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000
FXUS63 KLSX 020138
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
838 PM CDT Mon Sep 1 2014

.UPDATE:
Issued at 835 PM CDT Mon Sep 1 2014

In the process of pulling the flash flood watch northward a couple
of tiers of counties based on radar trends. Still believe that the
heaviest rainfall threat will be shifting south with time, but
current trends suggest that may not be fast enough to prevent some
hydro problems over the next few hours. However...did limit the
FFA to just this evening in COU area as heaviest rains should drop
south/east of their area by 05z. May be able to trim some other
northern areas as well by then but will watch radar trends for
this adjustment.

Truett

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 310 PM CDT Mon Sep 1 2014

Heavy rain threat is the primary forecast challenge for tonight.
Another shortwave is moving east-southeast through the longwave
pattern over the Great Plains.  This shortwave will trigger a
south-southwesterly low level jet to increase again this evening,
aimed right at the low level baroclinic zone left over from last
night`s storms.  With plenty of moisture in place over the area and
a baroclinic zone that`s parallel or nearly parallel to the mid
level flow, expect that thunderstorms will form and train over parts
of Missouri and Illinois this evening and tonight.  All short range
guidance shows a tremendous amount of moisture convergence on the
nose of the low level jet tonight...generally along and south of the
I-70 corridor.  Think the axis of heaviest rain will actually be
along and south of the I-44 corridor in Missouri and along and south
of I-70 in Illinois, but I cannot rule out heavy rain a little
further north either.  QPF forecast paints a swath of heavy rain
along this axis between 1.5 and 2 inches.  With the potential for
locally higher amounts, and flash flood guidance running around
2-2.5 inches per hour, will go ahead and issue a flash flood watch
for those areas.  Further north across northeast Missouri and west
central Illinois, there could be some widely scattered/isolated
showers and thunderstorms, but I don`t think these will train and
cause any flooding issues.

Carney

.LONG TERM:  (Tuesday through Next Monday)
Issued at 340 PM CDT Mon Sep 1 2014

(Tuesday - Wednesday)

Flat zonal upper flow will remain in the wake of the strong
shortwave expected to pull away by Tuesday morning, with the hot
upper ridge that had given us our period of well above average temps
lurking just to the south.  The synoptic cold front will probably
linger into the STL metro area at the start of Tuesday, but its
associated precipitation likely well out ahead of it by this time
into southern MO and far southern IL.  Any slowing down of the
eastward progress of the shortwave though will favor some
precipitation of some sort extending back close to the STL metro
area.

The upper level pattern at this point is not very favorable for much
more southward progress of the front and so this boundary is
expected to stall somewhere in the southern CWA Tuesday and into
Tuesday night.  The old frontal boundary will probably lose a lot of
its moisture convergence strength Tuesday afternoon and evening and
so only isolated convection is expected in the absence of a low
level jet or upper level support.  The low level jet that will help
refire up a more organized system later on Tuesday night will
probably begin well to the west of our region and not really reach
our area until Wednesday if it holds.

It is for this reason that Wednesday PoPs were tempered until we see
a clearer signal for how this will evolve and develop.

Above average temps expected thru this period but not hot enough to
warrant any sort of heat headline.

(Thursday - Friday)

Well above average temps are currently anticipated during this
stretch, with max temps in the lo-mid 90s.  Peak heat index values
are looking to be from 100-105 for many areas on Thursday and,
depending on whether or not thunderstorms can get going along
approaching cold front, may very well see these values again
on Friday.

Fortunately, it is now September and so these shots of heat should
be relatively short-lived...with it all expected to come to an end
once the front moves thru Friday night.  Boosted PoPs to just below
likely for Friday night.

(Saturday - next Monday)

A well deserved cool period still in the offing in the wake of this
front with a 1025mb high pressure to be the dominant influence
during this period.  Max temps may struggle to exit the 70s in many
areas.

TES

&&

.AVIATION:  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1238 PM CDT Mon Sep 1 2014

Expect VFR flight conditions to prevail through much of the
afternoon. Scattered light showers will continue through the early
afternoon across parts of southeast Missouri. West to southwest
wind will gust to around 24kts. Expecting thunderstorms to
redevelop somewhere over west central or southwest Missouri later
this afternoon and spread northeast into parts of central and
eastern Missouri and southwest Illinois this evening. Storms will
likely train along and south of the I-70/I-44 corridor tonight
producing IFR conditions in heavy rain. Storms should move south
and begin to dissipate between 08-12Z.

Specifics for KSTL:

VFR flight conditions are expected to prevail this afternoon at
Lambert. Latest thoughts are that thunderstorms will develop over
southwest/west central Missouri and spread east-northeast into
eastern Missouri by early this evening. A prolonged period of
thunderstorms with occasional heavy rain will likely impact the
terminal during the mid-late evening. Storms should move south of
the terminal between 06-11Z; timing is uncertain at this time.
After storms exit the STL Metro area, expect MVFR CIGs to rise to
VFR during the morning.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...FLASH FLOOD WATCH until 7 AM CDT Tuesday FOR Callaway MO-Cole MO-
     Crawford MO-Franklin MO-Gasconade MO-Iron MO-Jefferson MO-
     Lincoln MO-Madison MO-Moniteau MO-Montgomery MO-Osage MO-
     Pike MO-Reynolds MO-St. Charles MO-St. Francois MO-St.
     Louis City MO-St. Louis MO-Ste. Genevieve MO-Warren MO-
     Washington MO.

     FLASH FLOOD WATCH until Midnight CDT tonight FOR Boone MO.

IL...FLASH FLOOD WATCH until 7 AM CDT Tuesday FOR Bond IL-Calhoun IL-
     Clinton IL-Fayette IL-Greene IL-Jersey IL-Macoupin IL-
     Madison IL-Marion IL-Monroe IL-Montgomery IL-Randolph IL-
     St. Clair IL-Washington IL.

&&

$$

WFO LSX








000
FXUS63 KLSX 012041
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
341 PM CDT Mon Sep 1 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 310 PM CDT Mon Sep 1 2014

Heavy rain threat is the primary forecast challenge for tonight.
Another shortwave is moving east-southeast through the longwave
pattern over the Great Plains.  This shortwave will trigger a
south-southwesterly low level jet to increase again this evening,
aimed right at the low level baroclinic zone left over from last
night`s storms.  With plenty of moisture in place over the area and
a baroclinic zone that`s parallel or nearly parallel to the mid
level flow, expect that thunderstorms will form and train over parts
of Missouri and Illinois this evening and tonight.  All short range
guidance shows a tremendous amount of moisture convergence on the
nose of the low level jet tonight...generally along and south of the
I-70 corridor.  Think the axis of heaviest rain will actually be
along and south of the I-44 corridor in Missouri and along and south
of I-70 in Illinois, but I cannot rule out heavy rain a little
further north either.  QPF forecast paints a swath of heavy rain
along this axis between 1.5 and 2 inches.  With the potential for
locally higher amounts, and flash flood guidance running around
2-2.5 inches per hour, will go ahead and issue a flash flood watch
for those areas.  Further north across northeast Missouri and west
central Illinois, there could be some widely scattered/isolated
showers and thunderstorms, but I don`t think these will train and
cause any flooding issues.

Carney

.LONG TERM:  (Tuesday through Next Monday)
Issued at 340 PM CDT Mon Sep 1 2014

(Tuesday - Wednesday)

Flat zonal upper flow will remain in the wake of the strong
shortwave expected to pull away by Tuesday morning, with the hot
upper ridge that had given us our period of well above average temps
lurking just to the south.  The synoptic cold front will probably
linger into the STL metro area at the start of Tuesday, but its
associated precipitation likely well out ahead of it by this time
into southern MO and far southern IL.  Any slowing down of the
eastward progress of the shortwave though will favor some
precipitation of some sort extending back close to the STL metro
area.

The upper level pattern at this point is not very favorable for much
more southward progress of the front and so this boundary is
expected to stall somewhere in the southern CWA Tuesday and into
Tuesday night.  The old frontal boundary will probably lose a lot of
its moisture convergence strength Tuesday afternoon and evening and
so only isolated convection is expected in the absence of a low
level jet or upper level support.  The low level jet that will help
refire up a more organized system later on Tuesday night will
probably begin well to the west of our region and not really reach
our area until Wednesday if it holds.

It is for this reason that Wednesday PoPs were tempered until we see
a clearer signal for how this will evolve and develop.

Above average temps expected thru this period but not hot enough to
warrant any sort of heat headline.

(Thursday - Friday)

Well above average temps are currently anticipated during this
stretch, with max temps in the lo-mid 90s.  Peak heat index values
are looking to be from 100-105 for many areas on Thursday and,
depending on whether or not thunderstorms can get going along
approaching cold front, may very well see these values again
on Friday.

Fortunately, it is now September and so these shots of heat should
be relatively short-lived...with it all expected to come to an end
once the front moves thru Friday night.  Boosted PoPs to just below
likely for Friday night.

(Saturday - next Monday)

A well deserved cool period still in the offing in the wake of this
front with a 1025mb high pressure to be the dominant influence
during this period.  Max temps may struggle to exit the 70s in many
areas.

TES

&&

.AVIATION:  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1238 PM CDT Mon Sep 1 2014

Expect VFR flight conditions to prevail through much of the
afternoon. Scattered light showers will continue through the early
afternoon across parts of southeast Missouri. West to southwest
wind will gust to around 24kts. Expecting thunderstorms to
redevelop somewhere over west central or southwest Missouri later
this afternoon and spread northeast into parts of central and
eastern Missouri and southwest Illinois this evening. Storms will
likely train along and south of the I-70/I-44 corridor tonight
producing IFR conditions in heavy rain. Storms should move south
and begin to dissipate between 08-12Z.

Specifics for KSTL:

VFR flight conditions are expected to prevail this afternoon at
Lambert. Latest thoughts are that thunderstorms will develop over
southwest/west central Missouri and spread east-northeast into
eastern Missouri by early this evening. A prolonged period of
thunderstorms with occasional heavy rain will likely impact the
terminal during the mid-late evening. Storms should move south of
the terminal between 06-11Z; timing is uncertain at this time.
After storms exit the STL Metro area, expect MVFR CIGs to rise to
VFR during the morning.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...FLASH FLOOD WATCH from 7 PM CDT this evening through Tuesday
     morning FOR Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Madison MO-Moniteau MO-Osage MO-
     Reynolds MO-St. Charles MO-St. Francois MO-St. Louis City
     MO-St. Louis MO-Ste. Genevieve MO-Warren MO-Washington MO.

IL...FLASH FLOOD WATCH from 7 PM CDT this evening through Tuesday
     morning FOR Bond IL-Clinton IL-Fayette IL-Madison IL-Marion
     IL-Monroe IL-Montgomery IL-Randolph IL-St. Clair IL-
     Washington IL.

&&

$$

WFO LSX






000
FXUS63 KLSX 012011
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
311 PM CDT Mon Sep 1 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 310 PM CDT Mon Sep 1 2014

Heavy rain threat is the primary forecast challenge for tonight.
Another shortwave is moving east-southeast through the longwave
pattern over the Great Plains.  This shortwave will trigger a
south-southwesterly low level jet to increase again this evening,
aimed right at the low level baroclinic zone left over from last
night`s storms.  With plenty of moisture in place over the area and
a baroclinic zone that`s parallel or nearly parallel to the mid
level flow, expect that thunderstorms will form and train over parts
of Missouri and Illinois this evening and tonight.  All short range
guidance shows a tremendous amount of moisture convergence on the
nose of the low level jet tonight...generally along and south of the
I-70 corridor.  Think the axis of heaviest rain will actually be
along and south of the I-44 corridor in Missouri and along and south
of I-70 in Illinois, but I cannot rule out heavy rain a little
further north either.  QPF forecast paints a swath of heavy rain
along this axis between 1.5 and 2 inches.  With the potential for
locally higher amounts, and flash flood guidance running around
2-2.5 inches per hour, will go ahead and issue a flash flood watch
for those areas.  Further north across northeast Missouri and west
central Illinois, there could be some widely scattered/isolated
showers and thunderstorms, but I don`t think these will train and
cause any flooding issues.

Carney

.LONG TERM:  (Tuesday through Sunday)
Issued at 344 AM CDT Mon Sep 1 2014

The front and/or effective boundary should linger across the
region on Tue/Tue night before lifting northeastward as a warm
front on Wed/Wed night. The precipitation threat will also lift
northeastward with the warm front during the middle of the week.
Model solutions then depict a cold front moving into the area
towards the end of the week and into next weekend, bringing a
chance of rain and a cooler air mass into the region.

Kanofsky

&&

.AVIATION:  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1238 PM CDT Mon Sep 1 2014

Expect VFR flight conditions to prevail through much of the
afternoon. Scattered light showers will continue through the early
afternoon across parts of southeast Missouri. West to southwest
wind will gust to around 24kts. Expecting thunderstorms to
redevelop somewhere over west central or southwest Missouri later
this afternoon and spread northeast into parts of central and
eastern Missouri and southwest Illinois this evening. Storms will
likely train along and south of the I-70/I-44 corridor tonight
producing IFR conditions in heavy rain. Storms should move south
and begin to dissipate between 08-12Z.

Specifics for KSTL:

VFR flight conditions are expected to prevail this afternoon at
Lambert. Latest thoughts are that thunderstorms will develop over
southwest/west central Missouri and spread east-northeast into
eastern Missouri by early this evening. A prolonged period of
thunderstorms with occasional heavy rain will likely impact the
terminal during the mid-late evening. Storms should move south of
the terminal between 06-11Z; timing is uncertain at this time.
After storms exit the STL Metro area, expect MVFR CIGs to rise to
VFR during the morning.

Carney

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     72  87  71  90 /  90  20  20  40
Quincy          65  83  66  88 /  20   5  10  40
Columbia        68  87  68  91 /  80  10  30  40
Jefferson City  69  87  69  91 /  90  20  30  40
Salem           71  85  68  88 /  90  50  20  30
Farmington      72  85  68  87 /  90  50  30  40

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...FLASH FLOOD WATCH from 7 PM CDT this evening through Tuesday
     morning FOR Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Madison MO-Moniteau MO-Osage MO-
     Reynolds MO-St. Charles MO-St. Francois MO-St. Louis City
     MO-St. Louis MO-Ste. Genevieve MO-Warren MO-Washington MO.

IL...FLASH FLOOD WATCH from 7 PM CDT this evening through Tuesday
     morning FOR Bond IL-Clinton IL-Fayette IL-Madison IL-Marion
     IL-Monroe IL-Montgomery IL-Randolph IL-St. Clair IL-
     Washington IL.

&&

$$

WFO LSX








000
FXUS63 KLSX 012011
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
311 PM CDT Mon Sep 1 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 310 PM CDT Mon Sep 1 2014

Heavy rain threat is the primary forecast challenge for tonight.
Another shortwave is moving east-southeast through the longwave
pattern over the Great Plains.  This shortwave will trigger a
south-southwesterly low level jet to increase again this evening,
aimed right at the low level baroclinic zone left over from last
night`s storms.  With plenty of moisture in place over the area and
a baroclinic zone that`s parallel or nearly parallel to the mid
level flow, expect that thunderstorms will form and train over parts
of Missouri and Illinois this evening and tonight.  All short range
guidance shows a tremendous amount of moisture convergence on the
nose of the low level jet tonight...generally along and south of the
I-70 corridor.  Think the axis of heaviest rain will actually be
along and south of the I-44 corridor in Missouri and along and south
of I-70 in Illinois, but I cannot rule out heavy rain a little
further north either.  QPF forecast paints a swath of heavy rain
along this axis between 1.5 and 2 inches.  With the potential for
locally higher amounts, and flash flood guidance running around
2-2.5 inches per hour, will go ahead and issue a flash flood watch
for those areas.  Further north across northeast Missouri and west
central Illinois, there could be some widely scattered/isolated
showers and thunderstorms, but I don`t think these will train and
cause any flooding issues.

Carney

.LONG TERM:  (Tuesday through Sunday)
Issued at 344 AM CDT Mon Sep 1 2014

The front and/or effective boundary should linger across the
region on Tue/Tue night before lifting northeastward as a warm
front on Wed/Wed night. The precipitation threat will also lift
northeastward with the warm front during the middle of the week.
Model solutions then depict a cold front moving into the area
towards the end of the week and into next weekend, bringing a
chance of rain and a cooler air mass into the region.

Kanofsky

&&

.AVIATION:  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1238 PM CDT Mon Sep 1 2014

Expect VFR flight conditions to prevail through much of the
afternoon. Scattered light showers will continue through the early
afternoon across parts of southeast Missouri. West to southwest
wind will gust to around 24kts. Expecting thunderstorms to
redevelop somewhere over west central or southwest Missouri later
this afternoon and spread northeast into parts of central and
eastern Missouri and southwest Illinois this evening. Storms will
likely train along and south of the I-70/I-44 corridor tonight
producing IFR conditions in heavy rain. Storms should move south
and begin to dissipate between 08-12Z.

Specifics for KSTL:

VFR flight conditions are expected to prevail this afternoon at
Lambert. Latest thoughts are that thunderstorms will develop over
southwest/west central Missouri and spread east-northeast into
eastern Missouri by early this evening. A prolonged period of
thunderstorms with occasional heavy rain will likely impact the
terminal during the mid-late evening. Storms should move south of
the terminal between 06-11Z; timing is uncertain at this time.
After storms exit the STL Metro area, expect MVFR CIGs to rise to
VFR during the morning.

Carney

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     72  87  71  90 /  90  20  20  40
Quincy          65  83  66  88 /  20   5  10  40
Columbia        68  87  68  91 /  80  10  30  40
Jefferson City  69  87  69  91 /  90  20  30  40
Salem           71  85  68  88 /  90  50  20  30
Farmington      72  85  68  87 /  90  50  30  40

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...FLASH FLOOD WATCH from 7 PM CDT this evening through Tuesday
     morning FOR Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Madison MO-Moniteau MO-Osage MO-
     Reynolds MO-St. Charles MO-St. Francois MO-St. Louis City
     MO-St. Louis MO-Ste. Genevieve MO-Warren MO-Washington MO.

IL...FLASH FLOOD WATCH from 7 PM CDT this evening through Tuesday
     morning FOR Bond IL-Clinton IL-Fayette IL-Madison IL-Marion
     IL-Monroe IL-Montgomery IL-Randolph IL-St. Clair IL-
     Washington IL.

&&

$$

WFO LSX







000
FXUS63 KLSX 011752
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1252 PM CDT Mon Sep 1 2014

.SHORT TERM: (Today through Tonight)
Issued at 344 AM CDT Mon Sep 1 2014

There are three interconnected forecast issues covering today
through tomorrow: convective timing, the potential for severe
weather, and the potential for heavy rainfall. The main factors
involved with the forecast are the ongoing early morning
convection with its outflow boundaries, an upstream synoptic cold
front, and a couple of shortwaves moving through a broad longwave
trough.

If the early morning convection dissipates across our area, then the
air mass is likely to destabilize ahead of the approaching synoptic
cold front. Models are forecasting up to 2000-3000 J/kg of CAPE
and between 30-60 kts of 0-6 km bulk shear across most of the CWA
during the afternoon/evening hours ahead of the front. These
parameters are more than sufficient to support organized severe
thunderstorms. With at least a few models depicting a small but
nonzero perpendicular component to the shear vectors with respect
to the H85 boundary orientation, it would not be surprising to see
a few supercells somewhere across the region before convection
starts to congeal and become more linear with time. If the models
are correct with the orientation of the shear vectors with respect
to the cold front, then aftn/eve convection should become linear
very quickly.

As of 0830z, early morning convection appears to be diminishing
over northern/northeastern MO, lending credence to the above
scenario. However, if the early morning convection does not
dissipate and if the outflow boundary is pushed farther to the
south, then the overall coverage of severe thunderstorms would
probably be much lower and would tend to be limited to the
southern CWA.

Moving into tonight, the cold front becomes oriented nearly parallel
to the 0-6 km shear vectors, and the primary forecast issue then
shifts from severe weather to heavy rainfall. Overall, this looks
like a decent setup for locally heavy rainfall. PW values
increase to over 2" tonight, which is not only at +2SD and the 99th
percentile for August, but also exceeds both of those thresholds for
September. Models also depict broad lift from favorable jet coupling
(between the RER of a jet at H25 and the LER of a jet at H85) which
develops by 06z in response to a shortwave moving through NEB/IA.
In addition, MUCAPE remains quite high overnight and the mid-level
flow also appears to be nearly parallel to the cold front. Because
of these factors, I`m reasonably sure that there is going to be an
elongated band of convection overnight, but I`m not sure whether
it will be with the true synoptic cold front (resulting in a band
of rainfall near the I-70 corridor) or with the outflow/effective
boundary (resulting in a band of rainfall located much farther
south, possibly only affecting the southern CWA).

