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fxus63 kfgf 062039 
afdfgf 


Area forecast discussion 
National Weather Service Grand Forks ND 
339 PM CDT Sat Sep 6 2008 


Short term... 
main forecast challenge is precipitation. When looking at the latest 
surface analysis...an area of low pressure is centered in NE mb with 
a weak cold front that extends east mb to along a Rox to dtl line. When 
comparing the models...the models remain in pretty good agreement 
for the short term...so ended up using model compromise for the 
forecast. Blended the GFS and NAM for probability of precipitation as they differ on what 
part of the County warning forecast area will be most affected by tonight's trough passage. As 
far as temperatures...with adjmavbc still doing pretty well...used it as 
a starting point and then adjusted from there. 


Kmvx currently shows two areas of convection...one in the east and 
another in the west. East precipitation is ahead and along of surface front and west 
precipitation is associated with push of next wave as seen on WV in 
association with the 500mb trough. 500mb trough is expected move through 
the North Plains tonight and sun...so kept precipitation in the forecast. Models 
do keep showalters at or below zero over parts of the area until 06z 
tonight. With occasional lightning found in storms that have developed...kept 
thunder mention in for this evening and transitioned to rain showers after 
06z. 


For Sun night into Tuesday...surface high pressure dominates the 
weather...so kept the forecast dry. There is a another 500mb 
trough that moves through on Monday night...but with minimal upward vertical velocity at 
700mb...850mb q-vector divergence indicated and also stability 
indices above zero...believe that will only see clouds from this 
trough passage at this time. 


Long term (tue through sat)... 
medium-range models continue to differ with strength and timing 
of next Pacific short wave. 00 UTC Canadian and 12 UTC European model (ecmwf) 
solutions briefly cut-off weak 500 hpa low over the central 
rockies Thursday morning before ejecting primary energy eastward...whereas 
GFS is stronger and much more progressive. Current forecast 
primarily follows HPC guidance...which favored faster GFS. Model 
consensus shows best chance for measurable precipitation Wednesday and 
Thursday out ahead of primary middle-level wave...although this time 
frame may be pushed later or extended if slower Canadian/European model (ecmwf) 
solutions become reality. Either way...temperatures will continue 
to trend below seasonal normals through next week. 


&& 


Aviation... 
widely scattered showers this afternoon will increase in coverage from 
west to east after 00 UTC tonight as a weak cold front moves eastward 
across east ND and into northwest Minnesota. Best chance for measurable rain at 
any taf site will likely hold off until after 03 UTC...continuing 
through Sun morning. Cannot rule out an isolated lightning 
strike...but certainty too low to mention in current tafs. With 
showers...expect VFR ceilings to gradually lower below 3000 feet. 
Light west-SW surface wind will shift to the northwest later tonight after 
frontal passage. 


&& 


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


$$ 
Ng/Rogers