Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 132348

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
648 PM CDT Fri Oct 13 2017

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 238 PM CDT Fri Oct 13 2017

Much of the cloud cover over our forecast area has dissipated
this afternoon allowing the temperatures to finally make a
significant rise, although there was still patchy cloudiness
across central MO. A cold front extended from WI southwest to a
surface low over eastern KS. This front will make a slight shift
southeastward toward our area tonight, then lift back northward on
Saturday. There may be scattered showers and thunderstorms
tonight across northeast MO and west central IL due to low-mid
level warm air advection ahead of weak southwest flow shortwaves.
There will also be low level convergence on the nose of a
southwest low level jet over northwest MO. Lows will be warmer
tonight due to southerly surface winds, at least some cloud cover
especially across northeast MO and west central IL, and higher
surface dew points. Although unseasonably warm highs are expected
on Saturday, cloud cover may hinder warming enough that record
highs won`t be reached. Highs should be about 15 to 20 degrees
above normal for mid October. There will continue to be convection
across northeast MO and west central IL.


.LONG TERM...  (Saturday Night through Next Friday)
Issued at 238 PM CDT Fri Oct 13 2017

Convection will spread southeastward through our entire forecast
area Saturday night and Sunday morning as an upper level trough
moves eastward through the northern Plains and into the Great
Lakes region and sends a cold front southeastward through our
forecast area Saturday night. There may be severe storms, mainly
across northeast MO and west cental IL, and mainly Saturday
evening as the wind shear increases due to a strong southwest low
level jet and a mid level wind max in the base of the upper level
trough. The primary threat will be damaging winds as the
convection will be mainly linear along the front. The convection
will likely weaken some overnight as it moves through east central
and southeast MO and southwest IL. There will be lingering post
frontal showers across southeast MO and southwest IL Sunday
morning, with clearing Sunday afternoon as a surface ridge builds
eastward into our area. Much cooler temperatures can be expected
Sunday and Sunday night with strong cold air advection behind the
front. The models drop the 850 mb temperatures down to around 2 to
4 degrees C Sunday night. With a clear sky and diminishing
surface wind the lows may be cold enough for some light, patchy
frost late Sunday night and early Monday morning in the colder
locations. It looks dry for the remainder of the forecast with a
warming trend beginning Tuesday as upper level height begin to
rise, and southerly surface winds return as the surface ridge
shifts east of the region.



.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 632 PM CDT Fri Oct 13 2017

VFR conditions for all terminals during the TAF period are
expected. Some mid level clouds will move through the area this
evening and overnight. Winds will stay from the south/southwest
and stay less than 10kts. All terinmals will stay dry through the
period with the exception of UIN. UIN may see some showers and
thunderstorms overnight into tomorrow morning. LLWS is also
expected at UIN close to 6Z tonight.


VFR conditions for STL for the TAF period. Some mid level clouds
are expected overnight but the forecast period looks to remain
dry with south/southwest winds less than 10kts. Ahead of the cold
front that will approach STL tomorrow night there is some LLWS



Record max temperatures for Saturday, 14 October...

Saint Louis:  90/1899
Columbia:     92/1899
Quincy:       91/1938




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