035 
FXUS63 KLSX 030441
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1141 PM CDT Tue Apr 2 2019

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 329 PM CDT Tue Apr 2 2019

A weak cold front stretched from central IL through central MO
late this afternoon. This front will continue to push southeastward
through this evening before stalling across southern MO and 
southern IL overnight. Other than some clouds, little fanfare is 
expected with the front. During the later part of the evening and 
into the overnight hours we will begin to see increasing mid/high 
clouds spreading into the area from the Plains. Present 
indications are that any threat of precipitation from 06z-12z 
Wednesday will remain to the west of the CWA and most likely 
focused from northeast KS into northwest MO associated with a 
maturing southwesterly LLJ and associated moisture transport and 
forcing. 

The west-east stationary front initially draped across southern 
MO and southern IL at daybreak will lift northward to around I-70 
by early Wednesday evening. I think most of the area on Wednesday 
will remain dry but there will be abundant mid-high clouds across 
the region. Any threat of precipitation should be north of the 
boundary from central into northeast MO and west central IL 
associated with a broadening southwesterly LLJ and associated 
forcing, and these probabilities will be low. More extensive 
coverage of precipitation is expected well into the cool sector 
from Nebraska into Iowa.

Glass

.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 329 PM CDT Tue Apr 2 2019

The precipitation threat ramps up substantially Wednesday night,
especially after midnight from west to east. Large scale forcing 
associated with an upper trof tracking into the central Plains and
forcing with a veering southwesterly LLJ should result in
widespread showers and a few embedded tstorms within a broad warm
conveyor belt. Widespread precipitation should continue through 
Thursday morning but then there is some question on the longevity 
through the afternoon and into the evening. The NAM is the sole 
model quickly wanting to shut down the rain/showers by mid-late 
afternoon across the entire area, a reflection of much faster 
movement of the upper trof. Alternatively the global models, the 
GFS and especially the ECMWF are slower with the upper trof 
progression and still have isentropic upglide across eastern MO 
and western IL into early Thursday evening. At this time the 
forecast is a nod towards the slower solutions and we have POPS 
into the evening. 

I am worried I may be a bit warm on Friday. Weak high pressure
will dominate the area in the wake of the Thursday/night system
and low level flow is quite weak. If post-frontal clouds linger
then these temps may be hard to realize.

The weekend now looks a bit different than advertised 24+ hours
ago. There are model differences with an upper trof progressing
from the southwestern U.S. into the Nation's midsection and
preceding low amplitude disturbances. There are more questions on
Saturday at this point with the GFS most aggressive with moisture
return and chance of showers and storms, with greater model
agreement on the threat of showers and storms on Sunday.

Glass

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1128 PM CDT Tue Apr 2 2019

VFR conditions will prevail at all TAF sites through the period
and concerns remain limited to precipitation chances. Many of the
high resolution models continue to show a band of light showers 
developing across west central MO in the early morning hours 
before lifting to northern MO by noon. However, I'm not certain
that much of this shower activity will actually reach the surface
and given the expected light nature of any potential showers, I
have left the mention of precip out of the TAFs through the
morning.

By tomorrow afternoon, better upper level forcing will arrive to
the area. This will result in higher precipitation chances first 
in northern MO and west-central IL, along the same feature 
responsible for the chance at morning showers. As upper level
forcing continues to increase in the area on Wednesday night,
precipitation chances will continue to increase. The best precip
chances appear to be just after the end of the TAF period at all
sites, so have stuck with just VCTS at all sites.

SPECIFICS FOR KSTL: 

VFR conditions will persist through the TAF period and the STL 
area will likely remain dry through at least tomorrow night. By 
06z Thu, better support for precipitation will arrive to the area,
though the best chance for precipitation still appears to be just
beyond the tAF period. 

BSH

&&

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

$$

WFO LSX