Weather

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Area forecast discussion 
National Weather Service Goodland Kansas 
1054 PM MDT Friday Oct 10 2008 


Synopsis... 
226 PM MDT Friday Oct 10 2008 


Analysis of water vapor imagery showed longwave trough and 
associated middle/upper level low continuing to dig into the Great 
Basin region. A weak shortwave trough was moving from eastern 
Kansas into the middle Missouri River valley while another weak 
shortwave trough was located over Wyoming and southeastern 
Montana. At the surface...a pre-frontal trough was bisecting the 
County Warning Area with the northwest half experiencing temperatures in the upper 50s to 
middle 60s while the southeast portion was pushing close to 80. Based 
on surface analysis and visible satellite would put the cold front 
just to the northwest of the County Warning Area...ahead of schedule with regard 
to what was prognosticated by the deterministic numerical guidance. 


Foltz 
&& 


Discussion... 
226 PM MDT Friday Oct 10 2008 


Main concerns for this forecast package remain centered around 
probability of precipitation/quantitative precipitation forecast through the weekend and whether or not Hydro highlights 
will be needed. 


Forecast has become a bit more uncertain today as model guidance 
is now taking the closed 500 mb low further north rather than ejecting 
it out into the Central Plains. Also...significant differences 
between the ec and the deterministic GFS have begun to appear from 
Monday evening through Wednesday before they converge again by 
Wednesday evening. 


As mentioned above...front appears to be arriving ahead of 
schedule. 00z/10 guidance held the front off until after 00z 
Saturday but it has already started pushing into Yuma County. Will 
follow the quicker NAM guidance through the overnight hours as it 
had the best handle based on reality. 


Appears things will remain dry through the late morning hours Saturday 
before precipitation begins to break out over southeastern Colorado and 
southwestern Kansas. 12z/10 nam12/gfs40 310k isentropic surface shows 
strong moisture transport and upglide commencing by around 18z 
with condensation pressure deficits dropping to less than 50mb. 
Much like yesterday afternoon...forcing for ascent will be present 
over the entire County Warning Area which could lead to widespread moderate to heavy 
precipitation through the first part of next week. Have generally 
followed hpc's guidance for quantitative precipitation forecast in agreement with surrounding 
offices. Have bumped probability of precipitation into the likely category for Saturday 
night through Monday morning. Will see a very slow eastward 
progression of precipitation by midday Sunday so have trended probability of precipitation lower 
over the Colorado zones. Potential is there for Hydro issues but 
confidence in exact location of the greatest threat so will hold 
off on any highlights. Overnight shift will likely need to 
reassess. Essentially maintained going forecast for maximum/min temperatures 
through Monday. 


As alluded to earlier...ec and operational GFS diverge on handling of 
the middle/upper trough. GFS is quick to take the closed low 
northeastward into the western Dakotas eventually locating it over 
Ontario by Tuesday night. Ec breaks a piece of the middle/upper 
closed low off following a similar path as the GFS but hangs the 
main trough back over the intermountain west before weakening the 
closed low into an open wave and moving it into the Central High 
plains by Tuesday evening. Have gone with the more reasonable ec 
solution for this time frame. Monday will be a chilly and raw day 
with 850 mb temperatures around 0c. Have kept maximum temperatures for Monday in the 
low 50s but could easily see upper 40s if clouds hang tight. 


Will see a dry period and slow warming trend by the middle of next 
week as the mean flow becomes essentially zonal over the Continental U.S.. 
GFS ens mean and the ec are in agreement developing a trough over 
the northern rockies and sending a surface cold front through the 
County Warning Area sometime on Thursday. Appears moisture will be lacking so have 
left this period dry with just a shift to northerly winds. 


Foltz 
&& 


Aviation... 
1054 PM MDT Friday Oct 10 2008 


For the 06z taf cycle... hit low stratus deck hard...per latest 
satellite imagery. Low ceilings should persist well into Saturday 
morning with the low level upslope flow. Turbulent mixing in the 
boundary layer favors stratus over fog...so did not restrict visbys. 
Rain should develop at both taf sites by Saturday afternoon 
associated with lead shortwave disturbance rotating in from the 
south...with further aviation restrictions anticipated. 


24 
&& 


Gld watches/warnings/advisories... 
Kansas...none. 
NE...none. 
Colorado...none. 
&& 


$$