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Area forecast discussion 
National Weather Service Gaylord Michigan 
334 PM EDT Sat Jul 5 2008 


Discussion...high pressure remains over the western Great Lakes 
with the some diurnal clouds over east upper near Whitefish Bay and a 
few near apn along the Lake Huron shoreline. Winds remain light 
with the slack gradient. To the west the 500 mb ridge axis is in 
the Red River valley of the north, which the demarcs where the 
clouds that are being produced ahead of the next system start. 


The main concern for the package will be the Sunday night to 
Tuesday time frame with the rain showers and thunderstorms. 


Tonight...high pressure starts to slowly shift east, however the 
winds will decouple again and with the warm soil temperatures, low 
dewpoints, and lows in the upper 40s and lower 50s, fog doesn't 
look likely. In east upper, the gradient wind increases so it make 
the fog less likely. 


Sunday...the next system begins to push into the region with the 
high retreating. The main low, by 00z is over James Bay, but a 
secondary wave forms on the front and pushes in West Lake Superior. 
This makes the chance for rain increase from nothing to small 
chance probability of precipitation in east upper by the afternoon and early evening. Even 
then, the chance for precipitation will be in the western areas of 
Chippewa and Mackinac counties. 


Lutz 


Sunday night...a central Canada/upper Midwest storm system... 
will slowly become more of an influence over the Great Lakes 
region through the overnight period. The system will move near 
James Bay by 12z Monday...dragging a cold front into the western 
lakes early Monday. Upper support will be weak with 850/500 mb 
lows traveling north of the region...with most of the upper jet 
support way north of the region. Expect precipitation will have a difficult 
time at first working its way over the western Great Lakes...due to 
the lingering dry air in place over the state...from the nearly 
stationary high pressure system that was over the state through 
the July 4th Holiday weekend. However model soundings and moisture forecasts 
due show sings of increasing middle and low level moisture moving over Lake 
Michigan into east upper and northwest lower Michigan after 06z. Surface 
dew points will increase into the lower 60s overnight...while data 
suggests 850mb dew points increasing from under 0c to 12c over east 
upper and northwest lower Michigan. This moisture increase will 
overspread much of lower Michigan by 12z Monday. The increase in surface 
and middle level moisture will begin to introduce some instability over 
the state overnight...with the showalter and lifted index falling to 
around 0c...while model soundings show no real signs of cape. 
Overall will mention a chance of showers overnight...mainly over 
east upper and a narrow section of northwest lower. Will leave 
mention of thunder out due to lack of strong dynamics and marginal 
instability. Overnight lows will be mild generally in the upper 50s 
to lower 60s...due to SW flow in advance of the approaching storm 
system. 


Monday...model soundings and moisture forecasts continue to Show Low and middle level 
moisture increasing over the entire Great Lakes region through Monday 
night. 850mb dew points will increase to 14c...while surface dew points 
increase to between 60 and 65f. Increasing middle level moisture will continue 
to strengthen the instability over the region through the period... 
with convective available potential energy increasing to around 1200 j/kg away from the lakes... 
while the showalter and lifted index will be -2c/-3c. Lift will be 
supplied by the slow moving front dragging across the state... 
associated with the storm system moving from James Bay into Quebec. 
The front is currently prognosticated to move slowly south over the northern 
lakes in the afternoon...finally sinking south/washing out over Southern 
Lower Michigan overnight. Overall will mention showers and 
thunderstorms over the entire forecast area Monday due to 
instability and lift. Will keep the mention of showers and 
thunderstorms in the forecast Monday night over much of northern lower 
Michigan due to the front washing out in that area...and lingering 
instability and a 850/700 mb lapse rate near 6.5 c/km. However will 
only mention showers over east upper and The Straits region...where 
the airmass will be more stable and lapse rates drop under 5 c/km. 
Will mention afternoon highs in the upper 70s and lower 80s most of 
the County Warning Area...taking into account 850 mb temperatures nearing 14c combined with 
clouds and precipitation. 


Tuesday...will continue to mention showers and thunderstorms over 
the entire forecast area into Tuesday evening...due to available 
lift and moisture. Models show a surface storm system moving over Lake 
Superior/Ontario...sweeping a cold front over the state during the 
evening. Additional lift will be from upper level troughs moving 
over the northern lakes...as 850 and 500 mb lows move across Ontario. 850 
mb dew points will remain around 14c...with surface dew points in the 60s. 
Corresponding indices respond with convective available potential energy near 1200 j/kg with lifted 
index and showalter around -2c. Will mention only showers lingering 
over east upper and extreme northern lower Michigan Tuesday night...as much 
drier air begins to push into the region behind the passing cold 
front as 850 mb dew points drop to under 6c overnight. Will keep the 
mention of thunderstorms over the southern County Warning Area overnight until the front 
passes through the region. High temperatures Tuesday will be difficult as 850 
mb temperatures warm to 16c...however mixed with clouds and precipitation will only 
mention highs in the lower 80s most locations. 


Wednesday through Saturday...will keep a lingering chance of showers 
over portions of northern Michigan Wednesday...as the surface storm system pushes 
east of the region and the upper level trough moves into Quebec. 
However the rest of the forecast period should remain dry into the 
weekend...as a large area of high pressure builds into the upper 
Midwest and Great Lakes region Wednesday night. This area of high 
pressure will become centered over the state Thursday into Saturday. 
Will mention cooler afternoon highs Wednesday and Thursday as 850mb temperatures 
drop to around 9c Wednesday and around 7c Thursday...keeping highs into the 
70s...with overnight lows in the 40s/50s Wednesday and Thursday. Will 
mention afternoon highs in the 80s again Friday and Saturday...as 
850 mb temperatures warm between 12c and 14c in advance of a storm system 
approaching from the upper Midwest. 


Swr 


&& 


Previous discussion... /issued 144 PM EDT Sat Jul 5 2008/ 


Aviation...currently, the cumulus development has been slow, with most 
of it in NE lower. Looks like the dry air is beginning to mix out 
the moisture, and is keeping northwest lower cloud free. Will expect that 
there will be minor cumulus development over the afternoon in northwest lower. 


Lutz 


&& 


Apx watches/warnings/advisories... 
Michigan...none. 
Lm...none. 
LH...none. 
Ls...none. 
&& 


$$ 

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