566 
fxus63 kgrb 100957 
afdgrb 


Area forecast discussion 
National Weather Service Green Bay WI 
357 am CST Wednesday Mar 10 2010 


Short term...today through Thursday. Timing of bands of rain 
spiraling around upper low and amount of fog are the main 
challenges for this forecast. Looked around at different 
parameters and found that GFS 700mb Omega field has done very 
nicely with the rain for the last 24 hours and will use that as 
guidance for timing of the precipitation. This would bring the 
best chance of rain through the southwest half of the forecast 
area this morning and in the northeast half in the afternoon. 
Forcing for steady rain departs tonight and there shouldn/T be 
much more than some drizzle tonight and early Thursday. There is 
some support for rain Thursday afternoon. 


Highs today and Thursday will be sensitive to cloud cover... and 
there should be the thinnest clouds in the north. Very warm air in 
just a couple thousand feet above the ground so any breaks in the 
clouds at all will cause temperatures to rise quickly. But 
generally assume clouds will rule most of the next two days. 


Dense fog possible tonight and early Thursday as middle and upper level 
moisture leaves and allows some cooling. Wet ground and dewpoints 
above freezing argue for some dense fog and we may need an 
advisory at some point for tonight. 


Long term...Thursday night through Tuesday 
upper low will continue to linger across the central United States 
before gradually shifting to the East Coast by Sunday. First shortwave 
energy will pivot around the upper low...bringing more rain to the 
area Thursday night. Have highest chances across the south and did 
add drizzle over the north due to the lack of middle level moisture. 
The shortwave energy will continue to pivot around the upper low 
on Friday. Will continue with likely chances for rain on Friday. 
Still need to watch for the potential for an isolated thunderstorm 
as middle level lapse rates are between 6.5 and 7.5 c/km Thursday night 
into Friday. 


The new wrinkle in the forecast tonight will occur on Saturday. 
There will be a lull in the precipitation Friday night...but the 
new GFS/European model (ecmwf) pivot system northwest and would bring another good 
chance of rain Saturday into Saturday night. Have increased rain 
chances for both periods...but did not go likely at this point since 
this is new outcome to the model solutions. Early next week should 
be dry and seasonable. 
&& 


Aviation...generally MVFR ceilings and visibilities expected today with 
several hours of IFR as an area of rain moves from southwest to 
northeast. Expect dense fog and low clouds to form in most places 
tonight with IFR everywhere and LIFR possible. 
&& 


Marine...dense fog possible again tonight and early Thursday. 
&& 


Hydrology...the gradual snow melt will continue for the remainder 
of the week. There will be chance of rain or drizzle through 
Saturday night. At this time...the best chances of measurable 
rainfall appear to be today with up to a quarter inch of rain 
possible...and then again toward Thursday night and possibly again 
Saturday. Rainfall from Thursday night through Saturday could be 
up to an inch in some spots. There will be a good separation of 
time between these events to limit the flooding concerns...unless 
ice jams form on area rivers. 
&& 


Grb watches/warnings/advisories... 
none. 
&& 


$$ 
Rdm/eckberg