327 
fxus63 kict 080259 
afdict 


Area forecast discussion 
National Weather Service Wichita Kansas 
959 PM CDT sun Sep 7 2008 


Update... 


Only slight pop adjustments were made to the first 
period...keeping highest overnight probability of precipitation (70%) in our northwestern-most 
counties where the strongest 850 moisture convergence...moisture 
transport...and intense isentropic lift is targeted. Trimmed probability of precipitation 
down in our southeastern counties. 


Jmc 


&& 


Previous discussion... /issued 703 PM CDT sun Sep 7 2008/ 


Aviation...00z tafs [rsl/sln/hut/ict/cnu] 
frontal boundary at 23z stretched from southwestern Kansas to near swo to fyv. 
The front prognosticated to lift northward to central Kansas by 12z in response to 
shortwave trough approaching the northern/Central Plains. As the wave 
sweeps across...the front will then push southward as a cold front with 
the front reaching southeastern Kansas late Monday PM. Boundary layer looks to 
nearly saturate toward 12z in central Kansas via east-southeasterly flow and 
moisture convergence. IFR stratus and/or visibilities look highly 
probable at rsl/sln/hut during the morning hours. Both the NAM- 
WRF/GFS suggest a corridor of Post-frontal low clouds behind the 
front for several hours Monday affecting all of our taf sites. 
Ts complex likely to develop by late this evening in northwestern/N-cntrl 
Kansas...with this complex traversing slowly eastward into northestern Kansas Monday am. 
Will carry tempo ts groups at rsl/sln for this action. Other 
scattered ts possible along front Monday PM/evening during peak heating 
which could affect hut/ict/cnu. Will utilize thunderstorms in the vicinity there. 


Jmc 


Previous discussion... /issued 315 PM CDT sun Sep 7 2008/ 


Discussion... 
an active weather pattern is expected through much of the forecast 
with a number concerns including severe storm potential tonight... 
temperatures on Monday with a cold front slamming through and 
timing of additional fronts in the extended. 


Tonight - monday: 
the NAM and the GFS both show very strong isentropic lift developing 
tonight ahead of very strong cold front. Elevated instability is 
fairly impressive with parcels lifted from 850mb yielding 1500 to 
2000 j/kg cape. The best lift/ instability seems to be just north of 
our forecast area but given instability and 1-3 km and 1-6 km 
shear... strong storms are possible for our central Kansas counties. 
Have assigned highest precipitation chances to central Kansas as a 
result and have tapered to dry probabilities across southern Kansas. 
There is also the potential for fog across central Kansas just ahead 
of the front in the moist upslope flow. Have mentioned areas of fog 
for a brief period time as a result of this. Dense fog is not 
expected but would not be surprised to some visibilities drop to 2-3 
miles briefly. 


The cold front will continue to plow south through the day tomorrow 
with a sharp cool down expected. This should especially be true for 
south central and south East Kansas where prefrontal temperatures 
into the 80s are expected. With the cold front plowing through have 
assigned chance precipitation probabilities to the entire forecast 
area. The best chances may stay in central Kansas behind the front 
with tapered chances across southeast and south central Kansas. 
North winds will pick up behind the front as well but as of now Wind 
Advisory criteria is not expected. The front should be through 
southeast Kansas by the evening hours. Forecast confidence is high. 


Tuesday: 
high pressure will settle over northern Missouri/southern Iowa with 
surface ridge axis pointing into central Kansas. The NAM and the GFS 
show some potential for fog across central Kansas as the boundary 
layer should decouple. Surface relative humidities are near 100% but 
boundary layer relative humidity is much lower. This would limit the 
depth of the fog so for now have only mentioned patchy fog in the 
forecast. Forecast confidence is high 


Wednesday - thursday: 
nearly zonal upper flow is expected with a weak wave moving through 
that flow. The area should also be in the left front quadrant of the 
upper jet so that added diffluence may trigger a few showers and 
storms Wednesday afternoon/evening. By Thursday another front is 
expected to move into the area which will continue the chances for 
precipitation into Thursday night. Forecast confidence is medium. 


Rest of the extended: 
there is a lot of uncertainty with the extended part of the forecast 
and a lot of variability in the successive runs of the European model (ecmwf) and the 
GFS. The 00z European model (ecmwf) and to a lesser extent the 06z GFS brought Ike 
ashore in the central Gulf and moved up into Arkansas. The latest 
runs continue a trend further west into the western Gulf. The European model (ecmwf) 
dissipates Ike over southwest Texas while the GFS moves Ike ashore 
in the vicinity of Houston and then recurves it to the north. The 
extended forecast has low confidence due to lack continuity in the 
extended range models. 


Cdb 


Aviation...18z tafs...ict/sln/hut/cnu/rsl 
the main concern with this forecast is the low ceiling and 
visibility potential overnight in at the ict/hut/rsl and sln taf 
sites. Until then...we will see mainly MVFR ceilings (2-3kft) this 
afternoon and early this evening since the convective temperature 
has been reached fairly early. The surface boundary is expected to 
lift north tonight which will allow for the boundary layer 
moisture to increase...especially near the boundary. As a 
result...we have lowered ceilings into 400-800ft range at the 
rsl...sln...hut...and ict taf sites with visibilities generally 
ranging from 1 to 3sm after 05z. The cold front is then expected 
to move through central Kansas mainly around 12z. 


&& 


Preliminary point temps/pops... 
Wichita-kict 63 83 53 73 / 20 40 20 10 
Hutchinson 62 75 49 72 / 40 50 10 10 
Newton 62 77 50 71 / 40 40 20 10 
Eldorado 62 82 52 71 / 30 40 20 10 
Winfield-kwld 63 85 55 74 / 10 30 20 10 
Russell 55 60 45 69 / 70 50 10 10 
Great Bend 60 64 46 71 / 50 50 10 10 
Salina 61 66 45 72 / 70 50 10 10 
McPherson 62 74 47 72 / 60 50 10 10 
Coffeyville 64 84 54 73 / 10 30 30 10 
Chanute 63 85 52 72 / 20 30 30 10 
Iola 62 84 52 71 / 30 30 30 10 
Parsons-kppf 64 85 53 73 / 10 30 30 10 


&& 


Ict watches/warnings/advisories... 
none. 
&& 


$$