311 
fxus63 kmpx 231209 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
609 am CST Monday Nov 23 2009 


Update... 


12z aviation discussion added below. 


&& 


Discussion... 
the forecast challenges this period are precipitation chances and 
precipitation transition over to snow before Thanksgiving evening. 
In the near term...a nearly stationary front over central Minnesota...will 
move little today as a weak surface trough over the Central Plains 
drifts slowly east over the Midwest through Tuesday. 
Moist and warm air continue to lift north over the frontal boundary 
across the upper Midwest. Light rain should begin to push out of 
south central Minnesota and western Wisconsin later this morning with 
lingering light rain or drizzle over the rest of the forecast area 
through the remainder of the day. 


The models are in general agreement in the medium range... 
models have been consistent from run to run with upper low over the 
Central Plains...lifting northeast over the lower Great Lakes by 
Wednesday morning. Stronger upper level trough over the Pacific 
northwest...will begin to carve out a stronger trough over the 
northern plains/upper Midwest by Wednesday. 


The Gem-nhem model blend indicates the precipitation should be 
mainly rain through Tuesday...then become a mixture of rain or 
snow over portions of west central Minnesota Tuesday night then 
switch over to all snow over the entire forecast area on Wednesday 
as colder air sinks over the Midwest. 


Thanksgiving day and Friday...looks cold and dry as a surface ridge 
builds east over the upper Midwest during the period. 


&& 


Aviation.../12z taf issuance/ 


Conditions a bit chaotic this morning as area sits under strong 
warm air advection regime southeast of a warm front that has pushed northwest of all terminals. 
The warm air advection at low levels has impeded moistening of atmo and development 
of stratus all night. The lowest stratus has stayed along the 
front...which pushed LIFR clouds out of axn earlier. Over 
WI...rain all night...combined with a weakening in low level warm air advection 
has moistened atmo enough to bring in some MVFR clouds near the 
Minnesota/WI border. Rnh so far is the only terminal to be impacted...but 
following RUC 925 mb relative humidity...which nicely depicted the formation of 
the WI clouds...expect southeast winds over msp to bring these clouds 
over the field shortly. Also expect them to expand into eau and 
eventually make up into stc. Though have kept conditions MVFR at 
all but eau this afternoon...warmer/drier low level air may yet 
make it into the area from the south this afternoon...which could 
lead to a few hours of VFR conditions at msp...before conditions 
deteriorate again tonight. For tonight...front will turn into an 
inverted trough associated with a developing low over western 
Iowa...this will spread more light rain into western Minnesota first...then 
work east. Feel more confident about seeing IFR conditions 
overnight as best warm air advection will be off over the Great Lakes...which 
should keep low levels moist here and allow for stratus to lower 
into at least the IFR category. With winds...will remain at 10 
kts or less out of the east-southeast. Axn/rwf will see winds turn the north 
tomorrow morning however as they get on back side of trough. 


&& 


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


$$ 


Jvm/mpg