Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 300450
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1150 PM CDT Mon May 29 2017

.UPDATE...
Issued at 934 PM CDT Mon May 29 2017

Secondary cold front and its associated isolated-scattered
thunderstorms have pushed southeast of the area. Expecting a
mostly clear and dry night with lows near to slightly below
normal. Previous forecast for overnight tonight looks good with
only minor changes needed.


Gosselin

&&

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 325 PM CDT Mon May 29 2017

Cold front was approaching the St Louis metro area this afternoon.
A few showers have recently developed along this front in east
central MO, northwest of SET.  More showers and a few storms should
develop along this front as it moves southeastward through southeast
MO and southwest IL late this afternoon and this evening.  Coverage
should continue to be pretty sparse though, scattered at best.  This
activity should shift southeast of our forecast area by late
evening.  Will have good radiational cooling tonight with little if
any cloudiness, the surface wind becoming light, and relatively low
surface dewpoints.  Lows tonight will be about 5 degrees below
normal for late May.  The chance of convection will return Tuesday
afternoon as low-mid level warm air advection increases ahead of an
approaching shortwave.  It appears that the best coverage, albeit
only scattered should be across central MO along or just north of I-
70.  Highs on Tuesday will not be as warm as today and closer to
seasonal normals due to slightly cooler 850 mb temperatures over our
area, along with more cloud cover in the afternoon to limit solar
insolation.

GKS

.LONG TERM...  (Tuesday Night through Next Monday)
Issued at 325 PM CDT Mon May 29 2017

The synoptic pattern at the start of the long term period will
feature a broad trough across much of the Great Lakes region into
the Northeast. This trough will mostly remain in place through much
of the period, keeping the region within general northwest upper-
level flow.

The upper-level flow should remain amplified enough over the region
on Wednesday to help push a surface boundary into southwest MO and
northern AR.  In its wake, high pressure will dominate on Wednesday
with much of the region remaining dry. Highs will be near normal, in
the mid to upper 70s.

A low-level jet will develop across portions of the Central Plains
on Wednesday night. This will ascend the frontal surface, allowing
nocturnal convection to break out across portions of KS/NE.  This
convection will likely ride along the elevated instability gradient
overnight Wednesday, likely weakening as it makes its way into
central and northeast MO Thursday morning. Additional
showers/thunderstorms will likely develop across the region on any
lingering mesoscale boundaries on Thursday afternoon.

A cold front will slide down from the north on Friday into Saturday.
Guidance differs with the timing of this front a bit, but
showers/storms will be possible each of these days, with the best
coverage likely to be during peak heating, and again along the
frontal surface itself. Temperatures Thursday into the weekend will
be near seasonal normals, with highs in the upper 70s and lower 80s.

KD

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1143 PM CDT Mon May 29 2017

Added in some MVFR fog for early on overnight tonight at KSUS and
KCPS as higher dewpoints have lingered a bit behind the earlier
frontal passage with light/variable winds allowing for radiational
cooling. FEW- SCT midlevel clouds for the rest of tonight with
another boundary moving through late Tuesday afternoon and
evening. Isolated- scattered storms expected during this period
which will have potential to affect terminals. VCTS group added at
KCOU as it has potential of impacting them first. VC groups may
also eventually be needed for the metro terminals.


SPECIFICS FOR KSTL:

FEW-SCT midlevel clouds tonight. Increasing chances for
showers/storms very late Tuesday afternoon and evening. May need a
VCTS mention in future packages.

Gosselin

&&

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

$$

WFO LSX


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