603 
fxus63 kmkx 060855 
afdmkx 


Area forecast discussion 
National Weather Service Milwaukee/Sullivan WI 
355 am CDT sun Jul 6 2008 


Forecast focus on thunderstorm chances near term period. 


Latest water vapor imagery indicated polar jet stream over the 
Pacific northwest into southern Canada. Shortwave trough over 
Manitoba Canada moving eastward into Ontario Canada. A weak upper 
low with broad cyclonic flow was located over the southeastern 
portions of the country. At the surface...cold front over the 
eastern Dakotas combining with shortwave trough to produce 
thunderstorms. 


Short term...today through Tuesday... 


Tricky precipitation forecast for this period. Cold front expected 
to move into Wisconsin by 00z Monday...oriented from northeast to 
west central Wisconsin. This feature should bring showers and 
thunderstorms northwest of the forecast area. Kept the probability of precipitation only 
in the south central counties for this afternoon...in case 25 knot 
low level jet tries to develop elevated storms. 


Better chances exist tonight through Tuesday...as frontal boundary 
stalls across the region. The NAM has the low level jet pointing 
into the forecast area this evening...before focusing further 
south later tonight. It develops an mesoscale convective system in northern Iowa by 00z 
Monday...then moves it southeast through eastern Iowa into 
Illinois. The European model (ecmwf) supported this scenario. All models indicated 
that a more humid airmass should move into the region. Under the 
weak warm air advection regime...dew points in the middle to upper 
60s by late tonight into Monday are expected. 


The GFS brought the mesoscale convective system into northern Iowa by 12z Monday...then 
moved it across the northern portions of the forecast area on 
Monday. Quantitative precipitation forecast bullseye on this model seemed to be a convective 
feedback mechanism. Feel that the NAM/European model (ecmwf) was more plausible. 
Will carry high chance probability of precipitation for tonight and Monday given the 
uncertainty with the mesoscale convective system track. Heavy rainfall is possible if the 
mesoscale convective system does affect the area...as mesoscale Beta element velocities are 
low...and precipitable waters approach 2.00 inches. If forward 
propagating mesoscale convective system develops per Storm Prediction Center outlooks...may see some severe 
weather as well. 


NAM/European model (ecmwf) then bring another possible mesoscale convective system just to the north of the 
area Monday night...and then brings the stalled boundary through 
the area as a cold front by late Tuesday. The GFS does not have 
the mesoscale convective system Monday night...but does bring the cold front through on 
Tuesday. Given the continued uncertainty...will keep the probability of precipitation 
similar to the previous forecast. Mean layer convective available potential energy up to 2000 j/kg 
and modest deep layer wind shear may lead to some strong storms on 
Tuesday...especially in the far southern counties. 


Long term...Tuesday night through Saturday... 


Precipitation should end Tuesday evening...as front moves out of 
the area. European model (ecmwf) then indicated a dry stretch of weather from 
Wednesday through Friday night...as high pressure slides through 
the region. This should bring slightly cooler and drier conditions 
for this period. 


&& 


Aviation... 


High pressure centered over the eastern Great Lakes with return 
southerly flow increasing across southern Wisconsin. Ridge still 
bringing light winds and clear skies...with some MVFR and patchy 
IFR until 13 or 14z in low areas mainly far southeast closest to 
the ridge. 850 mb low level jet over the upper Mississippi Valley 
heads northeast into Lake Superior area and southern Canada...with 
the forecast area in weakening entrance region. Expect some cumulus 
late this morning with some vertical development this afternoon. 
Bases around 4 to 5 thousand feet by early afternoon. Small chance of 
thunderstorms late afternoon south central and mainly toward 
evening southeast as instability increases. Biggest forecast 
concern is with developing 850 mb low level jet increasing across 
Iowa later tonight. Some potential of an mesoscale convective system pushing across 
southern Wisconsin late tonight. 


&& 


Mkx watches/warnings/advisories... 
WI...none. 
Lm...none. 
&& 


$$ 


Short/long term...08/wood 
aviation/marine...06/hentz