Flash flood guidance numbers are around 2-3" for 1 hour, 2.5-3.5"
for 3 hours, and 3-5" for 6 hours. There hasn`t been much rainfall
over the last few days, therefore the ground is not saturated and
can probably absorb a fair amount of water before widespread
flooding becomes a concern. There is also a question about where
the axis of heaviest rainfall will occur. For these reasons, we
will hold off on any flood/flash flood watches for now.

Kanofsky

.LONG TERM:  (Tuesday through Sunday)
Issued at 344 AM CDT Mon Sep 1 2014

The front and/or effective boundary should linger across the
region on Tue/Tue night before lifting northeastward as a warm
front on Wed/Wed night. The precipitation threat will also lift
northeastward with the warm front during the middle of the week.
Model solutions then depict a cold front moving into the area
towards the end of the week and into next weekend, bringing a
chance of rain and a cooler air mass into the region.

Kanofsky

&&

.AVIATION:  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1238 PM CDT Mon Sep 1 2014

Expect VFR flight conditions to prevail through much of the
afternoon. Scattered light showers will continue through the early
afternoon across parts of southeast Missouri. West to southwest
wind will gust to around 24kts. Expecting thunderstorms to
redevelop somewhere over west central or southwest Missouri later
this afternoon and spread northeast into parts of central and
eastern Missouri and southwest Illinois this evening. Storms will
likely train along and south of the I-70/I-44 corridor tonight
producing IFR conditions in heavy rain. Storms should move south
and begin to dissipate between 08-12Z.

Specifics for KSTL:

VFR flight conditions are expected to prevail this afternoon at
Lambert. Latest thoughts are that thunderstorms will develop over
southwest/west central Missouri and spread east-northeast into
eastern Missouri by early this evening. A prolonged period of
thunderstorms with occasional heavy rain will likely impact the
terminal during the mid-late evening. Storms should move south of
the terminal between 06-11Z; timing is uncertain at this time.
After storms exit the STL Metro area, expect MVFR CIGs to rise to
VFR during the morning.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 011752
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1252 PM CDT Mon Sep 1 2014

.SHORT TERM: (Today through Tonight)
Issued at 344 AM CDT Mon Sep 1 2014

There are three interconnected forecast issues covering today
through tomorrow: convective timing, the potential for severe
weather, and the potential for heavy rainfall. The main factors
involved with the forecast are the ongoing early morning
convection with its outflow boundaries, an upstream synoptic cold
front, and a couple of shortwaves moving through a broad longwave
trough.

If the early morning convection dissipates across our area, then the
air mass is likely to destabilize ahead of the approaching synoptic
cold front. Models are forecasting up to 2000-3000 J/kg of CAPE
and between 30-60 kts of 0-6 km bulk shear across most of the CWA
during the afternoon/evening hours ahead of the front. These
parameters are more than sufficient to support organized severe
thunderstorms. With at least a few models depicting a small but
nonzero perpendicular component to the shear vectors with respect
to the H85 boundary orientation, it would not be surprising to see
a few supercells somewhere across the region before convection
starts to congeal and become more linear with time. If the models
are correct with the orientation of the shear vectors with respect
to the cold front, then aftn/eve convection should become linear
very quickly.

As of 0830z, early morning convection appears to be diminishing
over northern/northeastern MO, lending credence to the above
scenario. However, if the early morning convection does not
dissipate and if the outflow boundary is pushed farther to the
south, then the overall coverage of severe thunderstorms would
probably be much lower and would tend to be limited to the
southern CWA.

Moving into tonight, the cold front becomes oriented nearly parallel
to the 0-6 km shear vectors, and the primary forecast issue then
shifts from severe weather to heavy rainfall. Overall, this looks
like a decent setup for locally heavy rainfall. PW values
increase to over 2" tonight, which is not only at +2SD and the 99th
percentile for August, but also exceeds both of those thresholds for
September. Models also depict broad lift from favorable jet coupling
(between the RER of a jet at H25 and the LER of a jet at H85) which
develops by 06z in response to a shortwave moving through NEB/IA.
In addition, MUCAPE remains quite high overnight and the mid-level
flow also appears to be nearly parallel to the cold front. Because
of these factors, I`m reasonably sure that there is going to be an
elongated band of convection overnight, but I`m not sure whether
it will be with the true synoptic cold front (resulting in a band
of rainfall near the I-70 corridor) or with the outflow/effective
boundary (resulting in a band of rainfall located much farther
south, possibly only affecting the southern CWA).

Flash flood guidance numbers are around 2-3" for 1 hour, 2.5-3.5"
for 3 hours, and 3-5" for 6 hours. There hasn`t been much rainfall
over the last few days, therefore the ground is not saturated and
can probably absorb a fair amount of water before widespread
flooding becomes a concern. There is also a question about where
the axis of heaviest rainfall will occur. For these reasons, we
will hold off on any flood/flash flood watches for now.

Kanofsky

.LONG TERM:  (Tuesday through Sunday)
Issued at 344 AM CDT Mon Sep 1 2014

The front and/or effective boundary should linger across the
region on Tue/Tue night before lifting northeastward as a warm
front on Wed/Wed night. The precipitation threat will also lift
northeastward with the warm front during the middle of the week.
Model solutions then depict a cold front moving into the area
towards the end of the week and into next weekend, bringing a
chance of rain and a cooler air mass into the region.

Kanofsky

&&

.AVIATION:  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1238 PM CDT Mon Sep 1 2014

Expect VFR flight conditions to prevail through much of the
afternoon. Scattered light showers will continue through the early
afternoon across parts of southeast Missouri. West to southwest
wind will gust to around 24kts. Expecting thunderstorms to
redevelop somewhere over west central or southwest Missouri later
this afternoon and spread northeast into parts of central and
eastern Missouri and southwest Illinois this evening. Storms will
likely train along and south of the I-70/I-44 corridor tonight
producing IFR conditions in heavy rain. Storms should move south
and begin to dissipate between 08-12Z.

Specifics for KSTL:

VFR flight conditions are expected to prevail this afternoon at
Lambert. Latest thoughts are that thunderstorms will develop over
southwest/west central Missouri and spread east-northeast into
eastern Missouri by early this evening. A prolonged period of
thunderstorms with occasional heavy rain will likely impact the
terminal during the mid-late evening. Storms should move south of
the terminal between 06-11Z; timing is uncertain at this time.
After storms exit the STL Metro area, expect MVFR CIGs to rise to
VFR during the morning.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 011150
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
650 AM CDT Mon Sep 1 2014

.SHORT TERM: (Today through Tonight)
Issued at 344 AM CDT Mon Sep 1 2014

There are three interconnected forecast issues covering today
through tomorrow: convective timing, the potential for severe
weather, and the potential for heavy rainfall. The main factors
involved with the forecast are the ongoing early morning
convection with its outflow boundaries, an upstream synoptic cold
front, and a couple of shortwaves moving through a broad longwave
trough.

If the early morning convection dissipates across our area, then the
air mass is likely to destabilize ahead of the approaching synoptic
cold front. Models are forecasting up to 2000-3000 J/kg of CAPE
and between 30-60 kts of 0-6 km bulk shear across most of the CWA
during the afternoon/evening hours ahead of the front. These
parameters are more than sufficient to support organized severe
thunderstorms. With at least a few models depicting a small but
nonzero perpendicular component to the shear vectors with respect
to the H85 boundary orientation, it would not be surprising to see
a few supercells somewhere across the region before convection
starts to congeal and become more linear with time. If the models
are correct with the orientation of the shear vectors with respect
to the cold front, then aftn/eve convection should become linear
very quickly.

As of 0830z, early morning convection appears to be diminishing
over northern/northeastern MO, lending credence to the above
scenario. However, if the early morning convection does not
dissipate and if the outflow boundary is pushed farther to the
south, then the overall coverage of severe thunderstorms would
probably be much lower and would tend to be limited to the
southern CWA.

Moving into tonight, the cold front becomes oriented nearly parallel
to the 0-6 km shear vectors, and the primary forecast issue then
shifts from severe weather to heavy rainfall. Overall, this looks
like a decent setup for locally heavy rainfall. PW values
increase to over 2" tonight, which is not only at +2SD and the 99th
percentile for August, but also exceeds both of those thresholds for
September. Models also depict broad lift from favorable jet coupling
(between the RER of a jet at H25 and the LER of a jet at H85) which
develops by 06z in response to a shortwave moving through NEB/IA.
In addition, MUCAPE remains quite high overnight and the mid-level
flow also appears to be nearly parallel to the cold front. Because
of these factors, I`m reasonably sure that there is going to be an
elongated band of convection overnight, but I`m not sure whether
it will be with the true synoptic cold front (resulting in a band
of rainfall near the I-70 corridor) or with the outflow/effective
boundary (resulting in a band of rainfall located much farther
south, possibly only affecting the southern CWA).

Flash flood guidance numbers are around 2-3" for 1 hour, 2.5-3.5"
for 3 hours, and 3-5" for 6 hours. There hasn`t been much rainfall
over the last few days, therefore the ground is not saturated and
can probably absorb a fair amount of water before widespread
flooding becomes a concern. There is also a question about where
the axis of heaviest rainfall will occur. For these reasons, we
will hold off on any flood/flash flood watches for now.

Kanofsky

.LONG TERM:  (Tuesday through Sunday)
Issued at 344 AM CDT Mon Sep 1 2014

The front and/or effective boundary should linger across the
region on Tue/Tue night before lifting northeastward as a warm
front on Wed/Wed night. The precipitation threat will also lift
northeastward with the warm front during the middle of the week.
Model solutions then depict a cold front moving into the area
towards the end of the week and into next weekend, bringing a
chance of rain and a cooler air mass into the region.

Kanofsky

&&

.AVIATION:  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 639 AM CDT Mon Sep 1 2014

Weakening area of showers and spotty thunderstorms extending from
KUIN into central and east central MO will move eastward early
this morning and eventually dissipate. It will be exiting KUIN and
KCOU by 13z and should impact the St. Louis area terminals for
several hours this morning with predominately VFR conditions and
occasionally high-end MVFR vsbys with showers. After this
precipitation ends, a rather large lull is expected until 21z or
so when new thunderstorm development is anticipated along a
corridor impacting KCOU and the St. Louis area terminals. Some of
the guidance suggests this could be a rather prolonged period of
showers and thunderstorms, pushing south by late evening.
Confidence is low that any of this afternoon and evening
thunderstorm development will impact KUIN and hence just kept with
the mention of VCTS.

Specifics for KSTL:

Showers will impact the terminal until around mid-morning with
predominately VFR conditions and occasionally high-end MVFR vsbys
with the showers. After this precipitation ends, a rather large
lull is expected until after 21z or so when new thunderstorm
development is anticipated that will impact KSTL. Some of the
guidance suggests this could be a rather prolonged period of
showers and thunderstorms, pushing south by late evening.

Glass

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 011150
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
650 AM CDT Mon Sep 1 2014

.SHORT TERM: (Today through Tonight)
Issued at 344 AM CDT Mon Sep 1 2014

There are three interconnected forecast issues covering today
through tomorrow: convective timing, the potential for severe
weather, and the potential for heavy rainfall. The main factors
involved with the forecast are the ongoing early morning
convection with its outflow boundaries, an upstream synoptic cold
front, and a couple of shortwaves moving through a broad longwave
trough.

If the early morning convection dissipates across our area, then the
air mass is likely to destabilize ahead of the approaching synoptic
cold front. Models are forecasting up to 2000-3000 J/kg of CAPE
and between 30-60 kts of 0-6 km bulk shear across most of the CWA
during the afternoon/evening hours ahead of the front. These
parameters are more than sufficient to support organized severe
thunderstorms. With at least a few models depicting a small but
nonzero perpendicular component to the shear vectors with respect
to the H85 boundary orientation, it would not be surprising to see
a few supercells somewhere across the region before convection
starts to congeal and become more linear with time. If the models
are correct with the orientation of the shear vectors with respect
to the cold front, then aftn/eve convection should become linear
very quickly.

As of 0830z, early morning convection appears to be diminishing
over northern/northeastern MO, lending credence to the above
scenario. However, if the early morning convection does not
dissipate and if the outflow boundary is pushed farther to the
south, then the overall coverage of severe thunderstorms would
probably be much lower and would tend to be limited to the
southern CWA.

Moving into tonight, the cold front becomes oriented nearly parallel
to the 0-6 km shear vectors, and the primary forecast issue then
shifts from severe weather to heavy rainfall. Overall, this looks
like a decent setup for locally heavy rainfall. PW values
increase to over 2" tonight, which is not only at +2SD and the 99th
percentile for August, but also exceeds both of those thresholds for
September. Models also depict broad lift from favorable jet coupling
(between the RER of a jet at H25 and the LER of a jet at H85) which
develops by 06z in response to a shortwave moving through NEB/IA.
In addition, MUCAPE remains quite high overnight and the mid-level
flow also appears to be nearly parallel to the cold front. Because
of these factors, I`m reasonably sure that there is going to be an
elongated band of convection overnight, but I`m not sure whether
it will be with the true synoptic cold front (resulting in a band
of rainfall near the I-70 corridor) or with the outflow/effective
boundary (resulting in a band of rainfall located much farther
south, possibly only affecting the southern CWA).

Flash flood guidance numbers are around 2-3" for 1 hour, 2.5-3.5"
for 3 hours, and 3-5" for 6 hours. There hasn`t been much rainfall
over the last few days, therefore the ground is not saturated and
can probably absorb a fair amount of water before widespread
flooding becomes a concern. There is also a question about where
the axis of heaviest rainfall will occur. For these reasons, we
will hold off on any flood/flash flood watches for now.

Kanofsky

.LONG TERM:  (Tuesday through Sunday)
Issued at 344 AM CDT Mon Sep 1 2014

The front and/or effective boundary should linger across the
region on Tue/Tue night before lifting northeastward as a warm
front on Wed/Wed night. The precipitation threat will also lift
northeastward with the warm front during the middle of the week.
Model solutions then depict a cold front moving into the area
towards the end of the week and into next weekend, bringing a
chance of rain and a cooler air mass into the region.

Kanofsky

&&

.AVIATION:  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 639 AM CDT Mon Sep 1 2014

Weakening area of showers and spotty thunderstorms extending from
KUIN into central and east central MO will move eastward early
this morning and eventually dissipate. It will be exiting KUIN and
KCOU by 13z and should impact the St. Louis area terminals for
several hours this morning with predominately VFR conditions and
occasionally high-end MVFR vsbys with showers. After this
precipitation ends, a rather large lull is expected until 21z or
so when new thunderstorm development is anticipated along a
corridor impacting KCOU and the St. Louis area terminals. Some of
the guidance suggests this could be a rather prolonged period of
showers and thunderstorms, pushing south by late evening.
Confidence is low that any of this afternoon and evening
thunderstorm development will impact KUIN and hence just kept with
the mention of VCTS.

Specifics for KSTL:

Showers will impact the terminal until around mid-morning with
predominately VFR conditions and occasionally high-end MVFR vsbys
with the showers. After this precipitation ends, a rather large
lull is expected until after 21z or so when new thunderstorm
development is anticipated that will impact KSTL. Some of the
guidance suggests this could be a rather prolonged period of
showers and thunderstorms, pushing south by late evening.

Glass

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 010854
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
354 AM CDT Mon Sep 1 2014

.SHORT TERM: (Today through Tonight)
Issued at 344 AM CDT Mon Sep 1 2014

There are three interconnected forecast issues covering today
through tomorrow: convective timing, the potential for severe
weather, and the potential for heavy rainfall. The main factors
involved with the forecast are the ongoing early morning
convection with its outflow boundaries, an upstream synoptic cold
front, and a couple of shortwaves moving through a broad longwave
trough.

If the early morning convection dissipates across our area, then the
air mass is likely to destabilize ahead of the approaching synoptic
cold front. Models are forecasting up to 2000-3000 J/kg of CAPE
and between 30-60 kts of 0-6 km bulk shear across most of the CWA
during the afternoon/evening hours ahead of the front. These
parameters are more than sufficient to support organized severe
thunderstorms. With at least a few models depicting a small but
nonzero perpendicular component to the shear vectors with respect
to the H85 boundary orientation, it would not be surprising to see
a few supercells somewhere across the region before convection
starts to congeal and become more linear with time. If the models
are correct with the orientation of the shear vectors with respect
to the cold front, then aftn/eve convection should become linear
very quickly.

As of 0830z, early morning convection appears to be diminishing
over northern/northeastern MO, lending credence to the above
scenario. However, if the early morning convection does not
dissipate and if the outflow boundary is pushed farther to the
south, then the overall coverage of severe thunderstorms would
probably be much lower and would tend to be limited to the
southern CWA.

Moving into tonight, the cold front becomes oriented nearly parallel
to the 0-6 km shear vectors, and the primary forecast issue then
shifts from severe weather to heavy rainfall. Overall, this looks
like a decent setup for locally heavy rainfall. PW values
increase to over 2" tonight, which is not only at +2SD and the 99th
percentile for August, but also exceeds both of those thresholds for
September. Models also depict broad lift from favorable jet coupling
(between the RER of a jet at H25 and the LER of a jet at H85) which
develops by 06z in response to a shortwave moving through NEB/IA.
In addition, MUCAPE remains quite high overnight and the mid-level
flow also appears to be nearly parallel to the cold front. Because
of these factors, I`m reasonably sure that there is going to be an
elongated band of convection overnight, but I`m not sure whether
it will be with the true synoptic cold front (resulting in a band
of rainfall near the I-70 corridor) or with the outflow/effective
boundary (resulting in a band of rainfall located much farther
south, possibly only affecting the southern CWA).

Flash flood guidance numbers are around 2-3" for 1 hour, 2.5-3.5"
for 3 hours, and 3-5" for 6 hours. There hasn`t been much rainfall
over the last few days, therefore the ground is not saturated and
can probably absorb a fair amount of water before widespread
flooding becomes a concern. There is also a question about where
the axis of heaviest rainfall will occur. For these reasons, we
will hold off on any flood/flash flood watches for now.

Kanofsky

.LONG TERM:  (Tuesday through Sunday)
Issued at 344 AM CDT Mon Sep 1 2014

The front and/or effective boundary should linger across the
region on Tue/Tue night before lifting northeastward as a warm
front on Wed/Wed night. The precipitation threat will also lift
northeastward with the warm front during the middle of the week.
Model solutions then depict a cold front moving into the area
towards the end of the week and into next weekend, bringing a
chance of rain and a cooler air mass into the region.

Kanofsky

&&

.AVIATION:  (For the 06z TAFs through 06z Monday Night)
Issued at 1103 PM CDT Sun Aug 31 2014

Convection extending from IA southwest through northwestern MO and
KS just ahead of a cold front will drop southeastward into the
UIN and COU areas late tonight, and then eventually into the St
Louis metro area towards morning as it weakens. New convective
development is expected late Monday afternoon and early evening
mainly in COU and the St Louis metro area between the approaching
cold front and an outflow boundary left from the late
night/morning storm complex. S-sely surface winds late tonight
will gradually veer around to a swly direction Monday morning.

Specifics for KSTL: Weakening showers and storms are expected to
drop southeastward into STL area by early Monday morning. There
will be a break in the convection with redevelopment of storms
expected late Monday afternoon and evening. S-sely surface winds
late tonight wlll increase to around 14 kts by late Monday
morning from a swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 010854
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
354 AM CDT Mon Sep 1 2014

.SHORT TERM: (Today through Tonight)
Issued at 344 AM CDT Mon Sep 1 2014

There are three interconnected forecast issues covering today
through tomorrow: convective timing, the potential for severe
weather, and the potential for heavy rainfall. The main factors
involved with the forecast are the ongoing early morning
convection with its outflow boundaries, an upstream synoptic cold
front, and a couple of shortwaves moving through a broad longwave
trough.

If the early morning convection dissipates across our area, then the
air mass is likely to destabilize ahead of the approaching synoptic
cold front. Models are forecasting up to 2000-3000 J/kg of CAPE
and between 30-60 kts of 0-6 km bulk shear across most of the CWA
during the afternoon/evening hours ahead of the front. These
parameters are more than sufficient to support organized severe
thunderstorms. With at least a few models depicting a small but
nonzero perpendicular component to the shear vectors with respect
to the H85 boundary orientation, it would not be surprising to see
a few supercells somewhere across the region before convection
starts to congeal and become more linear with time. If the models
are correct with the orientation of the shear vectors with respect
to the cold front, then aftn/eve convection should become linear
very quickly.

As of 0830z, early morning convection appears to be diminishing
over northern/northeastern MO, lending credence to the above
scenario. However, if the early morning convection does not
dissipate and if the outflow boundary is pushed farther to the
south, then the overall coverage of severe thunderstorms would
probably be much lower and would tend to be limited to the
southern CWA.

