339 
fxus63 kiwx 212025 
afdiwx 


Area forecast discussion 
National Weather Service northern Indiana 
325 PM EST Sat Nov 21 2009 


Short term... 
upper ridge is building over the County Warning Area this afternoon as surface 
ridging slides slowly east resulting in a sunny day for most as an 
area of latent stratus clouds dissolves over south central 
counties. Significant morning fog developed upstream in the 
environment that will translate overhead by morning bringing a 
repeat of foggy conditions into middle/late morning as mostly clear 
skies and light winds on west side of departing surface ridge allows 
effective cooling while llevel moisture remains in place per time 
heights. 


On Sunday sunshine will again make its presence felt once morning 
fog/low stratus mixes out though as with today some locations may 
not clear out until middle to late morning. Tomorrow afternoon will 
be a bit warmer than today as temperatures aloft at h92 rise a bit with 
southerly flow developing in earnest to just to our west on the 
back side of retreating llevel ridge. Adequate mixing would see 
highs reach the middle to upper 50s which is in line with a met/mav 
guidance blend and very similar to inherited forecast. 


By Monday night deeper moisture beings to encroach from the south 
ahead of wave lifting away from the Gulf Coast with increasing 
gradient flow...so will hold off on any additional fog mention for 
Monday night at this point with slightly milder low temperatures. 


&& 


Long term... 
medium range guidance in good agreement into lt week before departing ways 
next weekend. Parade of SW troughs embedded within perturbed high 
momentum follow across the northern Pacific Promise an unsettled end to 
November. Lead SW into the SW US will do little other than dislodge 
intense southern stream SW over la short term. More potent wave out near 140w 
will dig inland sun and emerge over the Central Plains Monday. Continued 
intensification shld lead to a decent frontal rain band Tuesday although 
stream separation and weak middle level ridging across the Gomex suggest no 
sig ll moisture entrainment into this system and will continue to ride low chance 
probability of precipitation. More substantial amplification upstream of this system tied to 
more sig lw troughing developing across the nepac lt week allows secondary 
following wave to reinforce deepening Great Lakes trough and fairly 
impressive surge of cold air Thursday/Friday which looks favorable for continued 
rain/snow mention although 12z guidance would bodily fvr a btr chance 
of rain west/boundary layer looking a bit too warm. 


Otherwise temperatures near normal to start...tailing off to below normal by 
Thanksgiving and into next weekend. 


&& 


Aviation... 
main concern in taf is repeat of morning fog yet again Sunday 
morning as light winds and clear skies are expected again. 
Otherwise...as area of low stratus continues to dissolve this after 
terminals should remain VFR into tonight and return after morning 
fog lifts. 


&& 


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


$$ 


Short term...lud 
long term...holsten 
aviation...lud