Weather

584 
fxus63 kmqt 292327 aaa 
afdmqt 


Area forecast discussion 
National Weather Service Marquette Michigan 
725 PM EDT Friday Aug 29 2008 


Synopsis... 


Upper levels feature a trough over Ontario into Great Lakes while a 
ridge holds over western Continental U.S. Into SW Canada. Shortwave sliding into 
the trough may bring light precipitation to northern County Warning Area this evening...otherwise 
high pressure both at the surface and aloft with dry weather dominates 
into the middle part of the upcoming week. 


&& 


Short term (tonight and saturday)... 


Batch of clouds and steep lapse rates aloft contributing to a few 
light returns on kdlh radar. Stronger echoes and lightning strikes are 
just north of the Minnesota arrowhead in Ontario along track of tail of 
upper level shortwave. Kept isolated probability of precipitation for rain showers/thunderstorms and rain over Lake 
Superior this evening as shortwave and middle level moisture moves 
east. Observation over Minnesota indicate bases of clouds are around 10kft and no 
real moisture advection is expected over Upper Michigan. Will continue to 
carry a few sprinkles along northern tier of County Warning Area as the middle clouds 
roll across. All activity should be done by 03z since axis of 
shortwave is through the area by then. Once negative vorticity advection moves in and winds 
lighten up with approaching ridge temperatures could fall swiftly late 
tonight in the west half of County Warning Area. Precipitable water min expanding over time will 
only enhance radiational cooling potential. Given temperatures in this 
sector of the incoming ridge fell into the 30s in southern 
Saskatchewan this morning...really see no reason why favored cold 
spots in western Upper Michigan will not drop into the upper 30s. 


Dry air to begin the day will only enhance mixing with full sunshine 
on Saturday. Mixing to 850 mb-800 mb yields maximum temperatures in the Lower-Middle 80s 
inland...but Lakeshore areas will be cooler thanks to light winds 
and lake breezes. Relative humidity values may drop as low as 25 percent...but light 
winds will offset any fire weather issues. 


After coordinating with fire weather officials...will be issuing a 
wildfire potential statement for the upcoming Holiday weekend due to 
the increasing temperatures and prolonged dry weather (in some spots 
in the cwa). Expect increasing wildfire potential Sunday and Monday 
as south winds begin to increase. 


Long term (00z sun through day 7)... 


Main forecast concerns during this period are unseasonably warm 
temperatures for sun/Mon/Tue and arrival of next precipitation for 
Wednesday night through Friday. Latest model runs continue to show a 
strong upper level ridge building into the upper Great Lakes by 
Sunday aftn/evening. Both long range models...ECMWF/GFS...show 
slight differences in the strength of the ridge...592/590 dm 
respectively. This minor difference will not preclude the 
unseasonably warm air associated with this ridge from building into 
the forecast area for Labor Day weekend. Both Sunday and Monday will feel hot 
with high temperatures across the west half will reach well into the 
80s...some areas could reach 90 where downsloping is maximized. By 
Tuesday evening the ridge will shift east over New England allowing 
for return flow and next precipitation. Chance to move into the forecast area. Had to 
delay probability of precipitation into the forecast area as latest guidance shows dry air/remaining 
subsidence from strong ridge keeping Upper Michigan dry through 
Tuesday afternoon. For the time being it looks like the front will linger 
to the west long enough for Tuesday to be warm day as well. High 
temperatures on Wednesday are a bit trickier as the GFS brings the 
front into the west Wednesday morning..while the ec not only lags 
the front to our west but also weakens the front altogether as it 
moves into Upper Michigan. As a result there is 10+ degree 
difference in airmass temperatures for Wednesday night/Thursday. 


&& 


Aviation (for the 00z taf issuance)... 


VFR conditions to prevail through the forecast period. After the 
scattered-broken middle clouds this evening...plan on clear skies for Saturday 
as high pressure builds into region and lake breezes affect the wind 
direction Sat afternoon. 


&& 


Marine (for the 4 PM marine issuance)... 


High pressure to dominate the region for the next several days with 
winds expected to remain less than 20 knots. As the high shifts 
east...deepening low pressure over the northern plains to result in 
increasing pressure gradient over Lake Superior later Sunday into 
Tuesday with gusts up to 25 knots. Cold front shifts into Lake 
Superior late Wednesday into Thursday. Gusts on Wednesday may 
exceed 20 knots in association with the approaching front. 


&& 


MQT watches/warnings/advisories... 
Upper Michigan...none. 
Lake Superior...none. 
Lake Michigan...none. 


&& 


$$ 


Short term discussion...jla 
long term discussion...Pearson 
aviation...GM 
marine...jla