634 
fxus63 klbf 161924 
afdlbf 


Area forecast discussion 
National Weather Service North Platte NE 
224 PM CDT Tuesday Mar 16 2010 


Discussion... 
western U.S. Ridge has amplified across Nebraska quite nicely this 
afternoon. Very strong subsidence beneath the ridge has produced 
tremendous drying and adiabatic warming. The ridge is forecast to hold 
through Wednesday and then begin to flatten on Thursday. Highs in 
the 60s should rule many areas Wednesday. Highs Thursday are 
questionable as low pressure deepens across the western High Plains 
and winds will become easterly. Mosbc guidance suggested high mostly 
in the 50s with upper 40s Northwest. 


Arctic high pressure currently centered over the North Slope of Alaska 
will be dropping through the forecast area Friday. Temperatures are expected 
to remain steady or fall in the lower 30s. A coupled 250mb jet 
disturbance is forecast to traverse the forecast area early Friday morning 
and during the day producing rain changing to snow. The combination 
of strong midlevel frontogenesis and steepening lapse rates aloft 
is expected to produce a fairly robust area of precipitation. 


The NAM was used for the forecast Friday. Quantitative precipitation forecast was limited to 0.30 inches 
in 6 hours with an 8 to 1 ratio. This produced 3 to 5 inches of snow 
which was slightly less than the HPC forecast of 3 to 8 centered over 
northwest Nebraska. Blended surface wind guidance and 500m above ground level winds suggested 
25 to 30 miles per hour winds with blowing snow developing Friday. GFS and NAM 
model soundings indicated a few hours of heavy snow developing in 
some areas. 


Later forecasts may include a Winter Storm Watch for a few northwest 
counties where temperatures are expected to remain below freezing throughout 
the day Friday. Otherwise it looks like a wet snow and strong wind 
event requiring a Winter Weather Advisory. Stay tuned. 


This Arctic high should build directly through the forecast area Saturday 
limiting highs to the upper 20s to near 30. The high will move 
quickly south Sunday. Another Arctic high is forecast to slice through 
the Missouri Basin Monday with low pressure developing rapidly across 
the Dakotas Tuesday. Highs Tuesday and Wednesday are highly 
uncertain. The 12z European model (ecmwf) brings another Arctic high through the 
Central Plains Tuesday. The GFS and gefs maintain a more zonal flow 
aloft with warmer Pacific high pressure moving into the Central 
Plains. 


&& 


Aviation... 
VFR conditions over western Nebraska will continue into tomorrow as 
ridge of high pressure expands east from The Rockies. North central 
Nebraska...will remain in MVFR clouds into the evening and overnight 
hours. The western edge may erode some...but the bulk of the clouds 
will not clear out until tomorrow. 


&& 


Lbf watches/warnings/advisories...none. 


&& 


$$ 


Cdc/mm