629 
fxus63 kdtx 231057 
afddtx 


Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan 
557 am EST Monday Nov 23 2009 




Aviation... 


Pretty wide area of low stratus has formed again overnight...but the 
ragged eastern edge just happens to fall near dtw/det...so the early 
part of the forecast could see widely varying conditions at these 
two sites. Mbs/fnt are deeper into this stratus deck and will remain 
IFR until midday as this low level moisture Burns off/mixes out. Ptk 
will probably remain IFR as well...but may break out a bit earlier 
in the middle/late morning. As low pressure to the south edges slowly 
in this direction...the moist southeast flow will persist...so any 
clearing during the day will be replaced by the re-expansion of the 
stratus back over the area from late evening on into the overnight 
hours. So...persistence will be the forecast to end this forecast 
period. 


&& 


Previous discussion...issued 341 am EST Monday Nov 23 2009 


Short term...today 


Low stratus/areas of fog will be prevalent again this morning...and 
expect it to take much of the morning to burn this off. Even by the 
afternoon...skies will be partly/mostly cloudy as clouds lift north 
into the region as low pressure begins edging towards the area. The 
highs will climb to between 50 and 55 degrees again...so no major 
changes will be needed to the going forecast. 


Long term...tonight through next Sunday 


One more morning of fog to affect lower Michigan before the next 
storm system moves in...bringing rain and snow with it. High 
pressure stretching from the Great Lakes to the New England states 
will continue its track eastward through Tuesday when it will 
finally lose its influence on the weather in Southeast Michigan. The 
high pressure will again give US a weak easterly wind field off the 
lakes reinforcing the already high moisture values in the low 
levels. Surface dewpoints will remain near 40f under a strong 
inversion located around 975mb. Model soundings show higher 
potential to the north around fnt/mbs but due to the persistence of 
this pattern with moisture amounts and fog development...will leave 
mention for all areas. 


Models coming into better agreement with each New Run recently in 
regards to the middle week storm system heading for the Great Lakes 
region. The GFS is trending a bit slower each run becoming more in 
phase with the European model (ecmwf)...which has been the most consistent model in 
handling this system. The NAM digs the trough/low deeper into the 
plains then both the GFS and European model (ecmwf) which also acts to slow it down. 
This surface low should track north along Lake Michigan on Wednesday 
leading to precipitation chances beginning overnight Tuesday. This initial 
upper wave looks to weaken a bit as it moves over Michigan but will be 
quickly reinforced by a second stronger wave digging into the 
Central Plains from the northern branch of the jet stream on 
Wednesday. Models are once again showing a fairly cold airmass being 
brought in with this second impulse. 850mb temperatures around -5c are 
being advertised for Thursday into Friday with most models 
now...GFS/dgex/ECMWF. Temperatures have already been hedged lower to take 
this into account so will wait to see if this becomes a more 
consistent solution before acting further on it. As the models seem 
slower with each successive run...still believe Thanksgiving day 
will be a rain event changing over to rain/snow overnight into 
Friday though amounts should stay on the low side. 


Upper level ridging will move in behind this system on Saturday 
putting an end to precipitation chances although it looks like the colder 
temperatures...highs in the lower 40s...will remain with US. 


Marine... 


Light southeast winds will increase slightly into Tuesday as high 
pressure retreats east...away from the area. The pattern becomes 
more active middle/late next week as an upper level storm system lifts 
into the region late Tuesday into Wednesday and brings the chance of 
rain as well as increased winds. Another more aggressive disturbance 
will then dive southeast into the southern Great Lakes and Ohio 
Valley bringing colder temperatures and a mix of rain/snow showers 
late in the week. Winds/waves will be much more turbulent as this 
system waffles through the area. 


&& 


DTX watches/warnings/advisories... 
Michigan...none. 
Lake Huron...none. 
Lake St Clair...none. 
Michigan waters of Lake Erie...none. 


&& 


$$ 


Aviation.....Dg 
short term...dg 
long term....drk 
marine.......dg 




You can obtain your latest National Weather Service forecasts online 
at www.Weather.Gov/Detroit (all lower case).