Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 171759
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1259 PM CDT Fri Oct 17 2014

.UPDATE:
Issued at 1040 AM CDT Fri Oct 17 2014

Low clouds will continue to move southeastward out of Iowa and north
central Missouri into the CWA today which will bring partly to mostly
cloudy conditions to areas along and north of I-70. The cloud cover
has broken up this morning as it as moved southeastward, though there
should be some tendency for it to fill back in with diurnal cumulus
given the amount of low level moisture available and cyclonic flow.
Going highs look reasonable given current temperature trends.

Britt

&&

.SHORT TERM:  (Through Late This Afternoon)
Issued at 319 AM CDT Fri Oct 17 2014

A cold front extending from a surface low over WI southwest through
east central MO will continue moving southeastward through the rest
of our forecast area this morning as an upper level low over
northeast MN moves southeastward through the Great Lakes region
today.  Precipitation is not expected across our forecast area today
in association with this front, but cold air advection behind this
front will lead to cooler high temperatures for northeast and
central MO as well as west central IL today compared to yesterdays
maximum temperatures.  There was also a large area of low level
clouds across the northern Plains which will advect southeastward
into northeast MO later this morning and into west central IL and
parts of central MO this afternoon.  This cloudiness will limit
solar insolation this afternoon and hinder the diurnal rise in
temperatures along with the post frontal low level cold air
advection.

GKS

.LONG TERM:  (Tonight through Thursday)
Issued at 431 AM CDT Fri Oct 17 2014

Cooler low temperatures are expected tonight due to the upper level
trough over the Great Lakes region and low level cold air advection
across the entire area as a relatively strong and large surface
ridge over the northern Plains builds southeastward into MO.  The
models drop the 4 degree C 850 mb isotherm southward to just south
of STL by 12z Saturday.  The models bring a strong shortwave
southeastward through IL on Saturday.  Any precipitation associated
with this feature should remain east of our forecast area, but this
shortwave may bring a reinforcing shot of cold air to the region.
The coldest temperatures should occur Saturday night due to good
radiational cooling as the surface ridge axis moves through our
forecast area with a mostly clear sky along with light surface winds
and surface dew points dropping into the middle 30s to around 40.
There may be light patchy frost in the colder, low lying locations
late Saturday night.  Are only chance of rain this forecast period
will occur Sunday night and Monday as a northwest flow shortwave and
associated cold front drop southeastward through the region.  The
models do depict a narrow band of low-mid level warm air advection
and moisture ahead of this shortwave and cold front.  The NAM model
does not generate any precipitation across our forecast area, while
the ECMWF model keeps most of the precipitation just east of the
forecast area.  The GFS model does have some light QPF mainly across
east central and southeast MO as well as southwest IL late Sunday
night and Monday.  For now will just include slight chance pops
across parts of the forecast area late Sunday night and Monday.
Cooler temperatures are expected for Monday night and Tuesday,
particularly across IL with a deep upper level trough over the Great
Lakes and Ohio Valley regions.  Dry conditions for the remainder of
the extended forecast with surface ridging across our area, and as
an upper level ridge moves slowly eastward into MO.

GKS

&&

.AVIATION:  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1259 PM CDT Fri Oct 17 2014

Expect mainly dry and VFR conditions through the TAF period. Scattered
to broken cloud bases with ceilings between 3000-4000ft are moving
southeastward toward Columbia and the St. Louis metro TAF sites
and will be there between 18-20Z. Expect skies to scatter out
this evening before becoming broken again at KUIN and the St.
Louis metro TAF sites after 15Z Saturday morning. Northwest winds
gusts will diminish around sunset.

Specifics for KSTL: Low VFR ceilings will move into the terminal
between 18-19Z and then scatter out by this evening. Northwesterly
wind gusts will diminish around 00Z.

Britt

&&

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

$$

WFO LSX






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