Weather

301 
fxus63 kmpx 060838 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
338 am CDT Monday Oct 6 2008 


Discussion... 


Northern and southern stream short waves to March across the 
plains in tandem over the next 48 hours. This will drive a surface 
cold front across the Minnesota County Warning Area by Tuesday evening and the WI County Warning Area by 
Wednesday morning. GFS/NAM in better agreement with the European model (ecmwf) 
tonight on having a little faster movement with the aforementioned 
features. 


One change to the grids overnight included raising high 
temperatures about a category today with 850 mb temperatures 
running 11 to 13 degree c. This may not be enough if more breaks in 
the cloudiness occur...especially southern Minnesota. For now have highs 
from 65 to 75 north to south today. Best rain chances today across 
the western County Warning Area...which is closer to the upper jet and large scale 
Omega. Low level flow is actually prognosticated to become anticyclonic 
over WI and southeast Minnesota along with some drying in the column. Followed 
along with the previous forecast and went dry for parts of west 
central WI this afternoon and tonight. 4km NSSL WRF and nmm WRF 
both showing a flare up in convection over west central WI and 
east central Minnesota in the 14z to 18z time frame then basically dry 
during the afternoon and evening. 


Categorical probability of precipitation still in order for western Minnesota early tonight and 
for eastern Minnesota during the overnight hours as the frontal boundary 
moves slowly across the Minnesota County Warning Area. Pushed the drying trend across the 
entire Minnesota County Warning Area Tuesday night and by afternoon on Wednesday for west 
central WI. Inserted patchy fog for early Wednesday morning across 
western Minnesota with clearing...moist soil conditions and surface 
ridging expected. 


Only minor tweaks made beyond Wednesday. There remains 
considerable disagreement between the GFS and European model (ecmwf) for the late 
week and weekend period. European model (ecmwf) continues with a very deep trough 
in the far western U.S. While the GFS would have this feature over 
the northern plains. 500mb heights prognosticated by the European model (ecmwf) for 
Saturday are 5 Standard deviations below normal. The GFS and even 
the CMC are on the order of 3 Standard deviations below 
normal...but much further east-northeast. End of the week/weekend should be 
quite interesting. 


&& 


Aviation... /06z taf issuance/ 


Forecast continues to be complicated but it seems like a couple 
things are becoming more apparent. 850 mb warm air advection pattern and middle level 
frontogenetical forcing lifting slowly northeastward and is now generally 
along and NE of a line from axn to rgk. IFR conditions at this time 
associated with this area. Meanwhile...corridor of showers in 
broad diffluent flow pattern continue to stream north-northeast into the SW 
and wc portions of Minnesota...amid the best moisture and instability. Main 
question is the moist easterly low level flow north of warm front. 
Despite deep moisture pushing off to the NE...the east-southeast winds and 
residual surface moisture will be conducive to development of MVFR... 
and even IFR in some areas. Some areas south of the existing rain 
have bumped up to the 5k-7k ceilings and this area will be prone 
to a bit of MVFR fog later on tonight as well as lowering of 
ceilings. Best chance for heaviest rainfall mainly after 00z...and 
have added this to the latter portion of the tafs. 




&& 


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


$$ 


Rah/tdk