Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 240508
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1208 AM CDT Mon Apr 24 2017

.SHORT TERM...  (Through Late Monday Afternoon)
Issued at 344 PM CDT Sun Apr 23 2017

Quiet and mostly clear sky on tap for tonight as sfc ridge very
slowly slides across the CWA tonight. As pressure gradient relaxes
this evening, expect winds to diminish and become light and
variable. The light winds, clear sky, and low dewpoints should yield
another seasonably cool night and went a degree or two below the
cooler MAV guidance for tonight...particularly in favored
terrain/valleys. This yielded lows ranging from the upper 30s to low
40s.  Similar to this morning, also cannot rule out at least
some patchy frost for these favored locations.

Winds will become predominantly southeasterly by midday on Monday as
sfc ridge slides eastward. Should be another mostly sunny sky with
quickly warming temperatures. Due to the expected plentiful
sunshine, rising heights, and warming low-level
temperatures...leaned warm for tomorrow`s highs compared to
guidance. Expect highs to range from the low to upper 70s.

Gosselin

.LONG TERM...  (Monday Night through Next Sunday)
Issued at 344 PM CDT Sun Apr 23 2017

Warmer and dry weather for Monday night and Tuesday, then the
pattern gets more active for much of the rest of the forecast
period.  Convection will spread southeastward into at least
northeast and central MO and west central IL Tuesday night as an
upper level trough and associated cold front approaches the forecast
area.  The models depict increasing upper level divergence over our
area ahead of the approaching upper level trough.  The cold front
will move southeastward through our forecast area on Wednesday as
the upper level trough deepens.  Following the slower solution of
the GFS and ECMWF models over the quicker NAM solution.  There may
be the potential of severe storms Wednesday afternoon across
southeast MO and southwest IL with strong deep layer shear due to a
strong mid level wind max ahead of the upper level trough.  The
amount of instability is in question depending on the morning cloud
cover and convection and the speed and position of the cold front
during maximum diurnal heating.  Should have a break in the
shower/thunderstorm activity late Wednesday night and Thursday with
cooler temperatures as cooler air filters into the region behind the
cold front.  Still some discrepancy as to the start of the next
round of convection between the GFS and ECMWF model, but it appears
that precipitation should return to much of the forecast area on
Friday as we get into an active upper level southwest flow pattern
with a warm front shifting slowly northward through the region
leading to elevated convection Friday and Friday night.  May have
another break in the precipitation Saturday into Saturday night,
at least across southeast MO and southwest IL as the warm front
lifts north of this area. More convection, possibly severe will
move through our area Sunday ahead of a surface low and trailing
cold front.

GKS

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1202 AM CDT Mon Apr 24 2017

VFR through the period due to the influence of a high pressure
center located across the region. Light/variable winds at TAF
issuance will become prevailing southeasterly by 12z and increase
slightly after 15z.

Kanofsky

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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