Moving into tonight, the cold front becomes oriented nearly parallel
to the 0-6 km shear vectors, and the primary forecast issue then
shifts from severe weather to heavy rainfall. Overall, this looks
like a decent setup for locally heavy rainfall. PW values
increase to over 2" tonight, which is not only at +2SD and the 99th
percentile for August, but also exceeds both of those thresholds for
September. Models also depict broad lift from favorable jet coupling
(between the RER of a jet at H25 and the LER of a jet at H85) which
develops by 06z in response to a shortwave moving through NEB/IA.
In addition, MUCAPE remains quite high overnight and the mid-level
flow also appears to be nearly parallel to the cold front. Because
of these factors, I`m reasonably sure that there is going to be an
elongated band of convection overnight, but I`m not sure whether
it will be with the true synoptic cold front (resulting in a band
of rainfall near the I-70 corridor) or with the outflow/effective
boundary (resulting in a band of rainfall located much farther
south, possibly only affecting the southern CWA).

Flash flood guidance numbers are around 2-3" for 1 hour, 2.5-3.5"
for 3 hours, and 3-5" for 6 hours. There hasn`t been much rainfall
over the last few days, therefore the ground is not saturated and
can probably absorb a fair amount of water before widespread
flooding becomes a concern. There is also a question about where
the axis of heaviest rainfall will occur. For these reasons, we
will hold off on any flood/flash flood watches for now.

Kanofsky

.LONG TERM:  (Tuesday through Sunday)
Issued at 344 AM CDT Mon Sep 1 2014

The front and/or effective boundary should linger across the
region on Tue/Tue night before lifting northeastward as a warm
front on Wed/Wed night. The precipitation threat will also lift
northeastward with the warm front during the middle of the week.
Model solutions then depict a cold front moving into the area
towards the end of the week and into next weekend, bringing a
chance of rain and a cooler air mass into the region.

Kanofsky

&&

.AVIATION:  (For the 06z TAFs through 06z Monday Night)
Issued at 1103 PM CDT Sun Aug 31 2014

Convection extending from IA southwest through northwestern MO and
KS just ahead of a cold front will drop southeastward into the
UIN and COU areas late tonight, and then eventually into the St
Louis metro area towards morning as it weakens. New convective
development is expected late Monday afternoon and early evening
mainly in COU and the St Louis metro area between the approaching
cold front and an outflow boundary left from the late
night/morning storm complex. S-sely surface winds late tonight
will gradually veer around to a swly direction Monday morning.

Specifics for KSTL: Weakening showers and storms are expected to
drop southeastward into STL area by early Monday morning. There
will be a break in the convection with redevelopment of storms
expected late Monday afternoon and evening. S-sely surface winds
late tonight wlll increase to around 14 kts by late Monday
morning from a swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 010423
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1123 PM CDT Sun Aug 31 2014

.UPDATE:
Issued at 905 PM CDT Sun Aug 31 2014

Progressive UA trof and associated cold front, as well as outflow
boundaries produced by intense convection so far this evening,
should cause convection stretching from western Iowa to central KS to
push across the NW half of our FA overnight. Rough timing based
on extrapolation of upstream radar data suggests leading edge of
precip moving into the Edina area by 05z/midnight.  While we are
missing much of today`s explicit guidance, from the data that is
available believe that the latest HRRR output has a best handle on
overnight trends in two aspects...being faster with the eastward
progression and suggesting that some precip may be knocking on the
western door of the STL metro by daybreak, and secondly more of a
focus on late night/predawn convection over eastern KS/W MO where
there should be good cold pool/low level jet interaction which
should focus the most robust convection in this area.

Forecast inherited from dayshift already trended specifics towards
the trends mentioned above, so going forecast looks quite good and
only minor adjustments needed to speed up onset of higher PoPs by
1-2 hours. If HRRR scenario does pan out I`m not too certain
about how much of a severe weather threat will reach our area, but
as mentioned by day shift there will likely be at least some
impact from upstream outflows that propagate east and produce
gusty winds.

Specific trends for Labor Day and Monday night...including the
potential for severe weather and heavy rain...will largely hinge on
how convection evolves across the region during the predawn hours
and into Monday morning;  specifically how long the early morning
convection lingers and where the associated outflow boundary will be
located during the afternoon.  While there is still quite a bit of
uncertainty on how the convection will evolve, it certainly appears
that outdoor plans may be altered in many areas due to the
weather.

Update will be issued as soon as 02x surface data can be ingested
and assimilated into database.

Truett

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 350 PM CDT Sun Aug 31 2014

Isolated to widely scattered thunderstorms over southeast portions
of the CWFA should dissipate fairly quickly this evening.  Until
then, locally heavy downpours will continue over parts of the
eastern Ozarks.  Attention turns to tonight as a strong shortwave
will move from eastern Wyoming into the eastern Nebraska/northwest
Missouri.  An MCS is expected to develop ahead of it on the nose of
a 40kt low level jet over the eastern Plains.  The model consensus
keeps the vast majority of the precipitation over western/north
central Missouri tonight.  However, it does look like the leading
edge will nose into central and northeast Missouri between 08Z and
12Z.  Not sure how much of the strength of the storms by that
point.  Current thinking is that the cold pool may outrun the best
forcing causing the MCS to weaken as it moves east.  This scenario
would have the rain moving into western portions of the CWFA between
08Z and 10Z.  There may be some gusty winds as the outflow moves
through, but the most significant impact would likely be locally
heavy rain; and that looks more likely over western Missouri than in
central Missouri.

Carney

.LONG TERM:  (Monday through Next Sunday)
Issued at 350 PM CDT Sun Aug 31 2014

We will see a break in what has been a hot pattern for us this past
week, as the upper level ridge breaks down, thanks to a pair of
decently strong shortwave TROFs.  Much of the energy from these
shortwaves will pass us to the north, but nevertheless, we are
expecting high probabilities of rain from both of these systems
because of either a favorable position of the low level jet or
synoptic front and a very moist, deep warm-cloud atmosphere.

The first system is expected to be ongoing early Monday morning for
areas north and west of STL metro while in a slowly weakening
state.  This rain is expected to reach the STL metro area before
dissipating or scattering out, with an anticipated boundary setup
near or just south of the I-70 corridor for new development in the
afternoon.  There is also some potential for scattered development
Monday afternoon further north and west near the synoptic front in
northern MO and central IL.

The second system on Monday night should make more of a pass to the
south and interact with the synoptic front now deeper into our
region and favorable axis of the low level jet.  In addition, there
is potential for localized heavy rainfall with PWs of around 2
inches and warm-cloud depths in excess of 4km and training storms.

The front is then expected to stall over southern MO Tuesday before
pushing north as a warm front on Wednesday with persistent, but
lesser, chances for storms.

While the humidity air never really goes away thru late week, it
should be just cool enough to prevent any dangerous heat and
humidity conditions until perhaps when the warm front pushes thru
Wednesday and into Friday.

A period of dry weather is anticipated Thursday through early Friday
with a warm-sector setup, with the next, and what looks to be much
stronger, cold front pushing thru late Friday thru early Saturday.
Increased chances for rain will return with the front with all early
indications showing a cool and dry period next weekend for most
areas.

TES

&&

.AVIATION:  (For the 06z TAFs through 06z Monday Night)
Issued at 1103 PM CDT Sun Aug 31 2014

Convection extending from IA southwest through northwestern MO and
KS just ahead of a cold front will drop southeastward into the
UIN and COU areas late tonight, and then eventually into the St
Louis metro area towards morning as it weakens. New convective
development is expected late Monday afternoon and early evening
mainly in COU and the St Louis metro area between the approaching
cold front and an outflow boundary left from the late
night/morning storm complex. S-sely surface winds late tonight
will gradually veer around to a swly direction Monday morning.

Specifics for KSTL: Weakening showers and storms are expected to
drop southeastward into STL area by early Monday morning. There
will be a break in the convection with redevelopment of storms
expected late Monday afternoon and evening. S-sely surface winds
late tonight wlll increase to around 14 kts by late Monday
morning from a swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 010423
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1123 PM CDT Sun Aug 31 2014

.UPDATE:
Issued at 905 PM CDT Sun Aug 31 2014

Progressive UA trof and associated cold front, as well as outflow
boundaries produced by intense convection so far this evening,
should cause convection stretching from western Iowa to central KS to
push across the NW half of our FA overnight. Rough timing based
on extrapolation of upstream radar data suggests leading edge of
precip moving into the Edina area by 05z/midnight.  While we are
missing much of today`s explicit guidance, from the data that is
available believe that the latest HRRR output has a best handle on
overnight trends in two aspects...being faster with the eastward
progression and suggesting that some precip may be knocking on the
western door of the STL metro by daybreak, and secondly more of a
focus on late night/predawn convection over eastern KS/W MO where
there should be good cold pool/low level jet interaction which
should focus the most robust convection in this area.

Forecast inherited from dayshift already trended specifics towards
the trends mentioned above, so going forecast looks quite good and
only minor adjustments needed to speed up onset of higher PoPs by
1-2 hours. If HRRR scenario does pan out I`m not too certain
about how much of a severe weather threat will reach our area, but
as mentioned by day shift there will likely be at least some
impact from upstream outflows that propagate east and produce
gusty winds.

Specific trends for Labor Day and Monday night...including the
potential for severe weather and heavy rain...will largely hinge on
how convection evolves across the region during the predawn hours
and into Monday morning;  specifically how long the early morning
convection lingers and where the associated outflow boundary will be
located during the afternoon.  While there is still quite a bit of
uncertainty on how the convection will evolve, it certainly appears
that outdoor plans may be altered in many areas due to the
weather.

Update will be issued as soon as 02x surface data can be ingested
and assimilated into database.

Truett

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 350 PM CDT Sun Aug 31 2014

Isolated to widely scattered thunderstorms over southeast portions
of the CWFA should dissipate fairly quickly this evening.  Until
then, locally heavy downpours will continue over parts of the
eastern Ozarks.  Attention turns to tonight as a strong shortwave
will move from eastern Wyoming into the eastern Nebraska/northwest
Missouri.  An MCS is expected to develop ahead of it on the nose of
a 40kt low level jet over the eastern Plains.  The model consensus
keeps the vast majority of the precipitation over western/north
central Missouri tonight.  However, it does look like the leading
edge will nose into central and northeast Missouri between 08Z and
12Z.  Not sure how much of the strength of the storms by that
point.  Current thinking is that the cold pool may outrun the best
forcing causing the MCS to weaken as it moves east.  This scenario
would have the rain moving into western portions of the CWFA between
08Z and 10Z.  There may be some gusty winds as the outflow moves
through, but the most significant impact would likely be locally
heavy rain; and that looks more likely over western Missouri than in
central Missouri.

Carney

.LONG TERM:  (Monday through Next Sunday)
Issued at 350 PM CDT Sun Aug 31 2014

We will see a break in what has been a hot pattern for us this past
week, as the upper level ridge breaks down, thanks to a pair of
decently strong shortwave TROFs.  Much of the energy from these
shortwaves will pass us to the north, but nevertheless, we are
expecting high probabilities of rain from both of these systems
because of either a favorable position of the low level jet or
synoptic front and a very moist, deep warm-cloud atmosphere.

The first system is expected to be ongoing early Monday morning for
areas north and west of STL metro while in a slowly weakening
state.  This rain is expected to reach the STL metro area before
dissipating or scattering out, with an anticipated boundary setup
near or just south of the I-70 corridor for new development in the
afternoon.  There is also some potential for scattered development
Monday afternoon further north and west near the synoptic front in
northern MO and central IL.

The second system on Monday night should make more of a pass to the
south and interact with the synoptic front now deeper into our
region and favorable axis of the low level jet.  In addition, there
is potential for localized heavy rainfall with PWs of around 2
inches and warm-cloud depths in excess of 4km and training storms.

The front is then expected to stall over southern MO Tuesday before
pushing north as a warm front on Wednesday with persistent, but
lesser, chances for storms.

While the humidity air never really goes away thru late week, it
should be just cool enough to prevent any dangerous heat and
humidity conditions until perhaps when the warm front pushes thru
Wednesday and into Friday.

A period of dry weather is anticipated Thursday through early Friday
with a warm-sector setup, with the next, and what looks to be much
stronger, cold front pushing thru late Friday thru early Saturday.
Increased chances for rain will return with the front with all early
indications showing a cool and dry period next weekend for most
areas.

TES

&&

.AVIATION:  (For the 06z TAFs through 06z Monday Night)
Issued at 1103 PM CDT Sun Aug 31 2014

Convection extending from IA southwest through northwestern MO and
KS just ahead of a cold front will drop southeastward into the
UIN and COU areas late tonight, and then eventually into the St
Louis metro area towards morning as it weakens. New convective
development is expected late Monday afternoon and early evening
mainly in COU and the St Louis metro area between the approaching
cold front and an outflow boundary left from the late
night/morning storm complex. S-sely surface winds late tonight
will gradually veer around to a swly direction Monday morning.

Specifics for KSTL: Weakening showers and storms are expected to
drop southeastward into STL area by early Monday morning. There
will be a break in the convection with redevelopment of storms
expected late Monday afternoon and evening. S-sely surface winds
late tonight wlll increase to around 14 kts by late Monday
morning from a swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 010209
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
909 PM CDT Sun Aug 31 2014

.UPDATE:
Issued at 905 PM CDT Sun Aug 31 2014

Progressive UA trof and associated cold front, as well as outflow
boundaries produced by intense convection so far this evening,
should cause convection stretching from western Iowa to central KS to
push across the NW half of our FA overnight. Rough timing based
on extrapolation of upstream radar data suggests leading edge of
precip moving into the Edina area by 05z/midnight.  While we are
missing much of today`s explicit guidance, from the data that is
available believe that the latest HRRR output has a best handle on
overnight trends in two aspects...being faster with the eastward
progression and suggesting that some precip may be knocking on the
western door of the STL metro by daybreak, and secondly more of a
focus on late night/predawn convection over eastern KS/W MO where
there should be good cold pool/low level jet interaction which
should focus the most robust convection in this area.

Forecast inherited from dayshift already trended specifics towards
the trends mentioned above, so going forecast looks quite good and
only minor adjustments needed to speed up onset of higher PoPs by
1-2 hours. If HRRR scenario does pan out I`m not too certain
about how much of a severe weather threat will reach our area, but
as mentioned by day shift there will likely be at least some
impact from upstream outflows that propagate east and produce
gusty winds.

Specific trends for Labor Day and Monday night...including the
potential for severe weather and heavy rain...will largely hinge on
how convection evolves across the region during the predawn hours
and into Monday morning;  specifically how long the early morning
convection lingers and where the associated outflow boundary will be
located during the afternoon.  While there is still quite a bit of
uncertainty on how the convection will evolve, it certainly appears
that outdoor plans may be altered in many areas due to the
weather.

Update will be issued as soon as 02x surface data can be ingested
and assimilated into database.

Truett

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 350 PM CDT Sun Aug 31 2014

Isolated to widely scattered thunderstorms over southeast portions
of the CWFA should dissipate fairly quickly this evening.  Until
then, locally heavy downpours will continue over parts of the
eastern Ozarks.  Attention turns to tonight as a strong shortwave
will move from eastern Wyoming into the eastern Nebraska/northwest
Missouri.  An MCS is expected to develop ahead of it on the nose of
a 40kt low level jet over the eastern Plains.  The model consensus
keeps the vast majority of the precipitation over western/north
central Missouri tonight.  However, it does look like the leading
edge will nose into central and northeast Missouri between 08Z and
12Z.  Not sure how much of the strength of the storms by that
point.  Current thinking is that the cold pool may outrun the best
forcing causing the MCS to weaken as it moves east.  This scenario
would have the rain moving into western portions of the CWFA between
08Z and 10Z.  There may be some gusty winds as the outflow moves
through, but the most significant impact would likely be locally
heavy rain; and that looks more likely over western Missouri than in
central Missouri.

Carney

.LONG TERM:  (Monday through Next Sunday)
Issued at 350 PM CDT Sun Aug 31 2014

We will see a break in what has been a hot pattern for us this past
week, as the upper level ridge breaks down, thanks to a pair of
decently strong shortwave TROFs.  Much of the energy from these
shortwaves will pass us to the north, but nevertheless, we are
expecting high probabilities of rain from both of these systems
because of either a favorable position of the low level jet or
synoptic front and a very moist, deep warm-cloud atmosphere.

The first system is expected to be ongoing early Monday morning for
areas north and west of STL metro while in a slowly weakening
state.  This rain is expected to reach the STL metro area before
dissipating or scattering out, with an anticipated boundary setup
near or just south of the I-70 corridor for new development in the
afternoon.  There is also some potential for scattered development
Monday afternoon further north and west near the synoptic front in
northern MO and central IL.

The second system on Monday night should make more of a pass to the
south and interact with the synoptic front now deeper into our
region and favorable axis of the low level jet.  In addition, there
is potential for localized heavy rainfall with PWs of around 2
inches and warm-cloud depths in excess of 4km and training storms.

The front is then expected to stall over southern MO Tuesday before
pushing north as a warm front on Wednesday with persistent, but
lesser, chances for storms.

While the humidity air never really goes away thru late week, it
should be just cool enough to prevent any dangerous heat and
humidity conditions until perhaps when the warm front pushes thru
Wednesday and into Friday.

A period of dry weather is anticipated Thursday through early Friday
with a warm-sector setup, with the next, and what looks to be much
stronger, cold front pushing thru late Friday thru early Saturday.
Increased chances for rain will return with the front with all early
indications showing a cool and dry period next weekend for most
areas.

TES

&&

.AVIATION:  (For the 00z TAFs through 00z Monday Evening)
Issued at 533 PM CDT Sun Aug 31 2014

Could not rule out an isolated shower/storm in the St Louis metro
area until 02Z this evening, but it appears that the probability
is too low to include in the tafs. Convection developing across
eastern Nebraska and north central and northeastern KS along and just
ahead of a cold front will drop southeastward into the UIN and COU
areas late tonight, and then eventually into the St Louis metro
area Monday morning as it weakens. New convectve development is
expected late Monday afternoon mainly in COU and the St Louis
metro area between the approaching cold front and an outflow
boundary left from the late night/morning storm complex. Sely
surface winds this evening will gradually veer around to a sly
direction late tonight and a swly direction on Monday.

Specifics for KSTL: Will leave the STL taf dry this evening as
at most only isolated showers are expected until sunset. Weakening
showers and storms are expected to drop southeastward into STL
area Monday morning. There will be a break in the convection with
new development of storms expected late Monday afternoon and
evening. S-sely surface winds this evening will become sly late
tonight, then increase to around 15 kts by late Monday morning
from a swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 312306
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
606 PM CDT Sun Aug 31 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 350 PM CDT Sun Aug 31 2014

Isolated to widely scattered thunderstorms over southeast portions
of the CWFA should dissipate fairly quickly this evening.  Until
then, locally heavy downpours will continue over parts of the
eastern Ozarks.  Attention turns to tonight as a strong shortwave
will move from eastern Wyoming into the eastern Nebraska/northwest
Missouri.  An MCS is expected to develop ahead of it on the nose of
a 40kt low level jet over the eastern Plains.  The model consensus
keeps the vast majority of the precipitation over western/north
central Missouri tonight.  However, it does look like the leading
edge will nose into central and northeast Missouri between 08Z and
12Z.  Not sure how much of the strength of the storms by that
point.  Current thinking is that the cold pool may outrun the best
forcing causing the MCS to weaken as it moves east.  This scenario
would have the rain moving into western portions of the CWFA between
08Z and 10Z.  There may be some gusty winds as the outflow moves
through, but the most significant impact would likely be locally
heavy rain; and that looks more likely over western Missouri than in
central Missouri.

Carney

.LONG TERM:  (Monday through Next Sunday)
Issued at 350 PM CDT Sun Aug 31 2014

We will see a break in what has been a hot pattern for us this past
week, as the upper level ridge breaks down, thanks to a pair of
decently strong shortwave TROFs.  Much of the energy from these
shortwaves will pass us to the north, but nevertheless, we are
expecting high probabilities of rain from both of these systems
because of either a favorable position of the low level jet or
synoptic front and a very moist, deep warm-cloud atmosphere.

The first system is expected to be ongoing early Monday morning for
areas north and west of STL metro while in a slowly weakening
state.  This rain is expected to reach the STL metro area before
dissipating or scattering out, with an anticipated boundary setup
near or just south of the I-70 corridor for new development in the
afternoon.  There is also some potential for scattered development
Monday afternoon further north and west near the synoptic front in
northern MO and central IL.

The second system on Monday night should make more of a pass to the
south and interact with the synoptic front now deeper into our
region and favorable axis of the low level jet.  In addition, there
is potential for localized heavy rainfall with PWs of around 2
inches and warm-cloud depths in excess of 4km and training storms.

The front is then expected to stall over southern MO Tuesday before
pushing north as a warm front on Wednesday with persistent, but
lesser, chances for storms.

While the humidity air never really goes away thru late week, it
should be just cool enough to prevent any dangerous heat and
humidity conditions until perhaps when the warm front pushes thru
Wednesday and into Friday.

A period of dry weather is anticipated Thursday through early Friday
with a warm-sector setup, with the next, and what looks to be much
stronger, cold front pushing thru late Friday thru early Saturday.
Increased chances for rain will return with the front with all early
indications showing a cool and dry period next weekend for most
areas.

