Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 212228

528 PM CDT Sun Sep 21 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 138 PM CDT Sun Sep 21 2014

Focus tonight will be temps. Sfc ridge builds into the region with
winds diminishing with sunset. Current cloud deck over nrn IL and
ern IA shud continue to break up this afternoon as it moves ese
leaving much of tonight clear. Greater mixing has occurred today
than prev anticipated, lowering dewpoints. While tonight is not a
great setup for radiational cooling as winds may stay up around 5
kts, believe CAA will help compensate. Have therefore trended aob
the coolest guidance for tonight.

.LONG TERM:  (Monday through Next Sunday)
Issued at 307 PM CDT Sun Sep 21 2014

High pressure will dominate over the region this week, allowing for
cool temperatures, dry conditions, and mostly clear skies through
early next weekend. Monday and Monday night, given the proximity of
the surface ridge axis and 850mb temps in the 8-10C range, should
yield the coolest temperatures this week, with highs Monday in the
low 70s, and lows Monday night in the 40s,to around 50 degrees in
the St. Louis metropolitan area. By Tuesday, south/southeast flow
will return to the area and slow warming trend will get underway.
Temperatures are expected to gradually warm, rebounding to the upper
70s to around 80 degrees area- wide by Friday.

Precipitation chances look to remain quite low through the
extended, though there are two disturbances in question that could
potentially impact the area. The first disturbance, a low pressure
system that is currently over far western Nevada per water vapor
imagery, is progged to become absorbed into the mean flow by
midweek. However, models are in agreement indicating an axis
through the Plains where the ridge will be weakened due to this
feature, which could be a focus for precipitation through the end
of the week. Currently, it looks like any precipitation that would
be associated with this feature would remain well to the west of
the CWFA prior to high pressure once again building over the
nation`s midsection. The GFS is also indicating another
disturbance for the late Saturday night/early Sunday time frame
which could potentially impact far southeast portions of the CWFA,
but it is too early to tell how this could potentially pan out.
Thus, have maintained a dry forecast.



.AVIATION:  (For the 00z TAFs through 00z Monday Evening)
Issued at 523 PM CDT Sun Sep 21 2014

VFR through the period, except in river valleys where steam fog is
possible overnight due to the difference between the warmer river
waters and the rapidly cooling air. Gusty north to northwest winds
will subside this evening with the loss of diurnal mixing. Expect
winds to gradually veer through the period as a high pressure
center moves into the region.

Specifics for KSTL: VFR through the period. Gusty north to
northwest winds will subside this evening with the loss of diurnal
mixing. Winds will gradually veer through the period as a high
pressure center moves into the region.





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