

&&

$$





000
FXUS66 KSTO 201040
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
340 AM PDT Mon Apr 20 2015

.Synopsis...
Very warm weather continues across the region today. Isolated to
scattered late day showers and thunderstorms will be possible over
the mountains. Another low pressure system will move into the
region by the middle of the week bringing cooler temperatures and
continuing the threat of showers or thunderstorms into the end of
the week, mainly over the mountains.

&&

.Discussion...
Clear skies across the interior of NorCal early this morning as
the blow-off from yesterday afternoon`s convection moves off the
coast. Temperatures are a little cooler through much of the valley
early this morning compared to 24 hours ago due to stronger
onshore flow. Redding is considerably cooler than early Sunday due
to lighter northerly winds.

Another warm day is on tap for much of the interior of NorCal
today as the Rex Block moves overhead in response to the approach
of a stronger upstream trough. Most areas expected to see at least
a few degrees of cooling, but Delta Breeze influenced areas of the
valley should be down around 5 degrees or so from Sunday, and may
even see a little stratus in the Sacramento area around sunrise
given the marine layer depth now around 2000 ft and strong
southwest winds gusting through Travis AFB.

Diurnal convection is expected to spread back into the northern
mountains today as a little more moisture feeds up from the south
and soundings are less capped.

More substantial cooling is expected to spread across NorCal
Tuesday as the upstream trough splits as it approaches the west
coast. It is expected to be strong enough to bring stronger
onshore flow to the region along with more widespread mainly
mountain convection, and the northern Sacramento Valley may even
see some activity given its proximity to higher terrain compared
to the rest of the valley.

Southern portion of the splitting trough is forecast to develop a
closed low as it drops south off the coast on Wednesday. Depending
on where the low tracks, the deformation zone may set up favorably
for much of the region to see at least a slight chance of showers
or thunderstorms that day with scattered showers and thunderstorms
continuing over the mountains. Less activity is anticipated by
Thursday as the low moves into the desert southwest and weak
ridging moves into NorCal.

&&

.Extended Discussion (Friday through Monday)...
A shortwave trough will have moved into Nevada by Friday with a
flat ridge overhead. However, enough instability and orographic
flow will remain to generate some showers mainly over the Sierra/
Cascades Friday/Saturday. Meanwhile, a deepening longwave trough
remains over the eastern Pacific and moves closer to the West
Coast resulting in an increased potential for showery activity
Sunday/Monday with snow levels generally above pass levels. The
cold frontal boundary may move into northern CA on Monday/Monday
night, lowering snow levels to around 5500-6500 feet. JClapp

&&

.Aviation...
VFR conditions for the next 24 hours. Delta Breeze with gust 20 to
30kt in southern Solano Co this morning. Stratus filling in west
of KSUU with marine layer around 2000 ft thick. Decent probability
(50%) of some stratus forming over and east of KMHR 12-15Z, and
potentially a brief impact at KSAC. Isolated thunderstorms likely
over Sierra and Coastal Range this afternoon/early evening. JClapp

&&

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

&&

$$






000
FXUS66 KSTO 200515
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1015 PM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region through Monday.
Isolated to scattered late day showers and thunderstorms will be
possible over the mountains. Another low pressure system will move
into the region by the middle of the week bringing cooler
temperatures and continuing the threat of showers or thunderstorms
into the end of the week.

&&

.Discussion...
Some minor cooling in the Delta extreme Srn Sac and Nrn SJV on Sun
as onshore gradients gradually increased to sustain a Delta Breeze.
Otherwise...another warm day as all other areas were up to 5 degrees
warmer or so...with RDD AP establishing another record max of 93
which also tied the City record. This was the 4th consecutive day of
record maxes for the RDD AP.

Thunderstorm activity has diminished but CB blowoff has spread Wwd
from the Siernev across the Valley and towards the Coastal Range
zones as Ely flow has strengthened as the deformation zone from the
Rex Block sags Swd across Norcal and towards the I-80 corridor. To
the south of this...a meteorological col/saddle is evident. A benign
resemblance of this feature is forecast to remain over the Nrn
portion of CA on Mon...probably becoming oriented more SE to NW from
the central Siernev into the Coastal Range Mtns...so more afternoon
convection is expected again in the higher terrain/mtns.

Mins tonight will be generally cooler due to lack of Nly winds in
the far Nrn Vly...and stronger onshore gradients promoting cooling
in the Delta influenced areas. Stratus likely to creep into Wrn
Solano Co...but the stratus scheme came out negative due to wide
temp/dewpoint spreads this evening. The ML is about 1800 ft but more
expansive than last nite offshore. Given the location of the Rex
Block pattern along the coast and the Ely flow over Norcal...the
lower level support is not there (as evidenced from the KOAK evening
RAOB) for a stratus intrusion into the Sac Vly...although a small
area of low clouds may bank up on the E side of the Srn Sac Vly if
the onshore gradients remain strong enough.    JHM


.Previous Discussion...

Another warm day is on tap for much of the interior of NorCal on
Monday as the Rex Block moves overhead in response to the approach
of a stronger upstream trough. Most areas expected to see at least
a few degrees of cooling, but Delta Breeze influenced areas of the
valley should be down around 5 degrees or so from today. Also,
diurnal convection is expected to spread back into the northern
mountains as a little more moisture feeds up from the south and
soundings are less capped.

More substantial cooling is expected to spread across NorCal by
Tuesday as the upstream trough splits as it approaches the west
coast. It is expected to be strong enough to bring stronger
onshore flow to the region along with more widespread mainly
mountain convection, though favorable steering flow may bring
storms that form over the Coast Range down into the northern
Sacramento Valley.

Southern portion of the splitting trough is forecast to develop a
closed low as it drops south off the coast on Wednesday. Depending
on where the low tracks, the deformation zone may set up favorably
for much of the region to see at least a slight chance of showers
or thunderstorms that day with scattered showers and thunderstorms
continuing over the mountains.

&&

.Extended Discussion (Thursday through Sunday)...
A closed low that moves southward along the coast will be over
northern Baja by Thursday. However, the broad low will still
provide instability over NorCal and bring return flow moisture
from an easterly direction with thunderstorms looking like a
pretty good bet Thursday. The low will weaken and move to the east
by Friday, but the longwave trough will likely remain near the
west coast with potential showery activity through the weekend.

JClapp/Dang

&&

.Aviation...
VFR conditions for the next 24 hours. Isolated thunderstorms will
continue over the Sierra south of Lake Tahoe through 03z. Light
winds will continue except in vicinity of thunderstorms. Dang

&&

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

&&

$$








000
FXUS66 KSTO 200515
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1015 PM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region through Monday.
Isolated to scattered late day showers and thunderstorms will be
possible over the mountains. Another low pressure system will move
into the region by the middle of the week bringing cooler
temperatures and continuing the threat of showers or thunderstorms
into the end of the week.

&&

.Discussion...
Some minor cooling in the Delta extreme Srn Sac and Nrn SJV on Sun
as onshore gradients gradually increased to sustain a Delta Breeze.
Otherwise...another warm day as all other areas were up to 5 degrees
warmer or so...with RDD AP establishing another record max of 93
which also tied the City record. This was the 4th consecutive day of
record maxes for the RDD AP.

Thunderstorm activity has diminished but CB blowoff has spread Wwd
from the Siernev across the Valley and towards the Coastal Range
zones as Ely flow has strengthened as the deformation zone from the
Rex Block sags Swd across Norcal and towards the I-80 corridor. To
the south of this...a meteorological col/saddle is evident. A benign
resemblance of this feature is forecast to remain over the Nrn
portion of CA on Mon...probably becoming oriented more SE to NW from
the central Siernev into the Coastal Range Mtns...so more afternoon
convection is expected again in the higher terrain/mtns.

Mins tonight will be generally cooler due to lack of Nly winds in
the far Nrn Vly...and stronger onshore gradients promoting cooling
in the Delta influenced areas. Stratus likely to creep into Wrn
Solano Co...but the stratus scheme came out negative due to wide
temp/dewpoint spreads this evening. The ML is about 1800 ft but more
expansive than last nite offshore. Given the location of the Rex
Block pattern along the coast and the Ely flow over Norcal...the
lower level support is not there (as evidenced from the KOAK evening
RAOB) for a stratus intrusion into the Sac Vly...although a small
area of low clouds may bank up on the E side of the Srn Sac Vly if
the onshore gradients remain strong enough.    JHM


.Previous Discussion...

Another warm day is on tap for much of the interior of NorCal on
Monday as the Rex Block moves overhead in response to the approach
of a stronger upstream trough. Most areas expected to see at least
a few degrees of cooling, but Delta Breeze influenced areas of the
valley should be down around 5 degrees or so from today. Also,
diurnal convection is expected to spread back into the northern
mountains as a little more moisture feeds up from the south and
soundings are less capped.

More substantial cooling is expected to spread across NorCal by
Tuesday as the upstream trough splits as it approaches the west
coast. It is expected to be strong enough to bring stronger
onshore flow to the region along with more widespread mainly
mountain convection, though favorable steering flow may bring
storms that form over the Coast Range down into the northern
Sacramento Valley.

Southern portion of the splitting trough is forecast to develop a
closed low as it drops south off the coast on Wednesday. Depending
on where the low tracks, the deformation zone may set up favorably
for much of the region to see at least a slight chance of showers
or thunderstorms that day with scattered showers and thunderstorms
continuing over the mountains.

&&

.Extended Discussion (Thursday through Sunday)...
A closed low that moves southward along the coast will be over
northern Baja by Thursday. However, the broad low will still
provide instability over NorCal and bring return flow moisture
from an easterly direction with thunderstorms looking like a
pretty good bet Thursday. The low will weaken and move to the east
by Friday, but the longwave trough will likely remain near the
west coast with potential showery activity through the weekend.

JClapp/Dang

&&

.Aviation...
VFR conditions for the next 24 hours. Isolated thunderstorms will
continue over the Sierra south of Lake Tahoe through 03z. Light
winds will continue except in vicinity of thunderstorms. Dang

&&

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

&&

$$







000
FXUS66 KSTO 200515
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1015 PM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region through Monday.
Isolated to scattered late day showers and thunderstorms will be
possible over the mountains. Another low pressure system will move
into the region by the middle of the week bringing cooler
temperatures and continuing the threat of showers or thunderstorms
into the end of the week.

