Weather

400 
fxus63 kiwx 110738 
afdiwx 


Area forecast discussion 
National Weather Service northern Indiana 
338 am EDT Sat Oct 11 2008 


Short term... 


..record or near record highs possible Sunday... 


Today through Sunday night 


Very little change from yesterdays weather expected through the 
period. Deep troughing over the western Continental U.S. Continues to support 
eastern Continental U.S. Ridging spurred by deep southerly flow. The upper 
level jet maximum is transitioning itself east of the trough/S 
inflection point...a sign that the upper trough will begin to lift 
east. In response to this...surface low pressure will develop over the 
Western Plains and shift east...being very slow in the process due 
to massive ridge in place...a ridge that refuses to budge given a 
near Omega block per troughing over the western Atlantic. Bottom 
line...warm dry weather will continue through the period...with near 
abundant sunshine. Expect temperatures to slowly warm each day given 
continually modifying airmass per insolation and warm air advection. 


Have adjusted high temperatures to a h875 mix out in line with ilx/iln/dvn 
soundings...which has been the norm the past two days. Deeper mixing 
indicated by bufr forecasts is becoming more unlikely as we shift deeper 
into autumn...especially given weak ll flow. Have then blended temperatures 
to the FWC numbers which worked out quite well for Friday. 
Staggeringly dry air aloft will again mix down and should support 
dew point/S down into the 30s possibly upper 20s east...producing very 
comfortable relative humidity. A few cirrus per residual upper level moisture and a 
lingering weak vorticity maximum may be present once again. Otherwise...skies 
are expected to be sunny today. There is some indication that middle 
and upper level moisture may begin to arrive in the far west late 
Sunday...courtesy Norbert in the Pacific and a staunch 125-130 knot 
upper jet. So a few middle and high clouds are possible there. Near 
record highs look likely at sbn and FWA. Have went with 82 at both 
sites. The record high is 83 at both sites. This will have to be 
monitored as the potential to tie or break the records is there is 
deeper mixing is realized. Overall...look for mostly sunny skies 
with highs 15 to 20 degrees above normal. 


&& 


Long term... 
deep western trough and expanding downstream middle level ridge across the eastern 
US will dominate much of this period. Continued much above normal temperatures Monday 
west/core of ll thermal ridge just to the east yet some cooling toward middle 
week in association/west sub tropical moisture plume entrainment via Hurricane 
Norbert. Scraped 00z GFS which ejects western trough bodily northeastward into 
Canada and fails to grasp Norbert remnants. European model (ecmwf) on the other hand 
continues to show a high degree of continuity west/western trough...taking lead 
SW up through northern plains but develops secondary back across the 4 corners 
lt Monday and which then lifts out middle week into the Great Lakes. 
Given this has been the preferred solution for some time...feel its 
prudent at this stage to extend probability of precipitation through daytime Wednesday. 
Furthermore...much slower eastward frontal progression as indicated by European model (ecmwf) 
heralds another mild October day Tuesday. Remainder on track. 


&& 


Aviation.../06z tafs/ 
VFR conditions expected through the period as an upper level ridge 
will remain over the region. There is some concern for ll wind 
shear this morning with 1-2kft southeast flow at 25 to 30 knots as 
indicated on iwx VAD and Wolcott vwp. NAM 12 and NAM bufr forecasts 
support increased flow to 30 knots in this layer through sunrise 
until re-coupling occurs. Have left out of taf at this time given 
small directional change with height and continued southeast surface flow at 5-7 
knots. Otherwise...no other aviation concerns. 




&& 


Iwx watches/warnings/advisories... 
in...none. 
Michigan...none. 
Ohio...none. 
Lm...none. 
&& 


$$ 


Short term...Chamberlain 
long term...holsten 
aviation...Chamberlain