146 
fxus63 klbf 230927 aaa 
afdlbf 


Area forecast discussion 
National Weather Service North Platte NE 
327 am CST Monday Nov 23 2009 


Discussion... 
a few things are disconcerning this morning with respect to 
precipitation chances today...the extremely dry 00z klbf radiosonde observation and 
the lack of stronger returns upstream and limited metar sites 
reporting snowfall. Main area of precipitation at this time seems to limited to 
northern Colorado rockies...though Steamboat is reporting 1/4sm and heavy 
snow. Farther north in Wyoming snow had ended at most reporting stations 
at this time with 1/2 to 1 inch of new snowfall in local reports. 
Orographics of northern Colorado enhanced by main energy rotating 
through base of trough across much of the central and northern 
rockies...and by favored region of cyclonic jet maximum aloft. Much of 
the model data has come in to better agreement this morning in 
closing of the middle level low in vicinity of SW Nebraska/northwest Kansas by late this 
afternoon as system ejects onto plains and the jet begins to reform 
on downstream side of the circulation. Through the next 12 hours by 
12z Tuesday majority of the models cluster the low...now becoming more 
stacked...over far northeast Kansas. NAM and UKMET are slight 
outliers by this time...and Euro has been most consistent the past 
few days of runs. Bulk of the solutions take precipitation/moisture out 
of Colorado/Wyoming rockies and swing it through northeast Colorado into SW 
Nebraska in deformation zone of closing middle level low today...then 
precipitation should move off to the southeast through the early 
morning hours. Pattern will remain fairly progressive as next system 
already approaching the b.C. West Coast and will be dropping through 
northern plains and lower MO valley Tuesday night into Wednesday. With 
lack of significant cold air leading to questionable p-type/limited 
snow potential and progressive nature of system see no reason to 
issue any type of headlines with 2 inches of snow or less...much 
less...expected. Moisture trans vects seem to indicate that wcb is 
not tapped until system is more vertically stacked over ncentral 
Kansas late tonight and any trowal potential looks well east of this 
County Warning Area. Also concerning is ptype today with most 00z models not 
handling the strong radiational cooling across central and western 
Nebraska overnight. BUFKIT/plumes indicated rain this morning but strong 
low level inversion would hint at freezing rain with warm temperatures aloft. 
However think dry low layers will prevent most precipitation from reaching 
ground through middle morning as lift is fairly weak and will leave 
snow as main ptype this morning in the far west. Thickness values 
and icons support snow over much of th west through the afternoon 
with fairly good lift through the dendritic layer after 18z in the 
southwest probably enough to overcome dry low levels and provide 
cooling for snow as well. Soundings at this time also do not show prolonged 
or evident low level saturated isothermal layer so think snow should 
remain fairly light with temperatures in the middle to upper 30s and surface 
wet bulbs above freezing also hampering accumulations. And lastly 
fairly breezy northwest wind should not be real favorable for heavy snow as 
well. System should be into eastern plains by midnight with bulk of 
precipitation coming to an end and short wave ridge builds in for Wednesday ahead of 
clipper dropping into Dakotas. Westerly downslope should help bring 
temperatures back up to near normal in the middle to upper 40s and used blend 
of guidance. Expect clipper to come through dry though few flurries 
possible downstream from hills across northwest County Warning Area with jet maximum aloft as 
well. Cold air advection and breezy conditions behind front on Wednesday will bring 
bluster day for the north central. Upper ridge will amplify in west 
by Thursday...but keep cooler air in eastern County Warning Area for Thanksgiving 
will warmup will begin in west and continue eastward for Friday with 
dry weather expected. 


&& 


Aviation... 
the bulk of aviation forecast concerns will lie at the klbf terminal 
today and tonight as an upper level low lifts east along the Kansas 
and Nebraska border. Through middle morning...LIFR ceilings and 
visibilities are likely at the klbf terminal as low level 
moisture...advects westward from central Nebraska. This low level 
moisture is expected to remain south and east of the kvtn terminal 
this morning...so only middle to high level cloudiness is expected at this time 
at that location. LIFR ceilings are expected to lift by late 
morning...and be replaced by overcast middle to high level cloudiness. 
Northerly winds will increase behind a frontal boundary...which is 
expected to pass through the klbf and kvtn terminals during the 
16-20z time frame. Light rain...and or snow...will develop later 
this afternoon and this evening at the klbf terminal in association 
with the before mentioned upper level low. Based on the latest 
guidance and model trends...21z to 03z will see the greatest threat 
for precipitation with visibilities briefly down to a mile and 
ceilings ranging from 1000 to 2000 feet above ground level. Flight conds will improve 
after 06z tonight...as the upper level low tracks into northestern Kansas. 


&& 


Lbf watches/warnings/advisories...none. 


&& 


$$ 


13/clb