&&

.Discussion...
Some minor cooling in the Delta extreme Srn Sac and Nrn SJV on Sun
as onshore gradients gradually increased to sustain a Delta Breeze.
Otherwise...another warm day as all other areas were up to 5 degrees
warmer or so...with RDD AP establishing another record max of 93
which also tied the City record. This was the 4th consecutive day of
record maxes for the RDD AP.

Thunderstorm activity has diminished but CB blowoff has spread Wwd
from the Siernev across the Valley and towards the Coastal Range
zones as Ely flow has strengthened as the deformation zone from the
Rex Block sags Swd across Norcal and towards the I-80 corridor. To
the south of this...a meteorological col/saddle is evident. A benign
resemblance of this feature is forecast to remain over the Nrn
portion of CA on Mon...probably becoming oriented more SE to NW from
the central Siernev into the Coastal Range Mtns...so more afternoon
convection is expected again in the higher terrain/mtns.

Mins tonight will be generally cooler due to lack of Nly winds in
the far Nrn Vly...and stronger onshore gradients promoting cooling
in the Delta influenced areas. Stratus likely to creep into Wrn
Solano Co...but the stratus scheme came out negative due to wide
temp/dewpoint spreads this evening. The ML is about 1800 ft but more
expansive than last nite offshore. Given the location of the Rex
Block pattern along the coast and the Ely flow over Norcal...the
lower level support is not there (as evidenced from the KOAK evening
RAOB) for a stratus intrusion into the Sac Vly...although a small
area of low clouds may bank up on the E side of the Srn Sac Vly if
the onshore gradients remain strong enough.    JHM


.Previous Discussion...

Another warm day is on tap for much of the interior of NorCal on
Monday as the Rex Block moves overhead in response to the approach
of a stronger upstream trough. Most areas expected to see at least
a few degrees of cooling, but Delta Breeze influenced areas of the
valley should be down around 5 degrees or so from today. Also,
diurnal convection is expected to spread back into the northern
mountains as a little more moisture feeds up from the south and
soundings are less capped.

More substantial cooling is expected to spread across NorCal by
Tuesday as the upstream trough splits as it approaches the west
coast. It is expected to be strong enough to bring stronger
onshore flow to the region along with more widespread mainly
mountain convection, though favorable steering flow may bring
storms that form over the Coast Range down into the northern
Sacramento Valley.

Southern portion of the splitting trough is forecast to develop a
closed low as it drops south off the coast on Wednesday. Depending
on where the low tracks, the deformation zone may set up favorably
for much of the region to see at least a slight chance of showers
or thunderstorms that day with scattered showers and thunderstorms
continuing over the mountains.

&&

.Extended Discussion (Thursday through Sunday)...
A closed low that moves southward along the coast will be over
northern Baja by Thursday. However, the broad low will still
provide instability over NorCal and bring return flow moisture
from an easterly direction with thunderstorms looking like a
pretty good bet Thursday. The low will weaken and move to the east
by Friday, but the longwave trough will likely remain near the
west coast with potential showery activity through the weekend.

JClapp/Dang

&&

.Aviation...
VFR conditions for the next 24 hours. Isolated thunderstorms will
continue over the Sierra south of Lake Tahoe through 03z. Light
winds will continue except in vicinity of thunderstorms. Dang

&&

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

&&

$$








000
FXUS66 KSTO 192200
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
300 PM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region through Monday.
Isolated to scattered late day showers and thunderstorms will be
possible over the mountains. Another low pressure system will move
into the region by the middle of the week bringing cooler
temperatures and continuing the threat of showers or thunderstorms
into the end of the week.

&&

.Discussion...
Sunny skies and warm temperatures across the interior of NorCal
once again this afternoon. Temperatures are running a little above
readings of 24 hours ago across most of the region, except in the
Delta and northern San Joaquin Valley where a Delta trickle has
resulted in a few degrees of cooling. Current temperatures in the
valley range from around 70 at Travis AFB to about 90 at Redding
and Red Bluff.

Thunderstorms have so far been confined to the northern Sierra to
the south of Lake Tahoe this afternoon. Satellite imagery shows
some building cumulus further to the north up to around Blue
Canyon, and across portions of the Coast Range well to the north
of Clear Lake. The atmosphere further to the north is a little
drier and a little more capped as ridging builds into far northern
California, so development further north will likely be much more
isolated if something manages to pop. Similar to yesterday, the
storms will diminish rapidly by sunset with the loss of surface
heating.

Another warm day is on tap for much of the interior of NorCal on
Monday as the Rex Block moves overhead in response to the approach
of a stronger upstream trough. Most areas expected to see at least
a few degrees of cooling, but Delta Breeze influenced areas of the
valley should be down around 5 degrees or so from today. Also,
diurnal convection is expected to spread back into the northern
mountains as a little more moisture feeds up from the south and
soundings are less capped.

More substantial cooling is expected to spread across NorCal by
Tuesday as the upstream trough splits as it approaches the west
coast. It is expected to be strong enough to bring stronger
onshore flow to the region along with more widespread mainly
mountain convection, though favorable steering flow may bring
storms that form over the Coast Range down into the northern
Sacramento Valley.

Southern portion of the splitting trough is forecast to develop a
closed low as it drops south off the coast on Wednesday. Depending
on where the low tracks, the deformation zone may set up favorably
for much of the region to see at least a slight chance of showers
or thunderstorms that day with scattered showers and thunderstorms
continuing over the mountains.

&&

.Extended Discussion (Thursday through Sunday)...
A closed low that moves southward along the coast will be over
northern Baja by Thursday. However, the broad low will still
provide instability over NorCal and bring return flow moisture
from an easterly direction with thunderstorms looking like a
pretty good bet Thursday. The low will weaken and move to the east
by Friday, but the longwave trough will likely remain near the
west coast with potential showery activity through the weekend.

JClapp/Dang

&&

.Aviation...
VFR conditions for the next 24 hours. Isolated thunderstorms will
continue over the Sierra south of Lake Tahoe through 03z. Light
winds will continue except in vicinity of thunderstorms. Dang

&&

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

&&

$$






000
FXUS66 KSTO 192200
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
300 PM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region through Monday.
Isolated to scattered late day showers and thunderstorms will be
possible over the mountains. Another low pressure system will move
into the region by the middle of the week bringing cooler
temperatures and continuing the threat of showers or thunderstorms
into the end of the week.

&&

.Discussion...
Sunny skies and warm temperatures across the interior of NorCal
once again this afternoon. Temperatures are running a little above
readings of 24 hours ago across most of the region, except in the
Delta and northern San Joaquin Valley where a Delta trickle has
resulted in a few degrees of cooling. Current temperatures in the
valley range from around 70 at Travis AFB to about 90 at Redding
and Red Bluff.

Thunderstorms have so far been confined to the northern Sierra to
the south of Lake Tahoe this afternoon. Satellite imagery shows
some building cumulus further to the north up to around Blue
Canyon, and across portions of the Coast Range well to the north
of Clear Lake. The atmosphere further to the north is a little
drier and a little more capped as ridging builds into far northern
California, so development further north will likely be much more
isolated if something manages to pop. Similar to yesterday, the
storms will diminish rapidly by sunset with the loss of surface
heating.

Another warm day is on tap for much of the interior of NorCal on
Monday as the Rex Block moves overhead in response to the approach
of a stronger upstream trough. Most areas expected to see at least
a few degrees of cooling, but Delta Breeze influenced areas of the
valley should be down around 5 degrees or so from today. Also,
diurnal convection is expected to spread back into the northern
mountains as a little more moisture feeds up from the south and
soundings are less capped.

More substantial cooling is expected to spread across NorCal by
Tuesday as the upstream trough splits as it approaches the west
coast. It is expected to be strong enough to bring stronger
onshore flow to the region along with more widespread mainly
mountain convection, though favorable steering flow may bring
storms that form over the Coast Range down into the northern
Sacramento Valley.

Southern portion of the splitting trough is forecast to develop a
closed low as it drops south off the coast on Wednesday. Depending
on where the low tracks, the deformation zone may set up favorably
for much of the region to see at least a slight chance of showers
or thunderstorms that day with scattered showers and thunderstorms
continuing over the mountains.

&&

.Extended Discussion (Thursday through Sunday)...
A closed low that moves southward along the coast will be over
northern Baja by Thursday. However, the broad low will still
provide instability over NorCal and bring return flow moisture
from an easterly direction with thunderstorms looking like a
pretty good bet Thursday. The low will weaken and move to the east
by Friday, but the longwave trough will likely remain near the
west coast with potential showery activity through the weekend.

JClapp/Dang

&&

.Aviation...
VFR conditions for the next 24 hours. Isolated thunderstorms will
continue over the Sierra south of Lake Tahoe through 03z. Light
winds will continue except in vicinity of thunderstorms. Dang

&&

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

&&

$$





000
FXUS66 KSTO 192200
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
300 PM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region through Monday.
Isolated to scattered late day showers and thunderstorms will be
possible over the mountains. Another low pressure system will move
into the region by the middle of the week bringing cooler
temperatures and continuing the threat of showers or thunderstorms
into the end of the week.

&&

.Discussion...
Sunny skies and warm temperatures across the interior of NorCal
once again this afternoon. Temperatures are running a little above
readings of 24 hours ago across most of the region, except in the
Delta and northern San Joaquin Valley where a Delta trickle has
resulted in a few degrees of cooling. Current temperatures in the
valley range from around 70 at Travis AFB to about 90 at Redding
and Red Bluff.

Thunderstorms have so far been confined to the northern Sierra to
the south of Lake Tahoe this afternoon. Satellite imagery shows
some building cumulus further to the north up to around Blue
Canyon, and across portions of the Coast Range well to the north
of Clear Lake. The atmosphere further to the north is a little
drier and a little more capped as ridging builds into far northern
California, so development further north will likely be much more
isolated if something manages to pop. Similar to yesterday, the
storms will diminish rapidly by sunset with the loss of surface
heating.

Another warm day is on tap for much of the interior of NorCal on
Monday as the Rex Block moves overhead in response to the approach
of a stronger upstream trough. Most areas expected to see at least
a few degrees of cooling, but Delta Breeze influenced areas of the
valley should be down around 5 degrees or so from today. Also,
diurnal convection is expected to spread back into the northern
mountains as a little more moisture feeds up from the south and
soundings are less capped.

