800 
fxus63 kmpx 041108 
afdmpx 


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


Aviation.../12z taf issuance/ 
latest radar imagery shows patch of light snow moving through the 
central portion of the area at the current time... in association 
with an upper level shortwave and weak surface trough. This 
feature will swing east this morning... and the water vapor 
imagery and RUC upper air analyses show some decent shortwave 
ridging moving south through Saskatchewan and Manitoba which will 
work southeast through the day and into this evening. Cloud cover 
across the area at this time is not particularly homogeneous... 
with some thicker clouds associated with the aforementioned 
features and precipitation. In their wake... areas of broken mainly VFR and 
marginal MVFR ceilings could be found. Boundary layer moisture... 
as shown by the NAM... GFS... and RUC... are sufficient for some 
stratocu through the day... but cyclonic flow is minimal likely 
keeping things in check. However... with the thermal trough in the 
vicinity today and at least neutral if not slightly cyclonic 
flow... we should see more in the way of stratocu than 
yesterday... but forecast profiles suggest it should generally 
stay at or above 3k feet except for perhaps in some of the scattered snow 
showers which could develop given the good low level lapse rates 
which will linger through the day. Tonight... the general trend 
should be for improvement in conditions as winds back and warm 
advection starts to work its way down from the middle levels and 
dewpoint depressions increase. However... there could be some 
lowering in ceilings as the subsidence inversion lowers before the 
clouds are scoured out. Will include some hint of this trend... 
but otherwise anticipate a scattering out of any broken lower clouds 
from west to east through the night. 




&& 


Previous discussion... 
/issued 426 am CST Thursday Dec 4 2008/ 
an area of light snow continues to traipse across the forecast 
area early this morning...induced by faint shortwave energy in the 
base of the trough centered over Hudson Bay. The associated area 
of 850-500mb q vector convergence shifts east of the County Warning Area this 
morning...with measurable snowfall expected to end around 
daybreak. However...scattered flurries will be possible for a good portion 
of the day under the influence of the departing upper trough. Cold 
air advection and an 850mb temperature decline to around -20c will 
contribute to maximum temperatures around 10 to 15 degrees below 
climatological normals...as readings top out in the middle/upper 
teens and low 20s. 


After today...attention shifts to a clipper system prognosticated to dip 
across the north central Continental U.S. On Friday. There was good agreement 
between the latest runs of the GFS/NAM/ECMWF in bringing 
measurable snowfall to the County Warning Area between 00z and 12z Saturday. 
Snowfall amounts between one and two inches appear 
likely...especially across North/East central Minnesota and west 
central WI...where snow growth should be decent per forecasts of 4-5 
-ubar/S of Omega at the -15c temperature level. 


Chilly temperatures prevail over the weekend...with a low level 
high pressure ridge in control. The next shortwave trough in the 
parade is forecast to arrive late Sunday and Monday. Although 
there are still notable difference in the model solutions with 
respect to timing/placement aspects of this feature...agreement is 
decent enough to warrant high chance probability of precipitation between 00z Monday and 
00z Tuesday. High pressure will make a fleeting appearance late 
Monday into Tuesday...with yet another weak system expected by 
midweek. 


&& 


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


$$ 


Trh/ls