295 
fxus63 kmqt 181731 
afdmqt 


Area forecast discussion 
National Weather Service Marquette Michigan 
131 PM EDT Thursday Mar 18 2010 


Updated aviation discussion for 18z tafs 


Synopsis... 


09z water vapor loop and RUC analysis shows a broad ridge over the 
Central Plains and western Great Lakes with a well-defined vorticity maximum 
moving east through southern Manitoba. Warm air advection middle-high clouds associated with 
the approaching vorticity maximum over southern Canada and also aided by upper divergence 
in the right entrance region of 80 knots 3h near the Ontario/Quebec 
border are spilling across the County Warning Area as noted on infrared satellite. 


&& 


Discussion... 


Today...look for middle-high clouds to thin out during the day as right 
entrance region forcing weakens with upper jet over Quebec. There 
should be enough sunshine and associated mixing to see high temperatures to 
reach into the middle 60s at many inland locations given 4-5c 850 mb 
temperatures overhead. Wrly onshore flow over the Keweenaw peninsula and 
the development of lake breezes off Lake Michigan should keep temperatures 
a bit cooler (mid 50s) over these areas. 


Models still consistent in showing the vorticity maximum over southern Manitoba 
moving north of Lake Superior tonight and bringing a surface cold front 
across the County Warning Area. Colder air will gradually infiltrate the upper lakes on 
Friday...with GFS/NAM showing 850 mb temperatures falling to around -10c over the 
Keweenaw by 00z Sat. Although the incoming airmass may be marginally 
cold for les...will maintain going dry forecast for tonight into Friday 
since WRF-arw model forecast sdngs show strong subsidence inversion 
lowering below 3kft and very air beneath the inversion. 


Models no longer show phasing of Central Plains shortwave with next 
shortwave approaching in the northern branch of the upper flow. Northern branch 
flow dominates across the upper Great Lakes region for the weekend. 
Thus...have removed probability of precipitation and quantitative precipitation forecast over scntrl and eastern counties for 
Friday night into Sat as southern branch system now appears to stay well 
south. Although models still advertise continued cold advection Friday 
night into Saturday with 850 mb temperatures dropping to -12 to -14c...have 
decided to keep forecast dry for now as large scale flow remains 
anticyclonic and the surface ridge axis is forecast to build overhead late Friday 
night and Sat morning. Would expect low-levels to be prohibitively dry 
for les formation. 


&& 


Aviation /for the 18z tafs/... 


Expect VFR conditions through the overngt with relatively dry westerly flow 
predominating. Gusty winds at cmx will diminish this evening with loss of 
daytime heating...resulting in some low level wind shear after sunset. A strong cold 
fnt will pass the upper Great Lakes tonight...with gusty west-northwest winds developing at cmx 
with favorable terrain funneling in its wake as much colder air rushes 
to the east. Plan on low clouds with MVFR ceilings to develop at cmx/saw on Friday 
morning with the arrival of colder/moister air now over scntrl can. 


&& 


Marine /for the 4 am Lake Superior forecast/... 


A couple different weather systems will pass through Lake Superior 
over the next 5 days. The first is on Thursday night when a low out 
of Manitoba crosses the lake. Ahead of this system...winds will 
increase to 30 knots out of the west. High pressure briefly moves 
over the lake on Saturday and Saturday night. On Sunday a strong low 
moves over the lake out of the northwest...behind this low gales are 
possible for Sunday night and Monday. However due to the 
uncertainties regarding this low...gales were not included in the 
forecast yet. 


&& 


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


&& 


$$ 




Synopsis...Voss 
discussion...Voss 
aviation...kc 
marine...Pearson