More substantial cooling is expected to spread across NorCal by
Tuesday as the upstream trough splits as it approaches the west
coast. It is expected to be strong enough to bring stronger
onshore flow to the region along with more widespread mainly
mountain convection, though favorable steering flow may bring
storms that form over the Coast Range down into the northern
Sacramento Valley.

Southern portion of the splitting trough is forecast to develop a
closed low as it drops south off the coast on Wednesday. Depending
on where the low tracks, the deformation zone may set up favorably
for much of the region to see at least a slight chance of showers
or thunderstorms that day with scattered showers and thunderstorms
continuing over the mountains.

&&

.Extended Discussion (Thursday through Sunday)...
A closed low that moves southward along the coast will be over
northern Baja by Thursday. However, the broad low will still
provide instability over NorCal and bring return flow moisture
from an easterly direction with thunderstorms looking like a
pretty good bet Thursday. The low will weaken and move to the east
by Friday, but the longwave trough will likely remain near the
west coast with potential showery activity through the weekend.

JClapp/Dang

&&

.Aviation...
VFR conditions for the next 24 hours. Isolated thunderstorms will
continue over the Sierra south of Lake Tahoe through 03z. Light
winds will continue except in vicinity of thunderstorms. Dang

&&

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

&&

$$






000
FXUS66 KSTO 192200
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
300 PM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region through Monday.
Isolated to scattered late day showers and thunderstorms will be
possible over the mountains. Another low pressure system will move
into the region by the middle of the week bringing cooler
temperatures and continuing the threat of showers or thunderstorms
into the end of the week.

&&

.Discussion...
Sunny skies and warm temperatures across the interior of NorCal
once again this afternoon. Temperatures are running a little above
readings of 24 hours ago across most of the region, except in the
Delta and northern San Joaquin Valley where a Delta trickle has
resulted in a few degrees of cooling. Current temperatures in the
valley range from around 70 at Travis AFB to about 90 at Redding
and Red Bluff.

Thunderstorms have so far been confined to the northern Sierra to
the south of Lake Tahoe this afternoon. Satellite imagery shows
some building cumulus further to the north up to around Blue
Canyon, and across portions of the Coast Range well to the north
of Clear Lake. The atmosphere further to the north is a little
drier and a little more capped as ridging builds into far northern
California, so development further north will likely be much more
isolated if something manages to pop. Similar to yesterday, the
storms will diminish rapidly by sunset with the loss of surface
heating.

Another warm day is on tap for much of the interior of NorCal on
Monday as the Rex Block moves overhead in response to the approach
of a stronger upstream trough. Most areas expected to see at least
a few degrees of cooling, but Delta Breeze influenced areas of the
valley should be down around 5 degrees or so from today. Also,
diurnal convection is expected to spread back into the northern
mountains as a little more moisture feeds up from the south and
soundings are less capped.

More substantial cooling is expected to spread across NorCal by
Tuesday as the upstream trough splits as it approaches the west
coast. It is expected to be strong enough to bring stronger
onshore flow to the region along with more widespread mainly
mountain convection, though favorable steering flow may bring
storms that form over the Coast Range down into the northern
Sacramento Valley.

Southern portion of the splitting trough is forecast to develop a
closed low as it drops south off the coast on Wednesday. Depending
on where the low tracks, the deformation zone may set up favorably
for much of the region to see at least a slight chance of showers
or thunderstorms that day with scattered showers and thunderstorms
continuing over the mountains.

&&

.Extended Discussion (Thursday through Sunday)...
A closed low that moves southward along the coast will be over
northern Baja by Thursday. However, the broad low will still
provide instability over NorCal and bring return flow moisture
from an easterly direction with thunderstorms looking like a
pretty good bet Thursday. The low will weaken and move to the east
by Friday, but the longwave trough will likely remain near the
west coast with potential showery activity through the weekend.

JClapp/Dang

&&

.Aviation...
VFR conditions for the next 24 hours. Isolated thunderstorms will
continue over the Sierra south of Lake Tahoe through 03z. Light
winds will continue except in vicinity of thunderstorms. Dang

&&

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

&&

$$





000
FXUS66 KSTO 191445
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
745 AM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region today and Monday.
Isolated late day showers and thunderstorms will be possible over
the mountains. Another low pressure system will move into the region
by the middle of the week bringing cooler temperatures and
continuing the threat of showers or thunderstorms into the end of
the week.

&&

.Discussion...
Clear skies across the interior of NorCal this morning except for a
few remnant mid and high clouds to the south of Sacramento from
yesterday afternoon`s convection. Temperatures range from the upper
20s and 30s in the colder mountain valleys to the upper 40s and 50s
elsewhere. The warmer thermal belt areas in the foothills and
northern Sacramento Valley are in the 60s.

The surface thermal trough remains over the valley and a moderately
strong northerly pressure gradient across far northern California
has kept enough of a northerly breeze overnight in Redding to keep
the temperatures there in the upper 60s while just to the south,
readings at Chico and Red Bluff managed to lower in the mid and
upper 50s.

Little change today with another warm day expected across the
region. Most areas of the valley are forecast to once again climb
well into the 80s, with even some lower 90s possible. The marine
layer is about the same depth as yesterday morning (around 1500 ft),
though the onshore gradient from SFO to SAC has tightened a bit to
around 2 mbs, so a little more of a Delta trickle may keep Fairfield
down a few degrees from Saturday.

Diurnal mountain convection is expected to be confined to the Sierra
mainly to the south of I-80 today as the weak low backs off the
NorCal coast allowing ridging from the PacNW to cover far northern
California. This is expected to cap off deeper convection over the
northern mountains today. A return to more widespread diurnal
convection over the mountains is forecast Monday and Tuesday.

No updates.

&&

.Previous Discussion...
Weak upper low off the norcal coast which brought isolated mountain
thunderstorms on Saturday drifting to the southwest today. As a
result, instability associated with the low is moving southward as
well. Therefore, only expecting a threat of showers or thunderstorms
over the northern Sierra today south of about interstate 80. Overall
airmass under upper level ridging will be warming slightly today
bringing up high temperatures to near records for the date. The low
then shifts inland towards the Socal coast on Monday in response to
a larger trough dropping out of the Gulf of Alaska and into the
eastern Pacific. With the forecast area well north of the the Socal
low, moister is fairly limited but models show some increased
instability over the mountains Monday so isolated afternoon mountain
thunderstorms are not out of the question. Airmass remains very warm
on Monday but may see highs drop just a bit over Sunday highs. by
Tuesday afternoon, Gulf of Alaska through is forecast to dig in just
off the coast. Should see a few to several degrees of cooling as
upper flow becomes more onshore increasing marine influence.  Mid
range models in fairly good agreement in pivoting some sort of
shortwave out ahead of the trough bringing a threat of showers or
thunderstorms to most areas of the CWA afternoon and evening hours.
General idea of mid range models is to split the trough as it moves
inland into a close low off the socal coast and an open wave over
the Pacific Northwest. Models differ on details but agree on showing
enough instability and moisture over the North state to warrant
shower or thunderstorm threat most areas Wednesday. Daytime
temperatures continue to cool on Wednesday but at this time are
still forecast to remain above normal.

&&

.Extended Discussion (Thursday through Sunday)
The longwave trough will dominate through the latter portion of the
week, keeping temperatures moderated. A closed low that moves
southward along the coast will be over northern Baja by Thursday.
However, the broad low will still provide instability over NorCal
and bring return flow moisture from an easterly direction with
thunderstorms looking like a pretty good bet Thursday. The low will
weaken and move to the east by Friday, but the longwave trough will
likely remain near the west coast with potential showery activity
through the weekend. JClapp

&&

.Aviation...
VFR conditions next 24 hours. Afternoon isolated thunderstorms will
develop over the Sierra southward of Lake Tahoe. Light winds will
continue except in vicinity of thunderstorms. JClapp

&&

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

&&

$$





000
FXUS66 KSTO 191445
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
745 AM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region today and Monday.
Isolated late day showers and thunderstorms will be possible over
the mountains. Another low pressure system will move into the region
by the middle of the week bringing cooler temperatures and
continuing the threat of showers or thunderstorms into the end of
the week.

&&

.Discussion...
Clear skies across the interior of NorCal this morning except for a
few remnant mid and high clouds to the south of Sacramento from
yesterday afternoon`s convection. Temperatures range from the upper
20s and 30s in the colder mountain valleys to the upper 40s and 50s
elsewhere. The warmer thermal belt areas in the foothills and
northern Sacramento Valley are in the 60s.

The surface thermal trough remains over the valley and a moderately
strong northerly pressure gradient across far northern California
has kept enough of a northerly breeze overnight in Redding to keep
the temperatures there in the upper 60s while just to the south,
readings at Chico and Red Bluff managed to lower in the mid and
upper 50s.

Little change today with another warm day expected across the
region. Most areas of the valley are forecast to once again climb
well into the 80s, with even some lower 90s possible. The marine
layer is about the same depth as yesterday morning (around 1500 ft),
though the onshore gradient from SFO to SAC has tightened a bit to
around 2 mbs, so a little more of a Delta trickle may keep Fairfield
down a few degrees from Saturday.

Diurnal mountain convection is expected to be confined to the Sierra
mainly to the south of I-80 today as the weak low backs off the
NorCal coast allowing ridging from the PacNW to cover far northern
California. This is expected to cap off deeper convection over the
northern mountains today. A return to more widespread diurnal
convection over the mountains is forecast Monday and Tuesday.

No updates.

