Weather

178 
fxus63 kmpx 112039 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
339 PM CDT Sat Oct 11 2008 


Discussion... 


Scattered showers and thunderstorms over south central Minnesota will 
spread northeast this evening as moisture transport and elevated 
instability push north across the region. Laps profile showing lapse 
rates in the 700-500 mb layer quite steep and running at 7 degree 
c/km or better. After this surge of instability passes early 
tonight...middle level flow becomes more anticyclonic across eastern 
Minnesota and western WI. This should focus the precipitation chances 
more to western and northern areas of Minnesota. 


The large storm system over the western U.S. Still prognosticated to 
shear northeast Sunday and Monday. Good continuity today between 
the 12z NAM and European model (ecmwf). Todays run of the GFS has trended much 
faster with the surface and upper features and was considered an 
outlier. For the forecast area...the frontal boundary curving NE to SW across 
Minnesota is expected to push a little west and north on Sunday. This 
should allow for a really warm day over eastern and southern areas 
of the County Warning Area...provided extensive St/SC do not form. Have pushed 
highs into the upper 70s from the Twin Cities on east and south 
with best rain chances confined to western Minnesota. 


Raised probability of precipitation into the categorical range for Sunday night for much 
of the Minnesota County Warning Area as the cold front pushes slowly east across the 
state. The front should be near the Twin Cities Monday morning. 
The front will make slow progress across west central WI on Monday 
with likely to categorical probability of precipitation in place. Brought the rain to an 
end in the WI County Warning Area before daybreak Tuesday. Expected rain amounts 
from tonight through Monday night range from 1.5 to 2 inches from 
Fairmont to Little Falls on west. One to 1.5 inches east of this 
line to the I-35 corridor and a half inch to one inch across west 
central WI. 


Drying and high pressure for Tuesday then a short wave passing 
south of the forecast area Tuesday night and Wednesday. Added a small chance 
of showers to the WI County Warning Area for Tuesday night then went dry on 
Wednesday. Kept the mention of showers for Thursday night due to 
the GFS being an outlier today and the European model (ecmwf) not in phase with 
previous runs of the GFS. The period ends with a long wave ridge 
building across the plains with a warming trend. 


&& 


Aviation... /18z taf issuance/ 
inverted trough holding steady from SW Minnesota into north ctrl Minnesota. 
Along and to the northwest of this...ample cloud cover...including MVFR 
and IFR ceilings in parts of far western Minnesota. This will creep near axn and 
rwf this afternoon. Elevated moist upglide will allow for isolated -tsra 
development into the evening in western and ctrl Minnesota. These should be quick 
moving progressive showers and isolated storms. Tonight as some 
cooling occurs with the high dew points...do expect a little bit of 
overnight haze and some scattered 2-4 kft clouds east of the trough. 
Along and to the west.../axn/...think lower clouds will be a good 
bet along with all out fog being a realistic possibility. Some 
wind shear will be possible in the 1 to 2 kft layer above taf 
sites given the gusty southerly flow off the deck late tonight 
into Sun morning. However...have not mentioned at any taf sites as 
it looks below mentionable criteria. Chances for showers will 
increase Sun morning in western Minnesota as overall system shifts far enough 
east for some middle-level height falls and cooling above the low level jet to 
support showers/tsra. Sun looks breezy in the afternoon at all taf 
sites...with greatest precipitation chances at msp still looking to be 
more Sun night and moreso into Monday. 


&& 


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


$$ 


Rah/mtf