Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 291741
AFDLSX

Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
1241 PM CDT FRI JUL 29 2016

.UPDATE...
Issued at 1240 PM CDT Fri Jul 29 2016

Three areas to watch for shower/storm development this afternoon.

The first is along old frontal boundary just SE of SLO-SAR-FAM
line and already developing activity. This should be best
organized of what develops, but looks to be already out of much of
the CWA and should continue to drift away.

The second is more widely scattered activity that develops
underneath upper TROF digging in overhead and will largely be
restricted to where the best lift from this feature is--areas
south of I-70.

The third is from a surface TROF across northern IL and southern
IA providing additional low level convergence. This feature may
edge close enough into northern MO and west-central IL later this
afternoon but most of the activity produced from it will remain to
the north.

Otherwise, max temps on target for 80-85 most locations.

TES

&&

.SHORT TERM... (Today and Tonight)
Issued at 323 AM CDT Fri Jul 29 2016

The primary cold front is rather ill-defined early this morning
but best guess would place it across southwest IL and across
southern MO into northern OK at 08z. A shortwave trof will move
through the mid-upper MS Valley today and into the OH Valley
tonight. This will bring another secondary wind shift/front into
northern MO and central IL later this afternoon and across the
remainder of the area tonight. The combination of the boundaries
and the upper wave will result in a chance of showers and
thunderstorms, primarily across northern and southern sections of
the CWA this afternoon and this evening. Otherwise slightly cooler
and slight drier air will gradually filter into the region,
especially tonight in the wake of the second boundary as weak high
pressure settles southward from the upper MS Valley and Great
Lakes region.

Glass

.LONG TERM... (Saturday through Thursday)
Issued at 323 AM CDT Fri Jul 29 2016

The stalled front will be located in the vicinity of the MO/AR
border on Saturday and yet another weak wind shift will drop into
northern MO and central IL. Once again it would appear any threat
of precipitation, albiet low will be in close proximity to these
surface features. Heights aloft begin to rise a bit on Sunday as
ridging aloft begins building in from the west. In concert the
front will start a northward return, particularilly across the
central Plains and into western and southern MO. The front will
continue a slow northward retreat Sunday night-Monday-Monday
night, becoming increasingly north-south oriented. The threat of
precipitation should really ramp-up during this time frame as a
series of weak northwest flow disturbances traverse the area, and
as a west-southwesterly LLJ becomes established providing
increasing lift along and north/east of the boundary.

The boundary will lift well to the northeast by Tuesday with the
ridge aloft expanding through the MS Valley and into the Great
Lakes Tuesday-Thursday. The associated return of heat and humidity
is forecast to produce peak heat indices in the 100-105 range.

Glass

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1240 PM CDT Fri Jul 29 2016

VFR conditions and light northwesterly surface winds to prevail
thru the valid period. COU and STL metro terminals are expected
to be on the northern edge of what develops this afternoon with
activity to move further south with time, so have added a VCSH
group until late afternoon. Rain probs too low to add in for later
periods at this time. Some potential for minor VSBY reductions in
mist once again and have added in to most sites, save STL, with
additional potential for some low cloud/CIG intrusion from the
north at UIN which will need to be monitored closely this evening.

TES

&&

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

$$

WFO LSX


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