&&

.Previous Discussion...
Weak upper low off the norcal coast which brought isolated mountain
thunderstorms on Saturday drifting to the southwest today. As a
result, instability associated with the low is moving southward as
well. Therefore, only expecting a threat of showers or thunderstorms
over the northern Sierra today south of about interstate 80. Overall
airmass under upper level ridging will be warming slightly today
bringing up high temperatures to near records for the date. The low
then shifts inland towards the Socal coast on Monday in response to
a larger trough dropping out of the Gulf of Alaska and into the
eastern Pacific. With the forecast area well north of the the Socal
low, moister is fairly limited but models show some increased
instability over the mountains Monday so isolated afternoon mountain
thunderstorms are not out of the question. Airmass remains very warm
on Monday but may see highs drop just a bit over Sunday highs. by
Tuesday afternoon, Gulf of Alaska through is forecast to dig in just
off the coast. Should see a few to several degrees of cooling as
upper flow becomes more onshore increasing marine influence.  Mid
range models in fairly good agreement in pivoting some sort of
shortwave out ahead of the trough bringing a threat of showers or
thunderstorms to most areas of the CWA afternoon and evening hours.
General idea of mid range models is to split the trough as it moves
inland into a close low off the socal coast and an open wave over
the Pacific Northwest. Models differ on details but agree on showing
enough instability and moisture over the North state to warrant
shower or thunderstorm threat most areas Wednesday. Daytime
temperatures continue to cool on Wednesday but at this time are
still forecast to remain above normal.

&&

.Extended Discussion (Thursday through Sunday)
The longwave trough will dominate through the latter portion of the
week, keeping temperatures moderated. A closed low that moves
southward along the coast will be over northern Baja by Thursday.
However, the broad low will still provide instability over NorCal
and bring return flow moisture from an easterly direction with
thunderstorms looking like a pretty good bet Thursday. The low will
weaken and move to the east by Friday, but the longwave trough will
likely remain near the west coast with potential showery activity
through the weekend. JClapp

&&

.Aviation...
VFR conditions next 24 hours. Afternoon isolated thunderstorms will
develop over the Sierra southward of Lake Tahoe. Light winds will
continue except in vicinity of thunderstorms. JClapp

&&

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

&&

$$






000
FXUS66 KSTO 191445
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
745 AM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region today and Monday.
Isolated late day showers and thunderstorms will be possible over
the mountains. Another low pressure system will move into the region
by the middle of the week bringing cooler temperatures and
continuing the threat of showers or thunderstorms into the end of
the week.

&&

.Discussion...
Clear skies across the interior of NorCal this morning except for a
few remnant mid and high clouds to the south of Sacramento from
yesterday afternoon`s convection. Temperatures range from the upper
20s and 30s in the colder mountain valleys to the upper 40s and 50s
elsewhere. The warmer thermal belt areas in the foothills and
northern Sacramento Valley are in the 60s.

The surface thermal trough remains over the valley and a moderately
strong northerly pressure gradient across far northern California
has kept enough of a northerly breeze overnight in Redding to keep
the temperatures there in the upper 60s while just to the south,
readings at Chico and Red Bluff managed to lower in the mid and
upper 50s.

Little change today with another warm day expected across the
region. Most areas of the valley are forecast to once again climb
well into the 80s, with even some lower 90s possible. The marine
layer is about the same depth as yesterday morning (around 1500 ft),
though the onshore gradient from SFO to SAC has tightened a bit to
around 2 mbs, so a little more of a Delta trickle may keep Fairfield
down a few degrees from Saturday.

Diurnal mountain convection is expected to be confined to the Sierra
mainly to the south of I-80 today as the weak low backs off the
NorCal coast allowing ridging from the PacNW to cover far northern
California. This is expected to cap off deeper convection over the
northern mountains today. A return to more widespread diurnal
convection over the mountains is forecast Monday and Tuesday.

No updates.

&&

.Previous Discussion...
Weak upper low off the norcal coast which brought isolated mountain
thunderstorms on Saturday drifting to the southwest today. As a
result, instability associated with the low is moving southward as
well. Therefore, only expecting a threat of showers or thunderstorms
over the northern Sierra today south of about interstate 80. Overall
airmass under upper level ridging will be warming slightly today
bringing up high temperatures to near records for the date. The low
then shifts inland towards the Socal coast on Monday in response to
a larger trough dropping out of the Gulf of Alaska and into the
eastern Pacific. With the forecast area well north of the the Socal
low, moister is fairly limited but models show some increased
instability over the mountains Monday so isolated afternoon mountain
thunderstorms are not out of the question. Airmass remains very warm
on Monday but may see highs drop just a bit over Sunday highs. by
Tuesday afternoon, Gulf of Alaska through is forecast to dig in just
off the coast. Should see a few to several degrees of cooling as
upper flow becomes more onshore increasing marine influence.  Mid
range models in fairly good agreement in pivoting some sort of
shortwave out ahead of the trough bringing a threat of showers or
thunderstorms to most areas of the CWA afternoon and evening hours.
General idea of mid range models is to split the trough as it moves
inland into a close low off the socal coast and an open wave over
the Pacific Northwest. Models differ on details but agree on showing
enough instability and moisture over the North state to warrant
shower or thunderstorm threat most areas Wednesday. Daytime
temperatures continue to cool on Wednesday but at this time are
still forecast to remain above normal.

&&

.Extended Discussion (Thursday through Sunday)
The longwave trough will dominate through the latter portion of the
week, keeping temperatures moderated. A closed low that moves
southward along the coast will be over northern Baja by Thursday.
However, the broad low will still provide instability over NorCal
and bring return flow moisture from an easterly direction with
thunderstorms looking like a pretty good bet Thursday. The low will
weaken and move to the east by Friday, but the longwave trough will
likely remain near the west coast with potential showery activity
through the weekend. JClapp

&&

.Aviation...
VFR conditions next 24 hours. Afternoon isolated thunderstorms will
develop over the Sierra southward of Lake Tahoe. Light winds will
continue except in vicinity of thunderstorms. JClapp

&&

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

&&

$$





000
FXUS66 KSTO 191445
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
745 AM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region today and Monday.
Isolated late day showers and thunderstorms will be possible over
the mountains. Another low pressure system will move into the region
by the middle of the week bringing cooler temperatures and
continuing the threat of showers or thunderstorms into the end of
the week.

&&

.Discussion...
Clear skies across the interior of NorCal this morning except for a
few remnant mid and high clouds to the south of Sacramento from
yesterday afternoon`s convection. Temperatures range from the upper
20s and 30s in the colder mountain valleys to the upper 40s and 50s
elsewhere. The warmer thermal belt areas in the foothills and
northern Sacramento Valley are in the 60s.

The surface thermal trough remains over the valley and a moderately
strong northerly pressure gradient across far northern California
has kept enough of a northerly breeze overnight in Redding to keep
the temperatures there in the upper 60s while just to the south,
readings at Chico and Red Bluff managed to lower in the mid and
upper 50s.

Little change today with another warm day expected across the
region. Most areas of the valley are forecast to once again climb
well into the 80s, with even some lower 90s possible. The marine
layer is about the same depth as yesterday morning (around 1500 ft),
though the onshore gradient from SFO to SAC has tightened a bit to
around 2 mbs, so a little more of a Delta trickle may keep Fairfield
down a few degrees from Saturday.

Diurnal mountain convection is expected to be confined to the Sierra
mainly to the south of I-80 today as the weak low backs off the
NorCal coast allowing ridging from the PacNW to cover far northern
California. This is expected to cap off deeper convection over the
northern mountains today. A return to more widespread diurnal
convection over the mountains is forecast Monday and Tuesday.

No updates.

&&

.Previous Discussion...
Weak upper low off the norcal coast which brought isolated mountain
thunderstorms on Saturday drifting to the southwest today. As a
result, instability associated with the low is moving southward as
well. Therefore, only expecting a threat of showers or thunderstorms
over the northern Sierra today south of about interstate 80. Overall
airmass under upper level ridging will be warming slightly today
bringing up high temperatures to near records for the date. The low
then shifts inland towards the Socal coast on Monday in response to
a larger trough dropping out of the Gulf of Alaska and into the
eastern Pacific. With the forecast area well north of the the Socal
low, moister is fairly limited but models show some increased
instability over the mountains Monday so isolated afternoon mountain
thunderstorms are not out of the question. Airmass remains very warm
on Monday but may see highs drop just a bit over Sunday highs. by
Tuesday afternoon, Gulf of Alaska through is forecast to dig in just
off the coast. Should see a few to several degrees of cooling as
upper flow becomes more onshore increasing marine influence.  Mid
range models in fairly good agreement in pivoting some sort of
shortwave out ahead of the trough bringing a threat of showers or
thunderstorms to most areas of the CWA afternoon and evening hours.
General idea of mid range models is to split the trough as it moves
inland into a close low off the socal coast and an open wave over
the Pacific Northwest. Models differ on details but agree on showing
enough instability and moisture over the North state to warrant
shower or thunderstorm threat most areas Wednesday. Daytime
temperatures continue to cool on Wednesday but at this time are
still forecast to remain above normal.

&&

.Extended Discussion (Thursday through Sunday)
The longwave trough will dominate through the latter portion of the
week, keeping temperatures moderated. A closed low that moves
southward along the coast will be over northern Baja by Thursday.
However, the broad low will still provide instability over NorCal
and bring return flow moisture from an easterly direction with
thunderstorms looking like a pretty good bet Thursday. The low will
weaken and move to the east by Friday, but the longwave trough will
likely remain near the west coast with potential showery activity
through the weekend. JClapp

&&

.Aviation...
VFR conditions next 24 hours. Afternoon isolated thunderstorms will
develop over the Sierra southward of Lake Tahoe. Light winds will
continue except in vicinity of thunderstorms. JClapp

&&

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

&&

$$






000
FXUS66 KSTO 191051
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
351 AM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region into early next
week. Isolated late day showers and thunderstorms will be possible
over the mountains. Another low pressure system will move into the
region by the middle of next week bringing cooler temperatures and
continuing the threat of possibly more widespread showers or
thunderstorms during the middle and end of the week.

&&

.Discussion...
Weak upper low off the norcal coast which brought isolated
mountain thunderstorms on Saturday drifting to the southwest
today. As a result...instability associated with the low is moving
southward as well. Therefore...only expecting a threat of showers
or thunderstorms over the northern Sierra today south of about
interstate 80. Overall airmass under upper level ridging will be
warming slightly today bringing up high temperatures to near
records for the date. The low then shifts inland towards the Socal
coast on Monday in response to a larger trough dropping out of the
Gulf of Alaska and into the eastern Pacific. With the forecast
area well north of the the Socal low...moister is fairly limited
but models show some increased instability over the mountains
Monday so isolated afternoon mountain thunderstorms are not out of
the question. Airmass remains very warm on Monday but may see
highs drop just a bit over Sunday highs. by Tuesday
afternoon...Gulf of Alaska through is forecast to dig in just off
the coast. Should see a few to several degrees of cooling as upper
flow becomes more onshore increasing marine influence.  Mid range
models in fairly good agreement in pivoting some sort of shortwave
out ahead of the trough bringing a threat of showers or
thunderstorms to most areas of the CWA afternoon and evening hours.
General idea of mid range models is to split the trough as it
moves inland into a close low off the socal coast and an open wave
over the Pacific Northwest. Models differ on details but agree on
showing enough instability and moisture over the North state to
warrant shower or thunderstorm threat most areas Wednesday. Daytime
temperatures continue to cool on Wednesday but at this time are
still forecast to remain above normal.

