Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 290421

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1121 PM CDT THU APR 28 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 339 PM CDT Thu Apr 28 2016

Still expect a dry night as upper ridge approaches the area from the
west and surface low moves over Indiana moves off to the east.
Clouds currently across northern Missouri and central Illinois will
slowly move south through the night as the low moves to the east.
Lows tonight will be slightly cooler than MOS guidance, particularly
where clouds have kept temperatures down today.


.LONG TERM...  (Friday through Next Thursday)
Issued at 339 PM CDT Thu Apr 28 2016

...Friday through Sunday...

Not too much change to going forecast as showers and thunderstorms
will begin to overspread the area on Friday.  It still appears that
likely or categorical PoPs will be needed Friday night into
Saturday morning as strong moisture convergence will lie
underneath decent ascent ahead of mid level trough. There is some
differences between the ECMWF/NAM vs. the GFS with the ECMWF/NAM
showing a slightly more northerly track with the surface low on
Saturday evening than the GFS. The ECMWF/GFS could bring more of a
severe weather threat, so will need to watch this closely. The
chance of thunderstorms will linger into Sunday before the upper
low moves out of the area.

...Monday through Thursday...

While the details differ, the overall idea of the GFS and ECMWF
is the same with the upper pattern becoming more amplified next
week.  Shortwave trough will move southeast out of the Canada early
next week and phase with upper trough moving east out of the
southwest CONUS. This will cause northwesterly flow aloft to
develop by midweek. Rain chances look minimal at this point in the
northwesterly flow with near normal temperatures as the GFS Mean
ensemble and the ECMWF 850mb temperatures will be in the 5-10C



.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1101 PM CDT Thu Apr 28 2016

The low level cloudiness over UIN has been shifting slowly
northward this evening and may actually clear out of UIN, at
least briefly overnight. May have a period of MVFR cigs early
Friday morning at UIN. Further south, just high level cloudiness
will spread into the taf sites late tonight. VFR, low-mid level
cloudiness will move into COU and the St Louis metro area by
Friday afternoon as moisture spreads into the area ahead of an
approaching storm system in the southern Plains and north of a
warm front. Showers may move into COU and the St Louis metro area
as early as Friday afternoon, but more likely Friday evening. Cigs
and vsbys may lower into the MVFR catagory Friday evening with
these showers and as the low levels saturate. Weak northwest
surface winds will veer around to an easterly direction by Friday
afternoon as they gradually strengthen.

Specifics for KSTL: Light surface wind will gradually veer around
to an easterly direction and increase to around 8-10 kts Friday
afternoon. Just some high level clouds spreading into STL late
tonight and Friday morning, then the cloud ceiling will gradually
lower Friday afternoon and night as showers move into STL late
Friday afternoon or evening. Cigs and vsbys will lower into the
MVFR catagory Friday night.





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