680 
fxus63 kmpx 212012 
afdmpx 


Area forecast discussion 
National Weather Service Twin Cities/Chanhassen Minnesota 
300 PM CDT Thursday Aug 21 2008 


Discussion... 


Slug of moisture associated with upper trough lift north out of east Iowa has 
spread showers across southeast Minnesota into SW WI. There has been sufficient 
heating early this afternoon in ec Minnesota to probability of precipitation a few showers and 
thunderstorms as convective temperature in lower 80s has been 
reached. Expect these convective showers to become a bit more 
widespread the remainder of the afternoon before rapidly diminishing 
during the evening. Showers associated with middle level trough lifting 
out of Iowa will continue at least until 06z in southeast County Warning Area. Overnight 
temperatures will be mild with warm, moist southerly flow and mostly 
cloudy skies. Convection currently firing NE nodak in strong low 
level jet where airmass has destabalized...but should lift north of County Warning Area 
overnight. 


Attention then turns toward precipitation chances for tomorrow with 
approach of cold front and vigorous upper trough. Instability not 
overly impressive...but strong 0-6km bulk shear in 50 knot plus 
range vicinity of cold front could pop a few strong storms. Expect 
a scattered line of thunderstorms to develop in SW into central Minnesota 
in the early/middle afternoon moving across eastern areas mainly in the 
evening. 


Dry and cool Canadian pressure pushes in for the weekend with 
surface dewpoints likely dropping at least into the upper 40s across 
much of the area. Will also have some fairly gusty west winds on 
Saturday with nam80 prognosticated soundings showing 20 to 25 knot winds 
available for mixing. 


Another quite vigorous upper trough expected to move out of the 
northern rockies middle week driving another cold front across the area 
on Wednesday. Started probability of precipitation Tuesday night in west and spread across 
area on Wednesday. 


&& 


Aviation.../18z taf issuance/ 


Tough set of tafs...with strong winds...precipitation chances...and 
fog/stratus likely. Plume of moisture from the Gulf pouring into 
the area...as an upper low moves newrd across the area. 88d mosaic 
shows bulk of rain showers in southeast Minnesota and into eastern Iowa/southwestern WI at this time...and 
305k isen analyses project this to really only affect eau 
substantially this aftn/eve. Upstream conds brought on by upper low 
showed widespread IFR ceilings...with largely MVFR/occasional IFR 
visibilities. This airmass should spread across the rest of the area 
overnight...leading to widespread IFR ceilings from late evening through early 
to middle morning tmrw. Increase pressure gradient will lead to higher winds 
tmrw...as cold front approaches. After 18z tmrw...attention turns to 
convective potential as front pushes ewrd. Likelihood of thunderstorms and rain best 
from stc ewrd during the middle/late afternoon and into the evening. 


&& 


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


$$ 


Bap/kat