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fxus63 kiwx 220849 
afdiwx 


Area forecast discussion 
National Weather Service northern Indiana 
349 am EST sun Nov 22 2009 


Short term... 


..today through Monday night... 


Relatively quiet short term period before more active pattern begins 
to affect the area. Biggest concern will be amount of fog this 
morning and amount of cloud cover and probability of precipitation for Monday and Monday night. 


Surface high pressure over eastern Great Lakes providing clear skies 
and light winds for our area this morning. Fog was finally beginning 
to form around 07z and should continue and become locally dense by 
daybreak. No headlines planned at this time as no signs of 
widespread dense fog but will monitor further development. 


Fog should burn off this morning with mostly sunny conditions 
expected once again. A nearly Carbon copy of Saturday with more sun 
in the southeast. Temperatures may be just a few degrees warmer with mixing 
from 900mb indicated by nam12 soundings. This matches latest MOS and 
inherited grids so only some minor tweaks made. 


Short wave exiting the intermountain west this morning will help 
pick up wave sitting in deep south and lift it northeast. Models 
have been hinting at increasing moisture across our 
area...especially in the east...late tonight into Monday. 2100 UTC 
sref 12hr probabilities for measurable precipitation have increased to over 
70 percent in our east for Monday and Monday Monday night. Expect 
models are overdoing western periphery of moisture but some light 
showers are possible in far southeast and have added a low chance to 
account for this and for better collaboration. Amounts should be 
tenth of an inch or less and this is also supported by very low sref 
probabilities for more than a tenth of an inch. Cloud cover also 
expected to increase Sunday night and Monday across entire area as 
these waves phase and move across the region. Temperatures on Monday 
will be a little cooler but still above normal with increased cloud 
cover. Similar story Monday night ahead of more potent wave that 
will bring significantly cooler air for later in the week. 


&& 


Long term /Tuesday through Saturday/... 


GFS/European model (ecmwf) beginning to come into agreement in...at least in terms of 
slower arrival of precipitation with intensifying low pressure to the west. 
The result is a slow down in the onset of chance probability of precipitation for Tuesday from 
west to east. Best chance looks to arrive late afternoon Tuesday and 
more so Tuesday night into Wednesday. Have increased probability of precipitation to 50 percent Tuesday 
night but hold off on likely as exact track of low remains a bit 
problematic ranging from tracking across the County Warning Area to across portions 
of Wisconsin. Ensemble guidance shows the large disparity in 
confidence with probability of precipitation ranging from 20 to as high as 80. Also with the 
further west track...thermal profiles way too warm to support 
continued mention of mix precipitation Tuesday night so this has been removed. 


Precipitation chances will linger into Wednesday night when questions continue as 
to the speed and degree of the cold air in the wake of the system. 
GFS continues to be the faster of the medium range models in the 
arrival of the cold air by Wednesday night vs the European model (ecmwf) during the day 
Thursday. Will generally follow the mean 850 mb temperatures depicted by the 
GFS ensemble which brings readings into the -4 to -6 c range by 
Friday. Depending on amount of cloud cover...guidance may be a bit 
too warm with reading not far from climatology in the lower 40s. For now 
will leave temperatures and mix precipitation mention alone given enough timing 
issues in earlier periods to raise a bit of doubt on exact timing in 
later periods. Both models linger the cooler air around into late 
Friday when some moderation begins...with the GFS of course being 
the more extreme of the two models. 


&& 


Aviation... 
high pressure over the area with clear skies and light winds 
tonight. Expect MVFR br to develop with IFR possible toward 
daybreak. Should see this burn off quickly after sunrise with return 
to VFR conditions. 


&& 


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


$$ 


Short term...Lashley 
long term...Fisher 
aviation...Lashley