&&

.Extended Discussion (Thursday through Sunday)

The longwave trough will dominate through the latter portion of
the week, keeping temperatures moderated. A closed low that moves
southward along the coast will be over northern Baja by Thursday.
However, the broad low will still provide instability over NorCal
and bring return flow moisture from an easterly direction with
thunderstorms looking like a pretty good bet Thursday. The low
will weaken and move to the east by Friday, but the longwave
trough will likely remain near the west coast with potential
showery activity through the weekend.      JClapp


&&

.Aviation...

VFR conditions next 24 hours. Afternoon isolated thunderstorms
will develop over the Sierra southward of Lake Tahoe. Light winds
will continue except in vicinity of thunderstorms.     JClapp


&&

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

$$








000
FXUS66 KSTO 191051
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
351 AM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region into early next
week. Isolated late day showers and thunderstorms will be possible
over the mountains. Another low pressure system will move into the
region by the middle of next week bringing cooler temperatures and
continuing the threat of possibly more widespread showers or
thunderstorms during the middle and end of the week.

&&

.Discussion...
Weak upper low off the norcal coast which brought isolated
mountain thunderstorms on Saturday drifting to the southwest
today. As a result...instability associated with the low is moving
southward as well. Therefore...only expecting a threat of showers
or thunderstorms over the northern Sierra today south of about
interstate 80. Overall airmass under upper level ridging will be
warming slightly today bringing up high temperatures to near
records for the date. The low then shifts inland towards the Socal
coast on Monday in response to a larger trough dropping out of the
Gulf of Alaska and into the eastern Pacific. With the forecast
area well north of the the Socal low...moister is fairly limited
but models show some increased instability over the mountains
Monday so isolated afternoon mountain thunderstorms are not out of
the question. Airmass remains very warm on Monday but may see
highs drop just a bit over Sunday highs. by Tuesday
afternoon...Gulf of Alaska through is forecast to dig in just off
the coast. Should see a few to several degrees of cooling as upper
flow becomes more onshore increasing marine influence.  Mid range
models in fairly good agreement in pivoting some sort of shortwave
out ahead of the trough bringing a threat of showers or
thunderstorms to most areas of the CWA afternoon and evening hours.
General idea of mid range models is to split the trough as it
moves inland into a close low off the socal coast and an open wave
over the Pacific Northwest. Models differ on details but agree on
showing enough instability and moisture over the North state to
warrant shower or thunderstorm threat most areas Wednesday. Daytime
temperatures continue to cool on Wednesday but at this time are
still forecast to remain above normal.

&&

.Extended Discussion (Thursday through Sunday)

The longwave trough will dominate through the latter portion of
the week, keeping temperatures moderated. A closed low that moves
southward along the coast will be over northern Baja by Thursday.
However, the broad low will still provide instability over NorCal
and bring return flow moisture from an easterly direction with
thunderstorms looking like a pretty good bet Thursday. The low
will weaken and move to the east by Friday, but the longwave
trough will likely remain near the west coast with potential
showery activity through the weekend.      JClapp


&&

.Aviation...

VFR conditions next 24 hours. Afternoon isolated thunderstorms
will develop over the Sierra southward of Lake Tahoe. Light winds
will continue except in vicinity of thunderstorms.     JClapp


&&

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

$$









000
FXUS66 KSTO 191051
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
351 AM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region into early next
week. Isolated late day showers and thunderstorms will be possible
over the mountains. Another low pressure system will move into the
region by the middle of next week bringing cooler temperatures and
continuing the threat of possibly more widespread showers or
thunderstorms during the middle and end of the week.

&&

.Discussion...
Weak upper low off the norcal coast which brought isolated
mountain thunderstorms on Saturday drifting to the southwest
today. As a result...instability associated with the low is moving
southward as well. Therefore...only expecting a threat of showers
or thunderstorms over the northern Sierra today south of about
interstate 80. Overall airmass under upper level ridging will be
warming slightly today bringing up high temperatures to near
records for the date. The low then shifts inland towards the Socal
coast on Monday in response to a larger trough dropping out of the
Gulf of Alaska and into the eastern Pacific. With the forecast
area well north of the the Socal low...moister is fairly limited
but models show some increased instability over the mountains
Monday so isolated afternoon mountain thunderstorms are not out of
the question. Airmass remains very warm on Monday but may see
highs drop just a bit over Sunday highs. by Tuesday
afternoon...Gulf of Alaska through is forecast to dig in just off
the coast. Should see a few to several degrees of cooling as upper
flow becomes more onshore increasing marine influence.  Mid range
models in fairly good agreement in pivoting some sort of shortwave
out ahead of the trough bringing a threat of showers or
thunderstorms to most areas of the CWA afternoon and evening hours.
General idea of mid range models is to split the trough as it
moves inland into a close low off the socal coast and an open wave
over the Pacific Northwest. Models differ on details but agree on
showing enough instability and moisture over the North state to
warrant shower or thunderstorm threat most areas Wednesday. Daytime
temperatures continue to cool on Wednesday but at this time are
still forecast to remain above normal.

&&

.Extended Discussion (Thursday through Sunday)

The longwave trough will dominate through the latter portion of
the week, keeping temperatures moderated. A closed low that moves
southward along the coast will be over northern Baja by Thursday.
However, the broad low will still provide instability over NorCal
and bring return flow moisture from an easterly direction with
thunderstorms looking like a pretty good bet Thursday. The low
will weaken and move to the east by Friday, but the longwave
trough will likely remain near the west coast with potential
showery activity through the weekend.      JClapp


&&

.Aviation...

VFR conditions next 24 hours. Afternoon isolated thunderstorms
will develop over the Sierra southward of Lake Tahoe. Light winds
will continue except in vicinity of thunderstorms.     JClapp


&&

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

$$









000
FXUS66 KSTO 191051
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
351 AM PDT Sun Apr 19 2015

.Synopsis...
Very warm weather continues across the region into early next
week. Isolated late day showers and thunderstorms will be possible
over the mountains. Another low pressure system will move into the
region by the middle of next week bringing cooler temperatures and
continuing the threat of possibly more widespread showers or
thunderstorms during the middle and end of the week.

&&

.Discussion...
Weak upper low off the norcal coast which brought isolated
mountain thunderstorms on Saturday drifting to the southwest
today. As a result...instability associated with the low is moving
southward as well. Therefore...only expecting a threat of showers
or thunderstorms over the northern Sierra today south of about
interstate 80. Overall airmass under upper level ridging will be
warming slightly today bringing up high temperatures to near
records for the date. The low then shifts inland towards the Socal
coast on Monday in response to a larger trough dropping out of the
Gulf of Alaska and into the eastern Pacific. With the forecast
area well north of the the Socal low...moister is fairly limited
but models show some increased instability over the mountains
Monday so isolated afternoon mountain thunderstorms are not out of
the question. Airmass remains very warm on Monday but may see
highs drop just a bit over Sunday highs. by Tuesday
afternoon...Gulf of Alaska through is forecast to dig in just off
the coast. Should see a few to several degrees of cooling as upper
flow becomes more onshore increasing marine influence.  Mid range
models in fairly good agreement in pivoting some sort of shortwave
out ahead of the trough bringing a threat of showers or
thunderstorms to most areas of the CWA afternoon and evening hours.
General idea of mid range models is to split the trough as it
moves inland into a close low off the socal coast and an open wave
over the Pacific Northwest. Models differ on details but agree on
showing enough instability and moisture over the North state to
warrant shower or thunderstorm threat most areas Wednesday. Daytime
temperatures continue to cool on Wednesday but at this time are
still forecast to remain above normal.

&&

.Extended Discussion (Thursday through Sunday)

The longwave trough will dominate through the latter portion of
the week, keeping temperatures moderated. A closed low that moves
southward along the coast will be over northern Baja by Thursday.
However, the broad low will still provide instability over NorCal
and bring return flow moisture from an easterly direction with
thunderstorms looking like a pretty good bet Thursday. The low
will weaken and move to the east by Friday, but the longwave
trough will likely remain near the west coast with potential
showery activity through the weekend.      JClapp


&&

.Aviation...

VFR conditions next 24 hours. Afternoon isolated thunderstorms
will develop over the Sierra southward of Lake Tahoe. Light winds
will continue except in vicinity of thunderstorms.     JClapp


&&

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

$$








000
FXUS66 KSTO 190500
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
955 PM PDT Sat Apr 18 2015

.Synopsis...
Very warm weather continues across the region into early next
week. Isolated late day showers and thunderstorms will be possible
over the mountains. Another low pressure system will move into the
region by the middle of next week bringing cooler temperatures and
continuing the threat of mainly mountain showers and thunderstorms.

&&

.Discussion...
Diurnal convection has ended over interior Norcal although upper
trof lingers over the far Nrn zones and weak closed mid/upper level
low drifts off the far northern California coast. Cloud cover from
afternoon convection forecast to erode/dissipate overnight. Still
mins will be seasonably mild overnight especially in the thermal
belt areas due to warm air aloft. However...pressure falls from
heating in the valley have initiated a nearly 3 mbs SFO-SAC gradient
and a Delta Breeze.

Today was quite warm with max temps some 10-22 degrees warmer than
normal. RDD boasts a record max of 92 breaking the RDD AP (87 in
2009) and City records (90 in 1945).  JHM

.Previous Discussion...

The closed low over far northern California is forecast to drift
back to the southwest on Sunday as strong ridging over the eastern
Pacific moves closer, evolving into a Rex Block. This may cap off
deeper convection for a day across the northern mountains while the
focus of late day thunderstorms shifts to the Sierra to the south of
Lake Tahoe.

