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fxus63 kdtx 051938 
afddtx 


Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan 
338 PM EDT Sat Jul 5 2008 


Short term...tonight 


Ridging at all levels will persist over Southeast Michigan 
tonight...providing clear/mostly clear skies and calm/light winds. 
Further airmass modification supports mins 3-5 degrees warmer 
tonight compared to this morning...which places the majority of the 
County Warning Area in the low to middle 50s. 


&& 


Long term...Sunday through next Saturday 


Weather conditions will remain outstanding for those wrapping up 
Holiday weekend activities. Surface high pressure will drift 
slightly eastward but still maintain control of the weather in Southeast 
Michigan. The resulting southerly wind component will allow the 
humidity to creep upward but remain at reasonable levels for early 
July. This will go along with highs in the lower to middle 80s and 
plentiful sunshine. 


Southerly flow will then persist Sunday night and Monday ahead of 
the next frontal system. Boundary layer parcel trajectories will 
have a considerably larger component from the Gulf of Mexico which 
will noticeably increase humidity during this time. Deeper moisture 
transport is then shown to get underway by Monday in the 12z models. 
This will be fostered by veering flow in the 850 to 700 mb layer as 
the weak wave in the northern plains brushes through Upper Michigan. 
The veering flow with this wave will drive eastward the moisture 
axis located ahead of the frontal boundary. Theta-E advection in 
this pattern is marginal due to the weak wind field and the front is 
expected to stall to our north, both of which suggest maintaining 
just the low chance of showers and thunderstorms already in our 
forecast. 


The next upper wave will be digging into the northern plains by 
Monday night. This feature will turn the flow toward the southwest 
over lower Michigan and cause the front to stall nearby to our 
north. Surface low pressure associated with the wave will develop 
and track along the stalled front from the plains into the Great 
Lakes. A renewed surge of moisture ahead of this system will spread 
into our area late Monday night and through Tuesday and will usher 
in an active period of convection. Add this to the passage of the 
cold front Tuesday night and showers/storms are likely through the 
period. Among the 12z models, agreement is good on the timing of the 
front Tuesday night but low pressure looks overdone in the GFS 
solution due to convective feedback. The NAM is only slightly less 
guilty of enhanced surface development. Instead, preferred to stick 
with the more open solutions in earlier model runs for the wind 
forecast during this time. 


The latest global models are in reasonable agreement showing the 
front to our east and south by 12z Wednesday morning. Where there 
are timing differences between the models, prefer the faster 
solutions as there is not much amplification occurring in the long 
wave pattern heading into the second half of the week. This will 
maintain the progressive character of the flow and suggests keeping 
Wednesday dry, siding with the GFS/European model (ecmwf) models that offer faster 
timing on the wave and associated frontal passage. Cooler and less 
humid conditions will then settle in for Thursday and Friday as 
surface high pressure takes control under northwest flow aloft. Guidance 
temperatures look good offering highs in the 70s on Wednesday and 
Thursday gradually modifying back into the lower 80s on Friday and 
Saturday. 


&& 


Marine... 


Favorable wind and wave conditions will persist for the next few 
days, but the weather will become unsettled due to showers and 
thunderstorms during Monday and Tuesday. Rain potential will be on 
the increase as a weak front stalls over Northern Lake Huron by 
Monday night and another low pressure system travels along it during 
Tuesday and Tuesday night. Following cold frontal passage Wednesday, 
small craft advisories may be needed due to gusty northwesterly 
winds, especially off The Thumb region of Lake Huron. 


&& 


Previous discussion...issued 103 PM EDT Sat Jul 5 2008 


Aviation... 


Clear skies (outside of high cirrus) will continue over the next 24 
hours. Based on a persistence forecast...will maintain the mention 
of 5-6sm br/haze as high pressure lingers over the region...leading 
to calm winds overnight. Light southerly winds will then take hold 
tomorrow as we get into return flow. 


&& 


DTX watches/warnings/advisories... 
Michigan...none. 
Lake Huron...none. 
Lake St Clair...none. 
Michigan waters of Lake Erie...none. 


&& 


$$ 


Short term...sf 
long term....bt 
marine.......bt 
aviation.....Sf 




You can obtain your latest National Weather Service forecasts online 
at www.Weather.Gov/Detroit (all lower case).