916 
fxus63 kgrb 212035 
afdgrb 


Area forecast discussion 
National Weather Service Green Bay WI 
235 PM CST Friday Nov 21 2008 


Short term...tonight/Saturday. Initial challenge this afternoon 
into tonight is cloud trends and then resultant overnight low 
temperatures. At 19z...lake clouds from Lake Superior were mainly north 
of a line from pkf to rhi to grb and were gradually eroding 
northward. Patch of clouds in the 800 mb baroclinic zone over western WI 
generated some clouds earlier but approaching ridge and drier air 
eroding these clouds. With the exception of some lake clouds still 
hugging the WI/Michigan border this evening...clear skies anticipated 
tonight. 


Friday morning min temperatures in the ridge axis to the west were in 
the single digits with some some single digits below zero north 
over the Dakotas...and this region was struggling to rise this 
afternoon. This ridge passes over tonight so expect similar 
results over the forecast area with some sub zero readings north 
with a fresh snow cover. 


For Saturday...continued challenging maximum temperature due to increasing 
clouds on the periphery of the weakening short wave passing to 
the south. Models lift maximum temperatures in the lower to middle 30s into the 
forecast area. Will temper this due to cold start anticipated 
followed by increasing clouds to limit diurnal warming. Note that 
temperatures north of the feature were in the 20s. The only exception 
could be along the Lakeshore where the winds may turn southeasterly and 
could allow lake air and perhaps Clouds/Lake flurries to work in. 
But for that to happen the synoptic flow will need to overcome the 
convergent flow over the lake in this cold airmass. 


Long term...Sat night through next Friday. Main forecast concerns for the end 
of the weekend/early next week will be the potential of freezing 
drizzle and temperatures. Models thereafter are in decent agreement with 
the mean flow remaining highly amplified next week. One pronounced 
system will be moving from the Great Lakes to the NE Continental U.S....while two 
Pacific systems drop southeast into the SW and then southern U.S. Later in the 
week. For NE WI...expect relatively quiet conditions (aft mon) 
with temperatures at or slightly above normal for late Nov. 


Persistent S-SW winds will continue to bring warmer...more moist air 
across NE WI Sat night. Isen upglide/lift is advertised by the models 
and despite a dry middle-layer of the atmosphere...some patchy freezing 
drizzle is possible especially across northern WI where more of a stratus deck to 
be prevalent. Previous forecast already had the north taken care of and 
only removed the flurry chances. As for central and east-central WI...there 
is some doubt as to the extent of the freezing drizzle and prefer 
to only go with increasing clouds for now. Due to the warm air advection and 
thickening clouds...temperatures should not drop much if at all. Anticipate 
readings to bottom out during the evening and then hold steady or 
even slowly rise a couple of degrees toward daybreak. 


Possibility of freezing drizzle or drizzle continues into Sunday 
morning as warm air advection prevails across the area. By Sunday afternoon...the 
approach of a cold front into western WI may bring enough lift/mid-lvl moisture 
to bring a minimal chance of either rain or snow to NE WI as temperatures 
rise into the middle 30s to lower 40s. The cold front then sweeps across the 
rest of WI Sunday night bringing mainly light snow to the region. Have 
included a chance of mixed precipitation for east-central WI early in the evening 
where temperatures may initially be warm enough to support some liquid. 
Heavier quantitative precipitation forecast may slide just to our south where better forcing/lift 
to Colorado-exist near an eastward moving shortwave. Would not be surprised to see 
accumulations approach an inch by 12z Monday over parts of central and 
east-central WI. 


As the cold front continues to pull away from the region on Monday...the closed 
upper low will settle over WI. Expect to see some snow shower activity 
associated with the upper low...but since better forcing to pass to 
our south...do not see much in the way of addl accumulations. An 
exception could be north-central WI where winds veer more northwest through the 
day. Even though 800 mb temperatures are not that cold (around -9c)...there 
could be enough enhancment to add an inch of snow to the totals. 
This system becomes vertically stacked over the eastern Great Lakes Monday 
night and this keeps a cyclonic flow over the eastern half of WI. Various 
pieces of shortwave energy rotating around the upper low will bring 
spotty snow showers to mainly northern and eastern sections of the forecast 
area...while light lake effect snow persists across north-central WI. By 
Tuesday...the system is expected to pull far enough east such that most 
if not all the snow showers would come to an end. Even the lake effect 
will fizzle out as winds begin to back ahead of an approaching rdge of 
hi pressure. 


The ridge to then move into the western Great Lakes region Tuesday night and reside 
over the area through Wednesday. Quiet weather conditions to prevail with 
temperatures near seasonal norms. This hi pressure to remain in control of 
our weather through Thanksgiving day...thus providing for favorable 
travel conditions for the Holiday. There are some qstns as to the 
depth/strength of a NE Continental U.S. System as well as the forward speed of 
a system pushing across the Southern Plains toward the end of next week. 
The southern system should remain far enough to our south and not be a 
factor to NE WI. The strength of the NE Continental U.S. Would mainly impact 
wind speed and direction and with this much uncertainty involved...have 
leaned toward HPC for now. 
&& 


Aviation...patchy MVFR ceilings will continue to around 02z far 
north otherwise VFR conditions will prevail across the area. 
&& 


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


$$ 
Tdh/Alaska