Weather

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fxus63 kgrb 101957 
afdgrb 


Area forecast discussion 
National Weather Service Green Bay WI 
257 PM CDT Friday Oct 10 2008 


Synopsis...upper flow across noam split...with highly amplified southern 
stream dominating the Continental U.S. And much flatter northern stream way north in 
Canada. Southern stream trough will remain over the intermountain west 
though the weekend while ridge holds just east of the area. The southern 
stream will become slowly progressive next weak as the western trough starts 
to head eastward...with the flow consolidating into a much lower 
amplitude flow by late in the weak. 


Temperatures will start out way above normal under the strong southwesterly upper 
flow...then trend back toward normal next weak as the weakening upper 
trough heads eastward across the area. Since the trough will be weakening... 
Don/T expect an abrupt flip-flop to below normal temperatures. Would expect 
a widespread sig precipitation event once the upper support reaches the region. 
That will likely happen early next weak...though exact timing still 
uncertain. 
&& 


Short term...tngt/Sat. Southerly flow will dominate the area. Gradient 
still does not look tight enough to keep winds up all night. So 
assuming we lose the winds...dewpoints low enough and nights long 
enough to have a decent drop in temperatures. Went a bit below guidance most 
areas. Went close to guidance most areas Sat...but a bit above across the 
northwest part of the forecast area as that area should recover well with 
pretty mild 850 mb temperatures for this time of yr. 


Long term...Saturday night through Friday 
first shortwave swings across northwest Wisconsin Saturday 
night. This feature may trigger shower activity late Saturday 
afternoon over the far northwest and Saturday night across the 
north third of the forecast area. Have included rain chances 
over the northwest third with the highest chances over Oneida 
and Vilas counties. 


Sunday should be a fairly warm day and possibly the last 80 degree 
day of the year. 850mb temperatures warm to +13c at 850mb on the 
European model (ecmwf)/WRF with GFS a tad bit cooler. BUFKIT soundings off the GFS/WRF 
suggest we should mix close to 850mb...so have have bumped up 
high temperatures on Sunday...with Green Bay and the Fox Valley 
into the upper 70s. With a little Luck...a few locations 
across northeast Wisconsin could touch the 80 degree mark. 
Continued small chances for showers and isolated thunderstorms 
Sunday over the far northwest. 


Cold front a little slower moving into the region on Monday. 
Maximum temperatures will be tricky over the east. If there is a 
little more sun...temperatures could again warm well into the 
70s. Taken a conservative approach on high temperatures and 
bumped up temperatures over the east. Later shifts will need to 
monitor trends if front is even slower than forecast. 


Major differences arise Tuesday into Wednesday between the GFS and 
European model (ecmwf)...and between the different runs of the models as well. The 
GFS brings the front through Tuesday with dry conditions expected 
Tuesday night and Wednesday. The European model (ecmwf) and Canadian bring the front 
into the area Tuesday...with another wave moving up the front Tuesday 
night into Wednesday. The European model (ecmwf) is different on how it handles the 
second feature between the 12z run this morning and the 00z run 
last night. The new European model (ecmwf) this morning has a break in the action 
before the 2nd wave arrives Tuesday night into Wednesday. It also 
appears to be a little slower than the 00z run last night with this 
feature. If you look at the 12z WRF model...it appears that another 
shortwave will be rounding the base of the trough and will head northeast 
towards the Great Lakes more than likely on Tuesday. Also 
concerned that the GFS is breaking down the ridge too quickly 
between Monday and Tuesday. Have trended toward the 00z European model (ecmwf)/12z 
Canadian model for now. Later shifts will need to fine tune the 
timing of the evolutions of the 2nd feature. 
&& 


Aviation...VFR conditions expected. Main question was whether or 
not to include low level wind shear for tonight. NAM forecast soundings suggested including 
it. But looks like more of a broad southerly flow at 850 mb as opposed 
to a more directed southwesterly low level jet. Held off adding low level wind shear with the 18z 
issuance to allow the next shift to take another look. 
&& 


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


$$ 
Skowronski/eckberg