Temperatures will likely be the warmest of the past week on Sunday
as northerly/northeasterly flow briefly reinvigorates. Readings
through much of the Central Valley will likely climb into the upper
80s to lower 90s. These readings may flirt with records in the RDD
area again on Sun...especially the AP reading of 91 in 2009 while
the City record is 93 in 1945. The exception to the warming temps
may be in the Delta where a trickle may keep Fairfield in the lower
80s.

Diurnal mountain showers and thunderstorms are forecast to be on
the upswing again across NorCal on Monday as the ridge weakens
and a little more mid-level moisture is forecast to entrain up
from the southeast ahead of the weak low off the Central
California coast.

More widespread showers and thunderstorms along with cooler
weather will be possible beginning Tuesday as a stronger trough
moves into the region.

&&

.Extended Discussion (Wednesday through Saturday)...
The longwave trough will dominate through the early portions of
the extended period, keeping temperatures moderated. Showers and
thunderstorms still look like a pretty good for the mountains
Tuesday through Thursday, and possibly into Friday. A few of these
showers may make it down to the Valley as well, though timing and
location of these showers could be tricky.

Significant model differences arise by the end of next week. The
ECMWF and GEM both show a trough moving through Northern
California next Friday, whereas the GFS keeps a drier, broad
westerly flow solution. With no inkling toward any solution, our
forecast Friday and beyond leans heavily on climatology. Expect
temperatures to remain around or slightly warmer than normal. Dang

&&

.Aviation...VFR conditions next 24 hours. Light winds will continue
except in vicinity of Sun afternoon thunderstorms over Mtns.

&&

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

&&

$$







000
FXUS66 KSTO 190500
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
955 PM PDT Sat Apr 18 2015

.Synopsis...
Very warm weather continues across the region into early next
week. Isolated late day showers and thunderstorms will be possible
over the mountains. Another low pressure system will move into the
region by the middle of next week bringing cooler temperatures and
continuing the threat of mainly mountain showers and thunderstorms.

&&

.Discussion...
Diurnal convection has ended over interior Norcal although upper
trof lingers over the far Nrn zones and weak closed mid/upper level
low drifts off the far northern California coast. Cloud cover from
afternoon convection forecast to erode/dissipate overnight. Still
mins will be seasonably mild overnight especially in the thermal
belt areas due to warm air aloft. However...pressure falls from
heating in the valley have initiated a nearly 3 mbs SFO-SAC gradient
and a Delta Breeze.

Today was quite warm with max temps some 10-22 degrees warmer than
normal. RDD boasts a record max of 92 breaking the RDD AP (87 in
2009) and City records (90 in 1945).  JHM

.Previous Discussion...

The closed low over far northern California is forecast to drift
back to the southwest on Sunday as strong ridging over the eastern
Pacific moves closer, evolving into a Rex Block. This may cap off
deeper convection for a day across the northern mountains while the
focus of late day thunderstorms shifts to the Sierra to the south of
Lake Tahoe.

Temperatures will likely be the warmest of the past week on Sunday
as northerly/northeasterly flow briefly reinvigorates. Readings
through much of the Central Valley will likely climb into the upper
80s to lower 90s. These readings may flirt with records in the RDD
area again on Sun...especially the AP reading of 91 in 2009 while
the City record is 93 in 1945. The exception to the warming temps
may be in the Delta where a trickle may keep Fairfield in the lower
80s.

Diurnal mountain showers and thunderstorms are forecast to be on
the upswing again across NorCal on Monday as the ridge weakens
and a little more mid-level moisture is forecast to entrain up
from the southeast ahead of the weak low off the Central
California coast.

More widespread showers and thunderstorms along with cooler
weather will be possible beginning Tuesday as a stronger trough
moves into the region.

&&

.Extended Discussion (Wednesday through Saturday)...
The longwave trough will dominate through the early portions of
the extended period, keeping temperatures moderated. Showers and
thunderstorms still look like a pretty good for the mountains
Tuesday through Thursday, and possibly into Friday. A few of these
showers may make it down to the Valley as well, though timing and
location of these showers could be tricky.

Significant model differences arise by the end of next week. The
ECMWF and GEM both show a trough moving through Northern
California next Friday, whereas the GFS keeps a drier, broad
westerly flow solution. With no inkling toward any solution, our
forecast Friday and beyond leans heavily on climatology. Expect
temperatures to remain around or slightly warmer than normal. Dang

&&

.Aviation...VFR conditions next 24 hours. Light winds will continue
except in vicinity of Sun afternoon thunderstorms over Mtns.

&&

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

&&

$$







000
FXUS66 KSTO 182152
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
252 PM PDT Sat Apr 18 2015

.Synopsis...
Very warm weather continues across the region into early next
week. Isolated late day showers and thunderstorms will be possible
over the mountains. Another low pressure system will move into the
region by the middle of next week bringing cooler temperatures and
continuing the threat of mainly mountain showers and thunderstorms.

&&

.Discussion...
Very weak closed mid/upper level low drifting southward into far
northern California this afternoon from Oregon. Just enough
moisture (TPW around 1/2 an inch) and instability with day time
heating to kick off a few showers and thunderstorms over the
northern mountains and northern Sierra Nevada. Expect these to
dissipate shortly after sunset with loss of surface heating.

Temperatures remain very warm across the region once again this
afternoon with most areas running a few degrees ahead of yesterday
at this time. Mid-afternoon readings range from the 60s and 70s in
the mountains to mainly the 80s in the Central Valley. Warmest
readings are at the north end of the Sacramento Valley where
residual northerly wind is providing local enhanced downslope
warming, and readings at Redding may eclipse the 90 degree mark
later today.

The closed low over far northern California is forecast to drift
back to the southwest on Sunday as strong ridging over the eastern
Pacific moves closer, evolving into a weak Rex Block. This may cap
off deeper convection for a day across the northern mountains
while the focus of late day thunderstorms shifts to the Sierra to
the south of Lake Tahoe. Temperatures will likely be the warmest
of the past week on Sunday as northerly/northeasterly flow briefly
reinvigorates. Readings through much of the Central Valley will
likely climb into the upper 80s to lower 90s. The exception may be
in the Delta where a trickle may keep Fairfield in the lower 80s.

Diurnal mountain showers and thunderstorms are forecast to be on
the upswing again across NorCal on Monday as the ridge weakens
and a little more mid-level moisture is forecast to entrain up
from the southeast ahead of the weak low off the Central
California coast.

More widespread showers and thunderstorms along with cooler
weather will be possible beginning Tuesday as a stronger trough
moves into the region.

&&

.Extended Discussion (Wednesday through Saturday)...
The longwave trough will dominate through the early portions of
the extended period, keeping temperatures moderated. Showers and
thunderstorms still look like a pretty good for the mountains
Tuesday through Thursday, and possibly into Friday. A few of these
showers may make it down to the Valley as well, though timing and
location of these showers could be tricky.

Significant model differences arise by the end of next week. The
ECMWF and GEM both show a trough moving through Northern
California next Friday, whereas the GFS keeps a drier, broad
westerly flow solution. With no inkling toward any solution, our
forecast Friday and beyond leans heavily on climatology. Expect
temperatures to remain around or slightly warmer than normal. Dang

&&

.Aviation...
VFR conditions next 24 hours. Isolated thunderstorms will continue
over the mountains through 03z. Light winds will continue except
in vicinity of thunderstorms. Dang

&&

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

&&

$$





000
FXUS66 KSTO 182152
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
252 PM PDT Sat Apr 18 2015

.Synopsis...
Very warm weather continues across the region into early next
week. Isolated late day showers and thunderstorms will be possible
over the mountains. Another low pressure system will move into the
region by the middle of next week bringing cooler temperatures and
continuing the threat of mainly mountain showers and thunderstorms.

&&

.Discussion...
Very weak closed mid/upper level low drifting southward into far
northern California this afternoon from Oregon. Just enough
moisture (TPW around 1/2 an inch) and instability with day time
heating to kick off a few showers and thunderstorms over the
northern mountains and northern Sierra Nevada. Expect these to
dissipate shortly after sunset with loss of surface heating.

Temperatures remain very warm across the region once again this
afternoon with most areas running a few degrees ahead of yesterday
at this time. Mid-afternoon readings range from the 60s and 70s in
the mountains to mainly the 80s in the Central Valley. Warmest
readings are at the north end of the Sacramento Valley where
residual northerly wind is providing local enhanced downslope
warming, and readings at Redding may eclipse the 90 degree mark
later today.

The closed low over far northern California is forecast to drift
back to the southwest on Sunday as strong ridging over the eastern
Pacific moves closer, evolving into a weak Rex Block. This may cap
off deeper convection for a day across the northern mountains
while the focus of late day thunderstorms shifts to the Sierra to
the south of Lake Tahoe. Temperatures will likely be the warmest
of the past week on Sunday as northerly/northeasterly flow briefly
reinvigorates. Readings through much of the Central Valley will
likely climb into the upper 80s to lower 90s. The exception may be
in the Delta where a trickle may keep Fairfield in the lower 80s.

Diurnal mountain showers and thunderstorms are forecast to be on
the upswing again across NorCal on Monday as the ridge weakens
and a little more mid-level moisture is forecast to entrain up
from the southeast ahead of the weak low off the Central
California coast.

More widespread showers and thunderstorms along with cooler
weather will be possible beginning Tuesday as a stronger trough
moves into the region.

&&

.Extended Discussion (Wednesday through Saturday)...
The longwave trough will dominate through the early portions of
the extended period, keeping temperatures moderated. Showers and
thunderstorms still look like a pretty good for the mountains
Tuesday through Thursday, and possibly into Friday. A few of these
showers may make it down to the Valley as well, though timing and
location of these showers could be tricky.

Significant model differences arise by the end of next week. The
ECMWF and GEM both show a trough moving through Northern
California next Friday, whereas the GFS keeps a drier, broad
westerly flow solution. With no inkling toward any solution, our
forecast Friday and beyond leans heavily on climatology. Expect
temperatures to remain around or slightly warmer than normal. Dang

&&

.Aviation...
VFR conditions next 24 hours. Isolated thunderstorms will continue
over the mountains through 03z. Light winds will continue except
in vicinity of thunderstorms. Dang

&&

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

&&

$$






000
FXUS66 KSTO 181501
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
800 AM PDT Sat Apr 18 2015

.Synopsis...
Very warm weekend with temps in the 80s cooling to around 70 by
mid week next week. Slight chance of mountain showers this
weekend. Cloudy with chance of showers everywhere starting early
next week. Storm is not very strong so precipitation amounts not
expected to be significant.

