659 
fxus63 kgrb 060840 
afdgrb 


Area forecast discussion 
National Weather Service Green Bay WI 
340 am CDT sun Jul 6 2008 


Synopsis...main band of westerlies across noam currently rather 
flat...with mean ridge posn in the west and trough posn in the east. Expect 
a brief and modest amplification of the flow mid-wk. The stage then 
seems to be set for a reversal of the pattern by next weekend...with 
upper ridge shiftg into eastern noam. 


There will probably be a couple rounds to convection early in the 
forecast period...some of which could lead to heavy rainfall. A couple 
days of dry weather then expected as surface ridge slides eastward across the area 
in the northwesterly upper flow resulting from the brief amplification. Precipitation 
chances by late in the weak/next weekend will depend on whether upper ridge 
builds in strongly enough to shove frontal boundary well north or the 
area...or whether it lingers across the region. Temperatures will start out 
slightly above normal...cool back close to normal for mid-wk. Could 
be in for a period of very warm and humid weather starting late this 
weak and into the upcoming weekend. 
&& 


Short term...tda/tngt/Mon. Not much change from previous forecast. The air across 
the forecast area still quite dry...but moisture was returning northward 
through the plains. Several surface dewpoints near 70 out near the Red 
River. Humidities should increase across the northwest part of the forecast area as 
the front approaches...but will probably take longer to increase in the 
southeast as low-level flow will continue to be out of the dry departing high. 
00z soundings hint that capping may also be an issue. So perfer to 
keep probability of precipitation out closer to the front...and keep east-c WI dry today. Storm Prediction Center 
has removed most of the forecast area from the categorical slight risk on 
day 1. Hard to argue with that. Some of the storms across the north 
could reach severe levels...but limited shear and high freezing 
levels/wet-bulb zero heights suggest threat will be limited. Will 
attempt to convey that in the severe weather potential statement. 


Frontal boundary will sag into the area tonight. There will probably be an 
mesoscale convective system along the front. But best convergence at the nose of low level jet looks 
to be pretty far to the S...so again risk of severe in the forecast area 
somewhat limited. 


Models suggesting front will be across the area Monday as stronger southwesterly 850 
mb flow shifts northeastward in response to upper trough approaching from the northern 
plains. Do have to wonder...however...whether outflow from tngts 
convection will be located S of the forecast area and provide the primary 
focus for convection on Monday. Given these uncertainties...stuck 
with chance probability of precipitation for now. But given precipitable waters  forecast to increase above 2 inches 
across the area...heavy rain is possible. Will have heavy rain mentioned 
in the severe weather potential statement. May issue also esf later this morning after reviewing a 
few more things. 


Long term...Monday night through next Saturday 
frontal boundary expected to be across central or portions of 
southern Wisconsin early Monday evening. Models have various 
solutions on how to handle 850mb low level jet than will crank 
up to 40 to 45 knots Monday night. The WRF solution is further 
west with nose of low level jet to the west of the forecast 
area while GFS is pointing the nose of the low level jet across 
eastern portions of the forecast area Monday evening. Current 
belief is that complex of storms will form over or just to the 
west of the forecast area and then move across the area during 
the evening into the overnight hours. A few of the storms could 
produce damaging winds. 


For Tuesday morning...atmosphere will have been worked over 
by previous nights complex of storms. Have lowered rain 
chances during the morning until clouds can break and 
temperatures reach the convective temperatures during the 
afternoon. Plenty of low level moisture...so any thunderstorms 
that do develop could produce gusty winds and brief heavy rain. 
It will remain humid until secondary front sweeps across the 
area Tuesday night. Dew points should gradually fall during the 
day Wednesday as weak Canadian high pressure builds into the 
state. A few isolated showers are still possible over the north 
Wednesday afternoon due to daytime heating. 


Although GFS remains dry for Thursday night...steep middle level 
lapse rates and return flow could produce some showers and isolated 
thunderstorms Thursday evening. If timing of this feature continues 
to hold true...later shifts may be able to remove mention of 
rain after midnight. 
&& 


Aviation...chance of thunderstorms and rain will spread eastward/southeastward during the day. Will make 
issuance time decision on when/if to explicity carry thunderstorms and rain in the 
tafs. 
&& 


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


$$ 
Skowronski/eckberg