Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 272034
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
334 PM CDT Mon Oct 27 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 259 PM CDT Mon Oct 27 2014

The ongoing area of elevated showers and thunderstorms across west
central MO is located within the pre-frontal warm conveyor belt
and along the northern fringe of the low-level wind max. Mid level
lapse rates are rather steep and there is just enough MUCAPE at
200-300 j/kg to support thunder. Present indications are these
should spread northeast ahead of the advancing cold front through
the remainder of the afternoon and into the early evening. The
coverage of precipitation is expected to ramp up this evening both
ahead and behind the advancing cold front as the upper trof now
centered through the Plains progresses eastward producing increasing
large scale ascent. CAMs suggest the majority of the precipitation
will be in the form of showers/rain but that the coverage of
embedded thunderstorms will increase as well. Hard not to believe
them given the current amount of thunder with such meager instability.

Glass

.LONG TERM:  (Tuesday through Next Monday)
Issued at 259 PM CDT Mon Oct 27 2014

The cold front should be located on the fringes of the CWA across
southeast MO and southwest IL at 12z Tuesday with the precipitation
threat generally confined to the first half of the morning in the
vicinity of the frontal zone. Thereafter the main story will be
much cooler temperatures than today - more seasonable - as cooler
and drier advects into the region in the wake of the front. Low-
mid clouds will clear to the southeast rather quickly during the
morning with some increase in high clouds during the afternoon
across the southern half of MO into IL. Seasonably cool temperatures
are expected Tuesday night into Wednesday as high pressure builds
into and then dominates the area.

Impacts of the next system should begin late Wednesday night as
mid clouds spread into the area within the developing low level
warm advection regime ahead of a northwest flow short-wave. This
trof and the associated cold front will move across the area on
Thursday accompanied by decent mid level moisture and sufficient
lift for at least isolated showers. The cold air in the wake of
this front is more formidable with a 1030+ mb surface high, and
will produce a short-lived bout of the coolest weather thus far
this fall Friday-Saturday. Early indications are a light freeze
and frost may occur overnight Friday into early Saturday morning.

A highly amplified flow regime will be in place at the start of the
upcoming weekend with deep trofs in the vicinity of both coasts
and an upper ridge through the Plains. Despite the amplitude, this
flow will be progessive with the upper ridge pushing through the
mid MS Valley and into the OH/TN valley Saturday night into Sunday
resulting in seasonably warmer temperatures Sunday and Monday. Eventually
the the western trof and associated frontal system will progress
into the area late Monday-Tuesday bringing the next good chance of
precipitation.

Glass

&&

.AVIATION:  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1232 PM CDT Mon Oct 27 2014

Specifics for KUIN/KCOU: Widely scattered showers and a lone
thunderstorm (located just west of KCOU at TAF issuance) had
developed early this afternoon and may briefly affect the
terminals. There is a much higher chance of SHRA/TSRA later
tonight when a cold front moves through the region. FROPA is
expected around 3-7z at KCOU and KUIN. Confidence in TSRA was not
high enough to include in the TAFs due to relatively weak
instability. Gusty southwest winds will persist through the
afternoon hours. Expect gusty northwest winds behind the front
along with decreasing clouds.

Specifics for KSTL/KSUS/KCPS: Widely scattered showers may creep
towards the St. Louis metro area TAF sites over the next few
hours. Gusty winds will persist through the afternoon hours before
subsiding somewhat after sunset. However, the pressure gradient
will remain tight enough for winds to stay around 10-12 kts
overnight. An approaching cold front will bring a wind shift and a
chance of SHRA/TSRA to the terminals, generally between 07-11z.
Confidence in TSRA was not high enough to include in the TAFs due
to relatively weak instability. Expect gusty northwest winds
behind the front along with decreasing clouds.

Kanofsky

&&

.CLIMATE:
Issued at 355 PM CDT Sun Oct 26 2014

Record highs for 10/27:

STL    85 in 1950
COU    87 in 1927
UIN    84 in 1927


&&

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

$$

WFO LSX






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