432 
fxus63 kdlh 041630 aaa 
afddlh 


Area forecast discussion...updated 
National Weather Service Duluth Minnesota 
1030 am CST Thursday Dec 4 2008 


Update...quick update to adjust sky cover and probability of precipitation. Forecast 
soundings for Hurley area support an increase in les intensity my 
mid-day...as west-northwest increase and inversion heights rise. Winds should 
back enough by late afternoon...and result in a eastward migration 
to the main les bands. Will monitor however for a possible 
extension to the ongoing les warning. 


&& 


Previous discussion... /issued 346 am CST Thursday Dec 4 2008/ 


Discussion... 
short term focus on continuing lake effect snow along the South 
Shore of Lake Superior. Extended the current les warning in effect 
to go through 21z this afternoon. At this time...the Iron nugget web cam 
in Hurley, WI is showing that snow continues to fall with some 
additional accumulation overnight. Have not gotten any snowfall 
reports from spotters at this time. However...kiwd visibility has been 
persistently 2sm so a few inches of new snow is assumed. The kasx 
and kiwd surface stations have had a west to SW through the night...while 
the marine ob site at Port Wing has been gusting to around 20 knots. 
Suspect mesoscale lake produced trough with low level convergence and 
favorable lapse rates are allowing for the les to persist. Models 
are not picking up on this small scale trough...but the 
NAM/GFS/sref all produce quantitative precipitation forecast along northern Ashland and Iron counties 
through the day. Increased probability of precipitation to likely for an additional 3-5 
inches across the warned area...as well as 2-4 inches along the 
Bayfield Penn. Low confidence when the snow will end...but expected 
at least light shsn through Friday morning. NAM relative humidity fields suggest the 
moisture and blyr west to northwest flow remains in place through 12z 
Friday. 


Friday night through 
Tuesday...rather active weather is expected during this 
period...as a couple features in northwest flow bring the potential for 
accumulating snowfall. The 00z GFS/ECMWF/gemnam are actually in 
pretty decent agreement concerning the first clipper- type system. 
This low pressure system will move to southern Manitoba by 00z 
Saturday...spreading light snow into at least the northwest corner of the 
County Warning Area by Friday afternoon. The low is then expected to slowly deepen 
as it reaches Central Lake Superior by 12z Saturday. As is often 
typical with clippers...moisture will be limited. However...it 
looks like it will be fairly efficient at generating 
precipitation. Current thinking is a general 1 to 3 inch snowfall 
across the County Warning Area...but think there is the potential for perhaps 2 to 
4 inches of snow in spots. Most of the models bring 0.10 to 0.20 
inches of liquid precipitation...and ensemble members are in good 
agreement as well. The low pressure system will pull east of the 
area on Saturday...leaving lake effect snow in its wake for 
Saturday into Sunday. Cold and dry air will blanket the rest of 
the County Warning Area into Sunday night...before clouds and light snow move in 
again from the west. The models have also been consistent with 
this system...and although snowfall rates are likely to be a bit 
higher...it looks like this system may bring higher quantitative precipitation forecast. Could be 
another advisory type snowfall event starting Sunday night and 
continuing into Monday. Some of the coldest air of the season is 
then expected to move in Monday night and Tuesday as an Arctic 
front allows bitterly cold air to drain into our area from the 
Arctic. Highs toward the middle of next week may struggle to reach 
zero in spots. 


Aviation...infrared satellite imagery this morning indicates several 
areas of cloudiness...interspersed with areas of clear skies. This 
is likely to be the case for the forecast area today...with VFR 
conditions alternating to MVFR ceilings. Some MVFR visibilities are also 
possible for a time this morning. Looking ahead beyond the taf 
period...much lower ceilings/visibilities are expected to arrive by Friday late 
afternoon or night. 


&& 


Point temps/pops... 
dlh 14 1 18 10 / 20 20 20 60 
inl 13 -3 14 6 / 20 20 20 60 
brd 18 3 21 14 / 20 10 20 60 
hyr 16 -1 18 14 / 30 20 20 70 
asx 18 7 19 11 / 60 50 30 60 


&& 


Dlh watches/warnings/advisories... 


Minnesota...none. 
WI...lake effect snow warning until 3 PM CST this afternoon for 
Ashland-Iron. 


Ls...Small Craft Advisory until 4 PM CST Friday for lsz121-lsz146- 
lsz147-lsz148. 




$$ 


Liles