TES

&&

.AVIATION:  (For the 00z TAFs through 00z Monday Evening)
Issued at 533 PM CDT Sun Aug 31 2014

Could not rule out an isolated shower/storm in the St Louis metro
area until 02Z this evening, but it appears that the probability
is too low to include in the tafs. Convection developing across
eastern Nebraska and north central and northeastern KS along and just
ahead of a cold front will drop southeastward into the UIN and COU
areas late tonight, and then eventually into the St Louis metro
area Monday morning as it weakens. New convectve development is
expected late Monday afternoon mainly in COU and the St Louis
metro area between the approaching cold front and an outflow
boundary left from the late night/morning storm complex. Sely
surface winds this evening will gradually veer around to a sly
direction late tonight and a swly direction on Monday.

Specifics for KSTL: Will leave the STL taf dry this evening as
at most only isolated showers are expected until sunset. Weakening
showers and storms are expected to drop southeastward into STL
area Monday morning. There will be a break in the convection with
new development of storms expected late Monday afternoon and
evening. S-sely surface winds this evening will become sly late
tonight, then increase to around 15 kts by late Monday morning
from a swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 312306
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
606 PM CDT Sun Aug 31 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 350 PM CDT Sun Aug 31 2014

Isolated to widely scattered thunderstorms over southeast portions
of the CWFA should dissipate fairly quickly this evening.  Until
then, locally heavy downpours will continue over parts of the
eastern Ozarks.  Attention turns to tonight as a strong shortwave
will move from eastern Wyoming into the eastern Nebraska/northwest
Missouri.  An MCS is expected to develop ahead of it on the nose of
a 40kt low level jet over the eastern Plains.  The model consensus
keeps the vast majority of the precipitation over western/north
central Missouri tonight.  However, it does look like the leading
edge will nose into central and northeast Missouri between 08Z and
12Z.  Not sure how much of the strength of the storms by that
point.  Current thinking is that the cold pool may outrun the best
forcing causing the MCS to weaken as it moves east.  This scenario
would have the rain moving into western portions of the CWFA between
08Z and 10Z.  There may be some gusty winds as the outflow moves
through, but the most significant impact would likely be locally
heavy rain; and that looks more likely over western Missouri than in
central Missouri.

Carney

.LONG TERM:  (Monday through Next Sunday)
Issued at 350 PM CDT Sun Aug 31 2014

We will see a break in what has been a hot pattern for us this past
week, as the upper level ridge breaks down, thanks to a pair of
decently strong shortwave TROFs.  Much of the energy from these
shortwaves will pass us to the north, but nevertheless, we are
expecting high probabilities of rain from both of these systems
because of either a favorable position of the low level jet or
synoptic front and a very moist, deep warm-cloud atmosphere.

The first system is expected to be ongoing early Monday morning for
areas north and west of STL metro while in a slowly weakening
state.  This rain is expected to reach the STL metro area before
dissipating or scattering out, with an anticipated boundary setup
near or just south of the I-70 corridor for new development in the
afternoon.  There is also some potential for scattered development
Monday afternoon further north and west near the synoptic front in
northern MO and central IL.

The second system on Monday night should make more of a pass to the
south and interact with the synoptic front now deeper into our
region and favorable axis of the low level jet.  In addition, there
is potential for localized heavy rainfall with PWs of around 2
inches and warm-cloud depths in excess of 4km and training storms.

The front is then expected to stall over southern MO Tuesday before
pushing north as a warm front on Wednesday with persistent, but
lesser, chances for storms.

While the humidity air never really goes away thru late week, it
should be just cool enough to prevent any dangerous heat and
humidity conditions until perhaps when the warm front pushes thru
Wednesday and into Friday.

A period of dry weather is anticipated Thursday through early Friday
with a warm-sector setup, with the next, and what looks to be much
stronger, cold front pushing thru late Friday thru early Saturday.
Increased chances for rain will return with the front with all early
indications showing a cool and dry period next weekend for most
areas.

TES

&&

.AVIATION:  (For the 00z TAFs through 00z Monday Evening)
Issued at 533 PM CDT Sun Aug 31 2014

Could not rule out an isolated shower/storm in the St Louis metro
area until 02Z this evening, but it appears that the probability
is too low to include in the tafs. Convection developing across
eastern Nebraska and north central and northeastern KS along and just
ahead of a cold front will drop southeastward into the UIN and COU
areas late tonight, and then eventually into the St Louis metro
area Monday morning as it weakens. New convectve development is
expected late Monday afternoon mainly in COU and the St Louis
metro area between the approaching cold front and an outflow
boundary left from the late night/morning storm complex. Sely
surface winds this evening will gradually veer around to a sly
direction late tonight and a swly direction on Monday.

Specifics for KSTL: Will leave the STL taf dry this evening as
at most only isolated showers are expected until sunset. Weakening
showers and storms are expected to drop southeastward into STL
area Monday morning. There will be a break in the convection with
new development of storms expected late Monday afternoon and
evening. S-sely surface winds this evening will become sly late
tonight, then increase to around 15 kts by late Monday morning
from a swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 312050
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
350 PM CDT Sun Aug 31 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 350 PM CDT Sun Aug 31 2014

Isolated to widely scattered thunderstorms over southeast portions
of the CWFA should dissipate fairly quickly this evening.  Until
then, locally heavy downpours will continue over parts of the
eastern Ozarks.  Attention turns to tonight as a strong shortwave
will move from eastern Wyoming into the eastern Nebraska/northwest
Missouri.  An MCS is expected to develop ahead of it on the nose of
a 40kt low level jet over the eastern Plains.  The model consensus
keeps the vast majority of the precipitation over western/north
central Missouri tonight.  However, it does look like the leading
edge will nose into central and northeast Missouri between 08Z and
12Z.  Not sure how much of the strength of the storms by that
point.  Current thinking is that the cold pool may outrun the best
forcing causing the MCS to weaken as it moves east.  This scenario
would have the rain moving into western portions of the CWFA between
08Z and 10Z.  There may be some gusty winds as the outflow moves
through, but the most significant impact would likely be locally
heavy rain; and that looks more likely over western Missouri than in
central Missouri.

Carney

.LONG TERM:  (Monday through Next Sunday)
Issued at 350 PM CDT Sun Aug 31 2014

We will see a break in what has been a hot pattern for us this past
week, as the upper level ridge breaks down, thanks to a pair of
decently strong shortwave TROFs.  Much of the energy from these
shortwaves will pass us to the north, but nevertheless, we are
expecting high probabilities of rain from both of these systems
because of either a favorable position of the low level jet or
synoptic front and a very moist, deep warm-cloud atmosphere.

The first system is expected to be ongoing early Monday morning for
areas north and west of STL metro while in a slowly weakening
state.  This rain is expected to reach the STL metro area before
dissipating or scattering out, with an anticipated boundary setup
near or just south of the I-70 corridor for new development in the
afternoon.  There is also some potential for scattered development
Monday afternoon further north and west near the synoptic front in
northern MO and central IL.

The second system on Monday night should make more of a pass to the
south and interact with the synoptic front now deeper into our
region and favorable axis of the low level jet.  In addition, there
is potential for localized heavy rainfall with PWs of around 2
inches and warm-cloud depths in excess of 4km and training storms.

The front is then expected to stall over southern MO Tuesday before
pushing north as a warm front on Wednesday with persistent, but
lesser, chances for storms.

While the humidity air never really goes away thru late week, it
should be just cool enough to prevent any dangerous heat and
humidity conditions until perhaps when the warm front pushes thru
Wednesday and into Friday.

A period of dry weather is anticipated Thursday through early Friday
with a warm-sector setup, with the next, and what looks to be much
stronger, cold front pushing thru late Friday thru early Saturday.
Increased chances for rain will return with the front with all early
indications showing a cool and dry period next weekend for most
areas.

TES

&&

.AVIATION:  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1230 PM CDT Sun Aug 31 2014

Lingering MVFR CIGS across parts of eastern Missouri and
southern/central Illinois should continue to lift into VFR range
this afternoon. Isolated/widely scattered thunderstorms remain a
good possibility, especially across southeast Missouri...where a
few storms have already formed. VFR flight conditions should
prevail for the afternoon outside of thunderstorms. Afternoon
storms should dissipate quickly after sunset.

VFR flight conditions are expected to prevail for most of the
night. A complex of thunderstorms will develop over the eastern
Great Plains and move into Missouri and Iowa this evening. This
weakening complex of storms will move into central and northeast
Missouri area around sunrise Labor Day...and some of the
precipitation will likely make it as far as east central Missouri
by 14-16Z. Areas of MVFR CIGS/VSBYs with locally lower conditions
are possible.

Specifics for KSTL:

VFR flight conditions and southwest flow is expected at Lambert
this afternoon. There is a slight chance of an isolated
thunderstorm in the vicinity of the terminal this afternoon, but
think the probability is too low to mention in the TAF at this
time. VFR flight conditions are expected to prevail tonight as
well. The weakening edge of a complex of thunderstorms may make it
into the terminal by 14-16Z. Rain should be light enough by that
point that it should not significantly impact flight conditions.
Another round of thunderstorms...some possibly strong will likely
impact the terminal late Monday afternoon into the evening.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX





000
FXUS63 KLSX 312050
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
350 PM CDT Sun Aug 31 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 350 PM CDT Sun Aug 31 2014

Isolated to widely scattered thunderstorms over southeast portions
of the CWFA should dissipate fairly quickly this evening.  Until
then, locally heavy downpours will continue over parts of the
eastern Ozarks.  Attention turns to tonight as a strong shortwave
will move from eastern Wyoming into the eastern Nebraska/northwest
Missouri.  An MCS is expected to develop ahead of it on the nose of
a 40kt low level jet over the eastern Plains.  The model consensus
keeps the vast majority of the precipitation over western/north
central Missouri tonight.  However, it does look like the leading
edge will nose into central and northeast Missouri between 08Z and
12Z.  Not sure how much of the strength of the storms by that
point.  Current thinking is that the cold pool may outrun the best
forcing causing the MCS to weaken as it moves east.  This scenario
would have the rain moving into western portions of the CWFA between
08Z and 10Z.  There may be some gusty winds as the outflow moves
through, but the most significant impact would likely be locally
heavy rain; and that looks more likely over western Missouri than in
central Missouri.

Carney

.LONG TERM:  (Monday through Next Sunday)
Issued at 350 PM CDT Sun Aug 31 2014

We will see a break in what has been a hot pattern for us this past
week, as the upper level ridge breaks down, thanks to a pair of
decently strong shortwave TROFs.  Much of the energy from these
shortwaves will pass us to the north, but nevertheless, we are
expecting high probabilities of rain from both of these systems
because of either a favorable position of the low level jet or
synoptic front and a very moist, deep warm-cloud atmosphere.

The first system is expected to be ongoing early Monday morning for
areas north and west of STL metro while in a slowly weakening
state.  This rain is expected to reach the STL metro area before
dissipating or scattering out, with an anticipated boundary setup
near or just south of the I-70 corridor for new development in the
afternoon.  There is also some potential for scattered development
Monday afternoon further north and west near the synoptic front in
northern MO and central IL.

The second system on Monday night should make more of a pass to the
south and interact with the synoptic front now deeper into our
region and favorable axis of the low level jet.  In addition, there
is potential for localized heavy rainfall with PWs of around 2
inches and warm-cloud depths in excess of 4km and training storms.

The front is then expected to stall over southern MO Tuesday before
pushing north as a warm front on Wednesday with persistent, but
lesser, chances for storms.

While the humidity air never really goes away thru late week, it
should be just cool enough to prevent any dangerous heat and
humidity conditions until perhaps when the warm front pushes thru
Wednesday and into Friday.

A period of dry weather is anticipated Thursday through early Friday
with a warm-sector setup, with the next, and what looks to be much
stronger, cold front pushing thru late Friday thru early Saturday.
Increased chances for rain will return with the front with all early
indications showing a cool and dry period next weekend for most
areas.

TES

&&

.AVIATION:  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1230 PM CDT Sun Aug 31 2014

Lingering MVFR CIGS across parts of eastern Missouri and
southern/central Illinois should continue to lift into VFR range
this afternoon. Isolated/widely scattered thunderstorms remain a
good possibility, especially across southeast Missouri...where a
few storms have already formed. VFR flight conditions should
prevail for the afternoon outside of thunderstorms. Afternoon
storms should dissipate quickly after sunset.

VFR flight conditions are expected to prevail for most of the
night. A complex of thunderstorms will develop over the eastern
Great Plains and move into Missouri and Iowa this evening. This
weakening complex of storms will move into central and northeast
Missouri area around sunrise Labor Day...and some of the
precipitation will likely make it as far as east central Missouri
by 14-16Z. Areas of MVFR CIGS/VSBYs with locally lower conditions
are possible.

Specifics for KSTL:

VFR flight conditions and southwest flow is expected at Lambert
this afternoon. There is a slight chance of an isolated
thunderstorm in the vicinity of the terminal this afternoon, but
think the probability is too low to mention in the TAF at this
time. VFR flight conditions are expected to prevail tonight as
well. The weakening edge of a complex of thunderstorms may make it
into the terminal by 14-16Z. Rain should be light enough by that
point that it should not significantly impact flight conditions.
Another round of thunderstorms...some possibly strong will likely
impact the terminal late Monday afternoon into the evening.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX






000
FXUS63 KLSX 311749
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1249 PM CDT Sun Aug 31 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sun Aug 31 2014

Today will be the pick day of the remaining holiday weekend. Some
patchy fog will be possible during the early morning hours across
parts of northeast and central Missouri. There could also be a
spot shower across parts of southwest and south central IL through
around 15z in association with weak convergence at H85 and pooling
moisture. Otherwise the day will be rather seasonable with warm
temperatures and a threat of isolated diurnally driven thunderstorms
across southeast and east central MO and southwest IL.

Glass

.LONG TERM:  (Tonight through Saturday)
Issued at 330 AM CDT Sun Aug 31 2014

A rather active weather regime unfolds later tonight as the broad
progressive longwave trof currently centered in the Great Basin
moves into the central U.S. The combination of a lead fast-moving
shortwave and intensifying and veering southwesterly LLJ is
expected to help produce a progressive MCS, which should stretch
from NW IL across northern MO at daybreak on Labor Day. Showers
and thunderstorms should persist through at least mid morning
across northern MO into west central IL with the southwesterly LLJ
aiding development on the western flank and the spread into
central MO. The convective evolution from late morning into the
early afternoon is a little unclear. Overall the system should go
through a decaying stage with motion to the east, but there could
be continuous convective flare-ups on the western flank. By mid-
late afternoon the combination of the southward moving cold
front/residual boundaries and strongly buoyant air south of the
boundaries should result in new convective development. Improving
forcing from late afternoon into the evening via another shortwave
and the veering LLJ is expected to produce upscale growth into one
or more MCSs. Deep layer shear is rather impressive at 30-40+ kts
supporting an organized severe weather threat.

Any ongoing convection on Tuesday morning should be focused
across southern MO and southern IL in advance of the southward
moving cold front with convective cold pools and outflows well in
advance of the front. Tuesday afternoon and night the main threat
of showers and thunderstorms appears to be confined to southern MO
and southern IL in the vicinity of the stalling front. The front
will then retreat northward on Wednesday with heights aloft
beginning to rise in the wake of the progressive upper trof.
Heights will continue to rise through late Thursday as the upper
ridge once again establishes itself across the southern half of
the Nation, with summer heat in full swing. There is uncertainty
in the period Fri-Sat. Another cold front is forecast to move into
the through the area in this time frame with the ECMWF flattening
the northern extent of the upper ridge quicker and about 18h
faster with the cold front.

Glass

&&

.AVIATION:  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1230 PM CDT Sun Aug 31 2014

Lingering MVFR CIGS across parts of eastern Missouri and
southern/central Illinois should continue to lift into VFR range
this afternoon. Isolated/widely scattered thunderstorms remain a
good possibility, especially across southeast Missouri...where a
few storms have already formed. VFR flight conditions should
prevail for the afternoon outside of thunderstorms. Afternoon
storms should dissipate quickly after sunset.

VFR flight conditions are expected to prevail for most of the
night. A complex of thunderstorms will develop over the eastern
Great Plains and move into Missouri and Iowa this evening. This
weakening complex of storms will move into central and northeast
Missouri area around sunrise Labor Day...and some of the
precipitation will likely make it as far as east central Missouri
by 14-16Z. Areas of MVFR CIGS/VSBYs with locally lower conditions
are possible.

Specifics for KSTL:

VFR flight conditions and southwest flow is expected at Lambert
this afternoon. There is a slight chance of an isolated
thunderstorm in the vicinity of the terminal this afternoon, but
think the probability is too low to mention in the TAF at this
time. VFR flight conditions are expected to prevail tonight as
well. The weakening edge of a complex of thunderstorms may make it
into the terminal by 14-16Z. Rain should be light enough by that
point that it should not significantly impact flight conditions.
Another round of thunderstorms...some possibly strong will likely
impact the terminal late Monday afternoon into the evening.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 311212
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
712 AM CDT Sun Aug 31 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sun Aug 31 2014

Today will be the pick day of the remaining holiday weekend. Some
patchy fog will be possible during the early morning hours across
parts of northeast and central Missouri. There could also be a
spot shower across parts of southwest and south central IL through
around 15z in association with weak convergence at H85 and pooling
moisture. Otherwise the day will be rather seasonable with warm
temperatures and a threat of isolated diurnally driven thunderstorms
across southeast and east central MO and southwest IL.

Glass

.LONG TERM:  (Tonight through Saturday)
Issued at 330 AM CDT Sun Aug 31 2014

A rather active weather regime unfolds later tonight as the broad
progressive longwave trof currently centered in the Great Basin
moves into the central U.S. The combination of a lead fast-moving
shortwave and intensifying and veering southwesterly LLJ is
expected to help produce a progressive MCS, which should stretch
from NW IL across northern MO at daybreak on Labor Day. Showers
and thunderstorms should persist through at least mid morning
across northern MO into west central IL with the southwesterly LLJ
aiding development on the western flank and the spread into
central MO. The convective evolution from late morning into the
early afternoon is a little unclear. Overall the system should go
through a decaying stage with motion to the east, but there could
be continuous convective flare-ups on the western flank. By mid-
late afternoon the combination of the southward moving cold
front/residual boundaries and strongly buoyant air south of the
boundaries should result in new convective development. Improving
forcing from late afternoon into the evening via another shortwave
and the veering LLJ is expected to produce upscale growth into one
or more MCSs. Deep layer shear is rather impressive at 30-40+ kts
supporting an organized severe weather threat.

Any ongoing convection on Tuesday morning should be focused
across southern MO and southern IL in advance of the southward
moving cold front with convective cold pools and outflows well in
advance of the front. Tuesday afternoon and night the main threat
of showers and thunderstorms appears to be confined to southern MO
and southern IL in the vicinity of the stalling front. The front
will then retreat northward on Wednesday with heights aloft
beginning to rise in the wake of the progressive upper trof.
Heights will continue to rise through late Thursday as the upper
ridge once again establishes itself across the southern half of
the Nation, with summer heat in full swing. There is uncertainty
in the period Fri-Sat. Another cold front is forecast to move into
the through the area in this time frame with the ECMWF flattening
the northern extent of the upper ridge quicker and about 18h
faster with the cold front.

Glass

&&

.AVIATION:  (For the 12z TAFs through 12z Monday Morning)
Issued at 616 AM CDT Sun Aug 31 2014

Any lingering light fog should mix out this morning. Some diurnal
cumulus is possible, especially at KSUS/KCPS. Mid and high clouds
will increase later in the forecast period ahead of an approaching
cold front. A thunderstorm complex should be approaching KUIN some
time after 06z but the timing is not exact. Just beyond the end of
the 24-hr TAF period, showers and thunderstorms are expected to
affect most of the terminals.

Specifics for KSTL: VFR for at least the first 0-12 hours and
possibly through most of the 30-hr period. There may be some
diurnal cumulus clouds today followed by increasing mid/high
clouds later tonight. Thunderstorm chances increase considerably
after 12z due to an approaching cold front.

Kanofsky

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 311212
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
712 AM CDT Sun Aug 31 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sun Aug 31 2014

Today will be the pick day of the remaining holiday weekend. Some
patchy fog will be possible during the early morning hours across
parts of northeast and central Missouri. There could also be a
spot shower across parts of southwest and south central IL through
around 15z in association with weak convergence at H85 and pooling
moisture. Otherwise the day will be rather seasonable with warm
temperatures and a threat of isolated diurnally driven thunderstorms
across southeast and east central MO and southwest IL.

