Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 030005

705 PM CDT Sat May 2 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 340 PM CDT Sat May 2 2015

Low-mid level warm air advection ahead of weak shortwaves will bring
mid-high level cloudiness to the forecast area tonight.  Most of the
showers should be across northeast MO and west central IL where
better low level moisture along with instability exists, although
there may be a few sprinkles further south.  Low temperatures will
be warmer than the previous night, and at least slightly above
normal for early May, due to the cloud cover and southerly surface


.LONG TERM:  (Sunday through Next Saturday)
Issued at 340 PM CDT Sat May 2 2015

An upper level RIDGE will begin building over our region early next
week with it effectively in control after Monday and continuing thru
the work week.  This will result in an extended period of above
average temps with above average moisture thru the column--where
disturbances or areas of forcing will have not too much trouble
resulting in rain or thunderstorms.  As a result, we were hard
pressed to find any days next week with PoPs too low to mention.

Some sprinkles were possible for areas mainly N and W of STL metro
Sunday morning in a moist column, very weak forcing regime, but
otherwise PoPs look to be too low for measurable pcpn at this time.

A surface cold front will be the primary focus for Sunday night thru
Monday night as it drops into far northern MO Sunday night and
stalls during this period.  While at least high-end chance PoPs look
justified for areas near the front, they should taper off rapidly
heading towards I-70 with an absence otherwise of any forcing.

With a more traditional warm-sector setup for late Monday night thru
late Wednesday, this period looks warm but dry.

Finally, a more persistent period of forcing from upper level
disturbances and eventually a surface front will join with enhanced
levels of moisture for what should be the best widespread chances
for rain over the next seven days...from Thursday thru Saturday.

Persistent southerly flow and an ever-strengthening May sun angle
should help to propell temps over 80 just about each day during next



.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 641 PM CDT Sat May 2 2015

An area of showers with isolated VSBYS between 3-5SM will move
across northern portions of the forecast area. CIGS should stay
AOA 8,000 FT even where the heavier rain falls. The broader area
of rain should diminish as it moves southeast through the evening.
The remainder of the area will likely see only very isolated
showers or sprinkles with VFR flight conditions prevailing. Low
level wind shear is expected to develop across parts of central
and northeast early Sunday morning. The shear layer is quite
low...between 500-1000FT with wind speed increasing rapidly to
30+ kts. Shear should mix out by 13-14Z Sunday. VFR conditions are
expect on Sunday with south-southwest flow becoming gusty in the afternoon.

Specifics for KSTL:

VFR flight conditions with ceilings AOA 10,000 FT are expected to
prevail at Lambert through the night. There`s an off chance for a
sprinkle or two, but no impact to operations is expected. There`s
some indication in forecast soundings of low level wind shear at
the terminal during the pre-dawn hours of Sunday morning, but the
values of shear don`t quite meet criteria for including in the
TAF. Will watch this as more data comes in later tonight for
possibly including in the 03-06Z update. VFR conditions are
expected on Sunday with increasing south-southwest flow becoming
gusty in the afternoon.





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