Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 182336
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
636 PM CDT Fri Apr 18 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 303 PM CDT Fri Apr 18 2014

Dry and tranquil weather will be the rule tonight. High pressure
centered in Ontario and extending into the southern Plains will
slowly retreat to the east, prompting light winds and clear skies.
Low temperatures will be seasonable for mid April.

Glass

.LONG TERM:  (Saturday through Next Friday)
Issued at 303 PM CDT Fri Apr 18 2014

Warmer and dry weather Saturday through Sunday.  An upper level
ridge will extend from eastern TX northeast into MO and IL on
Saturday with a surface ridge extending from the Great Lakes region
southwest into eastern MO.  Temperatures will easily warm into the
lower to middle 70s on Saturday with full sunshine.  Cloud cover
should increase late Saturday night into Sunday as weak shortwaves
move northeastward through the region ahead of the main mid-upper
level trough over the Plains.  Low level moisture will also increase
as surface/low level flow becomes southerly.  Showers and a few
thunderstorms should spread into at least the northwestern half of
our forecast area, north and west of STL Sunday night as the mid
level trough and cold front approaches our area with increasing
low-mid level moisture and instability.  The best chance of rain for
most of our area will occur on Monday as the mid level trough and
cold front moves east southeastward through our forecast area.  Most
of the showers should shift southeast of our forecast area by late
Monday night as the cold front also shifts southeast of the region.
The GFS model appears colder for Monday night and Tuesday with a
relatively deep upper level trough/low moving southeastward through
the Great Lakes region with a large surface ridge building
southeastward into our area behind the cold front.  The ECMWF model
is not quite as far south with this upper level trough/low and not
quite as cold with its 850 mb temperatures in our area.  A warming
trend should begin on Wednesday as an upper level ridge moves
eastward through the region, and strengthening southerly low level
winds bring warmer 850 mb temperatures northeastward into our area.
Convection may return as early as Wednesday across northeast MO and
west central IL due to relatively strong low-mid level warm air
advection ahead of weak shortwaves moving through the upper level
ridge.  The threat for convection will increase Wednesday night and
Thursday, at least over the northwest half of our forecast area, as
the upper level ridge shifts east of the region while a deep upper
level low moves eastward through the northern Plains, along with
continued low-mid level warm air advection ahead of weak sw flow
shortwaves moving through our region.  The GFS model depicts a band
or line of convection moving eastward through our forecast area
Thursday night as a surface low moves into the Great Lakes region
and drags a trailing cold front through our area.  The ECMWF model
is about 6 hours quicker with this front and its associated
convection.  Cooler air should filter southeastward into our area on
Friday.

GKS
&&

.AVIATION:  (For the 00z TAFs through 00z Saturday Evening)
Issued at 635 PM CDT Fri Apr 18 2014

Surface ridge overhead with light winds and clear skies. Could see
some radiational fog along river valley areas, so kept mention in
KSUS taf for late tonight. Otherwise, winds to pickup a bit by mid
morning on Saturday from the southeast to south under clear skies for
rest of forecast period.

Specifics for KSTL:
Surface ridge overhead with light winds and clear skies. Otherwise,
winds to pickup a bit by 15z Saturday from the southeast under
clear skies for rest of forecast period.

Byrd
&&

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

$$
WFO LSX





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