890 
fxus63 kdlh 071324 
afddlh 


Area forecast discussion 
National Weather Service Duluth Minnesota 
724 am CST Wednesday Jan 7 2009 


Update...just did a quick touch-up to the zones/grids to shift 
the likely area a bit further west. Well defined area of 
circulation on kdlh 88d imagery and some light accumulation 
already. Have around an inch...but will have to watch for possibly 
a bit more in spots. 


&& 


Previous discussion... /issued 348 am CST Wednesday Jan 7 2009/ 


Discussion...main short term focus is the potential for light 
snow accumulation across the area today...with lake effect on the 
South Shore. The focus will then shift to the potential for an 
advisory-type snowfall event later Thursday night/Friday. 


Kdlh 88d showing developing snow showers across mainly NE Minnesota. 
Ruc13 picks up on an elongated area of higher vorticity stretching 
from kbji...through kinl...and northeastward into northwest Ontario. The 
snow was also developing in response to a weak low level 
circulation and the developing inverted trough across this area. 
The shortwave energy will eventually help to carve out a much 
deeper trough across the central/eastern Great Lakes as well as a 
strong low pressure system. 


The inverted trough as well as the 500 mb shortwave will definitely 
be the focus for today. Have increased probability of precipitation to likely across much 
of the eastern 1/2 of the County Warning Area today. The presence of the inverted 
trough...along with some weak isentropic upglide and the presence 
of a Theta-E ridge across the area should result in a fairly 
prolonged period of light snow...especially in the area from the 
inverted trough eastward into The Arrowhead and northwest WI. Also 
complicating matters is the likelihood for a lake-induced 
trough...which could result in bands from the North Shore into 
the South Shore and possibly a morning lake swirl due to light 
winds and possible bowl effect. Would not be surprised to see an 
inch or two of snow accumulation today...again mainly in The 
Arrowhead and northwest WI. Most other areas should see an inch or less. 
The high resolution WRF seems to hint at the above described 
scenario today and have been able to apply some of this information. 


The focus will then shift to the South Shore later today into 
Thursday. BUFKIT soundings become more favorable by tonight... 
especially given the presence of a well-defined lake trough. Think 
this may be a situation where the bands are not particularly 
heavy...but add up over a period of time due to multiple banding. 
Still...the presence of the lake trough and possibility for single 
band focused on the Bayfield peninsula always bring the risk for 
locally heavier amounts. Will go with a 24 hour 3-5 inch forecast 
for now...and we may need to alter amounts in later forecasts. The 
snow should diminish during the day Thursday...mainly afternoon. 


Extended...Thursday night through Tuesday... 
operational models continue to suggest that at least a few inches 
of snow may fall Thursday night into Friday as a strong clipper 
system moves into the Dakotas. Decent warm air advection combined 
with isentropic lift should lead to the development of snow by 00z 
Friday in the west and South County warning area...gradually pushing north overnight 
as frontogenetic forcing...mixing ratios and precipitable waters 
increase. Raised probability of precipitation to likely for the southern half of the 
region from Thursday night through Friday morning...with chance 
probability of precipitation still maintained farther north. An elevated warm layer will 
encroach at least a portion of the County Warning Area...but we believe the entire 
column will remain 0c...with all snow. However...there is a 
possibility that some sleet or more likely...freezing 
drizzle...may briefly occur for a brief time early Friday...mainly 
in the far south and southeast portions of our area. Kept precipitation 
all snow in all areas for now. At this time...it appears much of the area 
will likely receive advisory-level snows of 2 to 5 inches. 


Colder temperatures will return Friday night into Saturday as high 
pressure builds to the west. A weaker clipper will then affect the 
region on Sunday into Monday. The timing...track...and details of 
this system are a bit uncertain with some model disagreement. 
Maintained chance probability of precipitation for now. Even colder air will follow in the 
wake of this system...perhaps the coldest so far this season. 


Aviation...weak cyclonic flow will continue across the region 
today in wake of low pressure and a weak cold front. Mainly low 
VFR broken to overcast ceilings...and occasional MVFR ceilings... 
will prevail at all taf sites through 00z Thursday. Some 
improvement can be expected in the western one third of the area 
by 18z as drier air is advected into the region...with the trend 
slowly progressing eastward during the afternoon and evening. 
Areas of light snow will also be possible...especially in NE minn. 


&& 


Point temps/pops... 
dlh 21 -5 11 5 / 60 20 10 40 
inl 16 -15 5 -1 / 60 10 10 40 
brd 15 -5 13 9 / 30 10 10 60 
hyr 22 -2 12 3 / 60 20 10 40 
asx 25 3 15 5 / 60 50 20 30 


&& 


Dlh watches/warnings/advisories... 


Minnesota...none. 
WI...none. 
Ls...none. 


$$ 


Dap/bettwy