Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 220448
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1148 PM CDT Wed Jun 21 2017

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 323 PM CDT Wed Jun 21 2017

It looks like tonight should be a rather uneventful night. The weak
front which sagged from northern MO into south central IL has begun
to lift back northward. A few short-lived cells developed along the
front in Montgomery and Fayette Counties earlier, but they have
since dissipated. There could still be an isolated shower or storm
into the late afternoon along the boundary where an axis of
diurnally enhanced instability resides.

For most of tonight we will be watching an increase in high clouds
from the south associated with TS Cindy. In the predawn hours, the
low level flow will begin veering in the gradient region from
eastern AR/MS into southeast MO well to the east Cindy. This will
result in deeper moisture transport into southeast MO and possibly a
few showers. Present indications are Cindy will move in the vicinity
of the TX/LA border on Thursday. The increase in south to southwest
flow to the east of the center will continue to transport
deeper/tropical moisture northward into the area. The
moisture/clouds should result in cooler temps on Thursday,
especially the southern 2/3rd of the CWA. The best threat of any
precipitation should be across southeast MO and southern IL
coincident with the deeper moisture and also a north-northeast
lifting vort max within the south/southwest mid-upper flow to the
east of Cindy.

Glass

.LONG TERM...  (Thursday Night through Next Wednesday)
Issued at 323 PM CDT Wed Jun 21 2017

Showers and storms will end from northwest to southeast as the cold
front pushes through the area on Friday. The front should clear
the area by Friday night. High pressure at the surface from the
northern high plains will push into the area. In the upper levels,
the area will be under northwest flow with a series of weak short
waves pushing through the area. A few of the models attempt to
kick off an isolated shower or thunderstorm mainly during the
afternoon and evening Sunday and Monday, while others are
completely dry. The confidence level that any precipitation will
materialize is very low at this time and likely will remain dry.

 After a period of below climatological normal temperatures we will
moderate to normal values Wednesday ahead of the next storm
system organizing in the plains. This will bring a chance of
showers and thunderstorms to the area Wednesday night into north
central Missouri.

Kelly

&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1148 PM CDT Wed Jun 21 2017

High clouds will increase tonight, but VFR conditions will prevail
overnight. Low-level moisture will increase through the day on
Thursday, which will help MVFR cigs develop and move northward.
Latest indications are that the line between VFR cigs and MVFR
cigs will be very close to the St. Louis metro sites. Have highest
confidence in MVFR cigs at CPS thus have introduced them there,
but will continue to leave out MVFR cigs at STL/SUS. COU/UIN will
remain VFR through the period. Cannot rule out a few showers near
the St. Louis metro sites through the day on Thursday, but the
bulk of the activity should remain across southeast MO and IL.
Winds through the period will be out of the south around 10 knots,
with some higher gusts around 15 knots possible.

SPECIFICS FOR KSTL:
High clouds will increase tonight, but VFR conditions will prevail
overnight. Low-level moisture will increase through the day on
Thursday, which will help MVFR cigs develop and move northward.
Latest indications are that the line between VFR cigs and MVFR
cigs will be very close to STL. Given the main slug of moisture
should remain east of the terminal, will leave out any cig
restrictions for now and let the midnight shift re-evaluate.
Cannot rule out a stray shower through the day on Thursday, but
the bulk of the activity should remain across southeast MO and IL.
Winds through the period will be out of the south around 10
knots, with some higher gusts around 15 knots possible.

KD

&&

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

$$

WFO LSX


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