579 
fxus63 klbf 110909 
afdlbf 


Area forecast discussion 
National Weather Service North Platte NE 
409 am CDT Sat Oct 11 2008 


Discussion... 
..timing rain and cool temperatures will be the main forecast 
challenge this morning... 


Short term models in decent agreement as upper level low 
digs/closes over the western Continental U.S. Today...then ejects NE across 
The Rockies and the northern plains. Meanwhile Hurricane Norbert 
in the eastern Pacific pumping moisture northward across the 
Southern Plains. 


Cold front with sharp temperature/moist gradient has pushed into eastern 
Nebraska with entire County Warning Area now in the cold air mass and underneath 
a blanket of low clouds. As temperatures have dropped into the upper 30s 
across north central Nebraska...patchy fog has developed. Do not 
expect the fog to keep visibilities too low beyond middle morning as winds 
increase. Temperatures today dropped considerable from yesterday 
forecast as stratus and chance of rain from time to time going to 
limit warming considerable. Middle level moisture will be on the 
increase through the day from strong S winds. Also going to see a 
jet streak round the trough producing upper level divergence and 
combine with middle level moisture and wave ahead of upper low. Will 
have the potential for a few isolated rumbles of thunder. 


Overnight...moisture from tropical system...seen on water vapor 
gets pulled northward into the area and will produce some rich 
moist environment. Both GFS and NAM in agreement as strong isentropic 
lift to produce a potentially heavy cool October rain. 


Sunday has great uncertainty as the latest model runs have slowed the 
progression of the trough to the northeast. Also the NAM draws in 
more dry air into the dry slot. While high confidence the far 
east/northeast zones will continue to see rain on Sunday...how 
fast areas in the west will come to an end. Will continue to 
monitor this. 


System will be slow to push east of eastern zones Monday...then 
dry and season temperatures expected. If skies clear Monday night behind 
departing system...likely to see several 20s for lows and the 
first hard freeze for portions of the County Warning Area. 


&& 


Aviation... 
areas of fog and IFR ceilings should remain in place today with 
flight conditions deteriorating this afternoon and tonight. Rain and 
isolated thunderstorms will develop this afternoon through tonight 
as the remnants of tropical cyclone Norbert track northeast across 
old Mexico today and through the Central Plains tonight. Thus 
moisture will rapidly increase this afternoon and tonight ahead of 
an occluded front which will push slowly east overnight tonight 
producing widespread rain and IFR. Ceilings may lift to ovc012 today 
but decrease this afternoon once the rain commences. 


&& 


Lbf watches/warnings/advisories...none. 
&& 


$$ 


Masek/cdc