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fxus63 kilx 200448 
afdilx 


Area forecast discussion 
National Weather Service Lincoln Illinois 
1148 PM CDT Tuesday Aug 19 2008 


Discussion... 
issued 853 PM CDT Tuesday Aug 19 2008 


Skies mostly clear overnight with temperatures slowly falling. Winds have 
become light and will remain that way overnight. Forecast looks 
fine so no update required tonight. 


Auten 
&& 


Aviation... 
issued 1148 PM CDT Tuesday Aug 19 2008 


VFR conditions will continue next 24hrs at all taf sites. Skies 
mostly clear at moment with only high cirrus seen on satellite 
loops. Temperature/dewpoint spreads have been decreasing during the 
evening and spreads are closer than this time last night...which 
produced some light fog for an hour or two at some sites. 
Therefore believe some light fog still possible overnight...so 
will keep 4-5sm br at all sites from 09-12z. Then scattered cumulus 
still possible during the day with little more low level moisture 
than today. Winds light and will remain that way overnight then 
will become southeasterly during the day. 


Auten 
&& 


Previous discussion... 
issued 200 PM CDT Tuesday Aug 19 2008 


Latest surface analysis indicating a weak cold front located between 
valpariso Indiana and Kankakee...northwest to near Dubuque. Fairly decent 
area of middle 60 dew points pooling along this boundary early this 
afternoon. To our south...the cutoff low which has been tracking slowly 
south across The Rockies the past several days was now located over 
southern Oklahoma...and will be playing a part in our weather starting on 
Thursday. No real model choices with this forecast package with 
the NAM-WRF followed in the short term and a blend of the GFS and 
European model (ecmwf) with the weekend system. 


Short term...tonight through Friday 
weak cool front will settle into at least the northern portion of the 
forecast area this evening before gradually washing out as high 
pressure at the surface and aloft takes over for Tuesday and Wednesday. 
NAM-WRF best moisture convergence stays to our north tonight along the 
weak boundary so will continue with a dry forecast. The quiet weather 
continues Tuesday through Wednesday night as upper level ridging builds northward 
across the Midwest. The Southern Plains upper wave is forecast to 
track slowly northward starting late Tuesday and still think the slower 
solution (nam-wrf) is the way to go with this system as upper 
level winds remain weak across the plains and Midwest. Rain chances 
will start to increase across our far SW counties Thursday morning with low 
chance probability of precipitation extending into our east during the afternoon. Appears the 
better low and upper level support for showers will be across our 
west with more of a diurnal component indicated with this 
system...with the better chances for showers and thunderstorms 
during the late afternoon and evening hours Thursday and Friday with a 
decrease in activity at night. 


850 temperatures continue to edge up a degree or two each day and 
the NAM-WRF suggests this trend will continue into Thursday. Will follow 
the met guidance for afternoon highs with a blend of the mav/met working well 
in this pattern for overnight lows. 


Long term...Saturday through Tuesday 
rather strong upper level trough is forecast to track across the 
Canadian/U.S. Border at the start of this period which will push 
a cold front eastward across the middle-Mississippi Valley late Saturday 
into early Sunday. Latest European model (ecmwf) suggests the GFS depiction with 
frontal passage in our area late Saturday looks reasonable. That appears 
to be the best chance for seeing rain across the area with the 
boundary slipping just south of the state by Sunday morning. 
Still am a bit Leary regarding how quickly the models were moving 
the boundary across the Midwest...especially with the strength of 
both the upper level and surface ridges. Will continue with the highest 
chance probability of precipitation in the Sat-Sat night time frame and hold on to some 
low chance probability of precipitation on Sunday..esp across the southeast in case the boundary 
slows down. 


Confidence on just how the remnants of Fay will affect our 
weather...if at all early next week...remains low. Models offering 
different solutions with the latest GFS suggesting the trough that 
moves across our area over the weekend may actually help to steer the 
wave more to the northeast than what was projected earlier. The 
latest European model (ecmwf) takes a more westward track initially...but it too 
eventually forecasts a further NE track well to our south and 
east later Monday into Tuesday. For now...will keep only slight 
chances (not mentioned in the zfp) for precipitation starting in the 
south Monday night and across the rmdr of the forecast area on Tuesday. 


Smith 
&& 


Ilx watches/warnings/advisories... 
none. 
&& 


$$