Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 170030

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
730 PM CDT Wed Aug 16 2017

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 332 PM CDT Wed Aug 16 2017

A line of showers and isolated severe thunderstorms  currently in
central Missouri will rapidly move east through the region. This
first line of showers and thunderstorms will bring uncertainty to
the second line which will be highly dependent on if the atmosphere
has time to recover before the second line forms ahead of the cold
front.  The cold front is currently in northwest Missouri will move
into central Missouri late this afternoon, then through the rest of
the area this evening. An additional line of showers and
thunderstorms is expected and reflected through several HRRR/CAMS
runs. The CAMS runs have been inconsistent in evolution of storms.
If the atmosphere can recover. the primary threats will be damaging
winds and large hail. An isolated tornado is also possible late this
afternoon and evening particularly with the line of thunderstorms
just ahead of the cold front with sufficient bulk shear of 45 to 50
knots along with surface CAPE values in excess of 3500J/kg.

High pressure will move into the area with partly cloudy skies on
Thursday with seasonal temperatures expected and this is reflected
in forecast temperatures.


.LONG TERM...  (Thursday Night through Next Wednesday)
Issued at 332 PM CDT Wed Aug 16 2017

Thursday night through next Wednesday

A couple of strong systems will affect the area over the long term
however it looks like there will be just enough of a break in
between to get the eclipse in.

The first system moves through by Thursday evening with a clearing
sky and drier air moving in for Friday. However another short wave
moves in on the northwest flow Friday night into Saturday bringing
another chance of showers and storms. The surface front should be
clear of the area by midday Saturday. The models are now tending
to produce some ridging across the area Saturday into Monday. This
was best seen while looking at the ensembles of the GFS. The
ECMWF is also trending this way as it has now moved any
precipitation for Sunday night into Monday morning well to the
north. So conditions are looking pretty good for the eclipse in
the LSX CWA. Can`t rule out an isolated shower or thunderstorm
Monday, but it should hold off until later in the afternoon.

The next short wave and associated front moves in Tuesday afternoon
into Wednesday morning with chances for showers and thunderstorms.
Temperatures are pretty seasonable with the warmest day looking to
be Monday.



.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 715 PM CDT Wed Aug 16 2017

A line of showers and thunderstorms with brief gusty winds in
western Missouri will continue to push into central Missouri this
evening. A brief period of MVFR/IFR ceilings and visibilities are
possible as storms move from west to east across the region. All
showers and thunderstorms are expected to exit the region by early
Thursday morning. Otherwise, VFR ceilings and conditions for
through Thursday evening.


A line of showers and thunderstorms with brief gusty winds will
move east from western Missouri into central Missouri tonight. A
period of MVFR/IFR ceilings and visibilities are possible as the
line moves over the terminal later tonight. Otherwise, VFR
ceilings and conditions are expected for the terminal through
Thursday afternoon.





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