FXUS63 KLSX 171731

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1231 PM CDT Tue Jul 17 2018

.SHORT TERM... (Through Late Tonight)
Issued at 329 AM CDT Tue Jul 17 2018

The synoptic pattern early this morning features northwest flow
aloft in response to a trough digging into the Northeast. This flow
regime will persist through the period, finally bringing a relief
from the heat we have experienced as of late.

The bottom line for today, it is going to feel much more pleasant!
There are a couple of boundaries in the area this morning. A wind
shift and the effective cold front had pushed into southern MO.
Another cold front, in the form of a wind shift to northerly along
with much lower dewpoints had pushed into central MO near the I-70
corridor. This second front will be the one to monitor today into
tonight, as its passage will mark the arrival of the more pleasant
airmass as dewpoints dip into the low/mid 60s behind it (perhaps
even the upper 50s with daytime mixing this afternoon). Expect
mostly clear to partly cloudy skies today with generally dry
conditions. The one exception may be across central MO where a
shortwave passing to the southwest may provide just enough ascent to
spark an elevated shower/storm this afternoon. Even that threat
appears fairly low at this time.

For tonight, expect dry conditions to persist. It will be a cooler
night than we have seen of late, with lows dipping into the
mid/upper 60s.


.LONG TERM... (Wednesday through Monday)
Issued at 329 AM CDT Tue Jul 17 2018

Although a surface ridge will extend from the Great Lakes region
southwest into eastern MO on Wednesday, low-mid level warm air
advection ahead of northwest flow shortwaves may bring at least
weakening convection into central MO on Wednesday. As the surface
ridge shifts east of the region Wednesday night and low-mid level
moisture and instability increases the threat for convection will
also increase and shift eastward late Wednesday night. By Thursday
afternoon the best threat or coverage of showers/storms should be
across northeast MO and west central IL as an upper level low and
associated surface low move eastward through the northern Plains.
Warmer and more humid conditions can be expected on Friday,
particularly across central and southeast MO into southwest IL with
afternoon heat indices around 100. As the upper level low and
associated surface low move eastward into the Great Lakes region a
cold front will move southeastward through our forecast area Friday
afternoon and evening with convection expected along and just ahead
of this front. Could not rule out strong to severe convection
Friday afternoon into the evening with strong instability possible
coupled with relatively strong low-mid level wind shear for late
July. Cooler, less humid, and dry conditions are expected for the
weekend as a surface ridge builds into the region from the Plains
after passage of the cold front with north-northwesterly upper level
flow as the upper level low moves into the Ohio Valley region.
Temperatures this weekend should be slightly below normal for late



.AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1226 PM CDT Tue Jul 17 2018

Mid/high level clouds are streaming eastward out of thunderstorms
in far eastern Nebraska and southeastern Kansas. These storms are
expected to stay south and west of the terminals though may get
fairly close to KCOU at some point late this afternoon and/or late
tonight into early Wednesday morning.

Otherwise, dry/VFR conditions likely through the valid TAF period
with light northeast winds slowly veering to the southeast by
Wednesday morning.


Dry/VFR conditions likely through the valid TAF period. Light
east/northeast winds are expected to slowly veer to the southeast
by Wednesday morning.





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