374 
fxus63 kdlh 191120 
afddlh 


Area forecast discussion 
National Weather Service Duluth Minnesota 
620 am CDT Friday Mar 19 2010 


Aviation.../12z tafs/ 
widespread MVFR ceilings will prevail through 16z...then gradual 
lifting to VFR as cooler and drier Canadian air sinks into the 
region today and tonight. Light snow flurries will be possible 
this morning. Some clearing is expected this afternoon across the 
forecast area. However...any clearing will be brief as increased lapse rates 
due to the cool air aloft will result in scattered/broken cumulus development 
around 4 kft. Timing the clearing this evening is most uncertain 
in the western locations /kinl and kbrd/ as the nam12 and bufr 
soundings suggests a shallow saturated layer around 3-4 kft 
lingers over North Dakota and western Minnesota into the evening. Winds 
will remain gusty out of the northwest today...dissipating and backing 
west overnight as surface high pressure builds east into Minnesota. 


&& 


Previous discussion... /issued 254 am CDT Friday Mar 19 2010/ 


Discussion... 


Much colder temperatures expected into Saturday. 


Surface low pressure was just north of Lake Superior as of 
07z...with west to northwest winds and cold air advection occurring over our County Warning Area. 


Amdar sounding at khib at 04z was colder at 850mb than the NAM 
forecast at 06z. We should continue to see temperatures drop this 
morning...with a little recovery this afternoon. 


Area radars shows returns...but the weak echoes passing over 
northwest Wisconsin were just clouds...and observations over our 
County Warning Area have not reported any precipitation so far. We will continue the 
scattered flurries for the morning over our County Warning Area...and continue them 
along portions of the South Shore into this evening due to 
possible les. Lake effect snow is marginal with borderline 
Delta-t's and moisture. NAM shows low level relative humidity decreasing this 
afternoon...but we kept sky cover mostly cloudy. Cumulus should develop 
if we do become scattered...but still not completely sold that we 
will stay mostly cloudy. 


Tonight...as high pressure at the surface starts to nose 
in...drying should continue and we lowered sky cover after 06z for 
most areas. Lake effect clouds should remain over portions of 
northwest Wisconsin. 


We will get into a dry westerly flow on Saturday...but 
temperatures will remain around normal. 


Extended...Saturday night through Wednesday 
a fast moving vorticity maximum rotates southeast around the Hudson Bay low and 
skirts along the international border/far northern lek Superior Sunday morning. 
Models are pushing the track of the vorticity/precipitation further north into Canada 
with each run so continued with dry forecast sun and increased temperatures to 
account for additional sun and warm air advection across southern zones. Overall trend 
of nudging temperatures upwards as upper level ridging and 850/700 mb 
return flow/warm air advection persist through the beginning of the work week. The 
next chance for measurable precipitation arrives middle week as short wave with surface 
reflection cold front tracks east through the zonal flow and into 
the upper Midwest. Although the GFS/ecm have similar scenarios on 
the evolution of the wave/cf...the timing/strength/placement of 
greatest quantitative precipitation forecast have large differences with the GFS the faster and 
colder of the long term models. Kept broadbrush small probability of precipitation through 
Tuesday/Wednesday until more detail can be obtained. 


&& 


Point temps/pops... 
dlh 34 19 37 23 / 10 10 0 10 
inl 32 11 35 24 / 10 10 0 10 
brd 35 19 38 24 / 10 10 0 10 
hyr 39 19 41 20 / 10 10 0 10 
asx 38 22 39 22 / 10 10 10 10 


&& 


Dlh watches/warnings/advisories... 
Minnesota...none. 
WI...none. 
Ls...Small Craft Advisory until 10 am CDT this morning for lsz146-147. 


&& 


$$ 


Melde/graning