Weather

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fxus63 keax 280535 
afdeax 


Area forecast discussion 
National Weather Service Kansas City/Pleasant Hill MO 
1235 am CDT Thursday Aug 28 2008 


..updated aviation discussion... 


Discussion... 
/1005 PM CDT Wednesday Aug 27 2008/ 
raised lows over kc metropolitan. Convection now forming over southeast Minnesota 
into northwest Iowa will likely backbuild into northeast NE and 
gradually translate southward overnight and possibly reach northwest 
MO shortly before sunrise. 


Otherwise...primary change for this update was to raise rain chances 
for tomorrow afternoon from northeast into west central MO as 
thermodynamics looking better for convective chances. 00z NAM 
maintaining consistency in the evolution of a squalline forming 
along the southeastward advancing cold front. Also...based upon maximum 
temperatures today in the lower to middle 90s over central and 
eastern Kansas and the likelihood of 22c to 24c 850mb air spreading into 
the southern half of the County Warning Area opted to raise maximum temperatures a bit. 


Mj 


&& 


Previous discussion... 
short range (tonight-Friday night)... 
/405 PM CDT Wednesday Aug 27 2008/ 
currently watching an area in east central Kansas and west central 
Missouri where an outflow boundary from the northern convection has 
stalled. With temperatures climbing into the upper 80s...there may 
be enough destabilization late this afternoon for isolated showers 
or thunderstorms to develop in its vicinity. Will include a slight 
chance probability of precipitation to cover for now. 


For later tonight...attention turns to the northern stream short 
wave heading toward the upper Midwest. Attendant surface front 
should be lining up from northwest Iowa to northwest Kansas by late 
tonight...with a strengthening low level jet through eastern Kansas into 
western Iowa. This should place The Heart of the moisture axis 
across this region...with the better isentropic lift in the forecast 
area late tonight on the 310k surface aimed toward northwest 
Missouri. Will have chance probability of precipitation in the overnight period to cover the 
potential of convection in that region. 


Then during the day on Thursday...main focus for development will be 
the surface front...dropping southeast across the forecast area. 
Models are in fairly decent agreement on its timing...with it not 
reaching a Kansas City to Kirksville line until late in the 
afternoon. South to southwest flow of winds ahead of this front 
should produce a rapid warm up during the day. Looking at 
temperatures to our southwest today...the lower 90s look quite 
reachable...with possibly some middle 90s if skies stay clear for a 
longer period than currently anticipating. 


Once the front drops through the region Thursday night...surface 
ridge builds in which should result in dry weather through the 
Friday time period. 


Pc 


Medium range (sat-wed)... 


Only few changes made to the ongoing medium range forecast as a high 
degree of model uncertainty begins by Monday. 


For the Labor Day Holiday weekend...a general consensus continues 
that surface high pressure will prevail for much of the period. Have 
modified high temperatures only slightly trough the weekend...as 
east-northeast surface winds should keep warming to a minimum. Nevertheless near 
normal temperatures in the low-middle 80s can be expected. Some 
concerns continue with the potential for pop-up diurnal rain showers/thunderstorms and rain 
activity late in the day on Sunday and then again on Monday...as 
low-level Theta-E axis remains nearby. However...suspect GFS is the 
only solution which continues to advertise this happening and feel 
that with the continued advection of dry easterly surface flow we will 
remain dry. 


The high degree of model uncertainty begins by Monday night 
continuing through the remainder of the medium range. GFS/European model (ecmwf) 
continue to have differing opinions on what affects tropical system 
Gustav will have on the long wave pattern. The GFS has continued to 
struggle to initialize Gustav which allows next upper trough over The 
Rockies by Tuesday morning to rapidly race eastward. While the 
European model (ecmwf) shouldn't be trusted either with the handling of the long wave 
features in the medium range...it's general idea of a slower and 
further north solution is supported by the naefs and 12z 
Gem...keeping the affects of the upper trough out of the region until 
Wednesday at the earliest. For now will use a blend of these 
solutions. However...am expecting wild oscillations in the near 
future as the track of Gustav remains uncertain. 


Dux 


&& 


Aviation... 
for the 06z taf...except for some minor tweaks in wind direction 
made no major changes made to forecast. VFR conditions will prevail 
through the forecast. Scattered convection still expected from along 
a southeastward advancing cold front during the afternoon hours. 
Better chances for rain will be at kmci and kmkc. Have enough 
confidence that convection will occur with this front that upgraded 
to a tempo group for these two sites. Less confident that kstj will 
see storms at that point so opted to go with thunder in the vicinity 
of the site. Otherwise...winds will shift abruptly to the north with 
passage of the afternoon front with VFR middle level ceilings lasting 
through the rest of the forecast. Potential also exists that 
scattered Post frontal showers will linger in the evening but 
probability of occurrence at a single point not high enough to 
include in forecast. 


Mj 


&& 


Eax watches/warnings/advisories... 
MO...none. 
Kansas...none. 
$$