965 
fxus63 kmkx 041931 
afdmkx 


Area forecast discussion 
National Weather Service Milwaukee/Sullivan WI 
230 PM CDT Friday Jul 4 2008 


Discussion...forecast emphasis on returning threat of precipitation 
later Sunday and continuing off and on through Tuesday. 


Very short term.../tonight/. 


High pressure to remain over WI and the Great Lakes. Expect another 
night of calm winds and good radiational cooling. Low temperatures near or 
slightly warming from this mornings lows. Isolated to patchy fog 
possible in low lying areas near sunrise. 


Short term.../Saturday through Monday/. 


Northeast winds along Lakeshore finally beginning to veer to the 
southeast. Low level winds should be more southeast on Saturday and 
Sunday allowing temperatures to warm...even along Lakeshore areas. 
Northeast winds carried higher dewpoints in the middle to upper 50s 
over portions of southeast Wisconsin resulting in enough instability 
for scattered-broken cumulus development. With cooler temperatures aloft 
lingering for one more day and surface dewpoints generally in the lower 
50s...expect more cumulus development for Sat...but should remain scattered so 
M/S wording should work. Dry airmass lingers for most of Sunday so 
more sunshine likely for final day of long Holiday weekend. 


GFS having trouble resolving weakening frontal boundary pushing into 
Wisconsin later Sunday and Sunday night while NAM showing a bit 
better consistency...hence will follow NAM which shows bulk of 
precipitation remaining west of County Warning Area through 
00z/Mon...along weak front and north of developing warm front in Iowa. 
Too much cin to break considering minimal forcing expected Sunday 
afternoon over south central Wisconsin with surface dewpoints in the 
middle 60s. Southeast Wisconsin protected by lingering middle level 
ridging and subsidence from retreating upper low over Ohio Valley. 
For now will keep schc wording for far western third of County Warning Area for late 
afternoon. 


While NAM...GFS and candian place emphasis of forcing with low level 
jet expected to intersect warm front to the south of Wisconsin Sun 
night...latest European model (ecmwf) which has been model of choice shifts focus 
farther north along short wave trough over Wisconsin. Sref showing 
high percentage for measureable precipitation Sun night over southern 
Wisconsin. So for now will keep middle level chance probability of precipitation going for Sun 
night into Monday as lingering stationary boundary remains in area and 
cape is expected to exceed 1000 j/kg. 


Long term.../Monday night through next Friday/. 


More and more uncertainty creeping into later portion of extended 
period...generally Thursday and Friday due to run to run inconsistencies and 
disagreement between hi res European model (ecmwf) and GFS. GFS ensemble members 
showing quite a bit of variability at this time as well with mref 
percentage of measureable precipitation quite low. Hence leaned 
toward keeping dry wording for period from Wednesday night through Thursday 
night...despite GFS trying to develop stronger warm front over vicinity of southern 
WI. Latest hi res European model (ecmwf) showing more broadscale ridge with 
strengthening baroclinicity holding off until Friday. Would also 
like to avoid days and days of 20-30percent probability of precipitation in this weak flow 
taking into consideration time of year as well. 


In the earlier periods...period of potentially heavier precipitation 
Monday night into Tuesday. GFS..hi res ecwmf and Canadian in 
reasonable agreement on developing surface low pressure on lingering 
frontal boundary in the plains on Monday...tracking northeast into 
Wisconsin by 12z/Tuesday and exiting area by 00z/Wed. Hi res European model (ecmwf) 
showing nose of 40kt low level jet pivoting across southern WI Monday night...while GFS 
much stronger and farther north. 850 mb dewpoints around 15 degrees at 
this time. 


GFS 5 day 500 mb means showing persistent zonal flow across northern tier of 
Continental U.S. For much of the period with near normal heights. Thinking 
warmer more seasonal temperatures likely with occasional weak 
frontal boundaries pushing through every few days bringing hit and miss 
convection. 


&& 


Aviation...large Canadian high pressure will remain over the Great 
Lakes through Saturday. Daytime few-scattered cumulus clouds will continue 
this afternoon and occur during the day on Sat while isolated to patchy 
fog and MVFR visibilities are expected in low lying areas near sunrise. 


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


$$ 
Short term/long term..........mbk 
very short term/aviation/.....Mg