103 
fxus63 kdlh 131820 
afddlh 


Area forecast discussion 
National Weather Service Duluth Minnesota 
1220 PM CST Sat Mar 13 2010 


Update... 
we decided to issue a dense fog advisory for the head of the 
lake...as well as the South Shore of Lake Superior...effective now 
through Sunday morning. Visibilities were persistently near a 
quarter of a mile at the Duluth Airport and the Ashland area. 
Soundings and low level condensation pressure deficits remain very favorable 
for continued fog through Sunday morning on mesoscale RUC/NAM. Issued 
dfa for North Shore and arrowhead beginning at 00z tonight as low 
level winds veer more east-northeast. 


&& 


Previous discussion... /issued 1140 am CST Sat Mar 13 2010/ 


Aviation...03/13/18z issuance... 
low pressure over the East Coast is troughing deeply back along 
the Ohio Valley. A mild moist east flow...north of the low...will 
remain onshore...upslope with moisture continuing to condense out 
over our snowcover. During the next 36 hours...conditions will 
remain vlifr in ceilings and fog. There will remain areas... 
especially across the uplands around Lake Superior...of mvlifr in 
dense fog through the period. 


Previous discussion... /issued 1037 am CST Sat Mar 13 2010/ 


Update... 
only minor adjustments to mainly maximum T grids today. Used 
persistence with populating yesterdays maximum t's for today... as low 
stratus...fog/br will keep temperatures today on the cool side. Dense fog 
has become more patchy in nature...so let the dfa expire as 
scheduled. Early indications are that dense fog will return late 
this afternoon or early evening...and therefore added areas of 
dense fog to grids for tonight/early sun. May need another dense 
fog advisory for parts of the Northland tonight...especially areas 
near Lake Superior. 


Previous discussion... /issued 428 am CST Sat Mar 13 2010/ 


Update... 
added dense fog advisory for Cass County. Locations of Cass County 
have been reporting visibilities less than one half mile...and 
should expect those conditions to continue into late Saturday 
morning. 


Previous discussion... /issued 403 am CST Sat Mar 13 2010/ 


Discussion... 
patchy fog around the area this morning...dense in some 
areas...mainly from the Duluth/Superior area east along the WI 
shore of Lake Superior. Locations along the Northshore have been 
in and out of the dense fog and currently visibilities are 3/4 Michigan 
or better. Will keep the dense fog advisory going through 10 am 
this morning for near lake locations. Confidence is not high 
enough to remove areas in the advisory that have seen improved 
visibilities. Thinking there still might be a chance they will go 
back under. Otherwise...most locations will continue to see cloudy 
skies with patchy fog and light drizzle through most of Saturday. 
Northeast winds will diminish through Saturday evening with the 
strongest gusts...up to 20 miles per hour...near Lake Superior Sat afternoon. 


Have kept a slight chance of light rain in the forecast for Sat 
night along with continued patchy light drizzle and fog. There is 
fairly decent model agreement in bringing a weak...quick moving 
short wave through the region tonight. The European model (ecmwf)...GFS...NAM and 
Gem all have a weak middle level feature developing over the Great 
Lakes and moving into WI/Minnesota area late Sat night/early Sun morning. 
Could possibly see some slight improvement by late Sunday 
afternoon with conditions drying out with potentially some breaks 
in the clouds before sunset. Temperatures will increase slightly 
going into Sunday with highs into the upper 40s to near 50 away 
from the lake and in the lower 40s near the lake. 


Extended...Sun night through Friday... 
shortwave will swing through western Great Lakes Sun night through Monday night. GFS/Gem 
show a stronger feature than NAM/ECMWF...but all models show some 
moisture and small amount of quantitative precipitation forecast...so kept a slight chance pop in most zones for 
that period...even though there is not much of a surface system to provide low 
level lift. Temperatures should remain high enough for any precipitation to be liq. After 
that...models agree in building strong high amplitude upper ridge for 
a dry period the first half of next week. Some agmt among models on 
approach of strong upper level trough late next week. Could be cold enough 
for snow. 


&& 


Point temps/pops... 
dlh 34 44 35 46 / 30 10 20 20 
inl 35 43 35 46 / 20 10 20 10 
brd 36 48 35 46 / 30 30 20 20 
hyr 35 49 35 51 / 20 10 10 10 
asx 35 39 34 46 / 20 10 10 10 


&& 


Dlh watches/warnings/advisories... 
Minnesota...dense fog advisory from 6 PM CST this evening to 11 am CDT 
Sunday for mnz012-019>021. 


Dense fog advisory until 11 am CDT Sunday for mnz037. 


WI...dense fog advisory until 11 am CDT Sunday for wiz001>004. 


&& 


$$ 


Lonka/eom