684 
fxus63 kgid 210909 
afdgid 


Area forecast discussion 
National Weather Service Hastings NE 
309 am CST Sat Nov 21 2009 


Discussion...aloft...shortwave ridging was in place across the 
Central Plains while to the west...a trough stretched from British 
Columbia south through The Rockies. The shortwave ridge axis will 
shift eastward today as the western trough advances to the east. At 
the surface the associated trough will deepen in the Lee of The 
Rockies and the gradient will tighten...resulting in increasing 
southerly winds to the breezy category at times. Cloud cover for 
today is challenging as an area of stratus currently located 
across central/southeast Kansas will work its way northward during 
the day. Our southern County Warning Area may see some fog development this 
morning and will continue to monitor trends of this in the next 
few hours. Whether or not the low clouds mix out today remains in 
question as the NAM suggests this is more probable than the GFS 
which maintains cloud cover across the majority of our County Warning Area for 
much of the day. Confidence is not high in this regard and did opt 
for a conservative approach with some clouds around. 


Tonight...the trough axis begins to push east of The Rockies and 
southwesterly flow aloft is enhanced across the plains. Moisture 
continues to advect north ahead of the surface boundary which 
approaches our western County Warning Area Sunday morning. Stratus is expected to 
settle in across our County Warning Area ahead of the surface boundary. Winds will 
be light along the boundary axis and the NAM is the most 
aggressive in suggesting the potential for the development of 
dense fog vs the GFS. Sref probabilities lend credence to the NAM 
and have included some low visibility potential in the grids but 
stopped short of advisory criteria for now. Weak lift over the 
shallow low level moisture may lead to the development of some 
drizzle. 


The trough/wave moves through on Sunday and this system may generate 
some light precipitation in the afternoon in our east where better moisture is 
present. The wave does not effectively scour the low level moisture 
and have some concerns that the stratus will remain Sunday night and 
fog may develop again. Have introduced some patchy fog for now as 
a start. 


The forecast turns more interesting on Monday as another trough digs 
south from the northern rockies and is forecast to close off across 
the plains on Monday. Models have varied on where the low will 
close off/track with the GFS remaining farther north than the 
NAM/ECMWF/Gem. Have trended toward the southern solution for now 
with precipitation chances increasing on Monday ahead of the system and 
continuing Monday night/Tuesday in the deformation/wraparound. The 
predominate precipitation type should be rain initially but a r/S mix or a 
changeover to snow west/east on the back side of the system is possible 
Monday night into Tuesday. In addition the precipitation potential...very 
strong winds on the back side of the system will buffet our region 
Monday night/Tuesday with wind gusts over 40 miles per hour possible. 


&& 


Aviation...06z taf. Main concern for the taf period is the 
potential for the arrival of stratus just after daybreak on 
Saturday. The leading edge of the stratus clouds is located across 
south central Kansas at this time and with increasing southerly flow 
overnight and Saturday...the low clouds will advect northward. For 
now have kept ceilings in the MVFR range for a few hours and then 
scattered the clouds in the afternoon. In a tightening surface 
gradient...southerly winds will increase on Saturday with gusts 
around 25kts possible. 


&& 


Gid watches/warnings/advisories... 
NE...none. 
Kansas...none. 


&& 


$$