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Area forecast discussion...updated 
National Weather Service Marquette Michigan 
1156 am EST Thursday Dec 4 2008 


Updated aviation discussion for 18z tafs 


Discussion... 


Today through Saturday...latest radar trends show overall ragged 
les appearance east of Marquette and no echoes...as usual...across 
the far west. A quick look at the Canadian radar south of Wawa 
though shows a well defined band east of Grand Marais...while the 
echoes just to its west are not. Despite a lack of echoes over the 
far west snow continues to fall at most areas noted by low visible at 
iwd and persistent low visible/ceilings at cmx...thus ongoing 
warnings/advisories seem reasonable...except for northern Houghton 
County. 


Decided to put up a les warning for northern Houghton County through 
00z Saturday and extend les advisory for Keweenaw to the same time. 
This decision was primarily based on spotter reports from law 
enforcement and trend in nam12 output. In the higher terrain between 
Chassell and Painesdale as much as 9 inches of snow has fallen since 
the even began yesterday morning...and only around 2 to 4 inches 
fallen across the Keweenaw. The plan for today is for winds to 
gradually turn westerly by late this afternoon/early evening...which 
will allow for les bands over the western u.P. To shift north and 
intensify. Latest NAM BUFKIT soundings show inversion heights rising 
to near 700mb for a period this evening...thus periods of intense 
snowfall rates are anticipated this evening. At this point it 
appears the best quantitative precipitation forecast amounts will remains south of cmx. Looking at 
the eastern u... is some concern that areas of northern 
Schoolcraft County may need a warning today. All this is based on 
the land breeze from Ontario pushing into southern Luce creating a 
dominant band over northern Schoolcraft. Not convinced this setup 
will occur given that winds remain northwest at Grand Marais and 
westerly at early...though cwci and a ship 20 miles southwest of cwci 
have recently reported north winds hinting at the approaching land 
breeze. 


By Friday evening...low pressure moving into the upper Mississippi 
Valley will allow winds to shift offshore...ending les across the 
area. Increased probability of precipitation into Friday night as the low shifts across the 
Upper Peninsula. 




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


Conditions remain favorable for lake effect -shsn off Lake Superior 
under nwrly flow. Under nwrly flow...ksaw won't see any significant 
-shsn. Conditions there should generally be VFR...though with cool 
temperatures aloft/afternoon heating...there could be MVFR -shsn this afternoon. At 
kcmx...conditions should generally stay IFR...though some breaks of 
MVFR conditions are certainly possible during lulls in the snow 
showers. More concentrated/persistent LIFR conditions are expected 
by evening as winds back wrly which will increase low-level 
convergence and set up a longer fetch for lake effect into kcmx. As 
winds go SW Friday morning...conditions will slowly improve at kcmx. 


&& 


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


A trough of low pressure continues to shift away from the area while 
high pressure over western Canada makes its way into the northern 
plains. Northwest winds to 30 knots are expected between these two features 
but winds should stay below gales. Low pressure over the central 
Canadian provinces Friday afternoon quickly dives over northern 
Wisconsin/Upper Michigan Saturday. Low looks to deepen just east of 
Lake Superior and that could lead to a gale across central and Eastern Lake 
Superior Saturday afternoon into Saturday evening. Winds diminish by 
Sunday as high pressure moves across the Great Lakes. Srly gales 
possible on Monday...mainly eastern sections of Lake Superior...ahead of 
low pressure system dropping into the region from central Canada. 




&& 


MQT watches/warnings/advisories... 
Upper Michigan... 
lake effect snow warning until 10 am EST Friday for miz006-007. 


Lake effect Snow Advisory until 7 PM EST this evening for miz004. 


Lake effect snow warning until 7 PM EST this evening for miz002- 
084. 


Lake effect snow warning until 7 PM EST Friday for miz003. 


Lake effect Snow Advisory until 7 PM EST Friday for miz001. 


Lake effect snow warning until 3 PM CST today for miz009. 


Lake effect Snow Advisory until 1 am EST Friday for miz085. 


Lake Superior...none. 
Lake Michigan...none. 


&& 


$$ 


Discussion...Pearson 
marine...jla 
aviation...GM