Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 180457
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1157 PM CDT Fri Apr 17 2015

.UPDATE:
Issued at 945 PM CDT Fri Apr 17 2015

Other than some minor tweeks to temperatures and clouds, the
current forecast looks on track. The latest high res short range
guidance continues to give some indications that we could see a
few showers overnight, especially in the predawn hours, in central
and north central MO where low pops reside. This would be along the
eastern periphery of strongest 850 mb winds and deeper moisture
and thus looks reasonable.

Glass

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 317 PM CDT Fri Apr 17 2015

A weak upper level RIDGE continues to persist overhead this
afternoon with a vigorous upper LOW spinning over southern CO.  A
lobe of vorticity which was helping to drive a broken band of
showers and storms across far western MO is in the process of
weakening, and as a result, the pcpn associated with it is
fizzling.  Another stronger upper level disturbance was over far
western TN and northeast AR which was igniting convection there.
Once again we saw an explosion of flat diurnal cumulus with the
heating of the day, but it did not prevent temps from reaching well
into the 70s to near 80.

The lobe of vorticity should continue its weakening trend as it
slides N-NE and edges the western CWA/central MO this evening while
the stronger upper level disturbance will continue chugging east and
remain well to our south and southeast.  This will leave weak
lift--at best--for much of the duration of tonight across our region
and will favor a dry forecast for many areas.  Have only had to make
minimal changes to previous forecast, but backed off on the low
chances a bit further, limiting them to only some sections of
northeast and central MO and to just the hours immediately preceding
dawn.

Temps look to be a bit warmer than persistence with what should be
increasing clouds from the west late and a bit stronger southeast
flow but many areas should still get into the 50s, albeit only
briefly, before sunrise.

TES

.LONG TERM:  (Saturday through Next Friday)
Issued at 317 PM CDT Fri Apr 17 2015

Models are now a little slower with onset of showers and
thunderstorms on Saturday, with best chances over central MO
Saturday afternoon. Otherwise, will see highs in the low to mid 70s
with coolest temps over central MO due to the cloud cover and
precipitation.

Models persistent in developing a strengthening low along warm front
with it lifting northeastward from the MO bootheel to southern Lake
Michigan by Sunday evening. So now forecast area remains on cool
side of system with severe chances on Sunday afternoon and evening
looking less likely most locations, though far southern portions of
forecast area could still see some severe weather. Showers will be
predominant on Sunday with less instability expected so adjusted
weather grids to just mention showers with a chance of
thunderstorms. Overall could see widespread one inch rainfall
amounts through the weekend.

Precipitation comes to an end by Monday with cooler and drier
weather for the first part of the work week. Then extended models
try to bring in another wet period from Tuesday night through Friday
but confidence is low on timing and placement of precipitation so
kept slight chance/chance pops through this period. Highs will be
60s Monday through Friday with overnight lows in the 40s.

Byrd

&&

.AVIATION:  (For the 06z TAFs through 06z Saturday Night)
Issued at 1148 PM CDT Fri Apr 17 2015

Specifics for KCOU, KUIN: A few showers are possible at KCOU after
12z. MVFR conditions are possible if one of the showers happens to
move directly over KCOU. There is a much greater chance of
SHRA/TSRA after 19/03z at both KCOU and KUIN when a slow-moving
low pressure system approaches the region.

Specifics for KSTL, KSUS, KCPS: VFR conditions are expected for at
least the first 0-6 hours except at KSUS where light fog is
possible towards daybreak given the airport`s proximity to the
river. Elsewhere, increasing cirrus overnight and the lack of a
moisture source adjacent to the airport should limit any fog
formation. SHRA/TSRA chances increase greatly after 19/03z when a
slow-moving low pressure system approaches the region.

Kanofsky

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX





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