&&

.Discussion...
Water vapor imagery shows the weak mid/upper level system drifting
down through the PacNW this morning. This feature is forecast to
form a weak closed low over the far northern portion of the state
this afternoon, and may provide enough instability for a few late
day showers and thunderstorms over the northern mountains.

Otherwise, the remainder of the area will continue to see warm and
dry conditions as most areas are starting off considerably warmer
than 24 hours ago. Morning soundings show further warming inland,
though the marine layer has deepened to around 1500 ft and offshore
flow has weakened, so we`ll watch to see if we start to see the
delta breeze pick up this afternoon and provide some local cooling.

No updates.

&&

.Previous Discussion...
Little to no update to the going forecast. Another very warm day
today with temperatures in the upper 80s. Models still forecasting a
weak impulse to slide south across the area then stall and linger
around through Sunday. It will create some weak instability and
showers and possibly a stray thunderstorm is possible.

A cool down is still expected starting Monday as a trough slowly
gets carved out over the west coast. This will bring more widespread
instability and clouds with increasing chances of moisture. Still
not looking like a very strong system. Rasch

&&

.Extended Discussion (Wednesday through Saturday)...
Mid range models in fairly good agreement for the middle of next
week and if model solutions verify, An upper low pressure system
should be fairly well established over California on Wednesday. In
addition to the significant cooling expected, resulting instability
from the low will generate scattered showers over most of the north
state. Except for the far north state, farthest from the low center,
most of Norcal will be unstable enough for a chance of afternoon
thunderstorms as well. Thursday will see a bit more cooling as the
low remains over the region and still more cooler air filters in.
Although precipitation with this low is not substantial, some areas
could end up picking up a few tenths of an inch of rainfall under
heavier or more numerous showers. Precipitable water values
associated with this low predicted at around .75 inches so expect
any thunderstorm cells to contain at least some rainfall. Extended
models all lift the low northeastward into the Great Basin next
Thursday night and early Friday but differ on what happens next in
regards to the next upper low dropping out of the Gulf of Alaska.

ECMWF and GEM want to dig this next low into Norcal bringing another
round of convective showers to most of the north state next Friday
and Saturday. GFS shows more of an inside slider situation which
could leave most of Norcal dry although Sierra could see some
showers under this scenario. Have gone with GFS for now as it is
more in line with previous model thinking but trend may be towards a
wetter solution and will have to wait and see how this trend
develops. Either way, still relatively cool daytime temperatures
expected with daily highs near normal for the end of next week.

&&

.Aviation...
VFR conditions next 24 hours. Isolated thunderstorms possible over
the mountains after 18z today. Light winds generally below 15 knots
except in vicinity of thunderstorms.

&&

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

&&

$$






000
FXUS66 KSTO 180912
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
212 AM PDT Sat Apr 18 2015

.Synopsis...
Very warm weekend with temps in the 80s cooling to around 70 by
mid week next week. Slight chance of mountain showers this
weekend. Cloudy with chance of showers everywhere starting early
next week. Storm is not very strong so precipitation amounts not
expected to be significant.

&&

.Discussion...
Little to no update to the going forecast. Another very warm day
today with temperatures in the upper 80s. Models still
forecasting a weak impulse to slide south across the area then
stall and linger around through Sunday. It will create some weak
instability and showers and possibly a stray thunderstorm is
possible.

A cool down is still expected starting Monday as a trough slowly
gets carved out over the west coast. This will bring more
widespread instability and clouds with increasing chances of
moisture. Still not looking like a very strong system. Rasch


.Extended Discussion (Wednesday through Saturday)

Mid range models in fairly good agreement for the middle of next
week and if model solutions verify...An upper low pressure system
should be fairly well established over California on Wednesday. In
addition to the significant cooling expected...resulting
instability from the low will generate scattered showers over most
of the north state. Except for the far north state...farthest from
the low center...most of Norcal will be unstable enough for a
chance of afternoon thunderstorms as well. Thursday will see a bit
more cooling as the low remains over the region and still more
cooler air filters in. Although precipitation with this low is not
substantial...some areas could end up picking up a few tenths of
an inch of rainfall under heavier or more numerous showers.
Precipitable water values associated with this low predicted at
around .75 inches so expect any thunderstorm cells to contain at
least some rainfall. Extended models all lift the low
northeastward into the Great Basin next Thursday night and early
Friday but differ on what happens next in regards to the next
upper low dropping out of the Gulf of Alaska.

ECMWF and GEM want to dig this next low into Norcal bringing
another round of convective showers to most of the north state
next Friday and Saturday. GFS shows more of an inside slider
situation which could leave most of Norcal dry although Sierra
could see some showers under this scenario. Have gone with GFS for
now as it is more in line with previous model thinking but trend
may be towards a wetter solution and will have to wait and see how
this trend develops. Either way...still relatively cool daytime
temperatures expected with daily highs near normal for the end of
next week.


&&

.Aviation...

VFR conditions next 24 hours. Isolated thunderstorms possible over
the mountains after 18z today. Light winds generally below 15
knots except in vicinity of thunderstorms.


&&

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

$$









000
FXUS66 KSTO 180912
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
212 AM PDT Sat Apr 18 2015

.Synopsis...
Very warm weekend with temps in the 80s cooling to around 70 by
mid week next week. Slight chance of mountain showers this
weekend. Cloudy with chance of showers everywhere starting early
next week. Storm is not very strong so precipitation amounts not
expected to be significant.

&&

.Discussion...
Little to no update to the going forecast. Another very warm day
today with temperatures in the upper 80s. Models still
forecasting a weak impulse to slide south across the area then
stall and linger around through Sunday. It will create some weak
instability and showers and possibly a stray thunderstorm is
possible.

A cool down is still expected starting Monday as a trough slowly
gets carved out over the west coast. This will bring more
widespread instability and clouds with increasing chances of
moisture. Still not looking like a very strong system. Rasch


.Extended Discussion (Wednesday through Saturday)

Mid range models in fairly good agreement for the middle of next
week and if model solutions verify...An upper low pressure system
should be fairly well established over California on Wednesday. In
addition to the significant cooling expected...resulting
instability from the low will generate scattered showers over most
of the north state. Except for the far north state...farthest from
the low center...most of Norcal will be unstable enough for a
chance of afternoon thunderstorms as well. Thursday will see a bit
more cooling as the low remains over the region and still more
cooler air filters in. Although precipitation with this low is not
substantial...some areas could end up picking up a few tenths of
an inch of rainfall under heavier or more numerous showers.
Precipitable water values associated with this low predicted at
around .75 inches so expect any thunderstorm cells to contain at
least some rainfall. Extended models all lift the low
northeastward into the Great Basin next Thursday night and early
Friday but differ on what happens next in regards to the next
upper low dropping out of the Gulf of Alaska.

ECMWF and GEM want to dig this next low into Norcal bringing
another round of convective showers to most of the north state
next Friday and Saturday. GFS shows more of an inside slider
situation which could leave most of Norcal dry although Sierra
could see some showers under this scenario. Have gone with GFS for
now as it is more in line with previous model thinking but trend
may be towards a wetter solution and will have to wait and see how
this trend develops. Either way...still relatively cool daytime
temperatures expected with daily highs near normal for the end of
next week.


&&

.Aviation...

VFR conditions next 24 hours. Isolated thunderstorms possible over
the mountains after 18z today. Light winds generally below 15
knots except in vicinity of thunderstorms.


&&

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

$$








000
FXUS66 KSTO 180459
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
955 PM PDT Fri Apr 17 2015

.Synopsis...
Warm weekend then cooling trend into mid week. A weak weather
system will bring a slight chance of mountain showers and
thunderstorms this weekend into Monday. A cold upper level trough
moves into the area by mid week bringing cooler temperatures and a
chance of precipitation over all of interior Northern California.

&&

.Discussion...
Max temps on Fri were modestly warmer than Thu...except over the Nrn
mtns and Siernev where they were mostly 5-10 degrees warmer.
Additional warming up to 5 degrees or so is expected on Sat with
possible record maxes (or ties) at RDD AP and City (87 in 2009 AP
and 90 in 1945 City) if our forecast of 90 verifies. Sun also looks
as warm of just a couple of degrees warmer than on Sat...but record
maxes on that date (19th) are slightly warmer...all in the low to
mid 90s. Record maxes listed below...

April 18th                  April 19th
--------------------------------------
RDD AP      87 (2009)       91 (2009)
RDD City    90 (1945)       93 (1945)
RBL         94 (1939)       95 (1939)
DTS         91 (1939)       91 (1939)
SAC         89 (1954)       90 (2009)
MOD         92 (1954)       93 (2009)
SCK         90 (1954)       92 (2009)

Weakening trof moving through the ridge is forecast to move into the
Nrn part of our CWA Sat afternoon. Some instability is forecast with
this feature...but moisture is low/lacking. Can`t rule out an
isolated shower/storm over the Nrn Mtns and Nrn Siernev during the
late afternoon and early evening. Instability is focused a little
farther S on Sun as a weak low forms offshore and a secondary weak
impulse drops over the Siernev S of Tahoe. The Yosemite NP area Swd
may be the best location for any afternoon convection on Sun in the
proximity of our CWA.  JHM


.Previous Discussion...

Temperatures warm up a little more on Saturday with high in the mid
80s to around 90 in the Valley and upper 50s to 70s in the mountains.
Similar temperatures are expected on Sunday. Temperatures will be a
little cooler on Monday, especially near the Delta, as a trough
approaches the area and onshore flow increases. Air temperatures are
warm but water temperatures in rivers and lakes remains cold in the
low 40s to low 60s. People going in the rivers and lakes this
weekend should use caution since cold water can lead to hypothermia.

A weak disturbance moves into Northern California on Saturday then
moves off the Nor Cal coast on Sunday. This will
bring some instability for a slight chance of showers and
thunderstorms over the mountains of interior Northern California
on Saturday and Sunday, mainly in the afternoons and evenings. The
best chance on Sunday looks like it will be over the Sierra as the
disturbance moves southwest. Upper level trough trough digs
offshore of the West Coast on Monday for continued instability
over the mountains for a slight chance of showers and thunderstorms.


