253 
fxus63 kict 050448 
afdict 


Area forecast discussion 
National Weather Service Wichita Kansas 
1147 PM CDT Thursday Sep 4 2008 


Aviation... 


For 06z tafs...main aviation concern will be dense fog for southeast Kansas 
through the next several hours. 


Skies have cleared out across southeast Kansas with temperatures starting to plummet. 
Kcnu has dropped to 6sm and am expecting this trend to continue. 
Thinking hasn't changed much since last taf issuance with IFR visible 
and ceilings expected at kcnu by 09z. The airmass looks to be dry enough 
across the remainder of the sites to limit fog potential overnight. 
Our next weather disturbance...currently tracking over The 
Rockies...will start to spread middle level clouds across the western 
portion of the forecast area by the morning hours...with some 
scattered showers developing by the afternoon for all sites with the 
exception of kcnu. At this time not expecting any IFR conditions 
through the daylight hours on Friday. 


Lawson 


&& 


Previous discussion... /issued 926 PM CDT Thursday Sep 4 2008/ 


Update... 


Updated to make minor updates to dewpoints and cloud cover. 


Low clouds cleared out of southeast Kansas faster than previously thought. 
Therefore had to update to keep up with this current trend. 
Dewpoints have also dropped off a bit faster than expected so also 
had to tweak these. Fog still looks like a good possibility in southeast Kansas 
with dewpoints still lingering in the middle and upper 50s. Based on 
latest model forecast soundings the fog should be fairly shallow 
with all models forecasting decreasing dewpoints with height. 


Lawson 


Previous discussion... /issued 646 PM CDT Thursday Sep 4 2008/ 


Aviation... 


For 00z tafs...main aviation concern for this package will be dense 
fog potential in southeast Kansas. 


Short-lived surface high pressure will settle over the area tonight 
as our next upper disturbance approaches from the northwest. Southeast 
ks(kcnu) will have decent fog potential tonight due to clear 
skies...light winds along with saturated grounds from rains over the 
last couple of days. While the remainder of the sites will 
experience clear skies and light winds...they will be missing the 
saturated grounds which will be key. For now will get kcnu down to 
IFR conditions after 09z but will wait and see how things pan out 
before going below a mile. 


Middle level clouds will be on the increase from the northwest on Friday 
as our next upper wave approaches. At this time confidence is high 
enough to run with some vcsh for krsl and ksln after 18z on Friday. 


Previous discussion... /issued 314 PM CDT Thursday Sep 4 2008/ 


Discussion... 


The main concern with this forecast package will be the dense fog 
potential in southeast Kansas tonight and the timing of the chance 
of showers and thunderstorms through the forecast package. 


Tonight: 
latest visible imagery was showing the low clouds gradually exiting 
southeast Kansas. These clouds should continue to clear from west to 
east this evening as the remnants of Gustav lifts to the 
northeast. Meanwhile...the surface high pressure system will set 
up Camp over the forecast area tonight. This will allow for good 
radiational cooling for areas adjacent of the surface high this 
evening. Portions of southeast Kansas saw about 1 to 2 inches of 
rain last night. This combined with good radiational cooling and 
plenty of boundary layer moisture should allow for dense fog to 
develop over that region tonight from stratus build down effects 
or backbuilding stratus. As a result...we are issuing a dense fog 
advisory for the counties along and east of the Flint Hills. 
Latest water vapor loop was also showing a wave moving out of 
Montana. This feature will help enhance the isentropic lift across 
central Kansas late tonight and possibly cause some showers and 
thunderstorms to creep into central Kansas by daybreak. 


Friday: 
we went ahead and bumped up probability of precipitation across central Kansas during the 
morning due to the strength of the upper level wave and plenty of 
isentropic lift/moisture transport in the 305-310k layer. Most 
unstable convective available potential energy in this area will be around 500-1000j/kg with 1-6km 
shear values around 40-45kts which may be able to support a strong 
storm or two. This convection should begin to diminish as we 
approach the afternoon due to the wave pushing to the east of the 
area. We have kept a good chance of showers and thunderstorms in the 
picture for now...but it appears like most of the convection will be 
in the morning into the early afternoon. Meanwhile...the cool front 
will stall out somewhere over southern Kansas. 


Friday night-saturday: 
the models are in fairly good agreement in showing another fairly 
strong wave moving through the area Friday night and Saturday 
morning. This wave appears to have quite a bit of isentropic ascent 
and moisture transport which may bring a fairly good shot of 
rainfall to southern Kansas near the frontal boundary. As a 
result...we went ahead and bumped up probability of precipitation during this 
timeframe. 


Sunday-thursday: 
the models are still in fairly good agreement on the upper level 
pattern during this timeframe. The main question during the Sunday- 
Tuesday timeframe will be the position of the frontal boundary. 
The models are really not keying on any upper level feature moving 
through the area Sunday...but the boundary still may be hung up 
across central Kansas. We have kept a chance of showers and 
thunderstorms at this point. Another wave may try to move through 
the area on Monday and Monday night and cause the front to shove 
through the area. This may allow for a mild day on Tuesday. 
However...the return flow will setup again by the middle of next week 
and allow for more chances of showers and thunderstorms and warmer 
temperatures. 


Cox 


Aviation...18z tafs [rsl/sln/hut/ict/cnu] 
MVFR ceilings will likely persist this PM and possibly early this evening 
in southeastern Kansas (affecting cnu). The slower NAM-WRF clearing looks 
better than the faster GFS at this time. Both the GFS and NAM-WRF show 
some isentropic downglide with low-level flow turning anticyclonic 
this evening which may clear out cnu. The surface ridge axis will 
shift over southeastern Kansas/northwestern MO toward 12z Friday with the NAM-WRF and 
GFS both showing the boundary layer moistening (nam moreso). 
BUFKIT soundings would support a shallow layer of IFR ceilings and/or 
fog at cnu for several hours around 12z Friday. Otherwise...an 
approaching shortwave trough and strong isentropic lift/mid-level 
moistening may produce an area of light rain showers across mainly 
central Kansas Friday. 


&& 


Preliminary point temps/pops... 
Wichita-kict 54 75 57 73 / 0 40 60 40 
Hutchinson 51 71 54 72 / 0 60 60 40 
Newton 53 73 55 72 / 0 40 50 40 
Eldorado 53 75 56 72 / 0 30 40 40 
Winfield-kwld 55 78 58 74 / 0 20 50 50 
Russell 51 67 52 71 / 20 60 30 20 
Great Bend 52 68 54 72 / 20 60 50 30 
Salina 52 69 54 72 / 0 60 20 30 
McPherson 52 70 53 72 / 0 60 40 30 
Coffeyville 50 78 58 75 / 0 10 20 50 
Chanute 50 77 56 73 / 0 10 20 40 
Iola 50 76 56 72 / 0 20 20 40 
Parsons-kppf 50 77 57 73 / 0 10 20 50 


&& 


Ict watches/warnings/advisories... 
dense fog advisory from 4 am to 10 am CDT Friday for ksz070>072- 
094>096-098>100. 


&& 


$$ 

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