457 
fxus63 kdvn 281945 
afddvn 


Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois 
245 PM CDT Thursday Aug 28 2008 


Synopsis... 
a strong cold front will sweep through the region bringing an end to 
the recent rain. Canadian high pressure building in behind the front 
will bring quiet weather for the Holiday weekend. The next chance of 
rain looks to be around the middle of next week. 


&& 


Short term...tonight and Friday... 
cold front to sweep through the area late this afternoon/evening. 
Cold pool/clouds from the morning mesoscale convective system has put a damper on afternoon 
convection. Recent radar/satellite trends indicate some rain showers have 
developed ahead of the trough which is ahead of the cold front. 
Therefore the cold front will mark the back edge of the precipitation 
chances for late afternoon/evening. Current trends suggest the 
southeast two thirds of the County warning forecast area should see some precipitation this evening. 


Next concern is fog. A nice stripe of heavy rain runs from Benton 
County southeast to McDonough County. Clearing skies late tonight 
with fairly light winds should allow fog to form...especially in the 
heavy rain axis. Therefore will add mention of fog for that area. 
Quiet weather expected on Friday. Maximum temperatures should be at or 
slightly below normal. ... 


Long term...Friday night through next Thursday... 
quiet late Summer weather will dominate the early part of the 
forecast. Models are in good agreement moving surface high through 
the region over the weekend. About the only question regarding the 
weekend forecast will be temperatures...especially min temperatures 
Saturday. GFS/NAM are forecast dewpoints in the middle to upper 40s by 
Saturday morning which looks reasonable based on current dewpoints 
over the northern plains. The center of the surface high will be located 
just east of the County warning forecast area by 12z Saturday suggesting good radiational 
cooling overnight. Current forecast mins are in the lower 50s in the 
northeast...which may need to be lowered around a category. Low to 
middle 80s expected for highs on Saturday. Temperatures will return to above 
normal for Monday and Tuesday as return flow sets up ahead of cold 
front moving through the northern plains. For now have held temperatures 
in the middle/upper 80s...but low 90s are not out of the question based 
on 800 mb temperatures. GFS/European model (ecmwf) continue to differ on the timing of the 
frontal passage through the middle MS valley with the European model (ecmwf) continuing to lag the 
GFS by about 12 hours. Current indications are frontal passage will occur 
Tuesday night or Wednesday morning so have maintained low probability of precipitation for 
Tuesday into Wednesday. European model (ecmwf) continues to move remnants of Gustav 
into the the middle MS valley by the end of the week. This looks 
reasonable based on the expected track into the central or western 
Gulf...so have held on to low probability of precipitation into Thursday. ... 


&& 


Aviation... 
cold front passage to occur late afternoon/evening. Ceilings of 2-3kft should be seen 
through 03z. Clouds helping to inhibit afternoon convection and kdbq 
should remain thunderstorms and rain free. Kcid may see a cumulonimbus within sight of the field 
but cold front passage should occur before it would get close. Kbrl has the best 
chance of seeing a thunderstorms and rain with kmli next best. Ceilings to become VFR 
after 03z. Kcid/kbrl have greatest potential for fog late tonight and 
have gone with 1sm 10-14z. Potential there for below 1sm and ceilings below 
1kft around sunrise. Kdbq/kmli should see 3-5sm visibilities around sunrise. 
... 


&& 


Dvn watches/warnings/advisories... 
Iowa...none. 
Illinois...none. 
MO...none. 
&& 


$$