Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 240830
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
330 AM CDT Mon Jun 24 2019

.SHORT TERM...  (Through Late Tonight)
Issued at 304 AM CDT Mon Jun 24 2019

Upper level trough over the northern Plains will move eastward
today.  An associated cold front extending from a surface low over
north central IA southwest into north central OK will move eastward
through our forecast area later this morning. Although most of
the precipitation is currently south of our forecast area, at
least widely scattered showers should develop further northward by
12Z and then shift eastward, particularly through southeast MO
and southwest IL this morning. Most of the precipitation should
shift east of the forecast area by this afternoon, although could
not rule out isolated showers/storms mainly across west central
and southwest IL until the upper level trough and associated cold
mid level temperatures within the trough shift east of the
forecast area. Cooler low temperatures can be expected tonight due
to a clearing sky this evening and lower surface dew points.

GKS

.LONG TERM...  (Tuesday through Sunday)
Issued at 304 AM CDT Mon Jun 24 2019

Warmer temperatures can be expected on Tuesday as southwesterly
low level winds bring warm air advection to our area.  The
atmosphere will become quite unstable in the afternoon,
particularly across northeast MO. Convection may develop across
northern MO by late Tuesday afternoon ahead of a weak shortwave.
The NAM model in particular tries to develop an MCS Tuesday
evening which drops southward through much of MO by late Tuesday
night, and then shifts southeast of our forecast area by
Wednesday afternoon. Not real confident yet in this solution, but
it does appear that there will be at least scattered convection
late Tuesday afternoon and evening across northeast and central
MO and west central IL. An upper level ridge will try to build
northeastward into our region Wednesday and Thursday from the
southern Plains, and this along with persistent southerly surface
winds should lead to a more typical warm summertime weather
pattern with temperatures at or slightly above normal for late
June. Although this will be a less active weather pattern with
less potential for widespread and organized convection, there is
still some uncertainty as to the strength of the upper level ridge
with some of the models depicting a weakness in the ridge over
our area or weak "ridge runner" shortwaves over-topping this
ridge which could lead to scattered convection or even the
possibility of an MCS dropping southward into part of our forecast
area. For now will only include slight chance pops for later in
the work week and into the weekend.

GKS

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1210 AM CDT Mon Jun 24 2019

Both the stratus and showers have been slow to materialize thus
far. My confidence isn`t great but I still think we will see some
MVFR stratus develop overnight, and if this doesn`t occur, then we
may see the rapid development shortly after sunrise Monday as the
boundary layer begins to heat up. The best precipitation chances
overnight into early Monday morning are across southeast MO and
southern IL with spotty/scattered light showers possible up to the
St. Louis region hence the VCSH in the terminals. A cold front will
move through the area on Monday morning resulting in increasing
and gusty westerly winds and rising cloud bases and VFR flight
conditions by early afternoon.

SPECIFICS FOR KSTL:

Both the stratus and showers have been slow to materialize thus
far. My confidence isn`t great but I still think we will see some
MVFR stratus develop overnight, and if this doesn`t occur, then we
may see the rapid development shortly after sunrise Monday as the
boundary layer begins to heat up. The best precipitation chances
overnight into early Monday morning are across southeast MO and
southern IL. Spotty/scattered light showers are possible briefly
impacting KSTL hence the VCSH in the terminals. A cold front will
move through the area on Monday morning resulting in increasing
and gusty westerly winds and rising cloud bases and VFR flight
conditions by midday.

Glass

&&

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

$$

WFO LSX


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