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fxus63 klbf 211910 
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Area forecast discussion 
National Weather Service North Platte NE 
210 PM CDT sun Mar 21 2010 


Synopsis... 
analysis of the 18z surface data showed a warm front in the Lee 
side trough across the central and northern High Plains. There were 
also low pressure systems centered in southwest Saskatchewan and 
southeast Alberta and another off the coast of northwest British 
Columbia. A front was stretched across southern Canada from southern 
Manitoba through southern Saskatchewan and southern Alberta to the 
low off the coast of British Columbia. Surface dewpoints were 10 to 
20 over central and western Nebraska in the upper levels...the 6.7 
micron water vapor imagery showed moisture streaming across the 
northern rockies and southeastward across western Nebraska. The 
visible imagery showed high cloudiness associated with that upper 
moisture. 
&& 


Short/medium range...tonight through Thursday. 
Temperatures are the forecast challenge for tonight and Monday. 
With afternoon dewpoints 10-20f...it appears that lows tonight could 
fall into the teens again tonight. However...the high clouds 
streaming across the area and light west to southwest wind may help 
keep temperatures up. For lows tonight...we believe that 20 to 25 
should hold in the west and 25 to 30 in north central Nebraska. It 
is possible that the North Platte River Valley from Brady to 
Sutherland may have temperatures in the upper teens...but for now we 
will keep them around 20. Highs Monday will be well above normal... 
ranging from lower 60s in north central Nebraska to around 70 in the 
extreme southwest. 
After Monday...a middle-altitude trough pivots through Nebraska 
Monday night and Tuesday and...with it...a fairly strong front. 
System relative 295-300k isentropic lift and decent frontogenesis 
will give plenty of lift. However...with mixing ratio on those 
surfaces 3-4g/kg...moisture is available. In fact... the 
precipitable water is expected to be at or above 0.45 inch which is 
in the top 25 percent for the season. Add in elevated instability 
(lifted indices 0c to -1c) and there is even a possibility of 
isolated thunderstorms. After that...the front stalls across Kansas 
and the 295k surface shows some isentropic lift. Until 00z Wednesday 
(tuesday evening)...temperatures in the lowest 2km above ground level are right at 
0c. Therefore...I would expect rain or a mix to be favored. After 
00z...the 0-2km temperatures become more favorable for snow. On 
Wednesday afternoon...the low level temperatures support rain or a 
mix again. The net result is that snow may accumulate during the 
night...but will probably melt or be wash away during the day 
Wednesday. 
Temperatures Tuesday will be 20-25f colder than those Monday. 
Then...though temperatures will be warmer Wednesday through 
Sunday...they will continue to be near normal or a little below. 


Extended...Friday through Sunday. 
By late Friday...return flow from the Texas Gulf Coast will 
bring moisture northward and onto the northern plains as the active 
pattern continues. A combination of system-relative upglide and 
elevated 2d-frontogenesis will generate lift over much of western 
and north central Nebraska Friday night and Saturday. As the system 
GOES off to the east...the lift will go with it and precipitation 
will taper off Saturday night or Sunday. There is some difference 
between the 00z European model (ecmwf) and the 00z gfslr with this system...I.E. The 
gfslr being about twelve hours faster with the passage of the system 
and a little colder. The slower/warmer solution is supported by the 
00z Gem as far out as it GOES (sat/00z)...and the 00z naefs supports 
the slower and warmer solutions as well. Otherwise...the gfslr and 
European model (ecmwf) are showing similar tracks and dynamics. Therefore...some 
mention of precipitation is warranted Saturday with the greatest 
uncertainty being rain versus snow and the time of onset/end. 
Leaning toward the warmer solutions...we will use a mix of rain 
and/or snow for the weather. 
&& 


Aviation... 
extremely dry middle layers of the atmosphere will keep VFR 
conditions in place through the next 24 hours with only High Deck of 
cirrus moving ovhd. Light and variable winds overnight should give 
way to westerly winds on Tuesday...with winds remaining fairly light 
aloft...low level wind shear also not anticipated. 
&& 


Fire weather... 
fire weather concerns will be on the increase on Monday as 
favorable pattern sets up across western Nebraska. Upper ridge will 
be flattening over the High Plains overnight...pushing a surface 
trough into western Nebraska during the afternoon. The system 
responsible for squashing the ridge will move into Dakotas on Monday 
afternoon pushing a cold front through Nebraska during the evening 
and overnight hours. These two boundaries will need to be watched 
for wind shifts in burning is planned. Dew points/relative humidity 
should drop behind surface trough tomorrow...helping to push temperatures up well 
into the 60s in western Nebraska and the sandhills. At this time looks like 
critical levels will not be reached with winds/gusts remaining below 
25 miles per hour. Smoke dispersal should increase however with better mixing 
and an increase in low level winds. 
&& 


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


$$ 
Short/medium range and extended...Springer 
aviation...13