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fxus63 kgld 211056 
afdgld 


Area forecast discussion 
National Weather Service Goodland Kansas 
356 am MST Sat Nov 21 2009 


Discussion... 
221 am MST Sat Nov 21 2009 


0430z water vapor imagery indicates shortwave ridging across the County Warning Area 
with large trough across the western Continental U.S.. at the surface trough axis 
was present across eastern Wyoming with surface ridge axis draped across 
southern Kansas. 00z radiosonde observations indicated some warming over the last 24 
hours. Of some interest is deepening moisture profile observed at 
ddc. With this location currently directly under surface ridge could see 
a favorable set up for fog early this morning across eastern zones. 


Main concern for short term period will be approaching storm system 
during the beginning of the week. 


Today-tonight...some fog/stratus may sneak into eastern/southeastern 
County Warning Area as downstream soundings indicate airmass more favorable for 
radiation fog than previous nights. Winds will generally become more 
southerly advecting this airmass towards the region...but winds may 
offset any radiational cooling component. For now plan to wait until 
forecast issuance and use observational trends to determine fog 
threat. Otherwise large scale forcing for ascent will overspread the 
area late this afternoon and into the evening. As has been the case 
with the past several model runs...fairly strong forcing overspreads 
the area overnight with large scale and frontogenetic forcing peaking 
overnight...but there does not appear to be any quality moisture 
return ahead of this system...which based on current WV imagery 
looks likely. With large T-dew point spreads it would be unlikely that any 
level could be saturated and any instability be realized...so 
keeping current dry forecast looks like the way to go. Otherwise 
expect a large gradient in winds today with relatively light winds 
in the west...and sustained winds 15-20kts in eastern County Warning Area before 
cold front moves across the area overnight. 


Sunday-Sunday night...first of a series of short wave troughs will 
depart the area during the morning hours bringing a brief break to 
the clouds. Short range models seem to stall frontal zone along/just 
east of the County Warning Area during the morning hours bringing stratus...and 
point soundings suggest fog/-dz possible along and immediately behind 
frontal zones. Is going to take a lot of moisture advection for this 
to develop...but lower 40 dew points not to far from the County Warning Area so this 
scenario not totally unreasonable. Otherwise expect high clouds to 
once again overspread the area by the afternoon as next strong short 
wave trough approaches. Increased moisture advection will also limit 
how cold things will get in eastern County Warning Area which is handled well by 
going forecast. 


Monday-Tuesday...most important and unfortunately most uncertain 
forecast period will bring the potential for yet another winter 
storm to impact the area. Models still spread out in to numerous 
different camps with this storm. 12z European model (ecmwf) continues to suggest 
500 mb/surface low strengthening and occluding over Kansas...while GFS 
continues to hold onto more northerly and progressive solution. The 
00z European model (ecmwf) has continued to hold onto the strength and speed of the 
system...but has transitioned considerably farther north. Looking 
at other available models...the UKMET appears to be a much slower 
version of the GFS...while the NAM and Canadian appear to be deeper 
and somewhat slower versions of the GFS. This spread in solutions 
make the forecast very difficult as differences are not simply 
things like timing and track...but overall evolution of the system. 
Further complicating things are sref and GFS ensembles. While the 
gefs has 3 members (out of 20) that suggest a much more southerly 
and slower system...21z sref data firmly in more progressive/weaker 
Camp with mean actually showing little spread in 500 mb solution until 
system gets over Missouri. 12z/00z Canadian mean kind of leaning 
this direction as well. The European model (ecmwf) and UKMET have been the most 
stable with there solution...but it is hard to argue with the 
available ensemble data which performed fairly well the last two 
snowstorms. 


For all the reasons listed above...confidence in any particular set 
of model solutions remains low although some sort of compromise 
between an European model (ecmwf) and NAM solution would be a reasonable starting point as it 
would incorporate more of a worst case scenario while still putting 
a bit more weight on recent ensemble data. Cannot get too excited to 
much about things like trowals and potential instability when the 
confidence of a closed low even being there is low. 


Despite the uncertainty...there does look to be a window where 
accumulating snow is possible late Monday afternoon and overnight 
Tuesday. While amounts may differ between the models...all agree 
that strong northwesterly winds will develop behind the low creating 
a blowing snow problem if anything falls. While ensemble data would 
support a much drier forecast am going to try to maintain previous 
forecast as system not even on shore at this time. Will up probability of precipitation 
slightly where models generally agree chances are best on Monday and 
Monday night. 


Jrm 
&& 


Aviation... 
356 am MST Sat Nov 21 2009 


For the 12z tafs...a ridge of high pressure and subsidence will keep 
kgld and kmck in VFR conditions during this taf period. Fog product 
satellite indicating some stratus and fog advecting north over 
central and eastern Kansas but latest trends indicate it should stay 
east of the taf sites. There is some potential again Sunday morning 
in the east but time height cross sections indicate a lack of low 
level relative humidity. South winds increase to breezy category today in response 
to a surface trough in eastern Colorado. Expect wind to subside due 
to decoupling around sunset. A weak cold front is prognosticated to shift 
wind to the north early Sunday morning. 


Fs 
&& 


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


$$ 

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