358 
fxus63 kmqt 082014 
afdmqt 


Area forecast discussion 
National Weather Service Marquette Michigan 
415 PM EDT Friday Aug 8 2008 


Synopsis/short term... 


00z radiosonde observations and WV loop showing amplified pattern with trough from 
Hudson Bay into eastern Great Lakes/New England and a ridge over much of 
the western Continental U.S.. at the surface...high pressure is covers much of the 
Midwest and Central Plains. A trough and cold front is dropping down 
from Ontario associated with shortwave descending from northern 
Ontario/Hudson Bay. Convergence along a lake breeze boundary 
combined with diurnal instability has helped generate some isolated 
rain showers/thunderstorms and rain mainly over Delta County as noted on the MQT radar. Latest 
visible satellite loop reveals that diurnal cumulus covers much of Upper 
Michigan. 


Attention tonight turns to compact upper low dropping south from near 
James Bay. Nice 500 mb cold pool associated with system with temperatures dropping 
below -20c/0c by 18z Sat over eastern Upper Michigan. 700 mb-500 mb lapse rates at or above 
7.0c/km along with showalter indices below 0f aiding cluster of 
thunderstorms developing ahead of incoming cold front just north of 
Lake Superior this afternoon. This instability will move south over 
Upper Michigan later tonight and bring a chance of showers and thunderstorms 
to much of the area...with the best chance of rain over the eastern half 
of the County Warning Area closer to the track of the upper low. 


Looks like the cold front should be through much of the County Warning Area by 12z 
Sat however with lingering cold pool over the eastern County Warning Area into midday 
Sat...kept in low chance probability of precipitation for thunderstorms and rain scntrl and east. 800 mb temperatures behind 
the cold front lower to below 5c which will provide good mixing to the 
surface over land and water. Would not be surprised to see north wind to 
gust near 25 knots at times behind the front Sat afternoon. Gusty 
onshore north winds and lingering stratocu over the area will result 
in fall-like high temperatures in the low to middle 60s along Lake Superior 
zones. 


Moderate rip curent risk is possible between Marquette and Grand 
Marais. See the latest Lakeshore hazard message for details. 


Long term...Saturday night through Friday 


The low over the eastern u.P. Will rotate to southeast Ontario 
Saturday night. The surface ridge and dry air will push into the 
upper Great Lakes and remain over the forecast area through Monday. 
Meanwhile...a middle level low will develop over central Canada and 
settle into east central Alberta. A surface low and cold front will 
maneuver into the southern Manitoba and the northern plains. 
Forecast sounding show a deck of cumulus clouds will develop around 
4k feet...however...a significant cap will prevent showers and 
thunderstorm development. 


Models showing some significant variation for the periods after 
Monday...so plan to use a European model (ecmwf) dominated solution as recommended by 
HPC. The middle level low over New England will move off the East 
Coast. A cold front extends southeast from a low northeast Alberta 
through the Dakotas. Dry air accompanying the surface ridge over the 
upper Great Lakes will keep conditions dry Monday evening. A weak 
shortwave trough along will a low level moisture will edge into 
northern Minnesota and the end of Lake Superior. This should also 
slide southeast in the western u.P. 


The longwave trough will continue to dominate southeast Canada 
through Tuesday night. The low over south central Canada will become 
more focused. A middle level ridge separating these two systems will be 
over western Ontario. A weak shortwave sliding into northeast 
Wisconsin will bring a chance of showers and thunderstorms to the 
area along the Wisconsin border on Tuesday. At the surface the cold 
front will wash out as it moves into the ridge over the region. Dry 
air and more stable air overnight should contribute to some clearing 
over the region. 


The low over eastern Canada will slide into southeast Ontario on 
Wednesday...the ridge will remain over western Ontario...while the 
low over Alberta shift into Saskatchewan. A shortwave rotating 
around the eastern Ontario low will sweep through eastern u.P. Low 
level moisture will continue to be limited. 


&& 


Aviation (for the 18z taf issuance)... 


Kcmx...expect VFR conditions to prevail through the forecast period. There 
will some increase in middle-level clouds this evening ahead of 
approaching shortwave and cold front. Behind the cold front winds 
will shift more nearly. 


Ksaw...expect VFR conditions to prevail through this evening 
although look for some increasing in middle-level clouds after sunset. 
Kept a prob30 in late tonight for possible showers with MVFR ceilings 
along the cold front passing through area. Expect nearly winds gusting 
to 20 kts behind the cold front on Sat as steep low-level lapse rates 
lead to more cumulus formation with ceilings in the high MVFR range. 




&& 


Marine (for the 4 PM Lake Superior forecast issuance)... 


Cold front dropping south from Ontario late tonight will bring winds 
around to the north late tonight. Cold advection behind the front 
will allow for good mixing as winds may even approach 30 knots over 
portions of Eastern Lake Superior on Sat. Surface high building in from northwest 
of the lake will slacken gradient and allow winds to die down by 
late Sat evening. High pressure will then build over the upper Great 
Lakes on Sunday and persist into midweek keeping winds generally 
light (blo 20kt). 


&& 


MQT watches/warnings/advisories...none. 


&& 


$$ 


Short term...jv 
long term...dlg 
aviation...jv 
marine...jv