068 
fxus63 kmpx 042110 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
310 PM CST Thursday Dec 4 2008 


Discussion... 


A few flurries linger this afternoon across the County Warning Area as a cold 
trough aloft passes through. Strong high pressure over the western 
High Plains will be moving across the County Warning Area overnight and early 
Friday. Dew points are currently in the low single digits and with 
clearing overnight...it will be quite cold with low temperatures 
near zero. 


Winds will pick up on Friday out of the southwest ahead of fast 
moving clipper. The low will move across Minnesota and WI Friday night. 
Sref probabilities for measurable precipitation now at or above 80 percent 
and categorical probability of precipitation used over the eastern half of the County Warning Area. Sref 
plumes for msp and eau showing a mean of 0.13 and 0.16 inches 
respectively. NAM/GFS Cobb BUFKIT data indicating snow ratios 
around 17:1. Coupling the two together yields 2 to 3 inches of 
snow in a rather short 6 to 9 hour period Friday night across 
eastern Minnesota and west central WI. Severe weather potential statement updated to reflect the higher 
snow amounts. 


Brisk northwest winds still in the offing for Saturday in the 
wake of this system. Some snow showers early...then clearing and 
very cold again Saturday night with lows a few degrees either 
side of zero. 


Sunday is becoming more interesting as yet another clipper 
approaches. Warm air advection...isentropic upglide and saturation spread across 
the Minnesota County Warning Area during the day with precipitation chances on the rise. 
In fact...the sref is already pushing 60 to 80 percent 
probabilities for measurable precipitation on Sunday. Hence...began small 
probability of precipitation in the far west in the morning and then allowed them to 
spread east during the afternoon. High chance probability of precipitation still in place 
for Sunday night and Monday. Another round of likely to 
categorical probability of precipitation for the County Warning Area will be on the way if this system 
stays on track. NAM/GFS Cobb BUFKIT data suggest one to two inches 
of snow. 


More cold high pressure dropping in for Monday night and Tuesday. 
As was the case yesterday...disagreement continues on Wednesday 
between the European model (ecmwf) and GFS. The Arctic air continues to flow freely 
southward on the GFS with a very cold period depicted from 
Wednesday through Friday. On the other hand...the European model (ecmwf) still 
holds on to low pressure passing from ND to lsup on Wednesday. 
This would bring a brief period of warmth before the Arctic gates 
open on the European model (ecmwf) for Thursday and Friday. The result for days six 
and seven (wednesday and thursday) was to go very cold with highs 
in the single digits and teens with lows at or below zero. We kept 
a chance of snow on Wednesday for continuity. 


&& 


Aviation... /18z taf issuance/ 
band of -shsn moving through ec Minnesota at this time. Visibilities lower to 
around 1 mile in heavier band. This will likely affect krnh and 
lesser degree Keau during the afternoon. Otherwise...cold trough 
moving across region the remainder of the afternoon...should 
continue the threat of MVFR ceilings/-shsn through 23z-00z. Question 
remains if lower clouds will linger through the night. Appears NAM 
and to some degree the GFS holding onto lower level moisture... 
especially in the 2-4k feet range during the night. Will hold onto 
the clouds over the eastern forecast area until after 07z at kmsp/krnh and will 
hold overnight at Keau. Will hold them VFR for now. Later tonight 
and Friday...strong low level warm air advection develops ahead of next short 
wave. This will quickly spread middle/high level clouds east over the 
forecast area through midday Friday. Then expect lowering ceilings and perhaps S- 
affecting western taf sites before 00z Sat. 


&& 


Mpx watches/warnings/advisories... 
Minnesota...none. 
WI...none. 
&& 


$$ 


Rah/dwe