Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 311744

1244 PM CDT Thu Jul 31 2014

.SHORT TERM:  (Through Tonight)
Issued at 307 AM CDT Thu Jul 31 2014

Expect highs in the upper 70s to mid 80s followed by overnight
lows in the lower 60s. Such temperatures are 3-10 degrees below
average for this time of year. Light rain is possible across the
extreme southern CWA today on the northern fringes of an area of
precipitation which is being generated by a shortwave moving from
OK into AR. Isolated to scattered precip is also possible late
this afternoon and early tonight across the northern CWA ahead of
an approaching shortwave which is diving south-southeastward from
ND/MN per 06z water vapor imagery.


.LONG TERM:  (Tomorrow through Wednesday)
Issued at 307 AM CDT Thu Jul 31 2014

Diurnal instability combined with lift ahead of occasional weak
shortwaves might produce iso-sct SH/TS over the next couple of
days, especially during the afternoon hours. Slightly cooler than
average temperatures will continue until the northwest flow
pattern aloft begins to change over the weekend, eventually
becoming quasizonal. After an upper ridge de-amplifies and shifts
into the plains early next week while surface winds turn
southerly, seasonable levels of heat/humidity should return to the
region. The next opportunity for widespread rainfall appears to be
associated with a potential synoptic scale system during the
middle of next week.



.AVIATION:  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1225 PM CDT Thu Jul 31 2014

VFR conditions and generally light and variable winds will prevail
through the period for all TAF sites with just a couple
exceptions. First, recent guidance indicates the potential for
light showers overnight tonight over southern IA and northern MO,
but given uncertainty whether it will occur at the terminal, have
not mentioned in the TAF. Second exception is radiation fog
development during the late overnight and early morning, which
would be similar to what occurred last night. Have included a few
hours of fog for KSUS, KCPS, and KUIN, which could reduce
visibilities down to MVFR/IFR conditions. However, any fog that
develops should be quick to burn off after sunrise Friday.

Specifics for KSTL:

VFR conditions will prevail through the period. Scattered diurnal
cumulus today will return Friday, becoming broken by the early
afternoon. There is a possibility for some showers and
thunderstorms Friday afternoon, but given uncertainties regarding
timing and coverage, have not included mention in the TAF at this
time. Light and variable winds today and tonight will become
easterly around 05kt on Friday, and while some radiation fog is
expected around the area late tonight and early Friday morning,
temperature/dewpoint spreads at KSTL do not indicate impacts at
the terminal.





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