260 
fxus63 kmpx 151100 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
600 am CDT Monday Mar 15 2010 


Update... 
updated to include 12z aviation discussion below. 


&& 


Discussion... 


Sundays high temperatures were very interesting as a surge of 
drier air from the NE...and 850 mb temperatures around 6c...allowed for surface 
temperatures to rise into the 50s and 60s. Minneapolis even broke a 
daytime high of 64. The main forecast concerns today will be the 
amount of cloud cover to the east vs. The western forecast area and how the surface 
temperatures will relate to these conditions with snow cover 
becoming less. 


Will likely lean toward the higher guidance temperatures (western wis) in 
the short term as cloud cover will likely be minimal. Elsewhere...will 
likely keep temperatures in check...but may adjust based on gembc which 
was the Superior model on sundays afternoon temperatures. 


As for precipitation chances...two weak upper level waves continue 
to move slowly east/southeast across the eastern Dakotas this morning. 
Although the rainfall has been locally heavy where these 
disturbances have nearly been stationary the past 24/48 hours...the 
general trend is to have the deepest moisture in the western forecast area 
today...with a slight increase in the east later tonight/Tuesday. 
My concerns deal with the movement of these waves further 
eastward into more cyclonic flow and become more sheared 
out. There may be enough to warrant 20/40% of -ra for eastern Minnesota 
starting later tonight/early Tuesday. Will see how the latest ec 
model indicates on moisture depth before increasing the 
percentages too much. Once this system moves south of the 
region...there should be enough subsidence to scourer out any 
residual moisture across the upper Midwest. 


After Thursday...the pattern change which we have been advertising 
the past few days will lead to uncertainties in precipitation 
chances over the weekend...and what type of precipitation at the 
early stages as the cold front moves through on late 
Thursday/Friday morning. Too many uncertainties to change current 
forecast with rain changing to snow by Friday night...with small 
chances of snow throughout the weekend. Temperatures will once 
again drop below normal and should last through the middle of next 
week. 


&& 


Aviation.../12z taf issuance/ 
today looks to provide a Stark dichotomy in conditions across the 
area once again... with primary VFR across the east and primarily 
IFR/LIFR giving way to MVFR/IFR over the west. Embedded shortwaves 
in the weak upper ridge will be nudged eastward across a good part 
of the area today... but will continue to lose some punch as they 
do so. The thicker saturated conditions over the west will 
remain in place... hence little expectation for much other than 
the expected diurnal improvement in ceilings and visibilities for 
those area. There is some spotter drizzle/light rain moving 
through the area at the current time... but it isn/T having much 
of an impact on visibilities and is mainly falling from an ac 
cloud deck. The more meaningful precipitation is still well to the west... 
although it will impact that portion of the forecast area this 
morning. Overall... will allow for some marginal improvement out 
west today... then a worsening of conditions again tonight... 
although we should see a continuation of the trend we/ve seen with 
things becoming slightly better each day as the boundary layer is 
able to dry out some. This will be most marked once again over the 
east... where a good amount of sunshine should be seen... not as 
much as on Sunday since there will be more layered cloud cover... 
but enough to warm temperatures... raise any ceilings trapped at 
the top of the mixed layer... and further dry things out to help 
mitigate the potential for formation of low clouds/fog tonight. 
The only complicating factor for later tonight will be the arrival 
of a surface trough and some middle-level forcing with the upstream 
shortwaves... which will work to bring more widespread and 
synoptically forced low clouds and precipitation chances into the eastern 
portion of the area late tonight. Keau should escape this entirely 
during this forecast period... but expect kmsp to see MVFR 
ceilings return late tonight along with potential visibility 
restrictions from possible rain and some fog. 


Kmsp... it appears as though any MVFR conditions will be avoided 
this morning although there may be some MVFR visibilities not too 
far from the Airport during the first hour or two of the taf. 
After that... see no reason that VFR conditions won't prevail 
through the day. There is a slight possibility for some MVFR 
ceilings during the late morning and afternoon if enough moisture 
can be mixed up into the boundary layer while the mixing heights 
are still sufficiently low... but for now will allow for broken VFR 
ceilings at worst... with some lower scattered clouds. Main uncertainty 
in the forecast looks to be the arrival of lower clouds and 
perhaps some precipitation and associated lower visibility late tonight and 
Tuesday morning. Wouldn/T be surprised if timing is a little 
slower than advertised... but for now this matches up reasonably 
well with a NAM... GFS... sref consensus approach. 


&& 


Mpx watches/warnings/advisories... 
Minnesota...dense fog advisory until 11 am CDT this morning for Blue Earth- 
Brown-Chippewa-Faribault-Freeborn-Lac Qui Parle-Martin- 
Nicollet-Redwood-Renville-Sibley-Steele-Stevens-swift- 
Waseca-Watonwan-Yellow Medicine. 


WI...none. 
&& 


$$ 


Trh/jlt/trh