Glass

.LONG TERM:  (Tonight through Saturday)
Issued at 330 AM CDT Sun Aug 31 2014

A rather active weather regime unfolds later tonight as the broad
progressive longwave trof currently centered in the Great Basin
moves into the central U.S. The combination of a lead fast-moving
shortwave and intensifying and veering southwesterly LLJ is
expected to help produce a progressive MCS, which should stretch
from NW IL across northern MO at daybreak on Labor Day. Showers
and thunderstorms should persist through at least mid morning
across northern MO into west central IL with the southwesterly LLJ
aiding development on the western flank and the spread into
central MO. The convective evolution from late morning into the
early afternoon is a little unclear. Overall the system should go
through a decaying stage with motion to the east, but there could
be continuous convective flare-ups on the western flank. By mid-
late afternoon the combination of the southward moving cold
front/residual boundaries and strongly buoyant air south of the
boundaries should result in new convective development. Improving
forcing from late afternoon into the evening via another shortwave
and the veering LLJ is expected to produce upscale growth into one
or more MCSs. Deep layer shear is rather impressive at 30-40+ kts
supporting an organized severe weather threat.

Any ongoing convection on Tuesday morning should be focused
across southern MO and southern IL in advance of the southward
moving cold front with convective cold pools and outflows well in
advance of the front. Tuesday afternoon and night the main threat
of showers and thunderstorms appears to be confined to southern MO
and southern IL in the vicinity of the stalling front. The front
will then retreat northward on Wednesday with heights aloft
beginning to rise in the wake of the progressive upper trof.
Heights will continue to rise through late Thursday as the upper
ridge once again establishes itself across the southern half of
the Nation, with summer heat in full swing. There is uncertainty
in the period Fri-Sat. Another cold front is forecast to move into
the through the area in this time frame with the ECMWF flattening
the northern extent of the upper ridge quicker and about 18h
faster with the cold front.

Glass

&&

.AVIATION:  (For the 12z TAFs through 12z Monday Morning)
Issued at 616 AM CDT Sun Aug 31 2014

Any lingering light fog should mix out this morning. Some diurnal
cumulus is possible, especially at KSUS/KCPS. Mid and high clouds
will increase later in the forecast period ahead of an approaching
cold front. A thunderstorm complex should be approaching KUIN some
time after 06z but the timing is not exact. Just beyond the end of
the 24-hr TAF period, showers and thunderstorms are expected to
affect most of the terminals.

Specifics for KSTL: VFR for at least the first 0-12 hours and
possibly through most of the 30-hr period. There may be some
diurnal cumulus clouds today followed by increasing mid/high
clouds later tonight. Thunderstorm chances increase considerably
after 12z due to an approaching cold front.

Kanofsky

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 310848
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
348 AM CDT Sun Aug 31 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sun Aug 31 2014

Today will be the pick day of the remaining holiday weekend. Some
patchy fog will be possible during the early morning hours across
parts of northeast and central Missouri. There could also be a
spot shower across parts of southwest and south central IL through
around 15z in association with weak convergence at H85 and pooling
moisture. Otherwise the day will be rather seasonable with warm
temperatures and a threat of isolated diurnally driven thunderstorms
across southeast and east central MO and southwest IL.

Glass

.LONG TERM:  (Tonight through Saturday)
Issued at 330 AM CDT Sun Aug 31 2014

A rather active weather regime unfolds later tonight as the broad
progressive longwave trof currently centered in the Great Basin
moves into the central U.S. The combination of a lead fast-moving
shortwave and intensifying and veering southwesterly LLJ is
expected to help produce a progressive MCS, which should stretch
from NW IL across northern MO at daybreak on Labor Day. Showers
and thunderstorms should persist through at least mid morning
across northern MO into west central IL with the southwesterly LLJ
aiding development on the western flank and the spread into
central MO. The convective evolution from late morning into the
early afternoon is a little unclear. Overall the system should go
through a decaying stage with motion to the east, but there could
be continuous convective flare-ups on the western flank. By mid-
late afternoon the combination of the southward moving cold
front/residual boundaries and strongly bouyant air south of the
boundaries should result in new convective development. Improving
forcing from late afternoon into the evening via another shortwave
and the veering LLJ is expected to produce upscale growth into one
or more MCSs. Deep layer shear is rather impressive at 30-40+ kts
supporting an organized severe weather threat.

Any ongoing convection on Tuesday morning should be focused
across southern MO and southern IL in advance of the southward
movning cold front with convective cold pools and outflows well in
advance of the front. Tuesday afternoon and night the main threat
of showers and thunderstorms appears to be confined to southern MO
and southern IL in the vicinity of the stalling front. The front
will then retreat northward on Wednesday with heights aloft
beginning to rise in the wake of the progressive upper trof.
Heights will continue to rise through late Thursday as the upper
ridge once again establishes itself across the southern half of
the Nation, with summer heat in full swing. There is uncertainty
in the period Fri-Sat. Another cold front is forecast to move into
the through the area in this time frame with the ECMWF flattening
the northern extent of the upper ridge quicker and about 18h
faster with the cold front.

Glass

&&

.AVIATION:  (For the 06z TAFs through 06z Sunday Night)
Issued at 1037 PM CDT Sat Aug 30 2014

Most of the showers/storms have dissipated this evening, although
there was patchy clouds around 5000 feet in height along with mid-
high level clouds streaming northeastward through the St Louis
metro area. As the mid-upper level cloudiness shifts slowly
southeast of the taf sites late tonight and the surface wind
becomes light the MOS guidance is hinting at the formation of
stratus clouds and fog late tonight/early Sunday morning. The
stratus clouds and fog should dissipate by late Sunday morning,
although there will likely be scattered diurnal cumulus clouds in
the St Louis metro area during the late morning and afternoon.
S-swly surface winds can be expected on Sunday and Sunday evening.

Specifics for KSTL: Much of the mid-high level cloudiness may
shift southeast of STL late tonight with light fog developing
towards morning as the s-swly surface wind becomes light. The NAM
MOS guidance was also hinting at the possible formation of stratus
clouds as well. The fog and any stratus clouds should dissipate by
late Sunday morning, although there will likely be enough residual
low level moisture for the formation of scattered diurnal cumulus
clouds late Sunday morning and afternoon. The surface wind will
increase again to around 8 kts in the afternoon from a s-swly
direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 310848
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
348 AM CDT Sun Aug 31 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sun Aug 31 2014

Today will be the pick day of the remaining holiday weekend. Some
patchy fog will be possible during the early morning hours across
parts of northeast and central Missouri. There could also be a
spot shower across parts of southwest and south central IL through
around 15z in association with weak convergence at H85 and pooling
moisture. Otherwise the day will be rather seasonable with warm
temperatures and a threat of isolated diurnally driven thunderstorms
across southeast and east central MO and southwest IL.

Glass

.LONG TERM:  (Tonight through Saturday)
Issued at 330 AM CDT Sun Aug 31 2014

A rather active weather regime unfolds later tonight as the broad
progressive longwave trof currently centered in the Great Basin
moves into the central U.S. The combination of a lead fast-moving
shortwave and intensifying and veering southwesterly LLJ is
expected to help produce a progressive MCS, which should stretch
from NW IL across northern MO at daybreak on Labor Day. Showers
and thunderstorms should persist through at least mid morning
across northern MO into west central IL with the southwesterly LLJ
aiding development on the western flank and the spread into
central MO. The convective evolution from late morning into the
early afternoon is a little unclear. Overall the system should go
through a decaying stage with motion to the east, but there could
be continuous convective flare-ups on the western flank. By mid-
late afternoon the combination of the southward moving cold
front/residual boundaries and strongly bouyant air south of the
boundaries should result in new convective development. Improving
forcing from late afternoon into the evening via another shortwave
and the veering LLJ is expected to produce upscale growth into one
or more MCSs. Deep layer shear is rather impressive at 30-40+ kts
supporting an organized severe weather threat.

Any ongoing convection on Tuesday morning should be focused
across southern MO and southern IL in advance of the southward
movning cold front with convective cold pools and outflows well in
advance of the front. Tuesday afternoon and night the main threat
of showers and thunderstorms appears to be confined to southern MO
and southern IL in the vicinity of the stalling front. The front
will then retreat northward on Wednesday with heights aloft
beginning to rise in the wake of the progressive upper trof.
Heights will continue to rise through late Thursday as the upper
ridge once again establishes itself across the southern half of
the Nation, with summer heat in full swing. There is uncertainty
in the period Fri-Sat. Another cold front is forecast to move into
the through the area in this time frame with the ECMWF flattening
the northern extent of the upper ridge quicker and about 18h
faster with the cold front.

Glass

&&

.AVIATION:  (For the 06z TAFs through 06z Sunday Night)
Issued at 1037 PM CDT Sat Aug 30 2014

Most of the showers/storms have dissipated this evening, although
there was patchy clouds around 5000 feet in height along with mid-
high level clouds streaming northeastward through the St Louis
metro area. As the mid-upper level cloudiness shifts slowly
southeast of the taf sites late tonight and the surface wind
becomes light the MOS guidance is hinting at the formation of
stratus clouds and fog late tonight/early Sunday morning. The
stratus clouds and fog should dissipate by late Sunday morning,
although there will likely be scattered diurnal cumulus clouds in
the St Louis metro area during the late morning and afternoon.
S-swly surface winds can be expected on Sunday and Sunday evening.

Specifics for KSTL: Much of the mid-high level cloudiness may
shift southeast of STL late tonight with light fog developing
towards morning as the s-swly surface wind becomes light. The NAM
MOS guidance was also hinting at the possible formation of stratus
clouds as well. The fog and any stratus clouds should dissipate by
late Sunday morning, although there will likely be enough residual
low level moisture for the formation of scattered diurnal cumulus
clouds late Sunday morning and afternoon. The surface wind will
increase again to around 8 kts in the afternoon from a s-swly
direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 310357
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1057 PM CDT Sat Aug 30 2014

.UPDATE:
Issued at 845 PM CDT Sat Aug 30 2014

Very spotty convection continues to linger along and ahead of
weak mid-level shear axis, with remnants of weak surface boundary
also aiding a bit of development attm from just south and se of
UIN into central IL. PoPs should continue to ebb into the late
evening and overnight and slowly shift east with the shear axis, but
in spite of very spotty coverage/absence of radar returns it may
be that total cessation of the convective threat will be slow to
work its way east. Other sensible weather concern for tonight is
fog potential. Very humid low level ams will remain draped over
area, and while some higher level clouds may limit radiation in
the se part of the FA, very little cloud cover and fairly light
winds over the northwest half of the CWA should mean a greater
potential for fog development in this area. Will get update out
the door after 02z ob trends are ingested.

Truett

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 329 PM CDT Sat Aug 30 2014

Weakening trof of low pressure will move over the area tonight.  The
vast majority of the mid-upper level energy associated with this
system is well north of the area over the Upper Midwest, and what
little vorticity there is in our vicinity is moving northeast away
from the area.  The surface trof is already quasi-stationary, and is
providing a nice area of surface moisture convergence over eastern
Missouri and southwest Illinois.  Expect convection to continue to
develop in this area of moisture convergence through late afternoon
into early evening.  Convection should loose steam within a couple
of hours after sunset though.  Some isolated showers or storms could
continue to survive through the evening as a weak low level jet
develops and interacts with left over boundaries, but the vast
majority of the area should remain dry overnight.  Think there will
be some fog development before sunrise Sunday, though am not sure
how dense it will be.  First thoughts are 3-5 miles with some spots
dropping lower.  With weak southerly flow over the area, expect
overnight lows to remain in the mid 60s to low 70s.

Carney

.LONG TERM:  (Sunday through Next Saturday)
Issued at 329 PM CDT Sat Aug 30 2014

(Sunday - Tuesday)

Seasonably warm conditions with drier weather is expected on Sunday.
Tropical disturbance with origins in the Gulf of Mexico looks to track
southeast of area. Cannot rule out some showers/storms over portions of
southwest Illinois...but feel that the bulk of the precipitation should
be across KY/TN.

Fairly vigorous late summer shortwave trough will quickly eject out of
the lee of the Rocky Mountains and move northeastward into the Upper
Midwest by 1200 UTC Monday. Combination of strong DCPVA and diffluence
aloft should help force an area of widespread showers and thunderstorms
Sunday night somewhere across the mid-Missouri valley. Convective
evolution is difficult to ascertain heading into Monday...but current
thought is that MCS should be able to maintain itself east/southeastward
into at least portions of central and northeastern Missouri as well as
west-central Illinois as 30-40 kt LLJ veers. Uncertainty continues to
increase thereafter as best dynamics head toward the US-Canadian border.
Trailing cold front or effective boundary from prior night`s
convection will likely stall out somewhere over the CWFA and could
provide a focus for convection in the late afternoon. Shear/CAPE
combination certainly is supportive of organized severe
thunderstorms including supercells due to orientation of deep-
layer shear vector with respect to aforementioned boundary. Risk
does look quite conditional however due to many factors including:
1) degree of instability due to antecedent clouds/precipitation,
2) weak convergence along sfc fold front, and 3) UL
dynamics/forcing displaced well to the north of CWA. Temperatures
also will be a challenge on Monday and leaned toward the cooler
guidance for highs across northern areas and more of a blend of
model guidance for southern areas. However... actual high
temperatures do have the potential of being quite a bit cooler if
the overnight MCS from Sunday night propagates further
southeastward than currently forecast.

Monday night looks wet as frontal boundary will interact with strengthening
nocturnal LLJ should produce widespread showers and thunderstorms over
portions of the mid-Mississippi Valley. Main uncertainty is to exactly where
this would transpire across the area as exact positon of sfc boundary will
be important. For those reasons...upper PoPs a bit over some areas but did
not go with categorical PoPs just yet. Heavy rain may also be a threat
with convection Sunday night - Monday night due to anomalous precipitable
water values and deep warm cloud depths.

Did lower/shift PoPs on Tuesday a bit to the south and east as latest
guidance suggests cold front or effective boundary will finally clear
CWA by Tuesday morning. Skies should at least scatter out or partially
clear from north to south into early Tuesday afternoon. Consequently...
did bump up high temps a degree or two with afternoon temps topping out
in the mid 80s to near 90 degrees.

(Wednesday - Saturday)

Active weather with chances of showers and thunderstorms looks to return
to the region Tuesday night through Wednesday as frontal boundary moves
back northward across area as upper-level ridge begins to amplify once
again. Weather pattern will essentially revert to what we have seen
predominatly over the past two weeks with upper ridging across the central
United States and a trough in close proximity to the west coast. What it
means for us...above to well above normal temperatures day and night
along with mainly dry conditions. Look for lows largely in the low 70s
and highs in the upper 80s to low 90s to end the work week. Slightly
cooler conditions may occur by next Saturday as upper ridge flattens
out a bit allowing precipitation chances and cloud cover to increase
across the region.

Gosselin

&&

.AVIATION:  (For the 06z TAFs through 06z Sunday Night)
Issued at 1037 PM CDT Sat Aug 30 2014

Most of the showers/storms have dissipated this evening, although
there was patchy clouds around 5000 feet in height along with mid-
high level clouds streaming northeastward through the St Louis
metro area. As the mid-upper level cloudiness shifts slowly
southeast of the taf sites late tonight and the surface wind
becomes light the MOS guidance is hinting at the formation of
stratus clouds and fog late tonight/early Sunday morning. The
stratus clouds and fog should dissipate by late Sunday morning,
although there will likely be scattered diurnal cumulus clouds in
the St Louis metro area during the late morning and afternoon.
S-swly surface winds can be expected on Sunday and Sunday evening.

Specifics for KSTL: Much of the mid-high level cloudiness may
shift southeast of STL late tonight with light fog developing
towards morning as the s-swly surface wind becomes light. The NAM
MOS guidance was also hinting at the possible formation of stratus
clouds as well. The fog and any stratus clouds should dissipate by
late Sunday morning, although there will likely be enough residual
low level moisture for the formation of scattered diurnal cumulus
clouds late Sunday morning and afternoon. The surface wind will
increase again to around 8 kts in the afternoon from a s-swly
direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 310357
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1057 PM CDT Sat Aug 30 2014

.UPDATE:
Issued at 845 PM CDT Sat Aug 30 2014

Very spotty convection continues to linger along and ahead of
weak mid-level shear axis, with remnants of weak surface boundary
also aiding a bit of development attm from just south and se of
UIN into central IL. PoPs should continue to ebb into the late
evening and overnight and slowly shift east with the shear axis, but
in spite of very spotty coverage/absence of radar returns it may
be that total cessation of the convective threat will be slow to
work its way east. Other sensible weather concern for tonight is
fog potential. Very humid low level ams will remain draped over
area, and while some higher level clouds may limit radiation in
the se part of the FA, very little cloud cover and fairly light
winds over the northwest half of the CWA should mean a greater
potential for fog development in this area. Will get update out
the door after 02z ob trends are ingested.

Truett

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 329 PM CDT Sat Aug 30 2014

Weakening trof of low pressure will move over the area tonight.  The
vast majority of the mid-upper level energy associated with this
system is well north of the area over the Upper Midwest, and what
little vorticity there is in our vicinity is moving northeast away
from the area.  The surface trof is already quasi-stationary, and is
providing a nice area of surface moisture convergence over eastern
Missouri and southwest Illinois.  Expect convection to continue to
develop in this area of moisture convergence through late afternoon
into early evening.  Convection should loose steam within a couple
of hours after sunset though.  Some isolated showers or storms could
continue to survive through the evening as a weak low level jet
develops and interacts with left over boundaries, but the vast
majority of the area should remain dry overnight.  Think there will
be some fog development before sunrise Sunday, though am not sure
how dense it will be.  First thoughts are 3-5 miles with some spots
dropping lower.  With weak southerly flow over the area, expect
overnight lows to remain in the mid 60s to low 70s.

Carney

.LONG TERM:  (Sunday through Next Saturday)
Issued at 329 PM CDT Sat Aug 30 2014

(Sunday - Tuesday)

Seasonably warm conditions with drier weather is expected on Sunday.
Tropical disturbance with origins in the Gulf of Mexico looks to track
southeast of area. Cannot rule out some showers/storms over portions of
southwest Illinois...but feel that the bulk of the precipitation should
be across KY/TN.

Fairly vigorous late summer shortwave trough will quickly eject out of
the lee of the Rocky Mountains and move northeastward into the Upper
Midwest by 1200 UTC Monday. Combination of strong DCPVA and diffluence
aloft should help force an area of widespread showers and thunderstorms
Sunday night somewhere across the mid-Missouri valley. Convective
evolution is difficult to ascertain heading into Monday...but current
thought is that MCS should be able to maintain itself east/southeastward
into at least portions of central and northeastern Missouri as well as
west-central Illinois as 30-40 kt LLJ veers. Uncertainty continues to
increase thereafter as best dynamics head toward the US-Canadian border.
Trailing cold front or effective boundary from prior night`s
convection will likely stall out somewhere over the CWFA and could
provide a focus for convection in the late afternoon. Shear/CAPE
combination certainly is supportive of organized severe
thunderstorms including supercells due to orientation of deep-
layer shear vector with respect to aforementioned boundary. Risk
does look quite conditional however due to many factors including:
1) degree of instability due to antecedent clouds/precipitation,
2) weak convergence along sfc fold front, and 3) UL
dynamics/forcing displaced well to the north of CWA. Temperatures
also will be a challenge on Monday and leaned toward the cooler
guidance for highs across northern areas and more of a blend of
model guidance for southern areas. However... actual high
temperatures do have the potential of being quite a bit cooler if
the overnight MCS from Sunday night propagates further
southeastward than currently forecast.

Monday night looks wet as frontal boundary will interact with strengthening
nocturnal LLJ should produce widespread showers and thunderstorms over
portions of the mid-Mississippi Valley. Main uncertainty is to exactly where
this would transpire across the area as exact positon of sfc boundary will
be important. For those reasons...upper PoPs a bit over some areas but did
not go with categorical PoPs just yet. Heavy rain may also be a threat
with convection Sunday night - Monday night due to anomalous precipitable
water values and deep warm cloud depths.

Did lower/shift PoPs on Tuesday a bit to the south and east as latest
guidance suggests cold front or effective boundary will finally clear
CWA by Tuesday morning. Skies should at least scatter out or partially
clear from north to south into early Tuesday afternoon. Consequently...
did bump up high temps a degree or two with afternoon temps topping out
in the mid 80s to near 90 degrees.

(Wednesday - Saturday)

Active weather with chances of showers and thunderstorms looks to return
to the region Tuesday night through Wednesday as frontal boundary moves
back northward across area as upper-level ridge begins to amplify once
again. Weather pattern will essentially revert to what we have seen
predominatly over the past two weeks with upper ridging across the central
United States and a trough in close proximity to the west coast. What it
means for us...above to well above normal temperatures day and night
along with mainly dry conditions. Look for lows largely in the low 70s
and highs in the upper 80s to low 90s to end the work week. Slightly
cooler conditions may occur by next Saturday as upper ridge flattens
out a bit allowing precipitation chances and cloud cover to increase
across the region.

