925 
fxus63 kmpx 201707 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
1207 PM CDT Sat Mar 20 2010 


Update... 
updated to include 18z aviation discussion below. 


&& 


Aviation.../18z taf issuance/ 
with ridging building across the area... VFR conditions will 
prevail through the period... with light northwest winds backing 
around to the west and southwest. Boundary layer warm advection 
will continue to work to dry out the lower part of the 
atmosphere... so although a few cumulus can be expected this 
afternoon... they will mainly be confined over the west and there 
will be less potential for that tomorrow. 


Kmsp... taf reflects expectations with no additional issues of 
concern. 


&& 


Previous discussion... 
/issued 618 am CDT Sat Mar 20 2010/ 


Fairly tranquil weather pattern in place across the forecast area 
early this morning and will continue to be in place for much of the 
forecast period. Caveat will be some small precipitation chances during the 
middle of next week. Early morning water vapor imagery shows 
strengthening upper level trough moving into the Texas/OK panhandles 
working with an associated inverted surface trough to produce wintry 
weather across the southern and Central Plains. Zonal southwest to 
northeast flow lies ahead of the trough across the Ohio Valley and 
Great Lakes with upper ridging building into the West Coast behind 
the trough. The upper trough will further amplify causing a split 
flow pattern to develop with the low closing off across northeastern 
Texas and a col developing overhead of the local area. This combined 
with the arrival of surface high pressure will provide tranquil but cool 
conditions in the near term with a warming trend getting underway 
Sunday which will continue into the middle of next week. Details follow... 


Upper trough axis is still crossing the area this morning but is 
weakening with the trough to the south intensifying. Middle and high 
level moisture streaming in from the southwest will vacate the area 
this morning leaving a very dry atmosphere in place. Surface high 
pressure centered over the Dakotas this morning will settle 
southward through the day with ridging arcing northeastward over the 
County Warning Area into tonight. Thermal profile will change little through the day 
but sunshine will be abundant. Western areas will warm several 
degrees over yesterday while eastern areas will be similar with the 
wooded areas of west central WI likely being the warmest with some 
lower 40s possible. Ridging will remain overhead tonight with clear 
skies continuing leading to very cold temperatures. Am thinking 
guidance might be a few degrees too warm in some spots...mainly in 
the south...so will trim temperatures back into the upper teens there. Snow 
cover is none over most areas so that may preclude upper teens but 
feel the diurnal range will be greater than guidance indicates. Middle 
level air will be warming into Sunday morning with 850 mb temperatures warming 
above 0c by late Sunday afternoon. Sunny skies will continue with 
surface flow turning southerly but remaining rather weak. Modest mixing 
combined with a cold start should allow highs to be slightly cooler than 
guidance in most areas but things will be much warmer than Saturday 
with middle to upper 40s expected with the best chance for readings of 
50 or better from the Twin Cities eastward. 


The pattern starts to shift Monday as the now closed and cutoff 
upper low moves across the Tennessee Valley. Upper troughing will 
move into The Rockies spawning surface cyclogenesis in their Lee. The 
GFS and NAM are more progressive than the European model (ecmwf) with bringing the 
surface low eastward into the local area having it arrive Tuesday. All models 
have the low being weak and show little support for much 
precipitation but will stick with the slight probability of precipitation Tuesday and 
Tuesday night. Cold advection arrives behind the low so mixed precipitation 
will be possible Tuesday night. Flow ahead of the low will 
strengthen Monday allowing even warmer temperatures over sundays 
values. Following more of a GFS-like speed...Tuesday highs will be 
cooler with wednesdays cooler yet with the decent cold advection 
following the low. A slower solution would delay this keeping 
Tuesday dry and likely warmer than Monday. ..mdb.. 


&& 


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


$$