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fxus63 kiwx 202341 
afdiwx 


Area forecast discussion 
National Weather Service northern Indiana 
741 PM EDT Sat Mar 20 2010 


Aviation... 


Cold front continuing to move very slowly south across central in/Ohio this 
evening. Band of Post frontal precipitation over NE Illinois/Northwest Indiana/southwestern Michigan has 
made no southward progress over the last couple of hours, however scattered 
-shra have developed to the southeast over central Indiana. Forcing for 
precipitation over the area should weaken this evening as right entrance 
region of ulj over southern Great Lakes moves east. Thus, expect just some 
light showers with no significant impact on terminals this evening. MVFR/IFR 
conditions from southern Michigan-NE Illinois have also made little southeast-Ward progress 
this afternoon. With diurnal cooling there may be a little southward 
expansion to this cloud deck overnight with MVFR ceilings possibly 
reaching as far south as FWA by late tonight. Low ceilings in this 
area should dissipate Sunday as stalled northern stream 850 mb front over 
Northwest Indiana/southern Michigan weakens/mixes out while deepening southern stream low 
moves east across the southern U.S.. 


&& 


Previous discussion... /issued 322 PM EDT Sat Mar 20 2010/ 


Short term... 
tonight through Sunday night. 


Cold front has worked through the County Warning Area for the most part today. 
However...lift and moisture associated with this has struggled to move 
south all day. As a result...areas in the far northwest have remained 
cloudy and in the 30s and 40s...but dry...so far. Outside the clouds 
temperatures have rebounded into the upper 40s to middle 50s. An area of 
stratus attempted to advect south and west in the NE flow but has 
struggled to also work south across the remainder of the area. This 
poses a challenging forecast for tonight in terms of precipitation 
chances...cloud cover and temperatures. Clouds continue to increase back 
across Illinois and locations SW and this is showing signs of moving 
towards the area tonight. However...models have shown that this moisture 
may be slow to move NE until the main low begins to approach Sunday 
and Sunday night. Am concerned that lows could be off by several 
degrees potentially tonight...but also a rather large bust factor 
looms. If clouds stay away in southeast half...expected fast drop in temperatures 
will occur and lows to go to forecast levels. If cloud cover moves 
in and dewpoints remain up then lows will end up closer to lamp 
guidance in the low to middle 40s southeast and 30s northwest. 


Cloud cover may break for a bit during the day Sunday. If this 
occurs then temperatures will be warmer than currently forecast as well. 
Considering low confidence in models right now will just let things 
ride and let overnight crew see how things are moving along. Probability of precipitation 
still look good for Sunday night as decent low draws closer. Exact 
timing and extent of the precipitation will be a challenge but southeast half or 
so look to be in best shape to see measurable precipitation. Will maintain 
likely probability of precipitation in these areas. 


Long term... 


Mainly minor tweaks to the forecast for the entire 
period. Models in fair agreement pushing low pressure east from the 
Ohio Valley and building weak high pressure for most of the week. 
Another weak low pressure system slides to our south late in the 
week that could bring a small chance of rain to the area. 


Highs will mainly be in the 50s for the week with a few upper 40s 
possible northern sections Friday and Saturday. Lows in the 30s with 
the coolest morning Tuesday and Saturday when a few upper 20s will 
be possible. 


&& 


Iwx watches/warnings/advisories... 
in...none. 
Michigan...none. 
Ohio...none. 
Lm...Small Craft Advisory until 6 am EDT Sunday for lmz043-046. 


&& 


$$ 


Short term...Fisher 
long term...sabones 
aviation...jt