Gosselin

&&

.AVIATION:  (For the 06z TAFs through 06z Sunday Night)
Issued at 1037 PM CDT Sat Aug 30 2014

Most of the showers/storms have dissipated this evening, although
there was patchy clouds around 5000 feet in height along with mid-
high level clouds streaming northeastward through the St Louis
metro area. As the mid-upper level cloudiness shifts slowly
southeast of the taf sites late tonight and the surface wind
becomes light the MOS guidance is hinting at the formation of
stratus clouds and fog late tonight/early Sunday morning. The
stratus clouds and fog should dissipate by late Sunday morning,
although there will likely be scattered diurnal cumulus clouds in
the St Louis metro area during the late morning and afternoon.
S-swly surface winds can be expected on Sunday and Sunday evening.

Specifics for KSTL: Much of the mid-high level cloudiness may
shift southeast of STL late tonight with light fog developing
towards morning as the s-swly surface wind becomes light. The NAM
MOS guidance was also hinting at the possible formation of stratus
clouds as well. The fog and any stratus clouds should dissipate by
late Sunday morning, although there will likely be enough residual
low level moisture for the formation of scattered diurnal cumulus
clouds late Sunday morning and afternoon. The surface wind will
increase again to around 8 kts in the afternoon from a s-swly
direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 310145
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
845 PM CDT Sat Aug 30 2014

.UPDATE:
Issued at 845 PM CDT Sat Aug 30 2014

Very spotty convection continues to linger along and ahead of
weak mid-level shear axis, with remnants of weak surface boundary
also aiding a bit of development attm from just south and se of
UIN into central IL. PoPs should continue to ebb into the late
evening and overnight and slowly shift east with the shear axis, but
in spite of very spotty coverage/absence of radar returns it may
be that total cessation of the convective threat will be slow to
work its way east. Other sensible weather concern for tonight is
fog potential. Very humid low level ams will remain draped over
area, and while some higher level clouds may limit radiation in
the se part of the FA, very little cloud cover and fairly light
winds over the northwest half of the CWA should mean a greater
potential for fog development in this area. Will get update out
the door after 02z ob trends are ingested.

Truett

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 329 PM CDT Sat Aug 30 2014

Weakening trof of low pressure will move over the area tonight.  The
vast majority of the mid-upper level energy associated with this
system is well north of the area over the Upper Midwest, and what
little vorticity there is in our vicinity is moving northeast away
from the area.  The surface trof is already quasi-stationary, and is
providing a nice area of surface moisture convergence over eastern
Missouri and southwest Illinois.  Expect convection to continue to
develop in this area of moisture convergence through late afternoon
into early evening.  Convection should loose steam within a couple
of hours after sunset though.  Some isolated showers or storms could
continue to survive through the evening as a weak low level jet
develops and interacts with left over boundaries, but the vast
majority of the area should remain dry overnight.  Think there will
be some fog development before sunrise Sunday, though am not sure
how dense it will be.  First thoughts are 3-5 miles with some spots
dropping lower.  With weak southerly flow over the area, expect
overnight lows to remain in the mid 60s to low 70s.

Carney

.LONG TERM:  (Sunday through Next Saturday)
Issued at 329 PM CDT Sat Aug 30 2014

(Sunday - Tuesday)

Seasonably warm conditions with drier weather is expected on Sunday.
Tropical disturbance with origins in the Gulf of Mexico looks to track
southeast of area. Cannot rule out some showers/storms over portions of
southwest Illinois...but feel that the bulk of the precipitation should
be across KY/TN.

Fairly vigorous late summer shortwave trough will quickly eject out of
the lee of the Rocky Mountains and move northeastward into the Upper
Midwest by 1200 UTC Monday. Combination of strong DCPVA and diffluence
aloft should help force an area of widespread showers and thunderstorms
Sunday night somewhere across the mid-Missouri valley. Convective
evolution is difficult to ascertain heading into Monday...but current
thought is that MCS should be able to maintain itself east/southeastward
into at least portions of central and northeastern Missouri as well as
west-central Illinois as 30-40 kt LLJ veers. Uncertainty continues to
increase thereafter as best dynamics head toward the US-Canadian border.
Trailing cold front or effective boundary from prior night`s
convection will likely stall out somewhere over the CWFA and could
provide a focus for convection in the late afternoon. Shear/CAPE
combination certainly is supportive of organized severe
thunderstorms including supercells due to orientation of deep-
layer shear vector with respect to aforementioned boundary. Risk
does look quite conditional however due to many factors including:
1) degree of instability due to antecedent clouds/precipitation,
2) weak convergence along sfc fold front, and 3) UL
dynamics/forcing displaced well to the north of CWA. Temperatures
also will be a challenge on Monday and leaned toward the cooler
guidance for highs across northern areas and more of a blend of
model guidance for southern areas. However... actual high
temperatures do have the potential of being quite a bit cooler if
the overnight MCS from Sunday night propagates further
southeastward than currently forecast.

Monday night looks wet as frontal boundary will interact with strengthening
nocturnal LLJ should produce widespread showers and thunderstorms over
portions of the mid-Mississippi Valley. Main uncertainty is to exactly where
this would transpire across the area as exact positon of sfc boundary will
be important. For those reasons...upper PoPs a bit over some areas but did
not go with categorical PoPs just yet. Heavy rain may also be a threat
with convection Sunday night - Monday night due to anomalous precipitable
water values and deep warm cloud depths.

Did lower/shift PoPs on Tuesday a bit to the south and east as latest
guidance suggests cold front or effective boundary will finally clear
CWA by Tuesday morning. Skies should at least scatter out or partially
clear from north to south into early Tuesday afternoon. Consequently...
did bump up high temps a degree or two with afternoon temps topping out
in the mid 80s to near 90 degrees.

(Wednesday - Saturday)

Active weather with chances of showers and thunderstorms looks to return
to the region Tuesday night through Wednesday as frontal boundary moves
back northward across area as upper-level ridge begins to amplify once
again. Weather pattern will essentially revert to what we have seen
predominatly over the past two weeks with upper ridging across the central
United States and a trough in close proximity to the west coast. What it
means for us...above to well above normal temperatures day and night
along with mainly dry conditions. Look for lows largely in the low 70s
and highs in the upper 80s to low 90s to end the work week. Slightly
cooler conditions may occur by next Saturday as upper ridge flattens
out a bit allowing precipitation chances and cloud cover to increase
across the region.

Gosselin

&&

.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 527 PM CDT Sat Aug 30 2014

Widely scattered showers/storms continue to plague the St Louis
metro area ahead of a weak upper level disturbance and weak
surface trough. This activity should dissipate and/or shift
southeast of the taf sites later this evening. As the mid-upper
level clouds shift southeast of the taf sites later tonight and
the surface wind becomes light the MOS guidance is hinting at the
formation of stratus clouds and fog late tonight/early Sunday
morning. The stratus clouds and fog should dissipate by late
Sunday morning, although there may be scattered diurnal cumulus
clouds in the St Louis metro area during the late morning and
afternoon. S-swly surface winds can be expected on Sunday.

Specifics for KSTL: A few more showers/storms may impact STL until
01-02Z this evening. At least light fog is expected towards
morning as the s-swly surface wind becomes light with the NAM MOS
guidance also hinting at the possible formation of stratus clouds
as well. The fog and any stratus clouds should dissipate by late
Sunday morning, although there may be enough residual low level
moisture for the formation of scattered diurnal cumulus clouds
late Sunday morning and afternoon. The surface wind will increase
again to around 8 kts in the afternoon from a s-swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 310145
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
845 PM CDT Sat Aug 30 2014

.UPDATE:
Issued at 845 PM CDT Sat Aug 30 2014

Very spotty convection continues to linger along and ahead of
weak mid-level shear axis, with remnants of weak surface boundary
also aiding a bit of development attm from just south and se of
UIN into central IL. PoPs should continue to ebb into the late
evening and overnight and slowly shift east with the shear axis, but
in spite of very spotty coverage/absence of radar returns it may
be that total cessation of the convective threat will be slow to
work its way east. Other sensible weather concern for tonight is
fog potential. Very humid low level ams will remain draped over
area, and while some higher level clouds may limit radiation in
the se part of the FA, very little cloud cover and fairly light
winds over the northwest half of the CWA should mean a greater
potential for fog development in this area. Will get update out
the door after 02z ob trends are ingested.

Truett

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 329 PM CDT Sat Aug 30 2014

Weakening trof of low pressure will move over the area tonight.  The
vast majority of the mid-upper level energy associated with this
system is well north of the area over the Upper Midwest, and what
little vorticity there is in our vicinity is moving northeast away
from the area.  The surface trof is already quasi-stationary, and is
providing a nice area of surface moisture convergence over eastern
Missouri and southwest Illinois.  Expect convection to continue to
develop in this area of moisture convergence through late afternoon
into early evening.  Convection should loose steam within a couple
of hours after sunset though.  Some isolated showers or storms could
continue to survive through the evening as a weak low level jet
develops and interacts with left over boundaries, but the vast
majority of the area should remain dry overnight.  Think there will
be some fog development before sunrise Sunday, though am not sure
how dense it will be.  First thoughts are 3-5 miles with some spots
dropping lower.  With weak southerly flow over the area, expect
overnight lows to remain in the mid 60s to low 70s.

Carney

.LONG TERM:  (Sunday through Next Saturday)
Issued at 329 PM CDT Sat Aug 30 2014

(Sunday - Tuesday)

Seasonably warm conditions with drier weather is expected on Sunday.
Tropical disturbance with origins in the Gulf of Mexico looks to track
southeast of area. Cannot rule out some showers/storms over portions of
southwest Illinois...but feel that the bulk of the precipitation should
be across KY/TN.

Fairly vigorous late summer shortwave trough will quickly eject out of
the lee of the Rocky Mountains and move northeastward into the Upper
Midwest by 1200 UTC Monday. Combination of strong DCPVA and diffluence
aloft should help force an area of widespread showers and thunderstorms
Sunday night somewhere across the mid-Missouri valley. Convective
evolution is difficult to ascertain heading into Monday...but current
thought is that MCS should be able to maintain itself east/southeastward
into at least portions of central and northeastern Missouri as well as
west-central Illinois as 30-40 kt LLJ veers. Uncertainty continues to
increase thereafter as best dynamics head toward the US-Canadian border.
Trailing cold front or effective boundary from prior night`s
convection will likely stall out somewhere over the CWFA and could
provide a focus for convection in the late afternoon. Shear/CAPE
combination certainly is supportive of organized severe
thunderstorms including supercells due to orientation of deep-
layer shear vector with respect to aforementioned boundary. Risk
does look quite conditional however due to many factors including:
1) degree of instability due to antecedent clouds/precipitation,
2) weak convergence along sfc fold front, and 3) UL
dynamics/forcing displaced well to the north of CWA. Temperatures
also will be a challenge on Monday and leaned toward the cooler
guidance for highs across northern areas and more of a blend of
model guidance for southern areas. However... actual high
temperatures do have the potential of being quite a bit cooler if
the overnight MCS from Sunday night propagates further
southeastward than currently forecast.

Monday night looks wet as frontal boundary will interact with strengthening
nocturnal LLJ should produce widespread showers and thunderstorms over
portions of the mid-Mississippi Valley. Main uncertainty is to exactly where
this would transpire across the area as exact positon of sfc boundary will
be important. For those reasons...upper PoPs a bit over some areas but did
not go with categorical PoPs just yet. Heavy rain may also be a threat
with convection Sunday night - Monday night due to anomalous precipitable
water values and deep warm cloud depths.

Did lower/shift PoPs on Tuesday a bit to the south and east as latest
guidance suggests cold front or effective boundary will finally clear
CWA by Tuesday morning. Skies should at least scatter out or partially
clear from north to south into early Tuesday afternoon. Consequently...
did bump up high temps a degree or two with afternoon temps topping out
in the mid 80s to near 90 degrees.

(Wednesday - Saturday)

Active weather with chances of showers and thunderstorms looks to return
to the region Tuesday night through Wednesday as frontal boundary moves
back northward across area as upper-level ridge begins to amplify once
again. Weather pattern will essentially revert to what we have seen
predominatly over the past two weeks with upper ridging across the central
United States and a trough in close proximity to the west coast. What it
means for us...above to well above normal temperatures day and night
along with mainly dry conditions. Look for lows largely in the low 70s
and highs in the upper 80s to low 90s to end the work week. Slightly
cooler conditions may occur by next Saturday as upper ridge flattens
out a bit allowing precipitation chances and cloud cover to increase
across the region.

Gosselin

&&

.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 527 PM CDT Sat Aug 30 2014

Widely scattered showers/storms continue to plague the St Louis
metro area ahead of a weak upper level disturbance and weak
surface trough. This activity should dissipate and/or shift
southeast of the taf sites later this evening. As the mid-upper
level clouds shift southeast of the taf sites later tonight and
the surface wind becomes light the MOS guidance is hinting at the
formation of stratus clouds and fog late tonight/early Sunday
morning. The stratus clouds and fog should dissipate by late
Sunday morning, although there may be scattered diurnal cumulus
clouds in the St Louis metro area during the late morning and
afternoon. S-swly surface winds can be expected on Sunday.

Specifics for KSTL: A few more showers/storms may impact STL until
01-02Z this evening. At least light fog is expected towards
morning as the s-swly surface wind becomes light with the NAM MOS
guidance also hinting at the possible formation of stratus clouds
as well. The fog and any stratus clouds should dissipate by late
Sunday morning, although there may be enough residual low level
moisture for the formation of scattered diurnal cumulus clouds
late Sunday morning and afternoon. The surface wind will increase
again to around 8 kts in the afternoon from a s-swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX









000
FXUS63 KLSX 302317
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
617 PM CDT Sat Aug 30 2014

.UPDATE:
Issued at 615 PM CDT Sat Aug 30 2014

Minor adjustment for the next few hours, primarily to shave PoPs a
bit. The expected late afternoon increase in coverage has not
occurred, so a more hit and miss storm threat should be in the
offing for the southeast 2/3 of our CWA this evening. Update out
shortly.

Truett

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 329 PM CDT Sat Aug 30 2014

Weakening trof of low pressure will move over the area tonight.  The
vast majority of the mid-upper level energy associated with this
system is well north of the area over the Upper Midwest, and what
little vorticity there is in our vicinity is moving northeast away
from the area.  The surface trof is already quasi-stationary, and is
providing a nice area of surface moisture convergence over eastern
Missouri and southwest Illinois.  Expect convection to continue to
develop in this area of moisture convergence through late afternoon
into early evening.  Convection should loose steam within a couple
of hours after sunset though.  Some isolated showers or storms could
continue to survive through the evening as a weak low level jet
develops and interacts with left over boundaries, but the vast
majority of the area should remain dry overnight.  Think there will
be some fog development before sunrise Sunday, though am not sure
how dense it will be.  First thoughts are 3-5 miles with some spots
dropping lower.  With weak southerly flow over the area, expect
overnight lows to remain in the mid 60s to low 70s.

Carney

.LONG TERM:  (Sunday through Next Saturday)
Issued at 329 PM CDT Sat Aug 30 2014

(Sunday - Tuesday)

Seasonably warm conditions with drier weather is expected on Sunday.
Tropical disturbance with origins in the Gulf of Mexico looks to track
southeast of area. Cannot rule out some showers/storms over portions of
southwest Illinois...but feel that the bulk of the precipitation should
be across KY/TN.

Fairly vigorous late summer shortwave trough will quickly eject out of
the lee of the Rocky Mountains and move northeastward into the Upper
Midwest by 1200 UTC Monday. Combination of strong DCPVA and diffluence
aloft should help force an area of widespread showers and thunderstorms
Sunday night somewhere across the mid-Missouri valley. Convective
evolution is difficult to ascertain heading into Monday...but current
thought is that MCS should be able to maintain itself east/southeastward
into at least portions of central and northeastern Missouri as well as
west-central Illinois as 30-40 kt LLJ veers. Uncertainty continues to
increase thereafter as best dynamics head toward the US-Canadian border.
Trailing cold front or effective boundary from prior night`s
convection will likely stall out somewhere over the CWFA and could
provide a focus for convection in the late afternoon. Shear/CAPE
combination certainly is supportive of organized severe
thunderstorms including supercells due to orientation of deep-
layer shear vector with respect to aforementioned boundary. Risk
does look quite conditional however due to many factors including:
1) degree of instability due to antecedent clouds/precipitation,
2) weak convergence along sfc fold front, and 3) UL
dynamics/forcing displaced well to the north of CWA. Temperatures
also will be a challenge on Monday and leaned toward the cooler
guidance for highs across northern areas and more of a blend of
model guidance for southern areas. However... actual high
temperatures do have the potential of being quite a bit cooler if
the overnight MCS from Sunday night propagates further
southeastward than currently forecast.

Monday night looks wet as frontal boundary will interact with strengthening
nocturnal LLJ should produce widespread showers and thunderstorms over
portions of the mid-Mississippi Valley. Main uncertainty is to exactly where
this would transpire across the area as exact positon of sfc boundary will
be important. For those reasons...upper PoPs a bit over some areas but did
not go with categorical PoPs just yet. Heavy rain may also be a threat
with convection Sunday night - Monday night due to anomalous precipitable
water values and deep warm cloud depths.

Did lower/shift PoPs on Tuesday a bit to the south and east as latest
guidance suggests cold front or effective boundary will finally clear
CWA by Tuesday morning. Skies should at least scatter out or partially
clear from north to south into early Tuesday afternoon. Consequently...
did bump up high temps a degree or two with afternoon temps topping out
in the mid 80s to near 90 degrees.

(Wednesday - Saturday)

Active weather with chances of showers and thunderstorms looks to return
to the region Tuesday night through Wednesday as frontal boundary moves
back northward across area as upper-level ridge begins to amplify once
again. Weather pattern will essentially revert to what we have seen
predominatly over the past two weeks with upper ridging across the central
United States and a trough in close proximity to the west coast. What it
means for us...above to well above normal temperatures day and night
along with mainly dry conditions. Look for lows largely in the low 70s
and highs in the upper 80s to low 90s to end the work week. Slightly
cooler conditions may occur by next Saturday as upper ridge flattens
out a bit allowing precipitation chances and cloud cover to increase
across the region.

Gosselin

&&

.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 527 PM CDT Sat Aug 30 2014

Widely scattered showers/storms continue to plague the St Louis
metro area ahead of a weak upper level disturbance and weak
surface trough. This activity should dissipate and/or shift
southeast of the taf sites later this evening. As the mid-upper
level clouds shift southeast of the taf sites later tonight and
the surface wind becomes light the MOS guidance is hinting at the
formation of stratus clouds and fog late tonight/early Sunday
morning. The stratus clouds and fog should dissipate by late
Sunday morning, although there may be scattered diurnal cumulus
clouds in the St Louis metro area during the late morning and
afternoon. S-swly surface winds can be expected on Sunday.

Specifics for KSTL: A few more showers/storms may impact STL until
01-02Z this evening. At least light fog is expected towards
morning as the s-swly surface wind becomes light with the NAM MOS
guidance also hinting at the possible formation of stratus clouds
as well. The fog and any stratus clouds should dissipate by late
Sunday morning, although there may be enough residual low level
moisture for the formation of scattered diurnal cumulus clouds
late Sunday morning and afternoon. The surface wind will increase
again to around 8 kts in the afternoon from a s-swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 302317
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
617 PM CDT Sat Aug 30 2014

.UPDATE:
Issued at 615 PM CDT Sat Aug 30 2014

Minor adjustment for the next few hours, primarily to shave PoPs a
bit. The expected late afternoon increase in coverage has not
occurred, so a more hit and miss storm threat should be in the
offing for the southeast 2/3 of our CWA this evening. Update out
shortly.

Truett

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 329 PM CDT Sat Aug 30 2014

Weakening trof of low pressure will move over the area tonight.  The
vast majority of the mid-upper level energy associated with this
system is well north of the area over the Upper Midwest, and what
little vorticity there is in our vicinity is moving northeast away
from the area.  The surface trof is already quasi-stationary, and is
providing a nice area of surface moisture convergence over eastern
Missouri and southwest Illinois.  Expect convection to continue to
develop in this area of moisture convergence through late afternoon
into early evening.  Convection should loose steam within a couple
of hours after sunset though.  Some isolated showers or storms could
continue to survive through the evening as a weak low level jet
develops and interacts with left over boundaries, but the vast
majority of the area should remain dry overnight.  Think there will
be some fog development before sunrise Sunday, though am not sure
how dense it will be.  First thoughts are 3-5 miles with some spots
dropping lower.  With weak southerly flow over the area, expect
overnight lows to remain in the mid 60s to low 70s.

Carney

.LONG TERM:  (Sunday through Next Saturday)
Issued at 329 PM CDT Sat Aug 30 2014

(Sunday - Tuesday)

Seasonably warm conditions with drier weather is expected on Sunday.
Tropical disturbance with origins in the Gulf of Mexico looks to track
southeast of area. Cannot rule out some showers/storms over portions of
southwest Illinois...but feel that the bulk of the precipitation should
be across KY/TN.

