984 
fxus63 kmpx 212344 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
544 PM CST Friday Nov 21 2008 


Aviation... /00z taf issuance/ 


Low pressure system over western South Dakota this evening to move southeast 
overnight and pass across Iowa early on Saturday. Greatest impact 
during the early morning hours on Saturday will be at krwf where 
several hours of light snow are expected along with ceilings/visibilities 
deteriorating to MVFR. As this system weakens south of US on 
Saturday...low level warm air advection will commence with GFS/NAM profile data 
indicating MVFR ceilings expanding into kaxn..kstc and kmsp. 
Kept this trend going from the previous tafs. Scattered the MVFR 
ceilings in the kmsp taf in the 24 to 30 hour time frame as drying 
in the profile is shown. 


&& 




Discussion... /issued 249 PM CST Friday Nov 21 2008/ 


The shortwave trough entering the western Dakotas per 20z water vapor 
imagery will be the focus locally over the next 18 hours...as it 
closes off and slides east/southeast across southern Minnesota. Associated 
850-700mb Omega and 2d frontogenesis Blossom over the southern County Warning Area 
around 03z...but expect the bulk of the snowfall to occur between 
06z and 12z when the low level saturation occurs. The dynamics...while 
briefly impressive...are somewhat out of sync with the arrival of 
the low level moisture...so snowfall accumulations of one inch or 
less still appear reasonable along/south of the Minnesota River Valley. 
This is supported by NAM/GFS/RUC prognosticated Cobb outputs for kfrm and 
krwf. 


Temperatures at western County Warning Area locations will likely remain elevated in 
the low 20s tonight...especially considering the cloud cover and warm 
air advection. Eastern areas will have the potential to dip into the 
single digits again...especially across west central WI. Low/middle clouds 
will linger on Saturday...but temperatures will moderate to around 
freezing. 


Temperatures will warm even more on Sunday ahead of an approaching 
trough...with highs in the upper 30s and lower 40s expected. The related 
cold front passes across the County Warning Area on Sunday afternoon/night...as shortwave 
energy on the western periphery of an amplifying eastern Continental U.S. Trough 
streams across Minnesota and WI. The deeper moisture will be present across 
the eastern County Warning Area where 30 probability of precipitation were preserved...while 20 probability of precipitation were 
adequate elsewhere. 


The extended portion of the forecast will feature dry weather with near 
to above normal temperatures through the Thanksgiving Holiday...as the 
upper Midwest experiences middle level ridging while wedged between 
cyclones over both coasts. 


&& 


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


$$ 


Rah/ls