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Area forecast discussion 
National Weather Service North Platte NE 
301 PM CST Tuesday Jan 7 2009 


..forecast challenge is temperatures... 


Discussion... 


Near term...tonight through Saturday...three main forecasting 
challenges noted in the near term. The first is precipitation 
chances tonight...temperatures on Thursday and temperatures and 
frontal timing on Friday. 


Turning to tonight...high pressure over the eastern Dakotas at this time...will 
move slowly east into the middle Missouri Valley overnight. As this 
feature moves southeast...a warm front will begin to lift across the 
County Warning Area later tonight. Lift associated with the front and weak 
isentropic lift in the 650 to 700 mb range still enough to warrant 
low probability of precipitation in the north tonight. Further support for probability of precipitation has arisen 
from the fact the lower levels have moistened today with the ongoing 
precipitation across the area. 


The warm front will lift into northestern Nebraska tomorrow progressing 
just east of the County Warning Area by late in the day. Should be the warmest day 
of the period for most of the forecast area...as decent mixing 
potential exists west of a Springview to Burwell line. East of this 
line BUFKIT and forecast soundings are indicating a fairly significant 
inversion with a depth of 50 to 100 mb across northern Holt and Boyd 
counties. As a result...have opted for much cooler maximum temperatures in 
these areas. Across southwestern Nebraska...highs should reach the lower 
60s. 


Warmup will be brief though...as a shot of Arctic air will will dive 
south across western and north central Nebraska on Friday. Frontal 
timing remains fairly consistent around midday so early maximum temperatures 
are expected with steady to falling afternoon temperatures. Have modified 
temperature grids accordingly to account for this trend. Will need to 
address winds further for Friday...as an advisory may be needed 
based on the strong cold air advection behind the front and corresponding 850 mb 
winds. 


Long term...Saturday night through Wednesday...main forecasting 
issue in the extended deals with temperatures and the magnitude of 
Arctic air which backs into the forecast area early next week. 
Overall pattern will amplify early next week as a ridge builds 
across the Pacific coast...extending into southwestern Canada. A downstream 
trough will develop across the eastern half of the Continental U.S....placing the 
upper Midwest...Ohio Valley and northeast in the deep freeze next 
week. Further west...temperatures are more problematic...as Nebraska 
will be in the transition zone between Arctic air to the east and 
milder air further west. Though the models have a decent handle on 
the large scale features...as is the usual case...the Arctic front 
is not well defined...and this will be key to 
temperatures...particularly during the Monday to Wednesday time 
frame. The latest GFS has a higher degree of amplification in the 
pattern and pushes the colder air in and out quicker than the lower 
amplitude Euro solution...which seems problematic. Both models hint 
at a slight warmup in the southwest on Tuesday...followed by a 
weaker reinforcing shot of cold air on Wednesday. Kept the forecast 
dry during the period...however wouldn't be surprised to see some 
flurries along the Arctic front. Since its location is still fairly 
uncertain at this time...will forgo mention of flurries at this time. 


&& 


Aviation... 
VFR conditions in place across majority of County Warning Area due to minimal 
precipitation coverage this afternoon. Main area of prolonged light 
quantitative precipitation forecast has been in a narrow band across the central Panhandle to near 
Oga where MVFR ceilings are in place. Some convective nature to returns 
and expect some areas may be receiving light rainfall...otherwise 
most likely sprinkles and unlimited visibilities. At this time expect MVFR 
conditions to continue mainly across western Nebraska and areas north 
of Highway 2 where lower ceilings advecting in from S.Dakota along with 
light snow/flurries. Surface front looks to hang north to south across 
County Warning Area tonight and slowly drift into northeast Nebraska on Thursday. Low 
clouds and flurries possible near and along the front and IFR/MVFR 
conditions are expected. 


&& 




Lbf watches/warnings/advisories...none 


$$ 


Short and long term...buttler 
aviation...Phillips