Fairly vigorous late summer shortwave trough will quickly eject out of
the lee of the Rocky Mountains and move northeastward into the Upper
Midwest by 1200 UTC Monday. Combination of strong DCPVA and diffluence
aloft should help force an area of widespread showers and thunderstorms
Sunday night somewhere across the mid-Missouri valley. Convective
evolution is difficult to ascertain heading into Monday...but current
thought is that MCS should be able to maintain itself east/southeastward
into at least portions of central and northeastern Missouri as well as
west-central Illinois as 30-40 kt LLJ veers. Uncertainty continues to
increase thereafter as best dynamics head toward the US-Canadian border.
Trailing cold front or effective boundary from prior night`s
convection will likely stall out somewhere over the CWFA and could
provide a focus for convection in the late afternoon. Shear/CAPE
combination certainly is supportive of organized severe
thunderstorms including supercells due to orientation of deep-
layer shear vector with respect to aforementioned boundary. Risk
does look quite conditional however due to many factors including:
1) degree of instability due to antecedent clouds/precipitation,
2) weak convergence along sfc fold front, and 3) UL
dynamics/forcing displaced well to the north of CWA. Temperatures
also will be a challenge on Monday and leaned toward the cooler
guidance for highs across northern areas and more of a blend of
model guidance for southern areas. However... actual high
temperatures do have the potential of being quite a bit cooler if
the overnight MCS from Sunday night propagates further
southeastward than currently forecast.

Monday night looks wet as frontal boundary will interact with strengthening
nocturnal LLJ should produce widespread showers and thunderstorms over
portions of the mid-Mississippi Valley. Main uncertainty is to exactly where
this would transpire across the area as exact positon of sfc boundary will
be important. For those reasons...upper PoPs a bit over some areas but did
not go with categorical PoPs just yet. Heavy rain may also be a threat
with convection Sunday night - Monday night due to anomalous precipitable
water values and deep warm cloud depths.

Did lower/shift PoPs on Tuesday a bit to the south and east as latest
guidance suggests cold front or effective boundary will finally clear
CWA by Tuesday morning. Skies should at least scatter out or partially
clear from north to south into early Tuesday afternoon. Consequently...
did bump up high temps a degree or two with afternoon temps topping out
in the mid 80s to near 90 degrees.

(Wednesday - Saturday)

Active weather with chances of showers and thunderstorms looks to return
to the region Tuesday night through Wednesday as frontal boundary moves
back northward across area as upper-level ridge begins to amplify once
again. Weather pattern will essentially revert to what we have seen
predominatly over the past two weeks with upper ridging across the central
United States and a trough in close proximity to the west coast. What it
means for us...above to well above normal temperatures day and night
along with mainly dry conditions. Look for lows largely in the low 70s
and highs in the upper 80s to low 90s to end the work week. Slightly
cooler conditions may occur by next Saturday as upper ridge flattens
out a bit allowing precipitation chances and cloud cover to increase
across the region.

Gosselin

&&

.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 527 PM CDT Sat Aug 30 2014

Widely scattered showers/storms continue to plague the St Louis
metro area ahead of a weak upper level disturbance and weak
surface trough. This activity should dissipate and/or shift
southeast of the taf sites later this evening. As the mid-upper
level clouds shift southeast of the taf sites later tonight and
the surface wind becomes light the MOS guidance is hinting at the
formation of stratus clouds and fog late tonight/early Sunday
morning. The stratus clouds and fog should dissipate by late
Sunday morning, although there may be scattered diurnal cumulus
clouds in the St Louis metro area during the late morning and
afternoon. S-swly surface winds can be expected on Sunday.

Specifics for KSTL: A few more showers/storms may impact STL until
01-02Z this evening. At least light fog is expected towards
morning as the s-swly surface wind becomes light with the NAM MOS
guidance also hinting at the possible formation of stratus clouds
as well. The fog and any stratus clouds should dissipate by late
Sunday morning, although there may be enough residual low level
moisture for the formation of scattered diurnal cumulus clouds
late Sunday morning and afternoon. The surface wind will increase
again to around 8 kts in the afternoon from a s-swly direction.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 302301
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
601 PM CDT Sat Aug 30 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 329 PM CDT Sat Aug 30 2014

Weakening trof of low pressure will move over the area tonight.  The
vast majority of the mid-upper level energy associated with this
system is well north of the area over the Upper Midwest, and what
little vorticity there is in our vicinity is moving northeast away
from the area.  The surface trof is already quasi-stationary, and is
providing a nice area of surface moisture convergence over eastern
Missouri and southwest Illinois.  Expect convection to continue to
develop in this area of moisture convergence through late afternoon
into early evening.  Convection should loose steam within a couple
of hours after sunset though.  Some isolated showers or storms could
continue to survive through the evening as a weak low level jet
develops and interacts with left over boundaries, but the vast
majority of the area should remain dry overnight.  Think there will
be some fog development before sunrise Sunday, though am not sure
how dense it will be.  First thoughts are 3-5 miles with some spots
dropping lower.  With weak southerly flow over the area, expect
overnight lows to remain in the mid 60s to low 70s.

Carney

.LONG TERM:  (Sunday through Next Saturday)
Issued at 329 PM CDT Sat Aug 30 2014

(Sunday - Tuesday)

Seasonably warm conditions with drier weather is expected on Sunday.
Tropical disturbance with origins in the Gulf of Mexico looks to track
southeast of area. Cannot rule out some showers/storms over portions of
southwest Illinois...but feel that the bulk of the precipitation should
be across KY/TN.

Fairly vigorous late summer shortwave trough will quickly eject out of
the lee of the Rocky Mountains and move northeastward into the Upper
Midwest by 1200 UTC Monday. Combination of strong DCPVA and diffluence
aloft should help force an area of widespread showers and thunderstorms
Sunday night somewhere across the mid-Missouri valley. Convective
evolution is difficult to ascertain heading into Monday...but current
thought is that MCS should be able to maintain itself east/southeastward
into at least portions of central and northeastern Missouri as well as
west-central Illinois as 30-40 kt LLJ veers. Uncertainty continues to
increase thereafter as best dynamics head toward the US-Canadian border.
Trailing cold front or effective boundary from prior night`s
convection will likely stall out somewhere over the CWFA and could
provide a focus for convection in the late afternoon. Shear/CAPE
combination certainly is supportive of organized severe
thunderstorms including supercells due to orientation of deep-
layer shear vector with respect to aforementioned boundary. Risk
does look quite conditional however due to many factors including:
1) degree of instability due to antecedent clouds/precipitation,
2) weak convergence along sfc fold front, and 3) UL
dynamics/forcing displaced well to the north of CWA. Temperatures
also will be a challenge on Monday and leaned toward the cooler
guidance for highs across northern areas and more of a blend of
model guidance for southern areas. However... actual high
temperatures do have the potential of being quite a bit cooler if
the overnight MCS from Sunday night propagates further
southeastward than currently forecast.

Monday night looks wet as frontal boundary will interact with strengthening
nocturnal LLJ should produce widespread showers and thunderstorms over
portions of the mid-Mississippi Valley. Main uncertainty is to exactly where
this would transpire across the area as exact positon of sfc boundary will
be important. For those reasons...upper PoPs a bit over some areas but did
not go with categorical PoPs just yet. Heavy rain may also be a threat
with convection Sunday night - Monday night due to anomalous precipitable
water values and deep warm cloud depths.

Did lower/shift PoPs on Tuesday a bit to the south and east as latest
guidance suggests cold front or effective boundary will finally clear
CWA by Tuesday morning. Skies should at least scatter out or partially
clear from north to south into early Tuesday afternoon. Consequently...
did bump up high temps a degree or two with afternoon temps topping out
in the mid 80s to near 90 degrees.

(Wednesday - Saturday)

Active weather with chances of showers and thunderstorms looks to return
to the region Tuesday night through Wednesday as frontal boundary moves
back northward across area as upper-level ridge begins to amplify once
again. Weather pattern will essentially revert to what we have seen
predominatly over the past two weeks with upper ridging across the central
United States and a trough in close proximity to the west coast. What it
means for us...above to well above normal temperatures day and night
along with mainly dry conditions. Look for lows largely in the low 70s
and highs in the upper 80s to low 90s to end the work week. Slightly
cooler conditions may occur by next Saturday as upper ridge flattens
out a bit allowing precipitation chances and cloud cover to increase
across the region.

Gosselin

&&

.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 527 PM CDT Sat Aug 30 2014

Widely scattered showers/storms continue to plague the St Louis
metro area ahead of a weak upper level disturbance and weak
surface trough. This activity should dissipate and/or shift
southeast of the taf sites later this evening. As the mid-upper
level clouds shift southeast of the taf sites later tonight and
the surface wind becomes light the MOS guidance is hinting at the
formation of stratus clouds and fog late tonight/early Sunday
morning. The stratus clouds and fog should dissipate by late
Sunday morning, although there may be scattered diurnal cumulus
clouds in the St Louis metro area during the late morning and
afternoon. S-swly surface winds can be expected on Sunday.

Specifics for KSTL: A few more showers/storms may impact STL until
01-02Z this evening. At least light fog is expected towards
morning as the s-swly surface wind becomes light with the NAM MOS
guidance also hinting at the possible formation of stratus clouds
as well. The fog and any stratus clouds should dissipate by late
Sunday morning, although there may be enough residual low level
moisture for the formation of scattered diurnal cumulus clouds
late Sunday morning and afternoon. The surface wind will increase
again to around 8 kts in the afternoon from a s-swly direction.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     71  89  74  89 /  50  10  10  60
Quincy          65  87  72  83 /  20  10  40  70
Columbia        67  91  72  87 /  30  10  20  60
Jefferson City  68  90  72  87 /  40  10  20  60
Salem           69  85  71  88 /  50  30  10  40
Farmington      69  87  71  89 /  40  20  10  30

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 302301
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
601 PM CDT Sat Aug 30 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 329 PM CDT Sat Aug 30 2014

Weakening trof of low pressure will move over the area tonight.  The
vast majority of the mid-upper level energy associated with this
system is well north of the area over the Upper Midwest, and what
little vorticity there is in our vicinity is moving northeast away
from the area.  The surface trof is already quasi-stationary, and is
providing a nice area of surface moisture convergence over eastern
Missouri and southwest Illinois.  Expect convection to continue to
develop in this area of moisture convergence through late afternoon
into early evening.  Convection should loose steam within a couple
of hours after sunset though.  Some isolated showers or storms could
continue to survive through the evening as a weak low level jet
develops and interacts with left over boundaries, but the vast
majority of the area should remain dry overnight.  Think there will
be some fog development before sunrise Sunday, though am not sure
how dense it will be.  First thoughts are 3-5 miles with some spots
dropping lower.  With weak southerly flow over the area, expect
overnight lows to remain in the mid 60s to low 70s.

Carney

.LONG TERM:  (Sunday through Next Saturday)
Issued at 329 PM CDT Sat Aug 30 2014

(Sunday - Tuesday)

Seasonably warm conditions with drier weather is expected on Sunday.
Tropical disturbance with origins in the Gulf of Mexico looks to track
southeast of area. Cannot rule out some showers/storms over portions of
southwest Illinois...but feel that the bulk of the precipitation should
be across KY/TN.

Fairly vigorous late summer shortwave trough will quickly eject out of
the lee of the Rocky Mountains and move northeastward into the Upper
Midwest by 1200 UTC Monday. Combination of strong DCPVA and diffluence
aloft should help force an area of widespread showers and thunderstorms
Sunday night somewhere across the mid-Missouri valley. Convective
evolution is difficult to ascertain heading into Monday...but current
thought is that MCS should be able to maintain itself east/southeastward
into at least portions of central and northeastern Missouri as well as
west-central Illinois as 30-40 kt LLJ veers. Uncertainty continues to
increase thereafter as best dynamics head toward the US-Canadian border.
Trailing cold front or effective boundary from prior night`s
convection will likely stall out somewhere over the CWFA and could
provide a focus for convection in the late afternoon. Shear/CAPE
combination certainly is supportive of organized severe
thunderstorms including supercells due to orientation of deep-
layer shear vector with respect to aforementioned boundary. Risk
does look quite conditional however due to many factors including:
1) degree of instability due to antecedent clouds/precipitation,
2) weak convergence along sfc fold front, and 3) UL
dynamics/forcing displaced well to the north of CWA. Temperatures
also will be a challenge on Monday and leaned toward the cooler
guidance for highs across northern areas and more of a blend of
model guidance for southern areas. However... actual high
temperatures do have the potential of being quite a bit cooler if
the overnight MCS from Sunday night propagates further
southeastward than currently forecast.

Monday night looks wet as frontal boundary will interact with strengthening
nocturnal LLJ should produce widespread showers and thunderstorms over
portions of the mid-Mississippi Valley. Main uncertainty is to exactly where
this would transpire across the area as exact positon of sfc boundary will
be important. For those reasons...upper PoPs a bit over some areas but did
not go with categorical PoPs just yet. Heavy rain may also be a threat
with convection Sunday night - Monday night due to anomalous precipitable
water values and deep warm cloud depths.

Did lower/shift PoPs on Tuesday a bit to the south and east as latest
guidance suggests cold front or effective boundary will finally clear
CWA by Tuesday morning. Skies should at least scatter out or partially
clear from north to south into early Tuesday afternoon. Consequently...
did bump up high temps a degree or two with afternoon temps topping out
in the mid 80s to near 90 degrees.

(Wednesday - Saturday)

Active weather with chances of showers and thunderstorms looks to return
to the region Tuesday night through Wednesday as frontal boundary moves
back northward across area as upper-level ridge begins to amplify once
again. Weather pattern will essentially revert to what we have seen
predominatly over the past two weeks with upper ridging across the central
United States and a trough in close proximity to the west coast. What it
means for us...above to well above normal temperatures day and night
along with mainly dry conditions. Look for lows largely in the low 70s
and highs in the upper 80s to low 90s to end the work week. Slightly
cooler conditions may occur by next Saturday as upper ridge flattens
out a bit allowing precipitation chances and cloud cover to increase
across the region.

Gosselin

&&

.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 527 PM CDT Sat Aug 30 2014

Widely scattered showers/storms continue to plague the St Louis
metro area ahead of a weak upper level disturbance and weak
surface trough. This activity should dissipate and/or shift
southeast of the taf sites later this evening. As the mid-upper
level clouds shift southeast of the taf sites later tonight and
the surface wind becomes light the MOS guidance is hinting at the
formation of stratus clouds and fog late tonight/early Sunday
morning. The stratus clouds and fog should dissipate by late
Sunday morning, although there may be scattered diurnal cumulus
clouds in the St Louis metro area during the late morning and
afternoon. S-swly surface winds can be expected on Sunday.

Specifics for KSTL: A few more showers/storms may impact STL until
01-02Z this evening. At least light fog is expected towards
morning as the s-swly surface wind becomes light with the NAM MOS
guidance also hinting at the possible formation of stratus clouds
as well. The fog and any stratus clouds should dissipate by late
Sunday morning, although there may be enough residual low level
moisture for the formation of scattered diurnal cumulus clouds
late Sunday morning and afternoon. The surface wind will increase
again to around 8 kts in the afternoon from a s-swly direction.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     71  89  74  89 /  50  10  10  60
Quincy          65  87  72  83 /  20  10  40  70
Columbia        67  91  72  87 /  30  10  20  60
Jefferson City  68  90  72  87 /  40  10  20  60
Salem           69  85  71  88 /  50  30  10  40
Farmington      69  87  71  89 /  40  20  10  30

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 302035
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
335 PM CDT Sat Aug 30 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 329 PM CDT Sat Aug 30 2014

Weakening trof of low pressure will move over the area tonight.  The
vast majority of the mid-upper level energy associated with this
system is well north of the area over the Upper Midwest, and what
little vorticity there is in our vicinity is moving northeast away
from the area.  The surface trof is already quasi-stationary, and is
providing a nice area of surface moisture convergence over eastern
Missouri and southwest Illinois.  Expect convection to continue to
develop in this area of moisture convergence through late afternoon
into early evening.  Convection should loose steam within a couple
of hours after sunset though.  Some isolated showers or storms could
continue to survive through the evening as a weak low level jet
develops and interacts with left over boundaries, but the vast
majority of the area should remain dry overnight.  Think there will
be some fog development before sunrise Sunday, though am not sure
how dense it will be.  First thoughts are 3-5 miles with some spots
dropping lower.  With weak southerly flow over the area, expect
overnight lows to remain in the mid 60s to low 70s.

Carney


.LONG TERM:  (Sunday through Next Saturday)
Issued at 329 PM CDT Sat Aug 30 2014

(Sunday - Tuesday)

Seasonably warm conditions with drier weather is expected on Sunday.
Tropical disturbance with origins in the Gulf of Mexico looks to track
southeast of area. Cannot rule out some showers/storms over portions of
southwest Illinois...but feel that the bulk of the precipitation should
be across KY/TN.

Fairly vigorous late summer shortwave trough will quickly eject out of
the lee of the Rocky Mountains and move northeastward into the Upper
Midwest by 1200 UTC Monday. Combination of strong DCPVA and diffluence
aloft should help force an area of widespread showers and thunderstorms
Sunday night somewhere across the mid-Missouri valley. Convective
evolution is difficult to ascertain heading into Monday...but current
thought is that MCS should be able to maintain itself east/southeastward
into at least portions of central and northeastern Missouri as well as
west-central Illinois as 30-40 kt LLJ veers. Uncertainty continues to
increase thereafter as best dynamics head toward the US-Canadian border.
Trailing cold frontor effective boundary from prior night`s convection will
likely stall out somewhere over the CWFA and could provide a focus for
convection in the late afternoon. Shear/CAPE combination certainly is
supportive of organized severe thunderstorms including supercells due to
orientation of deep-layer shear vector with respect to aforementioned
boundary. Risk does look quite conditional however due to many factors
including: 1) degree of instability due to antecedent clouds/precipitation,
2) weak convergence along sfc fold front, and 3) UL dynamics/forcing
displaced well to the north of CWA. Temperatures also will be a challenge
on Monday and leaned toward the cooler guidance for highs across northern
areas and more of a blend of model guidance for southern areas. However...
actual high temperatures do have the potential of being quite a bit
cooler if the overnight MCS from Sunday night propagates further
southeastward than currently forecast.

Monday night looks wet as frontal boundary will interact with strengthening
nocturnal LLJ should produce widespread showers and thunderstorms over
portions of the mid-Mississippi Valley. Main uncertainty is to exactly where
this would transpire across the area as exact positon of sfc boundary will
be important. For those reasons...upper PoPs a bit over some areas but did
not go with categorical PoPs just yet. Heavy rain may also be a threat
with convection Sunday night - Monday night due to anomalous precipitable
water values and deep warm cloud depths.

Did lower/shift PoPs on Tuesday a bit to the south and east as latest
guidance suggests cold front or effective boundary will finally clear
CWA by Tuesday morning. Skies should at least scatter out or partially
clear from north to south into early Tuesday afternoon. Consequently...
did bump up high temps a degree or two with afternoon temps topping out
in the mid 80s to near 90 degrees.

(Wednesday - Saturday)

Active weather with chances of showers and thunderstorms looks to return
to the region Tuesday night through Wednesday as frontal boundary moves
back northward across area as upper-level ridge begins to amplify once
again. Weather pattern will essentially revert to what we have seen
predominatly over the past two weeks with upper ridging across the central
United States and a trough in close proximity to the west coast. What it
means for us...above to well above normal temperatures day and night
along with mainly dry conditions. Look for lows largely in the low 70s
and highs in the upper 80s to low 90s to end the work week. Slightly
cooler conditions may occur by next Saturday as upper ridge flattens
out a bit allowing precipitation chances and cloud cover to increase
across the region.


Gosselin


&&

.AVIATION:  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1240 PM CDT Sat Aug 30 2014

A trough of low pressure extending from north central Missouri
southwest into southeast Kansas will remain nearly stationary
today. This trough will provide a focus for thunderstorm
development across the area through the afternoon into early
evening. Expect scattered to numerous showers and thunderstorms
this afternoon...primarily east of the trough. MVFR/IFR flight
conditions can be expected in the areas of rain. Expect VFR flight
conditions and light south-southwest flow outside of thunderstorms
except for a few patches of higher MFR CIGS north of the STL Metro
area. Showers and storms will dissipate within an hour or two
after sunset. VFR conditions are expected until the pre-dawn hours
of Sunday morning when fog will develop. Areal coverage and
density of the fog is not certain at this time, but at least
patchy MFR fog is expected. Fog should dissipate within 2 hours
after sunrise Sunday.

Specifics for KSTL:

Expect showers and thunderstorms to increase in coverage this
afternoon. Timing and intensity is uncertain at Lambert, and there
is a definite chance there could be some intermittent heavy rain
which could reduce the visibility to IFR. However, expect VFR
conditions to prevail for the vast majority of the afternoon.
Showers/storms should dissipate quickly after sunset. With moist
air in place over the STL Metro, think there will be some light
fog at the terminal before sunrise Sunday. Fog should dissipate
within an hour or two after sunrise.

