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Area forecast discussion 
National Weather Service Grand Forks ND 
252 PM CST Sat Nov 21 2009 


Short term... 
the main forecast challenge is precipitation. When looking at the latest 
surface analysis...an area of low pressure is centered in east 
Saskatchewan...with a trough extending along through west ND. When looking at 
the models...they remain similar initially...then diverge with the 
European model (ecmwf) the slowest and the GFS the most progressive. Thus...ended 
up using a model blend for pop forecast and pretty much stuck with 
the adjmav for temperatures. 


The windy conditions will diminish with loss of insolation this 
evening as the trough passes and winds turn to the SW-west by Sun 
morning. Otherwise...only a few high clouds are anticipated with 
this trough. This surface trough is expected to be east of the area by Sun 
afternoon as a 500mb trough approaches...keeping the best lift and 
moisture east of the area...as well as the potential for any precipitation. 


On Sun night...a surface low develops in the plains as a 500mb low 
starts moving out of The Rockies. Models are still having trouble 
with the timing and track of this system. The overall theme for 
forecasting for this storm is that the atmospheric profiles stay 
warmer longer than previously thought...so now should see more 
rain for the areas that do get precipitation than snow. Also...the areas 
with the highest potential for seeing any precipitation area southeast ND...wc and 
northwest Minnesota. Thus...started cutting back and removing probability of precipitation for parts of 
NE ND for Sun night into Tuesday. 


Long term...(tue night to sat) 
although model run to run consistency has been rather poor the 
past several days...it appears the 12 UTC GFS/dgex/ECMWF have 
finally locked onto the position of an upper low to impact the 
upper Midwest mid-week. At 00 UTC Wednesday...all three models show 
upper low to be centered across east Iowa...weakening thereafter as 
it moves NE into the Great Lakes region. 


Behind this departing system...another piece of short-wave energy 
drops S across the Dakotas Tuesday night and Wednesday. Given northwest flow 
aloft...moisture will be less with this second wave...so kept probability of precipitation 
at 20-30 percent for now. However...any precipitation that does fall during 
this time looks to be mostly snow as 850 hpa temperatures drop to 
-6 to -8 c. Daytime highs Wednesday and Thanksgiving day will be in the 
low to middle 30s... closer to seasonal normals...but noticeably 
cooler compared to our recent warm streak. 


The latter half of the week into next weekend looks dry...but cool 
as an upper ridge/surface high pressure move into the region. 


&& 


Aviation... 
primary aviation impact concerns strong S winds with gusts to 30 
kts this afternoon and early evening. As sun sets...surface should 
decouple somewhat from much stronger winds aloft (40 to 50 kts at 
2000 to 3000 ft)...but do not expect surface flow to become calm. 
Overall...winds will decrease and gradually shift to the SW overnight 
with passage of a weak boundary. Expect periods of cirrus at all 
air fields...although some low VFR ceilings may approach kbji by 
midnight. Did not include this in current taf...but will need to 
watch for this as the evening progresses. 


&& 


Fgf watches/warnings/advisories... 
ND...none. 
Minnesota...none. 
&& 


$$ 
Ng/Rogers