.Extended Discussion (Tuesday through Friday)

Forecast for next week remains largely on track. Models still
drop large trough SE from near Gulf of Alaska to CA coast by
Tuesday. Although in general agreement, details still vary a bit
in timing and strength of system as it moves closer to shore. Latest
ECMWF and GEM show bulk of system`s energy skirting the coast while
GFS drops trough further inland across central/southern CA.
Regardless, with system of this size, think majority of area stands
a chance for scattered showers by later Tuesday into Thursday.
Amounts are expected to be light at this point as moisture remains
fairly limited (PWATS around 0.5 inch or less). Best chances look to
reside across the Sierra. As mentioned in previous discussion,
models show enough instability to warrant thunderstorm threat,
mainly across the mountains from Tuesday into Wednesday. Instability
spreads into the valley by Weds aftn so have added a chance for
thunder across central and southern portions of the valley. Aside
from the chance for precipitation, a cool down looks pretty certain.
Day to day temps will hinge a bit on cloud cover but in general,
highs will drop nearly 10 degrees from Monday to Tuesday and another
5-7 degrees by Weds/Thurs. This will bring temperatures back down to
near normal.

Model solutions diverge past Thursday with ECMWF continuing the
chance for active/wetter weather across the area into the weekend and
GFS/GEM showing a return to ridging.

CEO

&&

.Aviation...

VFR conditions next 24 hours. Isolated thunderstorms possible over
the mountains after 18z Saturday. Light winds generally 5-10 kts
except in vicinity of thunderstorms.

&&

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

$$






000
FXUS66 KSTO 180459
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
955 PM PDT Fri Apr 17 2015

.Synopsis...
Warm weekend then cooling trend into mid week. A weak weather
system will bring a slight chance of mountain showers and
thunderstorms this weekend into Monday. A cold upper level trough
moves into the area by mid week bringing cooler temperatures and a
chance of precipitation over all of interior Northern California.

&&

.Discussion...
Max temps on Fri were modestly warmer than Thu...except over the Nrn
mtns and Siernev where they were mostly 5-10 degrees warmer.
Additional warming up to 5 degrees or so is expected on Sat with
possible record maxes (or ties) at RDD AP and City (87 in 2009 AP
and 90 in 1945 City) if our forecast of 90 verifies. Sun also looks
as warm of just a couple of degrees warmer than on Sat...but record
maxes on that date (19th) are slightly warmer...all in the low to
mid 90s. Record maxes listed below...

April 18th                  April 19th
--------------------------------------
RDD AP      87 (2009)       91 (2009)
RDD City    90 (1945)       93 (1945)
RBL         94 (1939)       95 (1939)
DTS         91 (1939)       91 (1939)
SAC         89 (1954)       90 (2009)
MOD         92 (1954)       93 (2009)
SCK         90 (1954)       92 (2009)

Weakening trof moving through the ridge is forecast to move into the
Nrn part of our CWA Sat afternoon. Some instability is forecast with
this feature...but moisture is low/lacking. Can`t rule out an
isolated shower/storm over the Nrn Mtns and Nrn Siernev during the
late afternoon and early evening. Instability is focused a little
farther S on Sun as a weak low forms offshore and a secondary weak
impulse drops over the Siernev S of Tahoe. The Yosemite NP area Swd
may be the best location for any afternoon convection on Sun in the
proximity of our CWA.  JHM


.Previous Discussion...

Temperatures warm up a little more on Saturday with high in the mid
80s to around 90 in the Valley and upper 50s to 70s in the mountains.
Similar temperatures are expected on Sunday. Temperatures will be a
little cooler on Monday, especially near the Delta, as a trough
approaches the area and onshore flow increases. Air temperatures are
warm but water temperatures in rivers and lakes remains cold in the
low 40s to low 60s. People going in the rivers and lakes this
weekend should use caution since cold water can lead to hypothermia.

A weak disturbance moves into Northern California on Saturday then
moves off the Nor Cal coast on Sunday. This will
bring some instability for a slight chance of showers and
thunderstorms over the mountains of interior Northern California
on Saturday and Sunday, mainly in the afternoons and evenings. The
best chance on Sunday looks like it will be over the Sierra as the
disturbance moves southwest. Upper level trough trough digs
offshore of the West Coast on Monday for continued instability
over the mountains for a slight chance of showers and thunderstorms.


.Extended Discussion (Tuesday through Friday)

Forecast for next week remains largely on track. Models still
drop large trough SE from near Gulf of Alaska to CA coast by
Tuesday. Although in general agreement, details still vary a bit
in timing and strength of system as it moves closer to shore. Latest
ECMWF and GEM show bulk of system`s energy skirting the coast while
GFS drops trough further inland across central/southern CA.
Regardless, with system of this size, think majority of area stands
a chance for scattered showers by later Tuesday into Thursday.
Amounts are expected to be light at this point as moisture remains
fairly limited (PWATS around 0.5 inch or less). Best chances look to
reside across the Sierra. As mentioned in previous discussion,
models show enough instability to warrant thunderstorm threat,
mainly across the mountains from Tuesday into Wednesday. Instability
spreads into the valley by Weds aftn so have added a chance for
thunder across central and southern portions of the valley. Aside
from the chance for precipitation, a cool down looks pretty certain.
Day to day temps will hinge a bit on cloud cover but in general,
highs will drop nearly 10 degrees from Monday to Tuesday and another
5-7 degrees by Weds/Thurs. This will bring temperatures back down to
near normal.

Model solutions diverge past Thursday with ECMWF continuing the
chance for active/wetter weather across the area into the weekend and
GFS/GEM showing a return to ridging.

CEO

&&

.Aviation...

VFR conditions next 24 hours. Isolated thunderstorms possible over
the mountains after 18z Saturday. Light winds generally 5-10 kts
except in vicinity of thunderstorms.

&&

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

$$







000
FXUS66 KSTO 180459
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
955 PM PDT Fri Apr 17 2015

.Synopsis...
Warm weekend then cooling trend into mid week. A weak weather
system will bring a slight chance of mountain showers and
thunderstorms this weekend into Monday. A cold upper level trough
moves into the area by mid week bringing cooler temperatures and a
chance of precipitation over all of interior Northern California.

&&

.Discussion...
Max temps on Fri were modestly warmer than Thu...except over the Nrn
mtns and Siernev where they were mostly 5-10 degrees warmer.
Additional warming up to 5 degrees or so is expected on Sat with
possible record maxes (or ties) at RDD AP and City (87 in 2009 AP
and 90 in 1945 City) if our forecast of 90 verifies. Sun also looks
as warm of just a couple of degrees warmer than on Sat...but record
maxes on that date (19th) are slightly warmer...all in the low to
mid 90s. Record maxes listed below...

April 18th                  April 19th
--------------------------------------
RDD AP      87 (2009)       91 (2009)
RDD City    90 (1945)       93 (1945)
RBL         94 (1939)       95 (1939)
DTS         91 (1939)       91 (1939)
SAC         89 (1954)       90 (2009)
MOD         92 (1954)       93 (2009)
SCK         90 (1954)       92 (2009)

Weakening trof moving through the ridge is forecast to move into the
Nrn part of our CWA Sat afternoon. Some instability is forecast with
this feature...but moisture is low/lacking. Can`t rule out an
isolated shower/storm over the Nrn Mtns and Nrn Siernev during the
late afternoon and early evening. Instability is focused a little
farther S on Sun as a weak low forms offshore and a secondary weak
impulse drops over the Siernev S of Tahoe. The Yosemite NP area Swd
may be the best location for any afternoon convection on Sun in the
proximity of our CWA.  JHM


.Previous Discussion...

Temperatures warm up a little more on Saturday with high in the mid
80s to around 90 in the Valley and upper 50s to 70s in the mountains.
Similar temperatures are expected on Sunday. Temperatures will be a
little cooler on Monday, especially near the Delta, as a trough
approaches the area and onshore flow increases. Air temperatures are
warm but water temperatures in rivers and lakes remains cold in the
low 40s to low 60s. People going in the rivers and lakes this
weekend should use caution since cold water can lead to hypothermia.

A weak disturbance moves into Northern California on Saturday then
moves off the Nor Cal coast on Sunday. This will
bring some instability for a slight chance of showers and
thunderstorms over the mountains of interior Northern California
on Saturday and Sunday, mainly in the afternoons and evenings. The
best chance on Sunday looks like it will be over the Sierra as the
disturbance moves southwest. Upper level trough trough digs
offshore of the West Coast on Monday for continued instability
over the mountains for a slight chance of showers and thunderstorms.


.Extended Discussion (Tuesday through Friday)

Forecast for next week remains largely on track. Models still
drop large trough SE from near Gulf of Alaska to CA coast by
Tuesday. Although in general agreement, details still vary a bit
in timing and strength of system as it moves closer to shore. Latest
ECMWF and GEM show bulk of system`s energy skirting the coast while
GFS drops trough further inland across central/southern CA.
Regardless, with system of this size, think majority of area stands
a chance for scattered showers by later Tuesday into Thursday.
Amounts are expected to be light at this point as moisture remains
fairly limited (PWATS around 0.5 inch or less). Best chances look to
reside across the Sierra. As mentioned in previous discussion,
models show enough instability to warrant thunderstorm threat,
mainly across the mountains from Tuesday into Wednesday. Instability
spreads into the valley by Weds aftn so have added a chance for
thunder across central and southern portions of the valley. Aside
from the chance for precipitation, a cool down looks pretty certain.
Day to day temps will hinge a bit on cloud cover but in general,
highs will drop nearly 10 degrees from Monday to Tuesday and another
5-7 degrees by Weds/Thurs. This will bring temperatures back down to
near normal.

Model solutions diverge past Thursday with ECMWF continuing the
chance for active/wetter weather across the area into the weekend and
GFS/GEM showing a return to ridging.

CEO

&&

.Aviation...

VFR conditions next 24 hours. Isolated thunderstorms possible over
the mountains after 18z Saturday. Light winds generally 5-10 kts
except in vicinity of thunderstorms.

&&

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

$$






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