Carney

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     71  89  74  89 /  50  10  10  60
Quincy          65  87  72  83 /  20  10  40  70
Columbia        67  91  72  87 /  30  10  20  60
Jefferson City  68  90  72  87 /  40  10  20  60
Salem           69  85  71  88 /  50  30  10  40
Farmington      69  87  71  89 /  40  20  10  30

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 301800
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
100 PM CDT Sat Aug 30 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sat Aug 30 2014

Regional radar is showing a number of areas of showers and
thunderstorms across Missouri and western Illinois early this
morning. These are generally within a weak warm advection regime
ahead of a upper trof moving through the MS Valley and in advance
of the attendant cold front. While all the current activity should
continue moving east northeast this morning, the overall consensus
amongst the guidance and convection allowing models is that there
should be a general increase in the scattered activity currently
over southwest Missouri as the morning progresses and it moves
northeast. Additional development is also expected during the
later part of the morning into the afternoon in a broad southwest
to northeast zone ahead of the slowly advancing cold front and centered
through the southeast half of the CWA. Given the current temperatures
in the 70s, low-mid 80s looks reasonable for highs today.

Glass

.LONG TERM:  (Tonight through Friday)
Issued at 330 AM CDT Sat Aug 30 2014

Convective trends are not completely clear cut tonight. The main
upper trof axis should have passed to the east by early this
evening, but there is a weak lingering vort max still to pass and
the front appears to wash out across northeast Missouri and west
central Illinois. Sans the NAM, the model consensus keeps a chance
of showers and thunderstorms centered though the southeast half of
the CWA during the evening. Sunday looks largely dry and warmer
with possibly some isolated diurnal storms across southeast MO and
southwest Illinois. The threat of organized covection should
slowly spread into northeast Missouri late Sunday night with the
approach of a progressive long wave trof and attendant cold front and
intensifying southwesterly LLJ. Thunderstorms appear likely on
Labor Day and Monday night as the cold front moves slowly southward
into a moist unstable air mass, and as a southwesterly LLJ and the
upper trof contribute to lift and cap removal. This system will be
accompanied by deep layer shear of 30-40+ knots resulting in the
potential for organized severe storms. Showers and thunderstorms
could persist across the southern CWA Tuesday and maybe even into
Tuesday night and Wednesday in the vicinity of the front and then
as it retreats back northward late Wednesday.

Late in the week ahead the upper ridge is forecast to restablish
itself over the southeast half of the Nation, bringing a return of
more summer like weather/heat.

Glass

&&

.AVIATION:  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1240 PM CDT Sat Aug 30 2014

A trough of low pressure extending from north central Missouri
southwest into southeast Kansas will remain nearly stationary
today. This trough will provide a focus for thunderstorm
development across the area through the afternoon into early
evening. Expect scattered to numerous showers and thunderstorms
this afternoon...primarily east of the trough. MVFR/IFR flight
conditions can be expected in the areas of rain. Expect VFR flight
conditions and light south-southwest flow outside of thunderstorms
except for a few patches of higher MFR CIGS north of the STL Metro
area. Showers and storms will dissipate within an hour or two
after sunset. VFR conditions are expected until the pre-dawn hours
of Sunday morning when fog will develop. Areal coverage and
density of the fog is not certain at this time, but at least
patchy MFR fog is expected. Fog should dissipate within 2 hours
after sunrise Sunday.

Specifics for KSTL:

Expect showers and thunderstorms to increase in coverage this
afternoon. Timing and intensity is uncertain at Lambert, and there
is a definite chance there could be some intermittent heavy rain
which could reduce the visibility to IFR. However, expect VFR
conditions to prevail for the vast majority of the afternoon.
Showers/storms should dissipate quickly after sunset. With moist
air in place over the STL Metro, think there will be some light
fog at the terminal before sunrise Sunday. Fog should dissipate
within an hour or two after sunrise.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 301800
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
100 PM CDT Sat Aug 30 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sat Aug 30 2014

Regional radar is showing a number of areas of showers and
thunderstorms across Missouri and western Illinois early this
morning. These are generally within a weak warm advection regime
ahead of a upper trof moving through the MS Valley and in advance
of the attendant cold front. While all the current activity should
continue moving east northeast this morning, the overall consensus
amongst the guidance and convection allowing models is that there
should be a general increase in the scattered activity currently
over southwest Missouri as the morning progresses and it moves
northeast. Additional development is also expected during the
later part of the morning into the afternoon in a broad southwest
to northeast zone ahead of the slowly advancing cold front and centered
through the southeast half of the CWA. Given the current temperatures
in the 70s, low-mid 80s looks reasonable for highs today.

Glass

.LONG TERM:  (Tonight through Friday)
Issued at 330 AM CDT Sat Aug 30 2014

Convective trends are not completely clear cut tonight. The main
upper trof axis should have passed to the east by early this
evening, but there is a weak lingering vort max still to pass and
the front appears to wash out across northeast Missouri and west
central Illinois. Sans the NAM, the model consensus keeps a chance
of showers and thunderstorms centered though the southeast half of
the CWA during the evening. Sunday looks largely dry and warmer
with possibly some isolated diurnal storms across southeast MO and
southwest Illinois. The threat of organized covection should
slowly spread into northeast Missouri late Sunday night with the
approach of a progressive long wave trof and attendant cold front and
intensifying southwesterly LLJ. Thunderstorms appear likely on
Labor Day and Monday night as the cold front moves slowly southward
into a moist unstable air mass, and as a southwesterly LLJ and the
upper trof contribute to lift and cap removal. This system will be
accompanied by deep layer shear of 30-40+ knots resulting in the
potential for organized severe storms. Showers and thunderstorms
could persist across the southern CWA Tuesday and maybe even into
Tuesday night and Wednesday in the vicinity of the front and then
as it retreats back northward late Wednesday.

Late in the week ahead the upper ridge is forecast to restablish
itself over the southeast half of the Nation, bringing a return of
more summer like weather/heat.

Glass

&&

.AVIATION:  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1240 PM CDT Sat Aug 30 2014

A trough of low pressure extending from north central Missouri
southwest into southeast Kansas will remain nearly stationary
today. This trough will provide a focus for thunderstorm
development across the area through the afternoon into early
evening. Expect scattered to numerous showers and thunderstorms
this afternoon...primarily east of the trough. MVFR/IFR flight
conditions can be expected in the areas of rain. Expect VFR flight
conditions and light south-southwest flow outside of thunderstorms
except for a few patches of higher MFR CIGS north of the STL Metro
area. Showers and storms will dissipate within an hour or two
after sunset. VFR conditions are expected until the pre-dawn hours
of Sunday morning when fog will develop. Areal coverage and
density of the fog is not certain at this time, but at least
patchy MFR fog is expected. Fog should dissipate within 2 hours
after sunrise Sunday.

Specifics for KSTL:

Expect showers and thunderstorms to increase in coverage this
afternoon. Timing and intensity is uncertain at Lambert, and there
is a definite chance there could be some intermittent heavy rain
which could reduce the visibility to IFR. However, expect VFR
conditions to prevail for the vast majority of the afternoon.
Showers/storms should dissipate quickly after sunset. With moist
air in place over the STL Metro, think there will be some light
fog at the terminal before sunrise Sunday. Fog should dissipate
within an hour or two after sunrise.

Carney

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








000
FXUS63 KLSX 301233
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
733 AM CDT Sat Aug 30 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sat Aug 30 2014

Regional radar is showing a number of areas of showers and
thunderstorms across Missouri and western Illinois early this
morning. These are generally within a weak warm advection regime
ahead of a upper trof moving through the MS Valley and in advance
of the attendant cold front. While all the current activity should
continue moving east northeast this morning, the overall consensus
amongst the guidance and convection allowing models is that there
should be a general increase in the scattered activity currently
over southwest Missouri as the morning progresses and it moves
northeast. Additional development is also expected during the
later part of the morning into the afternoon in a broad southwest
to northeast zone ahead of the slowly advancing cold front and centered
through the southeast half of the CWA. Given the current temperatures
in the 70s, low-mid 80s looks reasonable for highs today.

Glass

.LONG TERM:  (Tonight through Friday)
Issued at 330 AM CDT Sat Aug 30 2014

Convective trends are not completely clear cut tonight. The main
upper trof axis should have passed to the east by early this
evening, but there is a weak lingering vort max still to pass and
the front appears to wash out across northeast Missouri and west
central Illinois. Sans the NAM, the model consensus keeps a chance
of showers and thunderstorms centered though the southeast half of
the CWA during the evening. Sunday looks largely dry and warmer
with possibly some isolated diurnal storms across southeast MO and
southwest Illinois. The threat of organized covection should
slowly spread into northeast Missouri late Sunday night with the
approach of a progressive long wave trof and attendant cold front and
intensifying southwesterly LLJ. Thunderstorms appear likely on
Labor Day and Monday night as the cold front moves slowly southward
into a moist unstable air mass, and as a southwesterly LLJ and the
upper trof contribute to lift and cap removal. This system will be
accompanied by deep layer shear of 30-40+ knots resulting in the
potential for organized severe storms. Showers and thunderstorms
could persist across the southern CWA Tuesday and maybe even into
Tuesday night and Wednesday in the vicinity of the front and then
as it retreats back northward late Wednesday.

Late in the week ahead the upper ridge is forecast to restablish
itself over the southeast half of the Nation, bringing a return of
more summer like weather/heat.

Glass
&&

.AVIATION:  (For the 12z TAFs through 12z Sunday Morning)
Issued at 732 AM CDT Sat Aug 30 2014

Cold front over northwestern Missouri to move southeast across
area today. South winds to veer to the southwest as front moves
through. VFR conditions expected though could see mvfr conditions
with storms that develop. Best chances of storms will be over taf
sites along I-70 corridor after 16z-17z and persist through the
afternoon hours before diminishing and moving out. Then frontal
boundary to washout and allow winds to become southerly once again
for the overnight hours.

Specifics for KSTL:
Cold front over northwestern Missouri to move southeast across
area today. South winds to veer to the southwest after 17z as
front moves through metro area. VFR conditions expected though could
see mvfr conditions with storms that develop, for now just have
vcts mention. Storms to persist through the afternoon hours before
diminishing and moving out by 00z Sunday. Then frontal boundary to
washout and allow winds to become southerly once again for the
overnight hours.

Byrd
&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$
WFO LSX








000
FXUS63 KLSX 301233
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
733 AM CDT Sat Aug 30 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sat Aug 30 2014

Regional radar is showing a number of areas of showers and
thunderstorms across Missouri and western Illinois early this
morning. These are generally within a weak warm advection regime
ahead of a upper trof moving through the MS Valley and in advance
of the attendant cold front. While all the current activity should
continue moving east northeast this morning, the overall consensus
amongst the guidance and convection allowing models is that there
should be a general increase in the scattered activity currently
over southwest Missouri as the morning progresses and it moves
northeast. Additional development is also expected during the
later part of the morning into the afternoon in a broad southwest
to northeast zone ahead of the slowly advancing cold front and centered
through the southeast half of the CWA. Given the current temperatures
in the 70s, low-mid 80s looks reasonable for highs today.

Glass

.LONG TERM:  (Tonight through Friday)
Issued at 330 AM CDT Sat Aug 30 2014

Convective trends are not completely clear cut tonight. The main
upper trof axis should have passed to the east by early this
evening, but there is a weak lingering vort max still to pass and
the front appears to wash out across northeast Missouri and west
central Illinois. Sans the NAM, the model consensus keeps a chance
of showers and thunderstorms centered though the southeast half of
the CWA during the evening. Sunday looks largely dry and warmer
with possibly some isolated diurnal storms across southeast MO and
southwest Illinois. The threat of organized covection should
slowly spread into northeast Missouri late Sunday night with the
approach of a progressive long wave trof and attendant cold front and
intensifying southwesterly LLJ. Thunderstorms appear likely on
Labor Day and Monday night as the cold front moves slowly southward
into a moist unstable air mass, and as a southwesterly LLJ and the
upper trof contribute to lift and cap removal. This system will be
accompanied by deep layer shear of 30-40+ knots resulting in the
potential for organized severe storms. Showers and thunderstorms
could persist across the southern CWA Tuesday and maybe even into
Tuesday night and Wednesday in the vicinity of the front and then
as it retreats back northward late Wednesday.

Late in the week ahead the upper ridge is forecast to restablish
itself over the southeast half of the Nation, bringing a return of
more summer like weather/heat.

Glass
&&

.AVIATION:  (For the 12z TAFs through 12z Sunday Morning)
Issued at 732 AM CDT Sat Aug 30 2014

Cold front over northwestern Missouri to move southeast across
area today. South winds to veer to the southwest as front moves
through. VFR conditions expected though could see mvfr conditions
with storms that develop. Best chances of storms will be over taf
sites along I-70 corridor after 16z-17z and persist through the
afternoon hours before diminishing and moving out. Then frontal
boundary to washout and allow winds to become southerly once again
for the overnight hours.

Specifics for KSTL:
Cold front over northwestern Missouri to move southeast across
area today. South winds to veer to the southwest after 17z as
front moves through metro area. VFR conditions expected though could
see mvfr conditions with storms that develop, for now just have
vcts mention. Storms to persist through the afternoon hours before
diminishing and moving out by 00z Sunday. Then frontal boundary to
washout and allow winds to become southerly once again for the
overnight hours.

Byrd
&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$
WFO LSX







000
FXUS63 KLSX 300846
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
346 AM CDT Sat Aug 30 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sat Aug 30 2014

Regional radar is showing a number of areas of showers and
thunderstorms across Missouri and western Illinois early this
morning. These are generally within a weak warm advection regime
ahead of a upper trof moving through the MS Valley and in advance
of the attendant cold front. While all the current activity should
continue moving east northeast this morning, the overall consensus
amongst the guidance and convection allowing models is that there
should be a general increase in the scattered activity currently
over southwest Missouri as the morning progresses and it moves
northeast. Additional development is also expected during the
later part of the morning into the afternoon in a broad southwest
to northeast zone ahead of the slowly advancing cold front and centered
through the southeast half of the CWA. Given the current temperatures
in the 70s, low-mid 80s looks reasonable for highs today.

Glass

.LONG TERM:  (Tonight through Friday)
Issued at 330 AM CDT Sat Aug 30 2014

Convective trends are not completely clear cut tonight. The main
upper trof axis should have passed to the east by early this
evening, but there is a weak lingering vort max still to pass and
the front appears to wash out across northeast Missouri and west
central Illinois. Sans the NAM, the model consensus keeps a chance
of showers and thunderstorms centered though the southeast half of
the CWA during the evening. Sunday looks largely dry and warmer
with possibly some isolated diurnal storms across southeast MO and
southwest Illinois. The threat of organized covection should
slowly spread into northeast Missouri late Sunday night with the
approach of a progressive long wave trof and attendant cold front and
intensifying southwesterly LLJ. Thunderstorms appear likely on
Labor Day and Monday night as the cold front moves slowly southward
into a moist unstable air mass, and as a southwesterly LLJ and the
upper trof contribute to lift and cap removal. This system will be
accompanied by deep layer shear of 30-40+ knots resulting in the
potential for organized severe storms. Showers and thunderstorms
could persist across the southern CWA Tuesday and maybe even into
Tuesday night and Wednesday in the vicinity of the front and then
as it retreats back northward late Wednesday.

Late in the week ahead the upper ridge is forecast to restablish
itself over the southeast half of the Nation, bringing a return of
more summer like weather/heat.

Glass

&&

.AVIATION:  (For the 06z TAFs through 06z Saturday Night)
Issued at 1042 PM CDT Fri Aug 29 2014

There were two areas of showers and storms this evening. The first
was across southeast MO and will likely remain southeast of the
taf sites late tonight, although they could get close to CPS.
There were scattered showers/storms across northwest MO ahead of
an approaching upper level disturbance which may impact the UIN
area late tonight. May include VCTS in the UIN taf. It appears
that there will be enough cloud cover and strong enough surface
winds to deter fog formation, although could not rule out light
fog late tonight/early Saturday morning in SUS and CPS where the
surface wind will be a little lighter and in areas which had
significant rainfall this evening. Should be at least scattered
showers/storms in the St Louis metro area Saturday afternoon along
and ahead of weakening cold front/surface trough dropping
southeastward through the area. Sly surface winds will become
more swly late tonight and Saturday morning.

Specifics for KSTL: Current shower/storm activity on radar will
likely miss STL late tonight, although could not rule out a
passing sprinkle. Will likely leave STL taf dry late tonight and
Saturday morning due to uncertainty in coverage and timing of
additional convection. Will include VCTS in the taf Saturday
afternoon with at least scattered showers/storms expected at this
time due to diurnal destabilization along and ahead of a weak
surface trough/cold front. Prevailing s-swly surface winds through
the period.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     86  72  90  74 /  60  30  20  10
Quincy          84  67  88  71 /  30  10   5  50
Columbia        86  68  91  72 /  40  20  10  40
Jefferson City  86  69  91  72 /  50  20  10  30
Salem           85  70  86  72 /  60  50  20  10
Farmington      84  69  87  72 /  60  50  20  10

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX







000
FXUS63 KLSX 300846
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
346 AM CDT Sat Aug 30 2014

.SHORT TERM:  (Through Late This Afternoon)
Issued at 330 AM CDT Sat Aug 30 2014

Regional radar is showing a number of areas of showers and
thunderstorms across Missouri and western Illinois early this
morning. These are generally within a weak warm advection regime
ahead of a upper trof moving through the MS Valley and in advance
of the attendant cold front. While all the current activity should
continue moving east northeast this morning, the overall consensus
amongst the guidance and convection allowing models is that there
should be a general increase in the scattered activity currently
over southwest Missouri as the morning progresses and it moves
northeast. Additional development is also expected during the
later part of the morning into the afternoon in a broad southwest
to northeast zone ahead of the slowly advancing cold front and centered
through the southeast half of the CWA. Given the current temperatures
in the 70s, low-mid 80s looks reasonable for highs today.

Glass

.LONG TERM:  (Tonight through Friday)
Issued at 330 AM CDT Sat Aug 30 2014

Convective trends are not completely clear cut tonight. The main
upper trof axis should have passed to the east by early this
evening, but there is a weak lingering vort max still to pass and
the front appears to wash out across northeast Missouri and west
central Illinois. Sans the NAM, the model consensus keeps a chance
of showers and thunderstorms centered though the southeast half of
the CWA during the evening. Sunday looks largely dry and warmer
with possibly some isolated diurnal storms across southeast MO and
southwest Illinois. The threat of organized covection should
slowly spread into northeast Missouri late Sunday night with the
approach of a progressive long wave trof and attendant cold front and
intensifying southwesterly LLJ. Thunderstorms appear likely on
Labor Day and Monday night as the cold front moves slowly southward
into a moist unstable air mass, and as a southwesterly LLJ and the
upper trof contribute to lift and cap removal. This system will be
accompanied by deep layer shear of 30-40+ knots resulting in the
potential for organized severe storms. Showers and thunderstorms
could persist across the southern CWA Tuesday and maybe even into
Tuesday night and Wednesday in the vicinity of the front and then
as it retreats back northward late Wednesday.

Late in the week ahead the upper ridge is forecast to restablish
itself over the southeast half of the Nation, bringing a return of
more summer like weather/heat.

Glass

&&

.AVIATION:  (For the 06z TAFs through 06z Saturday Night)
Issued at 1042 PM CDT Fri Aug 29 2014

There were two areas of showers and storms this evening. The first
was across southeast MO and will likely remain southeast of the
taf sites late tonight, although they could get close to CPS.
There were scattered showers/storms across northwest MO ahead of
an approaching upper level disturbance which may impact the UIN
area late tonight. May include VCTS in the UIN taf. It appears
that there will be enough cloud cover and strong enough surface
winds to deter fog formation, although could not rule out light
fog late tonight/early Saturday morning in SUS and CPS where the
surface wind will be a little lighter and in areas which had
significant rainfall this evening. Should be at least scattered
showers/storms in the St Louis metro area Saturday afternoon along
and ahead of weakening cold front/surface trough dropping
southeastward through the area. Sly surface winds will become
more swly late tonight and Saturday morning.

Specifics for KSTL: Current shower/storm activity on radar will
likely miss STL late tonight, although could not rule out a
passing sprinkle. Will likely leave STL taf dry late tonight and
Saturday morning due to uncertainty in coverage and timing of
additional convection. Will include VCTS in the taf Saturday
afternoon with at least scattered showers/storms expected at this
time due to diurnal destabilization along and ahead of a weak
surface trough/cold front. Prevailing s-swly surface winds through
the period.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     86  72  90  74 /  60  30  20  10
Quincy          84  67  88  71 /  30  10   5  50
Columbia        86  68  91  72 /  40  20  10  40
Jefferson City  86  69  91  72 /  50  20  10  30
Salem           85  70  86  72 /  60  50  20  10
Farmington      84  69  87  72 /  60  50  20  10

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX








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