387 
fxus63 kmpx 211025 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
525 am CDT sun Mar 21 2010 


Update...for 12z aviation discussion below 


&& 


Discussion.../issued 331 am CDT sun Mar 21 2010/ 


Not much change in forecast thinking from previous issuances with 
quiet weather and a steady warm up over the next few days. A cooling 
trend will commence from midweek Onward along with some minimal 
precipitation chances Tuesday. Water vapor imagery shows deepening upper 
level low continuing to churn across the arklatex working with 
associated surface low/inverted trough to bring significant precipitation to 
the Southern Plains and lower Mississippi River valley. Plenty of 
subsidence overhead keeping things basically clear. Flow pattern is 
splitting over the area as the big upper low cuts off. Sharp upper 
ridging over the western U.S. Is flattening as a deep low moving up 
the British Columbia coast overtops it. At the surface...high pressure 
ridging extends from eastern Colorado northeastward across southern 
Minnesota and northern WI. 


The first full day of Spring will see warmer temperatures and 
continued sunshine. 00z upper air analysis shows 850 mb temperatures of -9 c 
across the local area with warmer temperatures off to the west and heading 
this way. GFS looks to be a bit overdone on the low level warming 
today indicating 850 mb temperatures of +2 to +5 c by 00z Monday. 00z u/a 
analysis gives more support towards the NAM/European model (ecmwf) idea of 850 mb temperatures 
of +1 to +3 or so. Mixing does not look to be much deeper than about 
900 mb for most areas and upward adjustments for low albedo forested 
areas and for relatively light southwest winds support highs around 
50 for most areas except upper 40s for south central and portions of 
the west central County Warning Area where areal flood waters have contributed to 
higher dewpoints and cooler temperatures as of late. Forested areas of west 
central Minnesota may see lower 50s. Cirrus will increase tonight as will the 
surface pressure gradient which will help keep temperatures in the upper 20s 
and lower 30s. 


As mentioned...surface pressure gradient will be tightening into Monday 
in response to surface low pressure spreading across the Canadian 
prairies. Upper flow pattern will be zonal west to east by Monday 
morning allowing for increased warm advection. Southerly low level 
flow increases markedly but lacks the westerly component that would 
support a significant warm up. It will be warmer Monday but highs may 
top out in the upper 50s in warmer areas of the eastern County Warning Area with 
some isolated lower 60s readings possible there. May start to see a 
better downslope warming effect in the Canby area given very minimal 
area of remaining snow cover...which may be gone by that time. A 
weak upper trough will move through the zonal flow and push the surface 
low eastward allowing it to enter the County Warning Area Monday evening with better 
model agreement on timing. Little in the way of moisture associated 
with the system and the surface low actually weakens as it moves across 
into Tuesday. Associated cold front should be clear of the area 
Tuesday afternoon but cold air lags behind. Looks as though any 
precipitation will likely fall as sprinkles with some light rain 
possible in spots but it would be tough to have anything measurable. 
Will keep minimal slight probability of precipitation in for Tuesday but they may be able to 
be removed. Have removed them for Tuesday night. Temperatures will 
be cooler Wednesday and Thursday. Surface low pressure will be passing 
to the north with European model (ecmwf) and GFS at odds on how far to the north it 
will be. Upper flow will be turning northwesterly and much colder 
air will be poised to push southward into the area into Friday. 
Coldest air looks to stay off to the east but a cool down is 
expected but does not appear to be as dramatic as the one observed 
over the last two days. ..mdb.. 


&& 




Aviation.../12z taf issuance/ 
high pressure will dominate the area through the taf period...and 
yield VFR conditions into Monday. Southwest winds at 5 to 10 kts 
today will back closer to 180 degrees in direction this evening...and 
decrease below 5 kts. 


Kmsp...surface winds around 230/240 degrees will back to around 190 
degrees by 00z...then eventually to around 150 degrees by daybreak 
Monday. Sunny skies into this evening...and then cirrus clouds 
increase around/after sunrise on Monday. 




&& 


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


$$ 


Ls/mdb